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High Power Fusing

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High Power Fusing

Post by drdx » Monday, 14 April 2008, 10:28 AM

Hello all, just wondering, how does the big amp crew fuse their stuff? I have a 300 amp breaker I plan on using, but at 300 amps, I'd think the vehicle would be burning down by the time it tripped itself in the event of a short. Any thoughts on this? Do they just run it all direct and disconnect when not in use? I can understand a much lower rated fuse or breaker used for safety, and I use them at the equipment and the battery, but what about this higher amperage stuff? I typically unhook my stuff when not in use anyway, as it is on welder connectors, no big deal, but I'm moving to a more hard mounted setup. -drdx
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Re: High Power Fusing

Post by slydog » Monday, 14 April 2008, 12:17 PM

drdx wrote:Hello all, just wondering, how does the big amp crew fuse their stuff? I have a 300 amp breaker I plan on using, but at 300 amps, I'd think the vehicle would be burning down by the time it tripped itself in the event of a short. Any thoughts on this? Do they just run it all direct and disconnect when not in use? I can understand a much lower rated fuse or breaker used for safety, and I use them at the equipment and the battery, but what about this higher amperage stuff? I typically unhook my stuff when not in use anyway, as it is on welder connectors, no big deal, but I'm moving to a more hard mounted setup. -drdx
No one around here fuses their keydown mobiles but then again most of them are all trust fund CBers and in the event of a vehicle burning up.........they'll just buy another.
Fuses are not meant to protect equipment, just keep the vehicle from flaming up in the event of a dead short.
I don't fuse anything....I have a 92 F350 with half a million miles on it, no big loss if it smokes.

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Post by TX_Dj » Monday, 14 April 2008, 12:53 PM

If you must have everything run on the same circuit, then a quality breaker at the battery is a must in case of a serious dead short. Second, I believe heartily in fuses at the device which are sized to the device's need in case something bad happens inside one of the boxes.

I.E. if your device has a max rating of 60a, and you have it connected to a 300a breaker, if something busts in the device and pushes it past 60a, you're going to be in a world of hurt if the power line can only take 100a, for example. If your box shorts, and blows its 60a fuse, it will stop it from drawing too much power.

Batt -> Breaker -> Long Run -> Fuse -> Device

A better option may be to run separate circuits sized appropriately for each device, than to gang them all up on a common bus.

Also keep in mind your load should not be expected to exceed 80% of your breaker's rating, so that is to say all the devices behind that 300a breaker should be 240a or less at max draw. Or does that only apply in AC ? I dunno! :)

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Post by slydog » Monday, 14 April 2008, 14:46 PM

TX_Dj wrote:If you must have everything run on the same circuit, then a quality breaker at the battery is a must in case of a serious dead short. Second, I believe heartily in fuses at the device which are sized to the device's need in case something bad happens inside one of the boxes.

I.E. if your device has a max rating of 60a, and you have it connected to a 300a breaker, if something busts in the device and pushes it past 60a, you're going to be in a world of hurt if the power line can only take 100a, for example. If your box shorts, and blows its 60a fuse, it will stop it from drawing too much power.

Batt -> Breaker -> Long Run -> Fuse -> Device

A better option may be to run separate circuits sized appropriately for each device, than to gang them all up on a common bus.

Also keep in mind your load should not be expected to exceed 80% of your breaker's rating, so that is to say all the devices behind that 300a breaker should be 240a or less at max draw. Or does that only apply in AC ? I dunno! :)
But it is so cool when your floor board is glowing red! :P

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Post by Foxhunter » Tuesday, 13 May 2008, 23:36 PM

Dr.Dx I like alot of your posts they are very good and straightforward. Somehow I wonder how anywhere in Texas could be near "the center of the CB universe". Texas, isn't that now Northern Mexico? Okay, on topic: Yeah I couldn't imagine running high loads/amps without using appropriately rated fuses. Unless----are you a "trust-fund baby"? :wink: Did you say "breaker"? From what I read that's real dangerous and many fires have resulted. When I didn't know, I used 6 switch 300 amp circuit-breakers because I'm somewhat familiar with car audio amps & related. Then I was reading in an AARL manual how in dead-short conditions they often fuse---and weld themselves together, continuing the circuit. :shock: I'm not trying to re-hash but it is right to slightly underate the fuse rating for the device. Currently I'm using 2AWG cables with heavy copper lugs and they are fused within 1ft of the power source---both sides +/- and within 1 ft of each device (radio/amp/two 1.5 farad capacitors). I also use a main shut-off switch (automotive type) from Calterm as a master "killswitch". This comes with a removeable key so that when I exit my vehicle all power is removed from the radio system so no "amateur" :) will operate it in my absence nor will there be any further risk of electrical malfunction. I just bought some 0000AWG cable and am wondering how I might fuse such line---as it's diameter is indeed large, maybe AC house fuses.

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Post by Foxhunter » Wednesday, 14 May 2008, 0:10 AM

One more thing.....I know I've recommended one particular site to a couple others and judging from the nature of your post(s) it would be some good, simple, straight-forward reading. The site is: www.K0BG.com
The wiring section is good as well as the dozen or so others. He's a first-class operator and there's a few real tips and no myth. Hope it helps.

