How low should you take your batteries?

My suggestion is to factor-in the amount of time the batteries are less than 70% charged. Batteries that get discharged say at 5% per day then recharged on day 11 will not live nearly as long as batteries that get to 50% SOC in 2-days then get promptly recharged.

I always check My House Batteries Voltage in the Morning . If they read 12.2 I get concerned. And either run the Genset or Plug in. Usually mine show 76% or higher on the Trimetric Meter and recover fully by early afternoon ,just on the Solar Panels!

If you want 500-1000+ cycles, out of the batteries stay above 50% SOC. If you are willing to live with 250-500 cycles which I suspect very many of us will since in the even 10 year life of a battery, that's 25-50 such cycles/year, you can go down as low as 20%, at least according to trojan 6v graphs. But going below 20% SOC drops cycle life drastically.

My personal experience is that normally I go to 50% before charging, measured using my trimetric gauge, but we dry camp a lot, and 10-20 times/year I got my batteries down to 20% before I charged them. add in 50 cycles to 50%/year. After 8 years, I gave them to my daughters FIL, they still have very high SG and cycle life data says they are still at around 80+% of initial capacity and going strong.

Now, don't try this with a typical dual purpose 12V. Remember GC batteries in GC at clubs get cycled like crazy.

As long as the inverter doesn't go in to low voltage screaming mode, (about 10.5) I'm good. I see near 11.0 volts (on the sat tv circuit) many times while watching Sat tv, and 1 or 2 overhead led lites on.
At no load, that would be 12v and above I'm sure.
After 40 yrs of dry camping, you kinda just get the "feel" of how low to take the batteries.
I have said it a hunerd times, if the water pump sounds normal, and doesn't dim the lites or the tv while running, its not hurting the batteries... believe it.

Hi,

Voltage drop under load may tell you more. I try to stay above 50%. A solution is going to Lithium Ion batteries, if you never get below -20 c (-4 f) but the cost is still pretty high so far.

Set up the RV at home. Bring the batteries to 12.3 volts. Wait 24 hours, measure resting voltage again. If it is not 12.3 then add a load for a time. Wait until the 'magic' 12.3 is available. Now load the battery with something that you can duplicate easily when camping.

This will give you a 'set point' where you know it is time to start the generator.

Or you could skip all this and add a decent solar system.

N-Trouble wrote:
Waiting 2hr is not realistic.

No, it isn't, and I don't know where that came from. My experience is that the resting voltage will be stable after just a few minutes.

Have you ever read The 12 Volt Side of Life?

I think those numbers are for 70* F. Good guidance for warmer weather. Be aware that voltage will be lower at lower temps, so you can then go a little lower without harming the batteries.

When I had the TT with 2 X T-105's and was camping in cold weather, my rule of thumb was to charge before the batteries got below 12.2 when at rest.

Wayne

The 10.5 dead chart above assumes 25 amp load according to BCI RC standard testing.

12.3 keeps you in the green.