Originally Posted by Rapidly
snip........if I run jumper cables from my car (TV) battery to the RV battery and run the engine, I can get a much faster recharge? How long should it take to recharge a low 12V battery that way?
Yes, but the length of time to recharge is based on the DoD (Depth of Discharge) of your PUP battery, and of course the charging source. Standard 12V Marine/RV batteries are designed for a DoD of 50% providing a modest amount of discharge/charge cycles, and "jump" charging off your TV battery under these conditions (DoD of 50% or lower) is fine......, BUT
...., it should be noted that with any battery (TV, RV, Marine, Motorcycle, Deep Cycle, etc.,) the shallower the DoD average, the longer the battery life.
As 'Canucker' mentioned, we all have different dry camping and "AMP" consumption habits. If you find that your dry camping frequency is increasing, you may want to invest in a means of monitoring your battery DoD..., and as suggested consider upgrading your AMP storage capacity, possibly even looking into the advantages of a true Deep Cycle battery product.
Check out some of the Dual Battery systems installed by forum members over in the "Jayco Mods" section for some different ideas.
Prior to upgrading to my two 6V Deep Cycle batteries, I could 'solo' dry camp for four days with my standard 12V Marine/RV battery which included operating my power jack and slide....... but that's me. My original 12V Marine/RV battery was still in great shape after 6 years of service, but I did maintain it properly both in and out of use.