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Post by 209 first class » Wednesday, 14 May 2008, 5:50 AM

im wondering if the circuit breaker has less resistance than a fuse, and if it would open quicker in case of short. i know plenty of people who will not use a fuse saying it adds resistance and therefore limits the amperage/current just like a very long extension cord would. i have heard of a car burning up around here, and also a friend had a short while driving. the car was smoking ,(it was the insulation on the hot wire burning!) it died, they pulled over, if they had not had a hatchet to chop the hot wire at the battery, his truck would have burned. it would be nice if someone did a test, no fuse/ fuse/ breaker. see if any one of them limits your swing or deadkey. i only know what people say, it would be good to really know. 2zero9
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Post by drdx » Wednesday, 14 May 2008, 6:00 AM

That K0BG site has excellent information. This has been going a bit, but I'm not breakered under the hood and also at the amp tray in the back. I too use a racecar battery switch, mounted in a pvc box, next to the driver seat so I can disconnect the vehicle from the 2nd battery and amp setup. It came in handy recently when I left my lights on overnight. I got in and it was all dead, so I just turned the key and connected the rear battery for a jump start. I have wondered about the breakers, but haven't tested them. I do have a spare jump box and an extra 200 amp one, so I may do a controlled test shorting it out and see if it blows. -drdx
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Post by 209 first class » Wednesday, 14 May 2008, 7:38 AM

gee, i dont know if i would short it, however fast it breaks the circuit, it will still strain the battery and heat up the wire/insulation with that much amperage. however i would be curious to know if any wattage is lost thru using a fuse/breaker versus running straight to the battery. if none is lost, then the whole thing about "dont use a fuse,you will lose power " is a hoax . 2zero9
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Post by drdx » Wednesday, 14 May 2008, 8:45 AM

I've wondered about the loss myself but always saw the fusing as essential. It does make you think you'd see some loss if you have this huge #2 cable running back to an amp then you see all that power traveling through 4 30 amp fuses or whatever and see the size of the conductor in that fuse. -drdx
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Post by powerstrokin » Wednesday, 14 May 2008, 9:45 AM

would there be a difference in running a distribution box with X amount of midi style fuses vs running a single higher amp fuse?

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Post by drdx » Wednesday, 14 May 2008, 9:52 AM

That's what I do. I couldn't find a 120 amp fuse, so i run 4 30's to one of my amps using one of those monster distribution boxes. -drdx
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Post by PONY EXPRESS » Wednesday, 14 May 2008, 10:36 AM

drdx wrote:That's what I do. I couldn't find a 120 amp fuse, so i run 4 30's to one of my amps using one of those monster distribution boxes. -drdx
If I was running that much power I would have to do it that way as well. To much current before the wire would blow and it would look like this. I feel much safer those fuses blowing up front than after it catches the carpet and everything else on fire.Yes that is an actual USPS vehicle like I drive on fire .Odds are they will find the old fuel lines cracked and gas ran down to the red hot manifold and ignited .Heck I worry about 50 amp fuses blowing but I know in a direct short it will pop that fuse by battery quick.


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Post by drdx » Wednesday, 14 May 2008, 10:46 AM

The 4 30's are at the back on the ts 16. The front has a breaker, but it's only a 135. The rear battery, right at the amps, takes the brunt of the draw on keydown so I haven't blown the 135 breaker yet, though I have a bigger one thinking I'd need to replace it. The rear battery is fused to everything, and breakered goint to the front of the vehicle. The only thing not currently fused is the bigger box, and I don't have any 320 amp fuses or a dist. box with that combo, although I guess I could do the 4x80 amp deal for that. I have a 300 amp breaker but this amp is on quick disconnects (welder banana kind) and is not in there often, so I haven't breakered/fused it yet but I will. I don't leave it hooked up as I don't usually need it and it sleeps in the house. -drdx
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Post by Foxhunter » Wednesday, 14 May 2008, 23:48 PM

209 first class wrote:im wondering if the circuit breaker has less resistance than a fuse, and if it would open quicker in case of short. i know plenty of people who will not use a fuse saying it adds resistance and therefore limits the amperage/current just like a very long extension cord would. i have heard of a car burning up around here, and also a friend had a short while driving. the car was smoking ,(it was the insulation on the hot wire burning!) it died, they pulled over, if they had not had a hatchet to chop the hot wire at the battery, his truck would have burned. it would be nice if someone did a test, no fuse/ fuse/ breaker. see if any one of them limits your swing or deadkey. i only know what people say, it would be good to really know. 2zero9
That topic is addressed mostly at: www.K0BG.com (in the wiring protection section at the bottom of the list).

