Batteries for Starter

I have a pack of 10 NiCad's attached to my starter making it self contained. It's time to replace the batteries. They are sub C's.
The question is whether I should look at other than NiCad's?
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If you are starting average engines that don't take a lot of effort, NiMh cells will also work great. The extra capacity may be wasted though because of self-discharge. Smaller cells won't deliver the brute current for larger engines. NiCds are still the best in this case.
-- Paul McIntosh http://www.rc-bearings.com

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I haven't much luck with the NiMh I made up 2- 8 cell packs using AA cells at 2200Mah and they would barely start my 60 size engines. I went back to the Nicad packs of about 1800mah sub c size. When I went shopping one of the hobby shops had 6 cell car packs on sale for about $7 each. I bought 3 packs with the intent of splitting one pack and going with 2 -7cell packs. Before I got around to makeing up my custon packs I had a need to start a twin cly Saito 1.82 so I just wired all 3 packs (18 cells) to run the starter. If I back the prop so that the starter can get a run at the first compresion stroke it starts them just fine. In fact the engine slows down when I pull the starter off the engine :) My recomendation for general sport flying use would be 2-7cell NiCad packs of around 1800 MAh for anything up to 1.2. I have started my DF engines with that setup all week end. You need to have battery chargers that will charge these batteries correctly. Understand this isn't the best setup for a new or cantankerous engine that would drain any battery short of a car battery. Yes I know the Sullivan starter is rated at 12V but these are momentary use motors with some rated at 24V. I am using these batteries on a Sullivan starter that I have used since 1974 with no ill effects. I have come to really like the extra RPM this setup gives as it tends to really get the motors to start with less cranking. Sparky
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| I haven't much luck with the NiMh I made up 2- 8 cell packs using AA cells at | 2200Mah and they would barely start my 60 size engines.
AA cells? That's your problem. AA cells don't dump lots of power very well. sub-C cells do. The internal resistance of AA cells, especially NiMH AA cells, is just too high.
I imagine that the sub-C NiMH cells used by car racers would work fine, but not really any better than the NiCd cells he's currently using. Sure, they'd have more capacity, but they do self-discharge faster and so I'm guessing they'd last less time between needed charges (unless he's constantly starting his engine.) And they cost more.
| I went back to the Nicad packs of about 1800mah sub c size. When I | went shopping one of the hobby shops had 6 cell car packs on sale | for about $7 each. I bought 3 packs with the intent of splitting one | pack and going with 2 -7cell packs.
I used two 6 cell 1500 mAh sub-C packs on mine. Works pretty well. If you needed more oomph, try all three packs. The extra voltage isn't going to hurt your starter motor ...
| ... just wired all 3 packs (18 cells) to run the starter.
... which you obviously already know :)
--
Doug McLaren, snipped-for-privacy@frenzy.com
I may be getting older, but I refuse to grow up!
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One vendor is Cheap Battery Packs: http://www.unipros.com/cbpsite/customizer.asp?session_id 2680
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Ni-cads are the best choice, IMHO. They give lots of power when you need it.

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NiCads all the way. Plenty of "dump" power, and you don't have to worry about strange charging habits. For the weight you're carrying, you could almost tape a 12v 7aH battery to the starter. Plenty of oomph there! Dr.1 Driver "There's a Hun in the sun!"
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Thanks for the input, guess its nicads
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