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Hi,
I have a 225Ah battery fully charged. After some weeks of slow discharge the BMV indicates 85%.
Considering that -95.5Ah has been consumed and that the voltage is 12.00V, I don't understand why the BMV doesn't indicate something around 55% based on the Ah or something even lower based on the voltage.
Thanks you for enlightening me,
Denis
I'm having the same problem.
My travel trailer has two 12v 100 Ah flooded lead-acid batteries in series. The BMV shows 0.240 Kwh draw but only a 1% drop in SOC when it should show a 10% drop.
Battery capacity is set to 100Ah. The battery negative cable is only connected to the BMV-702.
With small load currents you can pull out more energy than with large currents ( Peukert exponent).
Guess is that there is a load bypassing the shunt. is anything connected between the shunt and the battery negative? If it's on a boat or vehicle, the battery should only be grounded/earthen on the load side of the shunt.
But the BMV will self synchronize when the battery is charged.
Good point @kevgermany, but there is nothing else but the shunt connected to the battery negative. Grounded on the load side. Nothing is bypassing the shunt.
Is there any way of splitting this into two questions? I'm getting mixed up with the two systems.
@kevgermany With a "normal" forum software that would be possible but I don't see an easy way to do that here, sorry.
@Sfidler please open a new question about your problem, it will become confusing if we try to solve two problems in one thread.
Add as much information about your system as possible. Batteries? Other components?
Your charged voltage setting looks very low. I'd expect to see it over 28V for a 24V system. Is there a reason for this?
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I think what's happening in both cases is that the charge voltage is set too low, meaning it synchronizes to 100% before the battery is fully charged. This should be the value specified by the battery manufacturer, for AGM usually over 14V
Thanks @kevgermany, The manufacturer doesn't provide this value, unfortunately. The vendor provided a chart indicating 12,65v as full charge voltage. A search on the internet shows that the full charge voltage of an AGM is ranging between 12.6 to 13.0v. As my battery has 13.8v after a full charge I suppose 13.2v is legit.
I could well be wrong. But there is a recommendation in the manual to increase the charged voltage setting, to just below absorption voltage on solar based systems. I had to do this on my system.
I wonder if you're seeing self discharge in the battery. But if you assume 3% per month, probably doesn't give enough difference.
How are you measuring remaining charge to come to the difference?