I still think you're mic collection is the real deal 209 1st class :mrgreen: green w/envy

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Post by Kojak » Monday, 03 November 2008, 6:52 AM

Foxhunter wrote:Dr.Dx I like alot of your posts they are very good and straightforward. Somehow I wonder how anywhere in Texas could be near "the center of the CB universe". Texas, isn't that now Northern Mexico? Okay, on topic: Yeah I couldn't imagine running high loads/amps without using appropriately rated fuses. Unless----are you a "trust-fund baby"? :wink: Did you say "breaker"? From what I read that's real dangerous and many fires have resulted. When I didn't know, I used 6 switch 300 amp circuit-breakers because I'm somewhat familiar with car audio amps & related. Then I was reading in an AARL manual how in dead-short conditions they often fuse---and weld themselves together, continuing the circuit. :shock: I'm not trying to re-hash but it is right to slightly underate the fuse rating for the device. Currently I'm using 2AWG cables with heavy copper lugs and they are fused within 1ft of the power source---both sides +/- and within 1 ft of each device (radio/amp/two 1.5 farad capacitors). I also use a main shut-off switch (automotive type) from Calterm as a master "killswitch". This comes with a removeable key so that when I exit my vehicle all power is removed from the radio system so no "amateur" :) will operate it in my absence nor will there be any further risk of electrical malfunction. I just bought some 0000AWG cable and am wondering how I might fuse such line---as it's diameter is indeed large, maybe AC house fuses.

Having done electrical work by trade, I tell you fuses are the only way to go. Household breakers react thermally to overload. Household circuit breakers sometimes weld themselves closed because they cannot react fast enough to the excessive heat generated by dead shorts. Car batteries under these conditions can generate upwards of 3-4k amps For a very short (no pun intended) time.

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Post by Foxhunter » Monday, 03 November 2008, 9:58 AM

Kojak wrote:
Foxhunter wrote:Dr.Dx I like alot of your posts they are very good and straightforward. Somehow I wonder how anywhere in Texas could be near "the center of the CB universe". Texas, isn't that now Northern Mexico? Okay, on topic: Yeah I couldn't imagine running high loads/amps without using appropriately rated fuses. Unless----are you a "trust-fund baby"? :wink: Did you say "breaker"? From what I read that's real dangerous and many fires have resulted. When I didn't know, I used 6 switch 300 amp circuit-breakers because I'm somewhat familiar with car audio amps & related. Then I was reading in an AARL manual how in dead-short conditions they often fuse---and weld themselves together, continuing the circuit. :shock: I'm not trying to re-hash but it is right to slightly underate the fuse rating for the device. Currently I'm using 2AWG cables with heavy copper lugs and they are fused within 1ft of the power source---both sides +/- and within 1 ft of each device (radio/amp/two 1.5 farad capacitors). I also use a main shut-off switch (automotive type) from Calterm as a master "killswitch". This comes with a removeable key so that when I exit my vehicle all power is removed from the radio system so no "amateur" :) will operate it in my absence nor will there be any further risk of electrical malfunction. I just bought some 0000AWG cable and am wondering how I might fuse such line---as it's diameter is indeed large, maybe AC house fuses.

Having done electrical work by trade, I tell you fuses are the only way to go. Household breakers react thermally to overload. Household circuit breakers sometimes weld themselves closed because they cannot react fast enough to the excessive heat generated by dead shorts. Car batteries under these conditions can generate upwards of 3-4k amps For a very short (no pun intended) time.
Hi there Kojak. Welcome on and glad to see your post & comments. Out of curiousity, did you choose the "bald-headed" eagle in relationship to the famously "bald-headed" Kojak you're using for a username/handle? Just wondering!

My last comment on the post you'd quoted mentioned me considering the possibility of using large "AC house fuses " for that industrial 0000AWG stranded-flex DC power cable I have. I shouldn't, I've learned. I bought that G-I-A-N-T cable for a future mobile amp install (hee). The problem is: finding connectors that size. Asking around, electrical supply retailers (not your local autostore either) automatically think I am confused and mean "4AWG" where as it is actually "4/0", aka "4-ought". Connectors and fusing that size will be the trick. I'll do a more extensive search when I get closer to being ready.

Here's a link to the AWG Wire Gauge & Current Limits Chart for any of our Forum vieweres who may be interested:
http://www.powerstream.com/Wire_Size.htm
Use it as a reference, to gauge whether your current install's supply lines are adequate or not.

If I may, I'd like to re-post an article written elsewhere on proper fusing & wiring protection. I won't include any of the charts or photos in the re-post. In the article, the process of "Hysteresis" (ie-"reaction-times") is explored demonstating that many circuits and boards in a radio system will suffer damage before a fuse or breaker will respond. I'd invite any of our viewers to read this article and consider the information provided. Comments/replies are welcome. After I'd read this, I had to "rethink" what I'd done in the past-----and what I considered "safe" or "protected" in prior installs.
*****************************************************************************


Quote:

"Installing an amateur transceiver in a vehicle entails a lot of work, and attention to detail. This includes proper wiring, protecting that wiring, and ultimately protecting the equipment as well. Far too often the details are overlooked, or circumvented, resulting is erratic operation, ground loop problems, and other maladies not easily traced or repaired.

Besides the wiring issues, proper fusing is also an important consideration. While the factory wiring harnesses are adequately fused, it's a rare mobile installation that doesn't have some ancillary equipment (SWR meter for example) requiring power. When there is, each device should be fused according to the manufacturer's recommendations.

This article is an effort to explain why proper fusing is so important.

Fusing and a Thing Called Hysteresis

It seems, no matter how many times a myth is dispelled, they keep raising their ugly head. One common myth is that power cable fuses protect the radio from damage. They don't. Myth number two is, that a fuse will open instantly as soon as the current exceeds the fuse's rating. It won't. Myth number three is, it's always okay to use fuses designed for 120 volts AC, in a nominal 12 volt DC system. It isn't.

