Monday, September 22, 2008

Battery monitor

Battery MonitorAs many of you regular readers will know, I spend a lot of time fussing about my battery bank.

With good reason I justify, it's my primary source of power on board.

I often, almost obsessively, check the voltage on the battery bank. To see how it's doing given the amount of wind, or which devices are running.

Recently, I came up with the idea of creating myself a monitor, where I could automatically track the batteries voltages over time on a PC. The image you can see is the result.

The green line, at 25.6 volts is when the battery refresher starts working on my bank, so it's good to be above that.

I am quite surprised at the voltage trace over the course of a day. I had no idea that's what was actually happening to the battery.

The initial slow downward curve, with some troughs, is the battery coming down from a full charge from the previous evening, while powering the (90W) monitoring PC. The periodic troughs you see there is the fridge kicking in.

The peaks you see are from running the generator for various tasks on board during the day.

You can also see there was a bit of wind about during the afternoon there, not much, which helped the overall voltage situation.

All the jagged stuff after 16.00 is made by the heating system producing hot water for my shower later, along with the fridge at the beginning there. The very last trough is the shower room light at about 18.30 or so.

All very fascinating. Well fascinating to me anyway.


  1. Anonymous5:01 PM


    You have inspired me to look into a scheme to do likewise for my solar/charge setup for my off-grid cottage.

    What are you using for your measurements and data logging? Would you consider posting details about this set up?

    It would be nice to see the current too. You might be able to bodge up something simple to measure the voltage drop across a shunt (an iron nail maybe, or something like that) as well as across the battery with alternate readings selected by a little relay.

  2. Hi Anonymous

    This is part of a bigger project I'm working on at the moment.

    I had thought of showing the current, but it's the voltage I'm primarily interested in right now.

    All will be revealed, including the details of the set-up, once I have things a little more complete.