Adding two new 6 volts to existing six volts

I have the same set up. I would run on the new batteries first for 20 cycles or so and not deep discharge them. Then when fully charged connect them and carry on. Have you checked the specific gravity of the ones you have now?

The new battery wont preform as well until it cycles 15 to 20 times or so. It just seems better to connect them after the new one is broke in.

Just curious about the SG. Have you equalized or top charged at a higher than normal voltage?

Purist POV, equalize charge to 16.0V and 5 amps constant current the older batteries, and hook all 4 up.

Strictly by the book? Don't mix and match them. Use the old pair while the new pair fully recharges, and then vice versa. They shouldn't be used at the same time together. Bad idea to mixed aged batteries with new fresh batteries.

Huntindog wrote:

rjxj wrote:


Just curious about the SG. Have you equalized or top charged at a higher than normal voltage?

Never did anything other than let the converter take care of it.

X2 Smart man !

Go for it. No worries, no issues.

Yes the existing two year old batteries may only have ten years left in them.
The newly added GC2 will probably only last the ten years instead of going twelve.
Big whoop-de-do

Ignorance is profound here, but what the heck. If you want to shorten the lifespan overall of the battery bank, and don't mind replacing the entire battery bank sooner, go for it. You should probably still get good service for "awhile" by adding new links to your already rusting and corroding chain. ( That is an analogy in case you did not get it. )

So the theory is that if you mix the old with new you may only get the life out of all 4 that the 2 old batteries were going to get. So you can take a hit now and core 2 perfectly good batteries and run 4 new ones or run a mixed pack and see how long they last. Seems that your 2 year old batteries have been living a good life so you dont seem to be mixing 2 terrible batteries with the new ones.

You could also use a battery selector switch to go between packs but it might not be too much fun if you are going out to switch it in the middle of the night. Are you running out of battery capacity because of furnace use at night or what? What are your needs for 2 more batteries? You will then have to charge 4 batteries.


I wouldn't worry about mixing them too much but then I was told mine would only last 6 months with the way I charged them on generator last year. They are now 2 years old and if even one battery of the 4 failed I'd probably throw one in and keep going. Is it right? No. Oh well. If they only continued on for 6 months and took out the newest battery my cost would still be the same per yr/month. It's no different than throwing tank after tank of fuel in the truck. If I got home and said it took me 2 more tanks of fuel over 7 months or 5 more nights of campgrounds I wouldn't quit camping.



I'll probably make it 3 years so $117 per year. I'm just throwing some stuff out there because people sometimes get all crazy over trying to have the battery last forever. Guy at sams said to only charge at 3 to 5 amps so my batteries would last a long time. Ok Captain, consider it done.

When I was working people would throw a set of 8 new trojan 145's in a 48 volt personnel carrier or sizzor lift because they were dirty or the terminals and cables were corroded. When we would run out of batteries and the heat was on we would go over to the junk battery pallet and throw a load tester on one and throw it in the guys cart. They might be different brands or even ah rating but the whole pack didn't die instantly. Half Arse for sure but it would run for months of 3 shifts, constantly on and off charge and being pushed to a wall plug when it wouldn't move any more.

Ed_Gee wrote:
Ignorance is profound here, but what the heck. If you want to shorten the lifespan overall of the battery bank, and don't mind replacing the entire battery bank sooner, go for it. You should probably still get good service for "awhile" by adding new links to your already rusting and corroding chain. ( That is an analogy in case you did not get it. )

So the best answer is for him to core 2 perfectly good batteries now? How many batteries have you mixed and have you documented their remaining life after mixing? Thanks