It gets better. Our ignitions only develop a full capacitive charge in the lower rpm bands. As the rpm increases that re-charge is reduced so that the faster our engines run the lower the amount of voltage will be delivered through the spark plug. The charge cycle can't work fast enough. It's called post delay. That's where a weak battery really starts to show up. It could be a 20v battery but if it's low in amperage or charge state you'll have a missing engine.

I agree with Jack about the Eneloops. Been using them for ignition batteries for about 2 years now. They retain a charge quite well and none of mine have ever let me down for a day's flying with a twin. 4.8v, 2,000 ma and they work out very well. Thanks for the original heads up Jack. They have worked out quite well.