Camper w 2/parallel batteries - Charging ?

SystemSystem Posts: 2,511 admin

I have tried to browse all of the other threads on the beginner forum to try to get my questions answered before posting my questions.

Some of them were but I still would like to be 100% positive im doing this correctly.

I have 2 115 Amp Hour deep cycle batteries connected in parallel. neg to neg and pos to pos.

I have a Siemens SR90 (90 W / 5.4 Amp) and a Sunforce 7 amp charge controller which is connected to the neg of battery 1 to the pos of battery 2.

I have access to a second SR90 watt panel and am wondering if I could use two panels with 2 controllers. One controller for each panel hooked only to 1 battery. Even though the batteries are connected in parallel ? Will this charge the batteries twice as fast ?

If I only have one panel/controller hooked to only one batter both batteries are still being charged since they are hooked in parallel ?

I also have a 1500 W inverter hooked to the batteries the same way the controller is. Neg of battery 1 to pos of battery 2. Is this the best way to hook up an inverter in a parallel config ?

I think my last question is regarding wire gauge. Bigger is better but if I run a 12 gauge wire from the panel to the controller, the controller's wire looks to be 16 gauge stranded. Is electricity just like a garden hose when I constrict from a 12 to a 16 dont I still have the same loss if I ran a 16 the whole way ?

Thanks for your time and assistance.


  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Camper w 2/parallel batteries - Charging ?

    Short answers to some of your questions,, and by the way welcome to the forum,,, there are some very smart, helpful folks here.

    1st,, yes you can always add a second panel and controller,,, although I would suggest that instead of two controllers I would consider getting single bigger/better controller that has battery temperature compensation capability.

    2nd.,,,Both batteries, while wired in parallel to any configuration of panels or controllers will act as 1 bigger battery

    3rd.,, wiring your inverter,, Positive of battery #1 to negative of battery #2 is fine. You want the load (and charging config) to ensure that all the cells of a string get similar charges, and similar loading. With just two batteries,, this is not a problem,,, with 4 or more batteries there are several combinations that work,, a few that are better.

    As for wire gauge,,, bigger is always better. And yes, having a few inches of #16 will create a minor "restriction", by up sizing the rest of the run to #14 or 12 or what ever will reduce line lose over distance. Wire loses are calculated over distance. There is a wiring loss calculator sticky at the top of one of these threads.

    I strongly suggest you read some of the following links:

    Good luck and shout if you have other questions,

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Camper w 2/parallel batteries - Charging ?

    Connecting on the "diagonal" will extend the life of the batteries by helping share the loads.
    What you described, if i understood it, should be good.

    The 16 ga wire resistance only applies to the section of 16ga. If you replace 9' of 16 gauge with 12ga, and keep 1 foot of 16 ga, you WILL have better performance and less loss that 10' of 16 ga. Almost like a garden hose, but a bit different in some respects
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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