Fuses are there to protect the cabling. For example, the Icom IC-7000 has a 5 amp (system) fuse mounted inside the radio, and 30 amp fuses in the cabling (plus and minus). If you short out a supply connection (pin 3 of the tuner port for example), a circuit board trace and/or switching transistor will fail long before the 5 amp fuse opens. The 30 amp fuses will never open in this particular case. It can be argued that the power cable fuses do protect the radio if something fails catastrophically, a final perhaps, but chances are some other component in the circuitry will be damaged beyond repair before the power cable fuse(s) opens.

The definition of a fuse is relatively simple. It is a wire, that when subjected to too high of a current, melts. When it does, the circuit opens... hopefully. I say hopefully, because if you've chosen the incorrect size for your application, it may not open. Or, it may open after a long delay. In any case, you want the fuse to do its job, well before your wiring becomes its own fuse.

All fuses exhibit hysteresis. This is the time lag between any given ampere overload and when the fuse opens. For example, a nominal 20 amp fuse will handle a 30 amp load for about 90 seconds. It will hold a 100 amp load for about 1 second. This is one reason slow blow fuses are not recommended for amateur devices.

Unless you're an engineer, you don't hear the word hysteresis very often. Hysteresis is used to describe a phenomenon, in which the value of a physical attribute lags behind changes in the effect causing it. I use it here because fuses have a hysteresis effect. This fact figures heavily on our choice of fuse amperage ratings, the wire size we choose as a result, and ultimately how safe our installation is should a dead short occur.

The chart at left (omitted---Home page link: ( http://www.littelfuse.com/index.html ) is courtesy of Littelfuse, Inc. and I thank them for allowing me to reproduce it here. The chart covers their 299 series fuses (shown below in colors which match their ratings), more commonly called Maxi fuses. They're popular in amateur mobile installations as they are a modern replacement for the older cylindrical style 5ag fuses. They're also available with LED failure indicators.


Note that a 30 amp Maxi fuse will take about 3 seconds to open when subjected to a 100 amp load! The same fuse will carry 40 amps for about 2 minutes! As the static temperature goes up, the vertical scale compresses slightly, and in very cold temperatures settings it elongates slightly. So, hysteresis is the time lag between applying an overload, and the fuse opening to protect the wire. Here is a pdf with more data on the Maxi fuse.

In the mean time, the wire being protected is getting rather warm. If it gets too warm, hot really, it could cause a fire. For a better understanding, let's look at some specific cases.

Most amateur transceivers' DC power cords are built using 10 AWG, or an equivalent (e.g.: Metric 6). Further, most are about 9 feet long, and most are fused with 30 amp fuses. If you subject them to 22 amps of current (nominal input for key down full power), they'll exhibit about a half volt drop (including the drop caused by the internal resistance of the fuse, and that of it's holder). This means the power cable will be dissipating about 11 watts.

If we subject the cable to a load of 100 amps (not a dead short) where the fuse would nominally require 3 seconds to open, our voltage drop is 2 volts, and our wire has to sustain 200 watts of dissipation for 3 full seconds! Now you know one of the reasons why it is so important to choose the correct wire size. To reiterate, the wire must be capable of handling the nominal ICAS load with a minimal amount of voltage drop, and it must also be capable of handling an impressive overload, albeit briefly.

Fuse Size

So, if the radio draws just 20 amps peak, why not use a 20 amp fuse instead? Here's why. Subjecting any given fuse to instantaneous loads close to their current rating will eventually cause them to fail due to element fatigue (sometimes referred to as erosion). Depending on the load characteristics (steady or varying), fuses are sized from 25% to 50% larger than their impressed loads.

In some cases, peak loads will exceed the rating of the fuse, like those encountered when starting an electric motor. Depending on the application, the designer may use a slow-blow fuse with an appropriately longer hysteresis rating. However, in an amateur application, it is only necessary to keep the average current draw below about 60% of the rating for any given fuse to avoid element fatigue.

The correct wire size should be based on the peak current, not the average, if you want to keep I2R losses low. In any case, should a dead short occur, the wire size needs to be large enough to carry the current imposed by the fuse's hysteresis time delay without exceeding the wire's temperature rating. After all, you don't want to turn the wire itself into a fuse!

As stated, part of the sizing calculation is the temperature rating the protected wire is designed for, as well as its ambient operating conditions. In other words, the fuse must open before the wire reaches its maximum rating for any given overload. Remember, underhood wiring should have a temperature rating of at least 90C, and preferably 105C.

For any given ampere rating, fuses designed for high voltage (nominal 250 volts maximum) service typically have lower resistance than those designed for low voltage (nominally 32 volts maximum). Thus, their low voltage hysteresis time is elongated, which means they take longer to open under a given overload. While these facts alone don't preclude their use in low voltage applications, the bottom line is, you should select fuses specifically designed for the voltage range in use.

Lastly, fuses protecting your wiring should be as close to the battery as possible. Remember, that short length of wire from the battery to the fuses is NOT protected. It should be mounted out of harms way (in case of a crash), and protected with an outer sheathe such as plastic split loom.

