backchannel: “how long would [a 100Ah battery] work?”

From this thread in /r/urbancardwellers .  

> > How long will that thing work? > >

Depends on what you mean.

Typical 12v AGM one finds on Amazon, for example, are rated for  400-600 duty cycles if charged correctly.. Under those conditions the thing would work for ~1.5 years.  In the more likely case of insufficient charging I’d expect the thing to work about a year (365 cycles) before it needs to be replaced.   That can a wise economic decision if one is using the vehicle as a temporary solution rather than long-term living.   For longer periods actual deep cycle AGM (like 2x 6v in series or Trojan’s group 31) or lithium will be cheaper due to greatly increased duty cycle rating.  

It would yield 50A if drained to the typical 50% depth of discharge at C/20 (5A for a 100Ah battery). So at that rate the thing would work for 10 hours.  Because of the Peukert effect it would deliver more total amps at  lower rates of discharge, and fewer at higher rates of discharge. The manufacturers of actual deep cycle batteries publish that kind of data.