Flanders
Well-Known Member
- Thread starter
- #1
I’ve seen indications that my Jeep’s charging algorithm is shit but this surprised me. Sometimes it doesn't even try.
After an hour on the trail yesterday I aired up from the battery with the engine off. This would have used less than 3Ah. Then I drove home. The charge controller had a chance to push a lot of current through the battery during the 6-minute 550-foot engine braking descent but the dash showed 12.8V the whole time.
Once home I immediately put a lab power supply on it at 13.8V. The battery took 24A – the power supply’s max – for a minute or two. It was still taking 8A about 10 minutes later when I finished topping up the tires. It took over 3.6Ah before the current had tapered below 100mA (less than 90 minutes total).
I've abused the batteries on other vehicles a lot more than that and never seen one fail to mostly recharge within a few minutes driving. I once turned on headlights and all accessories for 30 minutes on an Escalade that had been parked outside overnight on a 20 degree F morning, drove it a couple of miles to the gas station then plugged a charger in it at home and it only needed 1Ah or so.
It's no wonder the batteries fail on these things all the time.
In response to the obvious questions:
After an hour on the trail yesterday I aired up from the battery with the engine off. This would have used less than 3Ah. Then I drove home. The charge controller had a chance to push a lot of current through the battery during the 6-minute 550-foot engine braking descent but the dash showed 12.8V the whole time.
Once home I immediately put a lab power supply on it at 13.8V. The battery took 24A – the power supply’s max – for a minute or two. It was still taking 8A about 10 minutes later when I finished topping up the tires. It took over 3.6Ah before the current had tapered below 100mA (less than 90 minutes total).
I've abused the batteries on other vehicles a lot more than that and never seen one fail to mostly recharge within a few minutes driving. I once turned on headlights and all accessories for 30 minutes on an Escalade that had been parked outside overnight on a 20 degree F morning, drove it a couple of miles to the gas station then plugged a charger in it at home and it only needed 1Ah or so.
It's no wonder the batteries fail on these things all the time.
In response to the obvious questions:
- It was fully charged at the start of the trip.
- All connections go through the chassis ground. I never blind charge/discharge it.
- The IBS has never been disconnected.
- The Viair 400P specifies 30A max but I measure ~21.5A at 12.6V inflating a tire at around 30psi. I run it for 2 minutes per tire, enough to get from 20 to a little over 30psi for the highway. 8 minutes total run time at 21.5A = 2.87Ah.
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