Circuit Breakers

If you're thinking out loud to yourself about now with the admonition, I use circuit breakers, so I don't have this problem, you're kidding yourself! Fact is, circuit breakers exhibit a much longer hysteresis than any fuse except some specially designed slow-blow fuses. What's more, most circuit breakers will fail closed on dead shorts if the current exceeds 2,000 amps or so. A standard SLI (Starting, Lights, Ignition) car battery in good condition can easily supply this amount of current when subjected to a dead short.

Fuse Blocks

One very popular way of powering multiple ancillary devices is West Mountain Radio's RigRunner series. The unit shown has a main fuse, and five separately fused circuits. This particular one has a maximum rating of 40 amps. They use the very-popular Anderson Power Pole connectors (PP), which makes wiring easy.

They're typically wired directly to the battery, just like a transceiver should be. And like a transceiver, their leads (negative and positive) need to be fused close to the battery connections to protect the wiring should a short occur.

In-line fuse holders should be avoided for two reasons. First, they require butt splices which are very hard to solder. Secondly, the supplied wire size is universally too small. Here's a suggestion. The PP15-45 connectors will hold an ATU fuse for loads up to 40 amps. For larger loads, the PP75 connectors will accommodate a Maxifuse perfectly. What's more, the connectors are a lot cheaper than most decent fuse holders. This is one drawback, however. Getting the fuse inserted properly can be difficult if you don't make sure the connectors are pushed all the way into their respective housings. For the smaller ATO fuses, standard 1/4 inch, female blade connectors work well too.

Digi-Key, Fastenal, Mouser Electronics, and PowerWerx all carry a wide variety of fuse holders. However, for high-amperage loads, I prefer the Littelfuse MAB1 holders (at left), and here's why. Every Maxifuse holder I have seen has molded in pigtails. The largest wire size available is size 8 which is too small for for loads over 50 amps, the need for butt splices notwithstanding. Although the MAB1 is a discontinued item, Newark has a large supply on hand. They cost about $35 with a clear plastic cover (not shown).

If you're not into PP connectors, you might want to look into the Centech line of products. Under the cover are heavy-duty connectors for the primary wire, and a screw terminal block for the secondary wires. There are more photos on their web site."

Also:
Here is an additional PDF article link courtesy of Littelfuse on "Fuses vs. Breakers" which anyone may find of interest or fr reference.
http://www.littelfuse.com/data/en/Appli ... eakers.pdf

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Post by Kojak » Monday, 03 November 2008, 11:39 AM

@Foxhunter

Thanks for the welcome.

I chose the Eagle for two reasons.

1) Been cleanin' the ol' bean since 11/92.
2) No time to re-size a picture of myself.

That's good information you've added to the basics I posted.

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Post by drdx » Monday, 03 November 2008, 13:31 PM

Good topic. Well, I'm fused at the amp in back(an 8 pill tx star), where I have an optima as well. I have a breaker (300 amp one) there coming off the optima, then 2/0 cable running to the front battery, and it is breakered there. I like the breakers because my stuff is not always in the vehicle so when I remove it, it is just a button away from disconnecting power to the 2/0 cable running to the back. Since install, I have gotten a little agressive running things and I have blown the 300 amp breaker at the rear while running both the tx star and my WW amp, which makes sence. Their combined draws overcame the rear battery, which usually acts as a bit of an amperage cushion. I ran my rear battery down a little and it was looking for some serious amperage elsewhere, as in the front battery, so it blew I guess. The amps still had ample power but after a few keydowns I noticed a slight decrease in performance. I've seen this happen before when I put all of my stuff in and forgot to activate the breaker and it was all running on just the rear battery. I was surprised how long a single red top optima will run a low driven 8 pill without recharge and at nice output levels, but you can definitely tell when you reconnect the battery to the charging system as it pulls the volt meter down a little at idle until it gets back up to charge. I ran around for 2 days last week low driving my driver doing the old 250dk/600 swing deal before realizing it and hooking the battery back up, no harm done. I've also thought about a small solar panel hooked to the rear battery full time to keep it topped off.

-drdx
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Post by Kojak » Monday, 03 November 2008, 13:41 PM

@drdx

...Good Topic.

What ? Bean cleanin' ? ;)

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Post by drdx » Monday, 03 November 2008, 14:34 PM

Hey, it's your "bean" and you can clean it, or resize it, anytime you want to. -drdx
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Post by The Breeze » Friday, 19 December 2008, 22:15 PM

