Adding a 3rd battery

[BC_Explorer]

Looking to add a 3rd battery to my 2 existing group 27 deep cycle battery setup. I have read that adding a new battery to old should not be done as the new battery charge will be affected by the older?

Any truth to this?


The 2 existing batteries are 2 years old and do not see a lot of heavy use. Typically they are used 5-6 times per summer season to mainly power a 2 door compact fridge in the trailer. Batteries are charged with solar and or a generator and are kept up to charge in the off season. No issues with the existing batteries, but would just like some more amp hour reserve.

[BC_Explorer]

BFL13 wrote:
The starting/deep cycle is pretty much the same as the marine/RV for what you want to do.

Thanks. That is what I thought, but wanted to make sure before I purchased. I'll stop by Costco again tomorrow to purchase one.

[MEXICOWANDERER]

Oxymoron: BCI groups 24, 27, 31 "Deep Cycle Battery (flooded)"

[BFL13]

The starting/deep cycle is pretty much the same as the marine/RV for what you want to do.

[BC_Explorer]

Thanks all. Much to my disappointment, the 2 Costco stores in my area are not carrying the same group 27 deep cycle batteries that I currently have. However they do have a group 27, starting / deep cycle battery.

Any potential pitfalls of mixing different types of batteries?

[Lwiddis]

Adding a third battery will add a usable 50 amps or so and 65 pounds. Trojan's group 27 is about $250. Is the real answer buying a couple of good golf cart batteries?

[ppine]

Great idea, 4 are even better.

[MEXICOWANDERER]

Yep with solar I'm in agreement with BFL13 -- happy camper

[time2roll]

The only issue might be slightly lower resting voltage of the older batteries. No concern while in use. Remove the parallel connection if stored without float voltage.

If the old batteries are expected to last 3 more years then expect your new battery to be done at the same time.

[BFL13]

It won't hurt the two, and when it does pull down the new one to be like them, so what? Go for it.

If the two were on their last legs, then that would be another story.