Looking for some help with battery wiring

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  #1  
Old 06-19-13, 09:14 AM
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Looking for some help with battery wiring

Alright, so I've got two 6V 12ah batteries and a 12V solar panel with charge controller. I know how to wire in series/parallel and such, but my question is, is there any way to wire the batteries and solar charger up so that when I flip a switch, it'll change from 12V to 6V and kick out the charger, so I can have double the amp-hours @ 6V when in use, and still be able to charge the batteries @ 12V when I flip the switch back to 12V? I've sat here trying to figure out a way to do it for the last hour. I'd like to be able to draw off of the batteries no matter what voltage they're at, since I've got a 5V regulator.

12V mode = Charger connected, 5V regulator connected

6V mode = Charger disconnected, 5V regulator connected

Basically I just want to be able to charge from solar, and then double my usage time when done charging by switching to 6V @ 24ah

Edit: Even better. Is there a way that I can draw off of the batteries at 6V while charging at 12V?
 

Last edited by Chaotic; 06-19-13 at 10:18 AM.
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  #2  
Old 06-19-13, 10:22 AM
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Easiest to construct but cumbersome in use is to simply re-wire it depending on what you want to do. Batteries in series and connected to the solar panel and then batteries wired parallel and disconnected from the solar panel when you're using 6v.

Next step up in complexity and a bit easier to reconfigure is to basically wire the system up both ways; series and parallel. Then cut the wires that would be incorrect for the other configuration and install a switch. There would be a number of switches to flip but you can expand on the idea two ways. One is to simply mount single pole switches to a board and have all for one move 12 or 6v in a row so you just flip all the switches in one row on and the other row off. Next in wiring complexity would be to replace the single pole switches with double pole double throw's.
 
  #3  
Old 06-19-13, 11:03 PM
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The following circuit will do what you want. Use a double-pole double-throw center-off switch.
If you use a standard double-pole double-throw switch you risk a set of contacts making before the other breaks. With center off there is a cushion so that there is no cross interaction.

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  #4  
Old 06-19-13, 11:30 PM
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The following circuit will use both batteries equally. You won't need to switch batteries around. I don't know what your load is but you could use 1A adjustable regulators and set them at 5.7v. This way you would have 5.7v - .7v for the diodes would yield 5vdc. You could also use basic 6v regulators - .7 would yield 5.3vdc

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  #5  
Old 06-20-13, 06:59 AM
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I'm glad you did the diagrams. I was scribbling it out on paper and looking for a camera to post a picture.
 
  #6  
Old 06-20-13, 01:05 PM
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You guys are... awesome. Seriously awesome. I have no words for how helpful those diagrams are. Thank you so much!
 
  #7  
Old 06-20-13, 01:13 PM
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What is the charging current from that solar panel?

If the current is rather low, say 1/2 amp or less, you could simply put the batteries in parallel and charge them with a 5.5 volt zener in series. You end up applying half the charging power, other half heats that diode, but no switch and as long as you have more charging time than necessary, the batteries will still be fully charges.

Bud
 
  #8  
Old 06-20-13, 01:29 PM
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I think I'm going to combine that single 6V diagram that you came up with PJmax, with this one that I found yesterday. I'll make it so that the 12V from the charger is constantly connected, charging in series, while drawing off of one of the batteries at 6V, and when the one I'm drawing off of dies, I'll wire it to a switch so I can flip over to the second battery immediately. Thanks again for the help!
 
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