Great read you guys!! :D When I bought my 2X4 amp, I had to learn a lot about a lot of different things. These boards have helped a lot. But when I asked the locals and also the guy that built my amp about what they used to fuse the wire, they all looked at me like I was nuts, and said they don't fuse theirs. Well, that's when I started thinking they were nuts. I have seen wire burn, and really don't want to see mine light up and smoke. None of them could tell me where to even look for a good fuse except to go to a stereo install shop and ask. I use a 4G wire to my amp, and found what I think is a great, in-line fuse at radio shack. Gold connectors and the contact ends of the fuses are gold. The heaviest fuse there is a 60 amp, and none bigger can be ordered I guess, I wanted an 80 at least. So far it works just fine. As of yet I have not blown a fuse. Radio Shack has a couple different types of in-line fuses to choose from, and I opted with one that looks like a large automotive type, and they are water tight. Just thought I would pass this along. For the record, I would rather loose a little juice to the box than loose my whole rig.
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Post by jessejamesdallas » Friday, 19 December 2008, 22:38 PM

drdx...you can find 300amp fuse's and the holders at Car Toy's. They ain't cheap thou! :wink:
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Post by jessejamesdallas » Friday, 19 December 2008, 22:44 PM

jessejamesdallas wrote:drdx...you can find 300amp fuse's and the holders at Car Toy's. They ain't cheap thou! :wink:
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Post by wegarrett » Sunday, 21 December 2008, 17:00 PM

fuses = voltage loss.........

do a good clean install and there is really no need for
a fuse........im running a 2x6 in my truck no fuse guna
install a 1x4 in my semi this week sometime no fuse
and my base im running a 3x8 no fuse, and if i can find
something to run my 12 pill in its not going to have a fuse
either.......it is kind of a safety devise to leave yourself
room for error but i just double check everything and go
with it........been doing it that way for 5 years and so far
i havent smoked nothing but 1 pill in my 8 pill.....and yes
its a Davemade and yes their pills will also blow just as
any other amps will :lol:

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Post by Kojak » Sunday, 21 December 2008, 17:40 PM

wegarrett wrote:fuses = voltage loss.........

do a good clean install and there is really no need for
a fuse........im running a 2x6 in my truck no fuse guna
install a 1x4 in my semi this week sometime no fuse
and my base im running a 3x8 no fuse, and if i can find
something to run my 12 pill in its not going to have a fuse
either.......it is kind of a safety devise to leave yourself
room for error but i just double check everything and go
with it........been doing it that way for 5 years and so far
i havent smoked nothing but 1 pill in my 8 pill.....and yes
its a Davemade and yes their pills will also blow just as
any other amps will :lol:

Data please....

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Fuses are needed

Post by PONY EXPRESS » Sunday, 21 December 2008, 17:45 PM

wegarrett wrote:fuses = voltage loss.........

do a good clean install and there is really no need for
a fuse........im running a 2x6 in my truck no fuse guna
install a 1x4 in my semi this week sometime no fuse
and my base im running a 3x8 no fuse, and if i can find
something to run my 12 pill in its not going to have a fuse
either.......it is kind of a safety devise to leave yourself
room for error but i just double check everything and go
with it........been doing it that way for 5 years and so far
i havent smoked nothing but 1 pill in my 8 pill.....and yes
its a Davemade and yes their pills will also blow just as
any other amps will :lol:


They must have made Fuses for some reason................... :wink:
Homes are fused or circuit breakered & automobile inductry fuse .Must be a reason ...... :wink:
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Post by lonesome 500 » Sunday, 21 December 2008, 18:25 PM

wegarrett wrote:fuses = voltage loss.........

do a good clean install and there is really no need for
a fuse........im running a 2x6 in my truck no fuse guna
install a 1x4 in my semi this week sometime no fuse
and my base im running a 3x8 no fuse, and if i can find
something to run my 12 pill in its not going to have a fuse
either.......it is kind of a safety devise to leave yourself
room for error but i just double check everything and go
with it........been doing it that way for 5 years and so far
i havent smoked nothing but 1 pill in my 8 pill.....and yes
its a Davemade and yes their pills will also blow just as
any other amps will :lol:
fuses = voltage loss.........false
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Post by 3strucking » Sunday, 21 December 2008, 20:23 PM

i am not going to disagree with the voltage loss as i am not sure, but it seems to me that if you start with your charging system and make sure you have big enough power and ground wires what little bit of loss may be there wont matter. I dont understand why someone would do it backwards as in go buy a 12 pill and use a 70 amp alternator and 8 gauge wire to supply it, then wonder why they have problems. I know that alternators, batterys, and wire cost a great deal but if you do it right the first time and go ahead and buy everything larger than you need, when you do upgrade latter there is no problems. I will always fuse atleast the hot side of everthing I have. I would rather loose a little power than burn up my $150,000.00 peterbilt.
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Post by lonesome 500 » Sunday, 21 December 2008, 20:28 PM

if a fuse causes voltage drop......it creates heat.........then blows or melts from heat failure

ANL fuses go to at least 1000 amp......or that's the biggest i've seen
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Post by Foxhunter » Sunday, 21 December 2008, 21:01 PM

Fuses...

There does seem to be a small degree of voltage-drop associated with fuses, depending on the type and characteristics of the choice utilized by the selected fusing. In most cases it is not large, but it does depend on the type of fuse used. Certainly not all fuses "are created equal" and that probably can't be stressed enough.

I'd really encourage anyone interested in DC fusing and characteristics to read these small informative articles below I've linked from files saved to my desktop about fusing and various fuse characteristics. All articles ultimately in the end recommend fusing. But see why and which types specifically.

Personally, I eliminated all puny "stock fuses" on all of my amplifiers because I felt and agreed they were rather weak----as provided from the manufacturer. I eliminated them at the amplifier while at the same time upgrading my supply cable sizes. The amplifiers all get fused on both (+/-) lines at the battery with very high quality & expensive UL-listed (gold-plated contact) fuses designed for high-demand car audio amplifiers.

