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Model Forum / Radio Controlled / Air Models / June 2004Batteries 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? 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 > 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? >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. 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 | 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 :)  SignatureDoug McLaren, dougmc@frenzy.com I may be getting older, but I refuse to grow up! One vendor is Cheap Battery Packs: http://www.unipros.com/cbpsite/customizer.asp?session_id=142680 Ni-cads are the best choice, IMHO. They give lots of power when you need it. > 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? >The question is whether I should look at other than NiCad's? 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!" Thanks for the input, guess its nicads |
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