Major Battery Charging Configuration Via Vehicle Alternator

One time when I let a cheapo house group 24 drop to 10v, I used heavy (4ga) jumper cables from my idling truck to charge it for about a half hour. I was surprised how well it worked.

My truck has a 220a alternator, which likely has about 130a output at idle (Ford publishes a chart showing RPM vs amps). So I may have dumped a couple dozen amp-hours back into the house battery. All I need the battery for is the fridge and detectors, so for me, enough.