two bank battery chargers? Also inverter switch

theno1katzman
theno1katzman Registered Users Posts: 9
I have a few questions. The first, can you use a regular battery selection switch to determine which battery bank is giving power to the inverter? Just connect one battery bank to the 1 terminal. The other battery bank to the 2 terminal. And the inverter to the common terminal. And off would act as an inverter disconnect. Would this work? Or do battery switches must have an engine connected to the comm in order for them to work as they were designed?

Another question, is there a MPPT solar charger for charging two battery banks? Or do I need two chargers, one for each bank because there is no other way to separate them. Or is there a switch panel that you can wire to the positive terminal for the solar charger and then decide which bank you want to charge?

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: two bank battery chargers? Also inverter switch

    Yes you can switch an inverter between two different battery banks with a switch like this:
    http://www.solar-electric.com/basw1300amp.html
    Just as long as the peak current does not exceed the switch's rating. In this case 350 Amps which would be a whopping 4200 Watts on 12 Volts.

    There are MPPT controllers that can charge two battery banks. I believe Blue Sky makes some. However, they may not be suitable for all installations due to limitations such as V max in.
  • theno1katzman
    theno1katzman Registered Users Posts: 9
    Re: two bank battery chargers? Also inverter switch

    Thanks but I changed my mind about the system, since I think it would be riskier adding more components to the electrical system than it would be paralleling the batteries.

    Right now I have 4 Concorde Lifeline AGM batteries 6 V 220ah going to be wired in series parallel to be 12V 440Ah.

    I have 4 Grape Solar 100W panels going to be wired in parallel
    http://www.grapesolar.com/index.php/products/modulesandkits/gs-s-100-ts/

    I am converting a ford van to travel around the country and want this setup. Solar panels are mounted flat on the roof.

    Batteries are inside a vented compartment in the van.

    What do you think my options of solar chargers are to give me the quickest most efficient charge, money is not a problem for me.
    Thanks
    Seth
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: two bank battery chargers? Also inverter switch
    money is not a problem for me.

    That makes you unique in this world. :p

    Seriously, 440 Amp hours on 12 Volts is okay; lots of power there (about 2.6 kW hours). No problem with two parallel strings either, just be sure to wire them "diagonally". See "method 2" here: http://www.smartgauge.co.uk/batt_con.html

    Your panels will be very minimal for that much battery, bordering on "not enough even with the loads off" so if you can't add more panel you'll have to keep an eye on them and give them an occasional "strong charge" from a generator. The basic math looks like this:
    400 Watts @ 77% efficiency (possibly lower on a mobile application) = 308 / 12 Volts = 25 Amps.
    That's 5.6% charge rate, just barely above the minimum. Any loads running at the same time will detract from that of course. Any chance you could squeeze another panel in there somewhere? Probably not.

    As for charge controllers, you are just at the level where MPPT over PWM makes sense. You could go either way but the little extra advantage of the MPPT might be worth it here. You need something that can handle the 25 Amps max output. The Rogue 3024 could be a good choice: http://www.roguepowertech.com/products/mpt3024.htm Otherwise the Morningstar 45 MPPT: http://www.solar-electric.com/motr45ampmps.html No sense going with anything bigger in this case.

    You won't have the problem of long wires from the panels to the controller, but be sure to keep the wire size up so you can reduce V drop just the same as it's really important to maximize efficiency here, right? Perhaps wire your panels two in series * two parallel. That would give the array a Vmp of 35.4 and an Imp of 11.4.
  • theno1katzman
    theno1katzman Registered Users Posts: 9
    Re: two bank battery chargers? Also inverter switch

    Hi
    Thanks for the reply.
    Can you please explain why wiring the panels in series parallel will help charge the batteries more? This would increase the voltage by 2 and amperage by 2. I thought it was best to get the highest amperage possible, and that's why i was planning on wiring them all in parallel. Also where do all the other volts go if the batteries only need a little more than 12 V?
    Thanks

