Need advice for a 9AA configuration

So lately I've been thinking about ways I can increase the output from my Mag Charger and I had the idea of hooking up 12 NiMH AA together. 6 in series for 7.2V and 6 parallel to those in series (don't know how that would have worked out). Found that that I couldn't fit all 12 inside the body unless major boring was involved so I was thinking could you do with 9 AA or is that not possible.
I'm a bit new to this so I made a very crude diagram to depict what I was thinking about doing. The green ones were the ones I was going to connect in series and the blue ones parallel. So I humbly ask you battery gurus ... is my idea a dud.... (I can always fall back to a 6AA config). My Mag is currently running on a 6V 2.6AH NiCd

No, you can't configure nine cells in that way - the series string of six cells will dump a high charge current into the parallel string of three, severely overcharging them, and if left connected for long enough, the weakest cell in the six-string would drain and then start to reverse its polarity, followed by the next weakest in the string, and the next.

Eventually it would all reach a state of equilibrium with the series string of three being wrecked by overcharging, and the weakest cells in the string of six being wrecked by the reverse-polarity charge which they would have received. It's a complete non-starter.

While you can discharge NiMH cells that are in parallel, you cannot (for practical purposes) charge them in parallel.

Also, in your example you cannot put a 3s (3.6v) string in parallel with a 6s (7.2v) string. Your dilemna is one of the reasons I always avoided the MagCharger which is powered by 5 x 1/2D NiMH cells. Your best option is to find the highest mAh cells that are of decent brand.

Thanks for the quick reply guys, honestly I was expecting a response like that. Perhaps if I can get my hands on a 1/2 D cell...

Imon said:

Thanks for the quick reply guys, honestly I was expecting a response like that. Perhaps if I can get my hands on a 1/2 D cell...

Click to expand...

It will be cheaper to just get a pack already made, you can google for "mag charger battery pack" with a couple results to get you started below, but follow up to make sure there are some decent name brands, with NiMH being my preference over NiCad unless you let it sit in the cradle days upon days. The cheapest may be using the cheapest low quality cells.

http://www.batteryjunction.com/streamlight-fb-5h1.html
http://www.combattactical.com/maglite-charger-battery-pack-volt-nimh-p-72149.html

buying a another replacement battery pack would be your best bet...

Battery junction carries them for cheap and it has 3500mah vs the 2200mah old version. Should last you along time too.

They are only 24 bucks and shipping is cheap. and should total 33-34 bucks shipped.

You can find one via ebay for the same price and specs but batteryjunction has awesome customer service.

Combat tactical has the best price with 28bucks shipped and has the same specs.


Hope this helps...
Eric

ama230 said:

buying a another replacement battery pack would be your best bet...

Battery junction carries them for cheap and it has 3500mah vs the 2200mah old version. Should last you along time too.

They are only 24 bucks and shipping is cheap. and should total 33-34 bucks shipped.

You can find one via ebay for the same price and specs but batteryjunction has awesome customer service.

Combat tactical has the best price with 28bucks shipped and has the same specs.


Hope this helps...
Eric

Click to expand...

Let's see...what is that saying....Oh yeah. "They say imitation is the sincerest form of flattery--right down to the links!"