Technically in a perfect world we would not need fuses, but it is very much like driving without car insurance where one incident then can spell total disaster. A definite gamble and "roll of the dice" and I personally don't feel comfortable going without some form of insurance like fusing. My decision was to use the best possible quality fuses I could find period, and didn't be a cheap-skate when making selection.

At one time from my experience doing car audio amplifier installations I used the re-settable DC circuit breaker panels in a CB & amp install. They are very convenient to use and just trip instead of burning up fuses. But after reading about the dangers associated with using them I switched back to fusing but increased the quality of the fuses & holders. It would seem they can arc over and weld themselves closed to re-complete the circuit resulting in disaster. These breaker panels are excellent in some applications still I imagine. I did like them.
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It's interesting how widely varied so many fuses are from internal resistance, voltage handling (both high & low voltage type-rated fuses), fuse opening reaction times (critical) and more.

About the reaction times for instance, "note that a 30 A Maxi fuse will take about 3 seconds to open when subjected to a 100 A load! The same fuse will carry 40 A for about 2 minutes! So, there is a time lag between applying an overload, and the fuse opening to protect the wire. Enough to allow harm to a sensititve electronic device."

As a general statement, what are the fuse-type ratings & characteristics "protecting" your gear ?


Are You Using the Right-Sized Fuse?
by Alan Applegate K0BG & ARRL (3-page PDF File)

http://www.arrl.org/qst/2007/10/applegate.pdf


The DC Wiring Page: Connectors, Fuses and Wire
by Emergency Measures Radio Group ARES

http://www.emrg.ca/dc_wiring.htm


Focusing On Fuses
by John Stiles & Photovoltaic Systems Assistance Center (3-page PDF File)

http://photovoltaics.sandia.gov/docs/PDF/fusecdcrnr.pdf

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Post by 3strucking » Monday, 22 December 2008, 1:58 AM

i use fuses and holders mfg. by littelfuse. There megafuses are hard to beat. the only problem is if you use there midi and mega series you have to use the holders that are littelfuse also because a mega wont fit in a anl holder and the midi is just a smaller version of the mega. On the positive side the littelfuse brand is the highest quality that i have found and yes they are a little more expensive, but when you have $2000 in you mobile system why skimp on the fusing?
there are some brand names that set the standard of quality and performance by which all others are judged.

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Re: High Power Fusing

Post by 127 » Tuesday, 24 March 2009, 13:29 PM

slydog wrote:
drdx wrote:Hello all, just wondering, how does the big amp crew fuse their stuff? I have a 300 amp breaker I plan on using, but at 300 amps, I'd think the vehicle would be burning down by the time it tripped itself in the event of a short. Any thoughts on this? Do they just run it all direct and disconnect when not in use? I can understand a much lower rated fuse or breaker used for safety, and I use them at the equipment and the battery, but what about this higher amperage stuff? I typically unhook my stuff when not in use anyway, as it is on welder connectors, no big deal, but I'm moving to a more hard mounted setup. -drdx
No one around here fuses their keydown mobiles but then again most of them are all trust fund CBers and in the event of a vehicle burning up.........they'll just buy another.
Fuses are not meant to protect equipment, just keep the vehicle from flaming up in the event of a dead short.
I don't fuse anything....I have a 92 F350 with half a million miles on it, no big loss if it smokes.
Even if I had a POS truck, I would still fuse all hot lines. What if you are in the middle of nowhere and the truck flames up due to a short..........you see my point?
I fuse everything with ANL fuses.

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Re: High Power Fusing

Post by c+c » Friday, 27 March 2009, 11:07 AM

i feel safer with a fuse .i was into car stereo be for i came back to cb. so what i did is used the same wire set up. i got 4 guage wire 100 amp fuse block . i cut the wire to my desired size and used the two way splitter that down sizes gauge wire the run my amp on one and radio on other .i dont notice any power loss i have to have my car running to set full power on amp but if thats the worse case oh well. i made it clean install and use 0 gauge wire for my grounds [bit over kill but im i no im grounded well]but that was easiest way for me and great results!
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Re: High Power Fusing

Post by 626 » Friday, 27 March 2009, 18:48 PM

Ok old thread but, I have a great link to the best high power fuses and junction blocks I have found. Check it.....

https://www.vtewarehouse.com/content/el ... gafuse.php" onclick="window.open(this.href);return false;

If you cant find a fuse or junction block here you are lame.

**NON-SPONSOR**

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Re: High Power Fusing

Post by linearone » Monday, 30 March 2009, 16:11 PM

the big power folks do not fuse their equipment. sounds stupid but it does cost watts. ANL fuses like the above are awesome
Its CB radio, plug and play technology, its just not that hard folks...



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Re: High Power Fusing

Post by jessejamesdallas » Monday, 30 March 2009, 18:14 PM

linearone wrote:the big power folks do not fuse their equipment. sounds stupid but it does cost watts. ANL fuses like the above are awesome
OK...How can it cost watt's, or a voltage drop? All a fuse is, is a bridge that will pop if too much voltage or a voltage spike hit's the bridge...If your running 14v's threw a fuse, your going to have 14v's on each end of the fuse...You may have a voltage drop from the time the voltage leaves the battery, and gets to the Amp (or device) because of the feed wire. But I don't see how a fuse will cause the drop...