    Oh by the way, I uploaded pictures of my solar panels since people on the forum have been talking about them some times, and in a bad light. They aren't that bad. I am not perfectly satisfied with them probably only just because the inability to reach their max this time of year in New Jersey. Also because there are smudges on the glass, and I would have thought they would have cleaned the panels before they packed them, now I have to do that.
    Maybe the smudges aren't an issue, maybe they are, I have never owned panels so I don't know if that is just normal for panels. In the sun today I measured one while tilted at 2:30 PM and it was maximum 3.7 amps. 18.8 V.
    Shows details of Grape Solar panels so people will know what they really look like. I was however impressed with the quality of the back wiring. I have seen photos of panels with cheap wiring. The instructions come in a plastic bag that is taped to the back of the panel. I left them in the house and did not upload them either.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: two bank battery chargers? Also inverter switch
    Hi
    Thanks for the reply.
    Can you please explain why wiring the panels in series parallel will help charge the batteries more? This would increase the voltage by 2 and amperage by 2. I thought it was best to get the highest amperage possible, and that's why i was planning on wiring them all in parallel. Also where do all the other volts go if the batteries only need a little more than 12 V?
    Thanks

    MPPT controller will find the best power point for any available light condition. The higher Voltage array may have an extra couple of Volts available that a PWM controller could not make use of. Here's a more in-depth explanation: http://www.windsun.com/ChargeControls/MPPT.htm

    Nothing wrong with Grape panels as far as I know. They're made in China, as are many other products. Some stuff made there is not very good, but that's not exclusive to China!

    Small amounts of dust, dirt, or smudges won't affect panel output much. Clean them off now and then and you'll never notice a power drop due to dirty panels. Watch out for leaves and pollen sticking; that stuff can block cells fairly easily.
  • theno1katzman
    theno1katzman Registered Users Posts: 9
    Re: two bank battery chargers? Also inverter switch

    Hi,
    Today the sun was out a lot stronger, and I was able to get 21.5V and 4.0A lying flat and 21.9V 6.0A angled directly at the sun. So now I realize it really must have the sun directly hitting it with no clouds whatsoever. Not disappointed with the panels anymore.

    How would I wire them together. They have MC-4 connectors with locking safety clips on the ends of the wires and I have no idea how to deal with that. I'm going to go about simple ring terminal connections on bolts with most of my other wiring. I have a book called Automotive Wiring and Electrical Systems by Tony Candela. It doesn't explain how to wire MC-4s together.

    So if you can help by explaining what I'd do and which rv mounted junction box i can get, that would be great.
    Thanks
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: two bank battery chargers? Also inverter switch

    The simplest way, just purchase already made up Male/Female MC4 Connectors (and the MC4 pair of tools). Cut the cables in 1/2. Plug one end into the panels and wire the cut end into the balance of your system (bus bar, fuse/distribution box, etc.).

    wind-sun_2179_330730328 Foot MC4 Extender Cable Male/Female
    Price: $18.00

    wind-sun_2179_33122935Disconnect Tool for MC4 Connectors (set of 2)
    Price: $9.00

    They do make these latching connectors--but I am not sure they make economic sense for most people:

    wind-sun_2179_33111097Multibranch MC4 Connectors, Latching
    Price: $26.00

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • theno1katzman
    theno1katzman Registered Users Posts: 9
    Re: two bank battery chargers? Also inverter switch

    Hi Guys
    Thanks for the wiring suggestions. I like the Rogue Power Tech charger the best so far. Do you know anywhere I can buy "10 AWG stranded copper wire" by the foot?

    The store at Arizona Wind and Sun sells size 4-4/0 which is good, but too big for some of the wire runs I need.
    Thanks
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: two bank battery chargers? Also inverter switch

    Around here there's about a dozen places that sell wire by the foot, including stranded 10 AWG.
    If you can't find it at the local hardware/electrical supply go to an automotive shop. It will probably cost more, but I bet they have it.

    Remember that this wire is not meant for exposure to the elements like the panel extension cables are. Put it in conduit or watch the insulation deteriorate. :cry: