There’s always something to learn, I guess…

100_1772So yesterday I hooked up my Battery Minder to the second set of batteries, which basically meant I was using one set of batteries to charge another. What could possibly go wrong? It didn’t even occur to me until after sundown that this might not be my finest idea ever. The Minder has four charge settings: 2, 4 and 8 amps. I had it set for 4. A 4-amp after-dark draw on my little 4-battery bank is not the apocalypse, but it is noticeable. I wouldn’t want to leave it on all night. So around 8 PM I went out and unplugged it. Didn’t matter; the batteries were pretty much full anyway.

So this morning I figured I should finish hooking things up. I switched off the inverter and the circuit breakers to the solar panels, then used up the last of that heavy-gauge wire Big Brother sent me to run a line from the #2 charge controller to the … well, I guess I may as well call it the #2 battery bank. Up to today the only thing they were connected to was the powershed lighting, but now I disconnected the whole 12v circuit from the #1 battery bank and switched it to #2. Everything fine, no unexpected arky-sparky, I turned everything back on and everything works great. Just as hoped expected.


This is a minor problem but I’m very annoyed that it never occurred to me for a moment until I saw it happen: Now I have two separate battery banks, and of course my indoor voltage readout can only be connected to one of them. The one that runs my 12v lighting. Which is absolutely not the one whose voltage concerns me most of the time, because a 12v LED draws hardly anything while all the real draw is coming from the AC system.

I could fix it, but it would mean trenching yet another line between the cabin and the powershed. A much simpler solution would be to switch the cabin 12v lights back to the #1 battery bank. Which really eliminates any practical reason to have the #2 bank at all, but probably this is going to annoy me badly enough to actually do that. Bother.

About Joel

You shouldn't ask these questions of a paranoid recluse, you know.
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14 Responses to There’s always something to learn, I guess…

  1. Edward says:

    Joel, I can root around in the basement, am sure I can find an old voltage meter gauge for you. Might even have an aluminum box for same. As you don’t want it permanently on, I would add a push button switch and an LED backlight. you hook it up to the battery terminals and away you go. Push button to read voltage. Can add 10 feet of wire so you can put it where you need. Want alligator clips too? No drain and no internal batteries. I love old school stuff, exposed wiring, open rheostats, salt water dimmers – yes all dangerous as heck but I grew up with that stuff.

  2. Ben says:

    Having the two battery banks side-by-side and both charged means that you have an extra day or two of capacity, even though you might have to manually swap wires to use it.

  3. Wolfman says:

    I find myself wondering if there are enough runs in the ground that one could replace that switch with a self centering A-Off-B switch, so you could hit the switch either direction and see the voltage of the system in question. I think perhaps a length of signal wire, like phone or thermostat wire, would be enough to make that happen, if you do wind up trenching. Do you have any conduit running between, or is it direct bury?

  4. Mark Matis says:

    Or there is always the possibility of getting a wireless voltage reading to the cabin.

    Maybe something like this:

    although that is probably vastly overkill for your needs…

  5. Joel says:

    I’ve got conduit – lots of conduit, by now, since this’ll be the fourth one between the two buildings – but since I use whatever PVC pipes I have lying around the corners are too abrupt for fish tape. Kind of wish I’d planned that a bit more carefully, since it keeps coming back to bite me…

  6. Joel says:

    Ed, I’ve got lots of stuff to build another voltage display – but I think I like the idea of going with an a-off-b switch. Or just forgetting the whole thing and putting the lights back on the #1 bank. Whichever.

  7. JayNola says:

    I’m going to echo Wolf man. Fab up an on-off-on that will read off either bank. I don’t know what you’ve got to hand but it shouldn’t consume a lot of material.

  8. Wolfman says:

    Signal wire is a pretty light pull- If you have a run that is empty-ish, and a shop vac, a piece of bale twine or surveyor line can be vacuumed through and then pull the signal wire back. I might have some around that I can mail to you.

  9. Kentucky says:

    A three-position selector switch would do it . . . just don’t connect anything to the “center” terminal.

  10. Ben says:

    If I understand the lair’s power system (highly questionable) Joel would either need to pull new wires, or locate that switch in the power shed.

  11. Joel says:

    Ben, pretty much. There is a possible wireless solution, which a generous reader actually offered to buy in a private email. But it would involve Uncle Joel entering the world of apps and smartphones. I like my dumb digital display on the wall: I’ve a feeling running more wire would be a simpler solution in the long run.

    And anyway since I plan for the addition’s lighting to all be 12v, I’ll be pulling more wire this summer anyway so what the hell? Maybe this time I’ll spring for some actual electrical conduit, and leave a few lengths of string in it for future expansion.

  12. Mark Matis says:

    Is there any chance you could use your existing PVC with real conduit elbows:
    or whatever elbow size is appropriate for the “conduit” that you already have?

  13. Ben says:

    Actually Mark has it right. Except for possibly some bureaucratic code requirements, any pvc pipe should fit on electrical sweep 90′ and 45 degree fittings.

  14. John says:

    You might consider connecting all 4 batteries in parallel.

    You would get loads of amps and stay at your 12 volts.

    No need to expand your existing system or add pipe or wire that way.

To the stake with the heretic!