Electronic/Battery Guru's question

[RandyO]

Now, that said, if the goal is an emergency jumper in the cold, relying on amps alone is likely not the solution. A small 6V or 12v batt in line with the starter will get the starter spinning faster than trying to out AMP it. That'd be my goto for cold weather, spin that thing up with some REVs.

if I was to add a 6v booster battery in series, would I wire it between my 12v bank, and ground, or between the 12v battery bank, and the starter, the second, being the easier way, to wire

I shoulda thought of boosting the voltage, I used to run a 6v horn to get more volume

[ZX-12R]

I would take the input side of the starter solenoid and connect to to the positive terminal of the 6V battery, then connect the negative terminal of the 6V battery to the positive terminal of the 12V battery. In that arrangement, everything still uses the same ground and only the starter would see the full 18V potential when the solenoid is closed.

Depending on accessibility, you could also go
+12->solenoid in
solenoid out ->starter in
starter out -> -6V terminal
+6V terminal -> chassis GND.

[Kurlon]

Yeah, all the setups I've seen doing this put the 6v booster in series in the line between the solenoid and starter. I've also seen some people using 16v LiFePO4 batts as their main batt with the same idea, a bit more voltage for easier starts, but low enough to not piss off / fry the ECU/etc, and able to be charged with an adjusted reg/rect.