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ruds23 avatar image
ruds23 asked

Easy Solar II charge settings do not match actual charge

Hi there, first time poster here. I have an Easy Solar II system charging a 48V bank of A602/520 Sonnenschein batteries. There is a BMV 700 also installed. The charge voltages are set through the Victron Connect app at V absorb = 56.4V, V float = 55.2V, V equalization 57.6V as per the battery manufacturers recommendations. The actual charge rates, as measured by the battery monitor, are V absorb = approx 55.5, V float - approx 54.4V, which appears to be resulting in an undercharged battery.


I have double checked the settings, including via Victron Connect and VE Configure, and I think it looks as it should.


Any ideas why the actual charging does not match the charge settings? Is this something to be concerned about?


Thanks very much for your help

battery charging
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2 Answers
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klim8skeptic answered ·

What temperature compensation figures have you set?


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ruds23 answered ·

It is set ay -96.00 mV/deg C

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ruds23 avatar image ruds23 commented ·
Battery temp is currently 22 deg C. The system has been installed for about 2 years now. The charge voltage has been pretty much the same as described above the whole time. Winters aren't too cold here, minimum battery temp is probably around 15 deg C
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klim8skeptic avatar image klim8skeptic ♦ ruds23 commented ·

Handbook for Gel-VRLA-Batteries Part 1 ,Handbook for Gel-VRLA-Batteries Part 2 , A600 = A602 ?? , too confusing, and out (not) dated. Sonnenschein A600 series

Do you have a battery temp sensor linked/networked with your mppt? Or is your mppt relying on its internal temp sensor, to set battery temp at first light?

All Sonnenschein specs seem to be quoted as "20c" , until you read the guide pt2, 6. OPERATION 6.1 Float Voltage and Float Current · A temperature related adjustment of the charge voltage within the operating temperature of 15° C to 35° C is not necessary. If the operating temperature is permanently outside this range, the charge voltage has to be adjusted as shown in figures 3, 4 and 5.

I am well and truly beyond my competency to guess what the battery manufactures charging recommendations actually are. (and whether you can accurately link your mppt to the battery temp)

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ruds23 avatar image ruds23 klim8skeptic ♦ commented ·
I do not have a battery temp sensor linked to the mppt, so I am guessing it is using the internal sensor. I have changed the temperature compensation to 0 and the charge voltages are now as per the settings. Am I correct in thinking if it is 22 degrees then the calculation would bet 2 x -96mV = 0.192V. The actual compensation is much higher than that at around 1V, which doesn't make sense. Am I missing something here?
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kevgermany avatar image kevgermany ♦♦ ruds23 commented ·

Victron works from 25C, so would increase the charge voltage by approx 0.286 V at 22C. Perhaps you entered the compensation value incorrectly, Minus sign wrong, decimal point wrong.

Are you getting the se problem charging from grid?

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ruds23 avatar image ruds23 kevgermany ♦♦ commented ·
We are completely off grid, so not charging other than solar. I changed the compensation to zero yesterday - I'm pretty sure it was correct, but I'll put it in again to double check. As I understand it should be a negative number, right?
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kevgermany avatar image kevgermany ♦♦ ruds23 commented ·

Yes, negative. And get the amps/milliamps right. I had both wrong at one stage, despite thinking I'd checked it.


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