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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 my BMV 712 i have a problem also.
I looks like the same as yours.
The used Ah are a lot more then the % shows and i get no full load synchronized.
If I do the reverse, the capacity of my batteries will get bigger and bigger every day.
And that for free...
What i also understand never is why the BMV count with the real 100% capacity and not with my settings max. 75% DOD for example.
When i change the capacity down from 100% to 90% to compensate the deeper temperature in the winter now, i have to set at first thats that are the new 100% before the BMV accept the changing in his calculations. Because when i do that and the batteries haven't already 100% load at this time, i have a problem.
I think there is a lot to do for Victron.
For example a choice how the SOC is show to me, by the real capacity of the battery's or based on my individual settings who will be 75%. When i use for that a battery capacity less then the reality, the peukert effect never can been correct.
Actually it's not really useful.
My english is not the best and i hate googles translations.
But i hope everyone understand what i mean. :)
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.
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?
