On Thursday, April 16, 2020 at 10:35:35 AM UTC-7, wrote:
I got so mad the last time we fought this battery switching battle, I went out and hooked a fresh 12v battery to a low 10v battery with the parallel circuit completed with an amp-meter! I saw no spike and only 300m/a current flow as the fresh battery tried to charge the low battery.........the switches didn’t melt, the amp-meter didn’t explode and the fuses didn’t blow!
I have recently solved the issue by only using one battery............15a/h lithium iron battery............have t seen voltage below 12.2 v, even after 4 hours at 2a average current flow!
Please don’t stop arguing this issue, it’s so entertaining to watch the EE’s chase imaginary amps around!
JJ

I will add that Jon's concern about arcing is misplaced; arcing is associated with inductive loads when the current is interrupted. What happens in an inductor is that there is a magnetic field that is built up that has to have a place to go when the current is suddenly interrupted. The voltage in the circuit goes to very high levels as a result and will cause an arc in a mechanical switch. This is usually dealt with by a fly-back diode that allows the current to continue to flow and die off gradually.

If arcing had been taking place I would have seen it on the scope waveforms as a series of spikes in the current waveform. This did not occur in any of the many times I tested it, and it should not occur as capacitors are effective in minimizing or eliminating spikes.

Tom