Like on my work van, I can check the voltage to my battery under the hood when the motor is running, and it will show 14.3v's...But if I go and check the voltage at my battery bank in the back of the Van, the voltage will be like 13.3v's...I loose a whole volt because of the length of the cables running from the front to the back. (which is probably around 12'+) Think they call that resistance...Now there are fuse's in line...But I was seeing the same voltage drop "Before" I put the fuse in-line...There is always the possibility that I could cut that volt loss down some by going to a larger charging cable, but if all I loose is one tiny volt, I'm not going to worry too much about it...(plus, I don't think I'm going to be doing much Competition Key-Downing in my work van!) :biggrin:

Now..."IF" there is loss from using fuses, It would be so small, that Not using a fuse would be just plain stupid IMO, and a good way to have a major melt-down when it could have easily been avoided...
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Re: High Power Fusing

Post by linearone » Thursday, 02 April 2009, 17:54 PM

jessejamesdallas wrote:
linearone wrote:the big power folks do not fuse their equipment. sounds stupid but it does cost watts. ANL fuses like the above are awesome
OK...How can it cost watt's, or a voltage drop? All a fuse is, is a bridge that will pop if too much voltage or a voltage spike hit's the bridge...If your running 14v's threw a fuse, your going to have 14v's on each end of the fuse...You may have a voltage drop from the time the voltage leaves the battery, and gets to the Amp (or device) because of the feed wire. But I don't see how a fuse will cause the drop...

Like on my work van, I can check the voltage to my battery under the hood when the motor is running, and it will show 14.3v's...But if I go and check the voltage at my battery bank in the back of the Van, the voltage will be like 13.3v's...I loose a whole volt because of the length of the cables running from the front to the back. (which is probably around 12'+) Think they call that resistance...Now there are fuse's in line...But I was seeing the same voltage drop "Before" I put the fuse in-line...There is always the possibility that I could cut that volt loss down some by going to a larger charging cable, but if all I loose is one tiny volt, I'm not going to worry too much about it...(plus, I don't think I'm going to be doing much Competition Key-Downing in my work van!) :biggrin:

Now..."IF" there is loss from using fuses, It would be so small, that Not using a fuse would be just plain stupid IMO, and a good way to have a major melt-down when it could have easily been avoided...
try it and see.
Its CB radio, plug and play technology, its just not that hard folks...



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Re: High Power Fusing

Post by Foxhunter » Thursday, 02 April 2009, 19:53 PM

It's true, fuses do cause voltage-drop and are a narrow "bottleneck" of the supply line. In most cases I am all for safety and have many of my things fused. However there is enough of a drop present in a given fused line that recently I removed two inline fuses from two different amplifiers. Keeping fuses inline, or removing them completely-----will be up to the individual user but some guys (gamblers) will rather operate without them, exchanging risk for increased performance. Not that much, but it is a measurable amount.

Think about it-----you may have two heavy gauge supply lines, but then all that current and voltage is to pass through a much much smaller filament section-----far smaller than the gauge of the supply lines themselves. A definite bottlenecking of power, but not enough for many guys to worry about and they leave the line remaining fused. It is true that many of the comp guys don't fuses for the very reason of that small voltage drop that occurs across a fuse. Like in a coaxial cable system also wiring has an insertion-loss with multiple connections and it's often best to minimize the number of connections made in a line.

Voltage drop
"The values of the voltage drop across a fuse are usually given by the manufacturer. A fuse may become hot due to the energy dissipation in the fuse element at rated current conditions. The voltage drop should be taken into account particularly when using a fuse in low-voltage applications".

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Re: High Power Fusing

Post by Double J » Friday, 05 June 2009, 21:03 PM

Ok, I need help - last ime I wired a TRAM radio and a 150 watt Linear was in the early 1970's.......
Now - I have an F150 Ford truck and am trying to do the wiring correctly; so....

1. I bought one Oddysey battery with 1750 CCA ( battery place said Optima was last years best battery - go with this years best )
2. Bought a high output 250v alternator
3. Bought an RCI 69FFC2 radio ( from e-bay~ deadkey 25 watts & supposedly peaks at 325watts, tuned by Sparky's CB shop)
4. Am considering getting a TS sweet 16
5. Ordered RG8x Commercial grade coax
6. Currently running a 9ft metal whip antenna; considering a ground plane three prong thing at base of antenna....

Thinking about using 4 gauge wire to run power from Batt to Radio ( and Texas Star when I get it)

Will use a central ground for all equipment, and use ground cabling to make sure cab, truck bed, toolbox, etc are all grounded... antenna is currently mounted on diamond plate toolbox

I know I need fusing and have been thinking about going to a stereo shop for those large fuse holders they use in stereo amplifiers..... but
HELP.....What size fuses do I need?...
a. close to battery on radio power line
b. close to radio ( use fuse recommended by RCI Radio? )
c. Close to battery on Sweet 16 power line
d. close to Sweet 16

Thanks
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