Forum Discussion

BC_Explorer's avatar
BC_Explorer
Explorer
Jun 11, 2018

Adding a 3rd battery

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's avatar
    BC_Explorer
    Explorer
    Jun 11, 2018
    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.
  • BFL13's avatar
    BFL13
    Explorer II
    Jun 11, 2018
    The starting/deep cycle is pretty much the same as the marine/RV for what you want to do.
  • BC_Explorer's avatar
    BC_Explorer
    Explorer
    Jun 11, 2018
    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's avatar
    Lwiddis
    Explorer II
    Jun 11, 2018
    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?
  • time2roll's avatar
    time2roll
    Nomad
    Jun 11, 2018
    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's avatar
    BFL13
    Explorer II
    Jun 11, 2018
    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.

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