Forum Discussion

naemsmommy's avatar
naemsmommy
Explorer
Jul 16, 2015

Battery questions

I have read a lot of information online, but I'm finding it so confusing, and everyone says something different lol. We don't want anything fancy, we just want to know the best method for charging/using our batteries.

We just bought two new 12V deep cycle batteries. We also have a 70 watt solar panel.

1. Our trailer only has wiring for one battery. What is the best way to hook up the two batteries? I know we shouldn't totally discharge the batteries, so do we just use one until it's at a certain percentage (e.g.50%), then switch to the other one and charge the partially discharged one? Or can we hook both together so it's evenly drawing from both, but still with just a 12v output? And if we do that, how do we charge both at once?

2. We have a smart charger that does 6a/4a/2a. Do we just set it to 6a and then it will automatically switch to 2a when it's charged? The batteries are 115AH, do we need a higher amp smart charger?

3. What's the best way to use the solar panel? Hook it to the battery in use? Or the battery not in use? Or if we somehow wire them together, do we just connect it to one of them?

4. I keep reading that our batteries should be charging while we're towing, but I have no idea how that works? Is there wiring we need to connect from our truck to the battery for that to work?

I'm sure I'm making this much more difficult then it needs to be, but it's just totally confusing and we have had lots of trouble with batteries in the past, so we really want to make sure we do this right this time and don't ruin our batteries.

Thanks!
  • Dakota98's avatar
    Dakota98
    Explorer
    Jul 16, 2015
    naemsmommy wrote:
    Thanks everyone. It looks like we'll have to pick up a few more things. To answer the questions:

    1. Probably 95% dry camping, occasionally shore powered.

    2. Parallax Tower Components, model 7345

    3. Yes, we have a generator.

    4. 2 weeks

    5. I think it's portable? I don't know how to tell. It does have a controller.

    6. No

    7. Stored at home.

    8. We have a smart charger (6a/4a/2a), so from what I understand, we can set it to 6a and when the battery is charged, it will automatically switch to a 2a trickle charge. It's this one: http://www.canadiantire.ca/en/pdp/motomaster-eliminator-intelligent-battery-charger-6a-4a-2a-0111517p.html#.VafT-_mM6Yw

    9. No


    You stated that you've had ongoing problems with batteries. I suspect with your camping profile the reason is inadequate solar & battery charger.

    The solar, if permanently mounted to the roof of the coach, is not portable. I'll assume since it's only 70 watts, that you set it up each time you want to use it. The solar wattage you have is not much better than a trickle charger.

    If budget is a consideration & you've already decided to add a second battery, I'd recommend a higher capacity smart battery charger & run it directly from the generator to the batteries for 3-4 hours daily. Refer to the chart & don't let the batteries get below 12.2 volts. A decent charger would be a Black & Decker VEC1093DBD or similar.

    Obtain a volt meter, Trimetrics are nice, but all you really need is something like THIS

    Install a Blue Seas battery disconnect switch & use it when in storage. have the batteries close to 100% SOC to start with & connect the "trickle" charger on it during that time, that will work fine.

    PS: Definitely read what gbopp posted
  • mbopp's avatar
    mbopp
    Explorer
    Jul 16, 2015
    The Parallax converter is single-stage and not suited for quick charging off a generator. And the 6A charger is woefully inadequate for even a single 12V battery. 70W of solar will help but it won't supply all your power needs.

    If you're serious about being off the grid for 2 weeks at a time and plan on keeping the trailer a while I'd consider upgrading the converter to a PD, IOTA, or maybe a Boondocker from Bestconverters. Second choice would be to buy a 40A (minimum) battery charger.

    I installed an IOTA 55A deck-mount converter, mounting it to the ceiling of the front pass-through. It's a 3' wire run to the batteries and the factory WFCO converter is only used as a DC power distribution center. I run the genny an hour a day and my batteries are typically at 12.3V before I start a charge. I don't let them go below 12.00V before recharging them. And converting to all LED lights cuts the lighting power needed by over 80%.

    Pics are here
  • Vulcan_Rider's avatar
    Vulcan_Rider
    Explorer
    Jul 16, 2015
    Since nobody else has asked:

    Where are you going to MOUNT this second battery you now have ?

    If there is space adjacent to the first one, I vote for connecting them in parallel and treat it as just a bigger battery.

    The worst thing you can do for a conventional lead acid battery is to run it way down and then leave it sit that way for a long time.

    It is nice but not really necessary to have the coach charge from the truck.
    If you do that, you must be sure that the truck will not DIS-charge along with the coach batteries.

    Armed with the advice your getting here, I kind of get the feeling that you should let a local service shop help you make the final decision about modifications.
  • naemsmommy's avatar
    naemsmommy
    Explorer
    Jul 16, 2015
    Thanks everyone. It looks like we'll have to pick up a few more things. To answer the questions:

    1. Probably 95% dry camping, occasionally shore powered.

    2. Parallax Tower Components, model 7345

    3. Yes, we have a generator.

    4. 2 weeks

    5. I think it's portable? I don't know how to tell. It does have a controller.

    6. No

    7. Stored at home.

    8. We have a smart charger (6a/4a/2a), so from what I understand, we can set it to 6a and when the battery is charged, it will automatically switch to a 2a trickle charge. It's this one: http://www.canadiantire.ca/en/pdp/motomaster-eliminator-intelligent-battery-charger-6a-4a-2a-0111517p.html#.VafT-_mM6Yw

    9. No
  • Dakota98's avatar
    Dakota98
    Explorer
    Jul 16, 2015
    OP, For the best Forum advice provide the following information.

    #1 - What type of camping do you do? 100% shore power connected, occasional boondocking, etc.

    #2 - What is the make a model of your converter?

    #3 - Do you have a generator?

    #4 - What's the longest period of time, when & if you dry camp?

    #5 - Is the 70 watt panel a portable & do you have a controller?

    #6 - Do you have a battery disconnect switch installed?

    #7 - Is the coach stored at home or off site?

    #8 - Do you have a trickle charger?

    #9 - Do you have, at minimum, a hand held voltmeter?

  • RJCorazza's avatar
    RJCorazza
    Explorer
    Jul 16, 2015
    As stated, wire (2) 12v batteries in parallel, using battery cable (short sections available at auto parts store). If there is 120v power available, just plug your RV in and the batteries will charge (assuming you have a working converter / charger or inverter / charger).
    If you want to use an external charger, connect the charger to the positive post of one battery, and negative on the other. Your 6 amp charger will take a while to charge a 230 ah battery bank... I use a 40 amp charger occasionally on mine.
    Solar is connected to the batteries the same way at the battery, but you will need a charge controller between the panel and battery. I do not have solar, so I have no more specific suggestions.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Jul 16, 2015
    Two 12V Batteries wired in PARALLEL will provide 12V and double amp/hr




    Now........what RV do you have????

    Hard to answer questions when type of RV unknown.

    Converter should charge/maintain batteries when plugged into AC shore power (or generator)

    Tow vehicle will 'maintain' batteries IF you have a 7 pin connection (6 pin/4pin do not have vehicle charge line)

    IF you have 7 pin trailer cord then you need to check/verify that your tow vehicle has trailer charge fuses/relays in it's fuse panel

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