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
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
| 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
| 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 :)
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!
"There's a Hun in the sun!"