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Building a battery box

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petriach
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Building a battery box

Post by petriach » Wednesday, 10 November 2010, 2:08 AM

I like to camp alot,and I usually can find a trail whenever I camp somewhere high up and find a spectacular view,nothing like being king of the hill several thousand feet above people ;)

Now,I usually will have some stuff with me,including an old Uniden 40 channel handheld,which runs off of a 12 AA battery pack,but I recently popped it open and ran some wire out the back,and soldered it to the connectors inside,and sealed it up,and it's been great to plug it up to a wall-wart and use it for testing antennas near my bench,and not having to worry about breaking or blowing anything. Anyways,I must digress.

The cogs in my mind started spinning,and I thought of making a "battery box",pretty much a toolbox with some screw down posts on the top to power all my 12V goodies. There are some plans for stuff like this on the internet,but most of them use stuff like AGM/SLA lead-acid batteries. I don't want to have to haul a 100lb+ box around with only 20-40A of power in it that I can't let drop below 10.5V(or whatever the threshold of permanent damage is).

So I got to thinking about something like NiMH batteries. I've gotten them for my cameras before,and I was really surprised you can get a AA with 2450mah. This actually pales in comparison to some of the D batteries they make with 10-15Ah of juice in 'em.
Plan is to get some plumbing supplies,springs,and some wire,and pretty much cut some PVC pipes and end caps(gonna get arrested for them thinking I'm making a pipe bomb),and thread the tubes for about 12 of the batteries(1.2*12=14.4V),put some springs in the end caps after soldering the wires to them,drill holes in the caps,and screw them on.

Big thing I am unsure of that I want to clear up,is when I combine these batteries(end to end,like a flashlight),I know the voltage increases,but does the available amperage increase too? If so,I could be seeing about 30A on each of those battery "tubes". And with some of those larger C's and D's..could probably start my car with it :P

I could easily fit many of those in my box,and they would weigh much less. Also,I would be able to discharge them without worry. So...will it work how I think?

If it does,I'm making it,taking that handheld and an amp,go up to my favorite spot with a dipole,and see who all can hear me :D


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'Doc
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Re: Building a battery box

Post by 'Doc » Wednesday, 10 November 2010, 8:14 AM

NiMH batteries will certainly work, but I think you may have to do a bit of re-configuring to end up with that current availability. Assemble those 'tubes' so that you have 12 volts and whatever the average current ends up as. Then parallel those tubes to keep that 12 volts and multiply the current availability by the number of 'tubes'.
All this assumes that all of those single cell batteries are the -same-, voltage and current ratings. Voltage 'adds' in series, and current stays the same. Voltage stays the same in parallel, but the current 'adds'.
Something else to remember is that NiMH batteries charge at a different rate than others do, so having a charger for NiMH batteries is a very good idea.
I think your NiMH battery pack just got a little heavier...
- 'Doc

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petriach
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Re: Building a battery box

Post by petriach » Wednesday, 10 November 2010, 21:32 PM

Oh ok,I didn't really expect it to be that easy :P

And yes,while I may end up with something slightly heavier than I originally wanted,it still sure as heck beats having to drag around a bunch of SLA batteries. The gel battery I have for my UPS's is 12v/3ah,and it probably weighs around 8-12lbs,where 10 of the AA's will give me about the same capacity at only 3-5lbs each tube.

And yeah,I have several chargers,especially for the AA ones,so that's no problem.


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