ORIGINAL: apalsson
ORIGINAL: TimBle
I'd opt for a LiFePO4 through a diode or BEC to drop the voltage under 6V. They're not as unreliable as NiMH cells under load.
Sorry Tim but with the utmost respect, that is nonsense. Where does this keep coming from?
1. An Rcexl ignition places very little load on the battery (200 - 400mAh) where the rated discharge current of NiMh (Eneloop) cells is in excess of 10C
2. It has been established more times than I care to remember, a 4-cell NiMh (Eneloop) battery is probably an optimum power source for these ignitions. They typically have a capacity of 2,000 - 2,300mAh which easily gives you 4 - 5 hours run time at wide open throttle
3. Running at 6V only increases the power consumption of the ignition (therefore heat dissipation) but doesn't give any better spark (these are digital devices)
4. I fail to see how it can be of an advantage to use a battery with nominal cell voltage above the safe operating voltage of the ignition and then use a semiconductor to drop the same voltage down to a save (yet marginal) level
If I had a dollar for every time I have seen this have to be explained, I'd be better off than I'm now
Point 4: The ignition is rated as suitable for 4.8V packs and 6V packs. That means a range from 4.4V to 7.2V. LiFe battery packs fal within that. The semiconductor is merely an additional safety device.
Point 2: LiFePO4 for the same capacity is lighter and can be fast charged at up to 10C. This means I can use a smaller, lighter battery and charge it at the field while the dodgy pilots fly. I'd rather this than place my hope and faith in battery packs that IMEhave failed too often.
So even though you don't "see"a reason to use them, I certainly do. And its still within the manufacturers specifications.