Low Batteries Are No Longer Scary

I never did get to recalibrate the battery monitor since the big winds the other day because I’ve needed to use an inordinate amount of juice to keep the office running this week. I’ve been keeping an eye on the amp hour count up and down and the voltage at the end of the evening to make sure that my battery levels are at acceptable level until I can get a full charge.

All would have been well if we had gotten the sun we were supposed to get today, instead of a low cloud cover, which meant I drained almost 30A today. When the solar charger clicked off tonight, I unplugged my fully charged computer, and looked at my voltmeter. The reading was 11.9V, which is about 40% capacity, but I didn’t freak out because I know now that within an hour of unplugging the computer, my voltage creeps back up a few points as the batteries get to rest.

Regardless, I was low and I was pretty sure I’d have to run the electric blanket tonight as I should have done so last night and I ran the furnace for a full hour this morning! So I turned on the engine while I made dinner.

To my delight, a steady 17A began to flow into my batteries! It’s true! If you’re below 80% capacity, your alternator charges more quickly to bring you up to that 80% mark! It didn’t take long for the amount to slowly taper down and I cut the engine at 10A coming in. I’m now sitting at about 12.46V, which is about 80% capacity. Not great, but we should be getting sun tomorrow, plus I have errands to run so I can take some load off the house batteries by charging the computer in the truck.

So I now know that, really, there’s little point to running the engine to get a charge if I’m above 80% capacity, but it is totally worth doing so when I go below that.

I’ve been boondocking for over a month now in okay weather and it keeps getting better and easier as I slowly figure out how to use all the information available to me to manage my power use. The new solenoid has been a big help, as has been able to borrow a generator twice, that’s for sure, but they’re just a tiny part of a much larger puzzle I’m putting together.

And with that, I’m off to plug in my electric blanket. It’s going to be another coooooold night.

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  • Hi Rae
    Your comments about the engine charging rate and how fast it tapered off reminded me of how we delt with similar problems when my wife & I were sailing off shore. Automotive alternator regulators are designed to quickly replace the Amps drawn by the starter motor and not ovrcharge the battery when driving at highway speeds. The marine industry uses “Smart Regu;ators” ( See West Marine for examples and more info). These adjust the charging rate to better charge deep cycle batteries like those you are using. Also at idle engine rPMs the alternator functions at a much lower output. This can be improved by replacing the alternator pulley with what is called a “curb idle pulley” . These pulleys are smaller in diameter than the standard OEM supplied pulley, consequently the alternator turns faster and provides a better output. If you decide to do this, work with a reliable alternator repair firm. It s not some thing I would recomend doing on your own.

  • One of the pieces of advice I got that I found helpful was to do my high energy things early in the day when possible so the bulk charging will replace them. So, if I’m going to do a lot of cooking on my induction hot plate, for instance, I do it in the morning then just do quick reheats in the microwave later in the day.

  • Ken, modifying my alternator is definitely NOT something I would bother having done. I’m still using it as a backup charging source only!

    Linda, that’s what I do. It’s rare that I will do something really power heavy from 3PM onwards. Boondocking is good for my housekeeping since the rare time I find the courage to pull out the vacuum, it’s before noon. 😀 I can run the office in the evenings and even print without any problem as the total drive is under a couple of amps for that.

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