I put an electric motor into my 30' sailboat to propel it. I'm also using 8x12V Deep Cycle Marine Batteries to create 48V system (4 in series twice, connected in parallel) I have a 24V Wind Generator, 24V Solar Pannel and 24V Hybrid (wind and sollar) Charge Controller. I also purchased a high powered diods, 8 of them, thinking I can isolate batteries as pairs (24V each pair).

I have a whole bunch of switches I think I'll need to use to isolate the batteries. Can it be done outomatically, with out switches and will the batteries charge properly?

enter image description here

  • \$\begingroup\$ You can insert images by editing your question and clicking the little photo icon, on the same row as the formatting buttons ;) \$\endgroup\$
    – Matt
    Commented Aug 17, 2012 at 23:55
  • 2
    \$\begingroup\$ You can also post links to images and others will edit them into your post. \$\endgroup\$
    – AndrejaKo
    Commented Aug 18, 2012 at 8:44

1 Answer 1


I don't see a workaround without switches.

Closing any of your 4 lower switches will short your Charge Controller.

If your drive motor needs 48 volts, the other bank of batteries can be charging.

1 - DPDT switch can create a 24/48 volt battery bank.

A wiring diagram of 2 Series/Parallel switch arrangement for 2 banks of 4 batteries plus your 24v charge controller.

As you can see, any number of banks of 4 batteries can be added to the chain.

Keeping things simple.

Any bank switched to “Parallel” will charge.

Any bank switched to “Series” will provide 48v to the motor

All banks in “Parallel”, will provide only 24v to the motor. enter image description here Series/Parallel bank switch

I hope this will make boating more enjoyable. I have an old 'S2' 8.0 sailboat.

  • \$\begingroup\$ Thank you so much for responding to my problem I will definitely will sink my teeth into your diagram, meanwile, here is what I came up with. Unfortunately, I can't put a picture into this comment, so I'm going to change the original one. \$\endgroup\$ Commented Sep 19, 2012 at 22:32
  • \$\begingroup\$ ... also, it seems that the DPDT switch will have to handle 100Amps at 48V at some point to run the motor. I searched the net and couln't find anything like that. Can you recomend the switch to use for that, please, may be the website, the name or # of the item... Thank you. \$\endgroup\$ Commented Sep 20, 2012 at 3:20
  • \$\begingroup\$ I studied your diagram, very good. The only thing is that I can' \$\endgroup\$ Commented Sep 20, 2012 at 3:21
  • \$\begingroup\$ ... sory, pushed inter by mistake. So, the only problem was that I need to find a very powerful DPDT stitch, the one that can handle 100A at 48V. \$\endgroup\$ Commented Sep 20, 2012 at 3:22
  • \$\begingroup\$ Voltage may not be a problem, but be careful with tools, rings, etc. around that much power. Metal will heat quickly. You might consider 100a fuses at each battery pair. Another DPDT on the motor would make it reversable. ('H' circuit) good for breaking. 24v on the motor should give 1/4 the power (for trolling), and could give you more range. Unless 48v gets you up on plane (efficient). \$\endgroup\$ Commented Sep 20, 2012 at 8:55

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