Forum Discussion

way2roll's avatar
way2roll
Navigator II
Oct 16, 2020

Installing a second battery

Our FW is new. That said it's a 2020 and I am sure sat on the lot for a few months. It has one battery and it has solar so it keeps it topped off. I've never run it lower than 70%. As I think about boondocking, I was going to add another one in series. I had done this on previous MH's we had. But my question is really around the battery itself. Knowing Batts perform best when they are all the same. When I did my MH it was time to change them so when I added them they were all the same brand, type and age. Since my FW is pretty new, do I need to be overly concerned with the exact same brand and model battery? Any concerns about one being potentially a year older than the new one? And putting them in a series shouldn't change a thing as far as the solar/shore power charging them both right?

Thanks!
  • pianotuna's avatar
    pianotuna
    Nomad III
    Oct 17, 2020
    Super Dave,

    The way you have them wired is correct, and can not be improved on.
  • Super_Dave's avatar
    Super_Dave
    Explorer
    Oct 16, 2020
    In my 5th wheel, I've got 2 batteries. I put the negative cable from the 5er on the negative post of battery 1 and the positive cable on the positive post of battery 2. The + to + and - to - from each battery is tied together. It works, someone can tell me if I'm screwing anything up.
  • KD4UPL's avatar
    KD4UPL
    Explorer
    Oct 16, 2020
    If your battery is a year or less adding a similar one in parallel shouldn't cause any problems. If it were, say, 3 years old it would not play as well with the new one.
    Ideally parallel batteries should be the same type (AGM or flooded) and size. Brand shouldn't be that big of a deal, particularly since all batteries are made by about 4 companies anyway.
    In the future, when you need to replace all your batteries I would look at using 6 volt golf cart batteries in series.
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Oct 16, 2020
    "As I think about boondocking..."

    Do an energy survey (what you will use or what you want to use) and then times 1.5. That number will help you determine what battery amp hours you need. I use 70 or so amps per day so my number is 100. My T125 are 240 amps hours. Plenty and a reserve for boondocking.
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Oct 16, 2020
    Just might be time to buy two 6s and not waste time and money on another 12. Solar watts should equal or exceed total batter amp hours.
  • way2roll's avatar
    way2roll
    Navigator II
    Oct 16, 2020
    RoyF wrote:
    If you have a 12-volt battery then you want the second battery to be in parallel because your systems require 12 volts only. Charge both batteries to the same voltage before connecting them in parallel. (If there were much difference in voltage then you would get a large current when they were first connected in parallel -- I don't know what might actually happen).


    I think I meant parallel - POS to POS, NEG to NEG. So I should bench charge them to the same Voltage. Makes sense.
  • RoyF's avatar
    RoyF
    Explorer
    Oct 16, 2020
    If you have a 12-volt battery then you want the second battery to be in parallel because your systems require 12 volts only. Charge both batteries to the same voltage before connecting them in parallel. (If there were much difference in voltage then you would get a large current when they were first connected in parallel -- I don't know what might actually happen).

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