6 VOLT BATTERIES, MINIMUM VOLTAGE

Boon Docker wrote:

ktmrfs wrote:

Boon Docker wrote:
Yes, you are killing your batteries.
11.8 is 30% SOC
Should never let the batteries get below 12.1 (50% SOC)

big misconception on never going below 50%SOC. A good rule of thumb for 12V RV/marine but not for a GC2 true deep discharge battery.

Many many many GC2 batteries are speced for hundreds of charge discharge cycles down to 25% SOC. IIRC the common garden variety Trojan T105 is spec'd for 500 charge discharge cycles down to 25% SOC, and they define end of life at something near 75% of spec'd new capacity.

Totally Wrong

Quote from Trojan web site regarding GC2 6v batteries.

Shallow discharges will result in a longer battery life.
50% (or less) discharges are recommended.
Do not fully discharge flooded batteries (80% or more). This will damage (or kill) the battery.

Yes 50% will give you fantastic cycle life, but you can go much deeper and still have long life.

And without knowing application specifics, I can understand why Trojan gives a "rule of thumb" of 50%. Now if I was doing a deep discharge every day, 50% would be a good compromise between life and battery capacity.

If I only use the batterys for 30 or so days of dry camping/year, I'd not worry at all about going to 75%, I'd still get close to 10 years of life out of the batteries if I maintained them well.

And I'd never fret about "what do I need to turn off, we are at 50% and outside of generator run hours" it would be well, I'll watch but not worry.

Look at the trojan cycle life chart for various Trojan Deep discharge batteries

https://pbase.com/mainecruising/image/164698591

true, 50% gives longer cycle life and if you really need huge cycle life stay in the 50% or less. But even the venerable std t105 gives 700 ish cycles at 75% DOD and yes 50% DOD gives well over 1000.
how many RV'rs will ever need 1000+ cycles of deep discharge.

Now look at the 12V deep discharge line, yup those don't want to go below 50%, and at 50% are well below in cycle life compared to the GC2. and at 75% cycle life is in the few hundred.

I agree, going below 80% is BAD

And as mentioned I've run multiple sets of Trojan GC2's down to 25% hundreds of times w/o any noticeable loss of life, consistent with the data on the graphs.