Quick question spawned from an eariler idea --

I have two of these neat little RAYOVAC NiMH 9V batteries in front of me. Looking at the specs, they are really 8.4V or seven cell packs, perfect for my two planes currently using the GWS DX-A drive.

However, they are only 150mah capacity.

I'd like to make pack soldering two of these standard cells in parallel but I'm concerned about charging NiMH that way. Given the heat/current draw curves of most batteries, usually trying to charge packs in parallel doesn't work well.

I'm not that familiar with NiMH characteristics, could some one give me some insight?

What about breaking open the packs and soldering 7 pairs in parallel then soldering those in series?

My mind at work

A single 9V can fly a Lite Stik for 5 minutes but 2 in parallel will provide more current and 12 minute flights. You should charge them separately (or in series) then reconnect them in parallel for flying. You can remove the metal case but keep the snaps. Radio Shack has the connectors so you can wire one in series and one in parallel.

If you do try charging in parallel, you will need to peak at least twice or charge at C/10 for an hour after peak to keep the cells at the same level. This overcharging is not good for these small sealed NiMH but they are cheap so you might want to try it anyway.

Rick.

I have a Zagi pack that I constructed from 850 mah cell phone NiMH cells. The pack is two 8 cell packs in parallel. It works fine (over 50 flights), peaks fine. I slow charge it at home, peak in the field.

I was going to solder each pair of cells together also, but when I got to looking the layout, I didn't want to mess with it.

I took apart an old Eveready Camcorder NiCd pack. It was ten cells, two packs of five paralleled at the ends only. So this is an accepted commercial practice.

Please explain putting two batteries "in parallel". I have heard it so many times but never asked how to do it. Thanks

Spaulding,
Batteries in parallel means that you have 2 packs working together, ie. positive to positive and negative to negative.
You keep the same voltage as each pack, but double the amperage.
If you have 2 packs of 7.2 volts, 500 mAh and wire them in parallel you get 7.2 volts @ 1000 Mah, if you wire them in series, ie, positive to negative you get 14.4 volts @ 500mAh..
At least that's how it works in theory, actual findings in the field will vary, it will vary with cells and pack construction, temp. and such..

Hope this helps

Lynn

Two cells wired neg to pos are in series, voltage is the total of the cells added together and mah is the same as one cell.
Two cells wired pos to pos and neg to neg are in parallel, voltage
is the same as one cell and mah is the total of the cells added together.

Parallel connection is to connect both + ends together, and both - ends together. Take + and - leads to the esc/motor from the connected cell packs.



( + bat. pack #1 - )
( )
plus to esc-----( )----- minus to ESC
( + bat. pack #2- )

( used to show connection between battery packs or separate batteries)

Thanks for the input everyone.

I will go ahead and try soldering the two batteries together. After flying with just one, the flight time is tolerable, but there is a notable drop in the power. I think I'm pushing the capability of these little 8.4V's trying to pull 2 amps. One amp a piece should correct help immensely.

Thanks!