Another thing I don't quite understand is how the capacitor can take a significant load off of the battery when starting the engine. Since the capacitor has a relatively low capacity, the voltage would rapidly deteriorate when starting. Since the capacitor is wired in parallel with the battery, it would maintain the same starting voltage. That means the capacitor would immediately drop below the voltage of the battery and start pulling amps from it.
I'd imagine the battery would supply the majority of the cranking amps, unless voltage sag is significant enough to shift the draw to the capacitor. I would still be afraid of a small LiFePo4 drawing too many amps during cranking. The
battery used by Laserhacker is rated for 30C discharge, which is 126A. What is even more troubling is the battery charge rating is 2C, which is only 8.4A. I'd be afraid the alternator would charge the battery too quickly after starting, and I'm not sure the capacitors would significantly buffer the charge.
I suppose this is another area where I will have to test and report my findings. I just ordered a clamp-style DC ammeter, so I hope to get started soon. When I got off work at 1am this morning, the 'ol Cummins with 2 massive batteries decided it didn't want to start... and this reminds me of something;
the voltmeter that plugs into the cigarette lighter draws 40mA! I had left this plugged into a lighter socket that retains power with the ignition off, and during my 13hr shift consumed 0.52 Ah.