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Cold weather battery charging
I keep my bus in a pole barn at home it is exposed to hot and cold weather but not the sun.I keep it plugged in 24-7, same as the last motor homes Foretravel. I installed a Victron battery monitor in bus 3 years ago to keep an eye on the batteries. It has two MS2812 Magnum’s inverters that I installed 3 years ago, when it parked at the house I turn off 1 of the charges on 1 of the inverters because the Magnum’s will cycle to off every so many hours and cycles batteries from 12.8v to 13.5v in Float charge. I haven’t used the bus in a couple of months now,I pulled out and drove 24 miles it last week and then pulled it out again and let it sit outside 1 night not plugged in (no load) and a day while I replaced a customers Aqua Hot unit.It was 28 degrees that night, The Victron said batteries were 12.6v, Pulled the bus back in Plugged it back in and the Magnum went to Absorb charge at 14.7v in a hour or so it was still there so I unplugged bus and shut off batteries. Next day unplugged I turned on house batteries and a bunch of lights and ran Aqua Hot up to temp and ran all three heating zones and basement heat for a couple of hours, Batteries dropped to 12.5 volts and held there. I called Magnum and talked to them and they said the temp sensor from batteries to Magnum controls that and when the temp is that low it will charge at a higher rate and when it’s hot a lower rate. Where we live it has been unusually cold the last couple of weeks down to 28 degrees, I have never paid attention to charging when it is that cold. I have four 8D Lifeline batteries does that sound about right for cold weather??
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5 Replies
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We’ve had our coach outside since we bought in 2014. We’ve had it plugged in to 50amp shorepower with the charger/inverters on all the way down to -15*F. Four Lifeline 8D AGMs. Never gave it a thought, haven’t had a problem.
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That’s the same with us, You know when you look at something then you think about it. Our old Heart Interface inverters didn’t give you that much info, And I don’t think they had temperature compensation
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Tom! What do you think charging Lifeline AGM batteries at 14.7v in cold weather on Absorb charging??
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Won’t hurt them, they’ll pretty much take whatever you through at them. The charge voltage for 0 degrees is 15.7 for absorption and 14.7 for float.
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I was reading the Magnum manual last night and there is a temperature graph in there and it shows 77 degrees is the middle point, and below 77 voltage starts coming up, 32F +0.75v and 122F voltage -0.75v thanks Tom
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