Another battery question

[uintafly]

Over the course of the next few months I really want to figure out how much juice I have in my batteries and what draws them down. We do a fair amount of boondocking so I would like to know timelines of how long I can go without briging a gen. I have a multimeter and can measure how full my batteries are, but how do I measure what is drawing what, and how many amp hours I have left? A couple times last year we would park our trailer and use it in consecutive weekends, but the parasitic draws would really run the batteries down over the course of the week, to the point I didn't really trust it to leave any perishables in the fridge for fear it would kick off. Any advice woud be greatly appreciated.
Thanks,
Chris

[MNtundraRet]

If you really let the battery-bank go down during a week without recharging you have problems.

Batteries should be recharged immediately after a weekend trip to full charge. During the trip the batteries should be brought back to at least 85 to 90% every day or two with a generator or other source.

Your batteries have been allowed to sulfate and you might find out the hard way that their capacity is now far below new capacity when you start out this new camping season.

A clamp-on meter can easily read current amps coming out of the battery-bank at any given moment based on the total load on at the time. The reading represents how many amps would be used over a hour's time. Reading is taken at one of the battery cables next to the battery. The POS terminal would show (-) amps reading output correctly. The NEG terminal would read (+) amps reading for output. Incorrect but you already know you are discharging the battery. The amp reading is correct for amount discharging.

Knowing the amps used at any given time for different items gives you an early warning. Much better than just checking voltage to find out your battery is already 50%soc or worse Saturday morning.

By the way; if your battery is already shot you might find the battery-bank you thought was full (12.7 volts) reading 50% (12.06 volts) after only an hour or two due to lost capacity on your next trip.

[2oldman]

12v amperage usage in RV

[BFL13]

If you know how full they are then you know how much they have left.

Meanwhile, you can get some detail on which items are using up your AH if you get a Trimetric, but you don't really need that. Your voltmeter is telling you what is generally happening.

You could do with "some" solar. I have left the fridge on propane with us gone for a few days. Battery draw turned out to be 17AH/day which a little solar can easily stay on top of.