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Making Sanyo AA 2300 NiMH flight packs?

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Old 01-11-2005, 08:15 AM
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RLefebvre
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Default Making Sanyo AA 2300 NiMH flight packs?

I hate to cross-post, but this isn't getting any attention in the battery forum.

I got a package of Sanyo NiMH at Costco, 2 800mAh AAA and 6 2300mAh for $20CDN.

I was going to make a 5 cell AA pack, just by soldering it together, the way I've always done making sub-C RC Car battery packs. But, doing some research, I read that it's bad to solder packs, and they have to be welded. What's the deal?

Are these cells suitable for an Rx pack? Do you have to use welded tabs, or can you just solder some wire like car guys do?
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Old 01-11-2005, 08:31 AM
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Default RE: Making Sanyo AA 2300 NiMH flight packs?

ORIGINAL: RLefebvre
I read that it's bad to solder packs, and they have to be welded. What's the deal?
well, the soldering can crack in the air. then youve got a cracked aircraft
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Old 01-11-2005, 09:00 AM
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Default RE: Making Sanyo AA 2300 NiMH flight packs?

How much of a risk is it really? I won't do it if it's a real risk, or is it just fear-mongering by the battery pack manufacturers?

I've really abused car battery packs and NEVER had a solder joint come loose. I've had them ejected from the car and slam into the track barrier at 40mph, the cells glue seperate from eachother, but they're typically held together by the solder joints.

I realize the results of having a battery pack fail in flight is MUCH worse than for a car. But also, the stresses are much lower too.
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Old 01-11-2005, 05:06 PM
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Default RE: Making Sanyo AA 2300 NiMH flight packs?

I've soldered cells into battery packs for years without problems -- however I can see why manufacturers might advise against it.

*IF* you are skilled with a soldering iron and know how to create a reliable joint in the absolute minimum of time (so as to avoid overheating the cell) then everything should be fine.

*HOWEVER* I've seen the results of some people's "wonderful" soldering and realize just how much of a mess they can make of such a task.

If you can't make the join without keeping the iron on the cell for less than 3-4 seconds then don't bother -- you run the risk of damaging the cell in a way that may not show up for some time -- probably not until your plane is in the air.

Careful preparation, a clean hot iron, the right sized solder, well tinned wires and plenty of practice can make this a safe, quick and efficient way to create a battery pack. If you've never done much soldering before then practice on some old, cheap dry-cells until you can get a nice shiny, smooth, indestructable joint in under 5 seconds before you go anywhere near those new rechargables though.
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Old 01-12-2005, 08:50 AM
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Default RE: Making Sanyo AA 2300 NiMH flight packs?

I've got a 40 watt iron, and it used to be a PITA to do Sub-C packs with it. Just didn't have enough power. Most of the guys really into it had 240W gun style iron for making battery packs. The tips would heat up red hot and they'd solder in 1 second and transfer little heat.

I think 40W should be enough for AA's however. The fact that I'll be using wire instead of battery bars should help too.

One thing I was thinking, why not make twin wires on each connection, then you've got double redundancy.

I'm surprised nobody else does this. Why are these cells so cheap?
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