tom-bell avatar image
tom-bell asked

My 712 monitor currently reads 96% SOC but voltage of 11.92V.

I have 660 Ah house battery bank, lead acid, Centaur charger installed last year and recharge religiously. I am concerned about the SOC differing from the voltage. I am seeking guidance.

battery chargingBMV Battery Monitor
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2 Answers
JohnC avatar image
JohnC answered ·

Hi Tom. Your BMV will need tuning-in to get an accurate/reproducible SOC. Until you do that, just ignore the SOC.

I can understand this task could be viewed as complex and onerous, but it must be undertaken to give useful results for SOC.

Treat it as a challenge/hobby and have fun.. :-)

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tom-bell avatar image
tom-bell answered ·

thanks for the reply John. I am electronically challenged, so despite reviewing manual I see no instructions on "tuning in". Same as sync? Continuing to tap your brain, once tuned in and the voltage still requires prolonged charging is this an indication of need for new batteries? all other variants being accounted for.



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kai avatar image kai ♦ commented ·

It sounds like your system has been well cared for. Assuming that the appropriate charge and discharge limits have been observed, you should be getting way more than 1 year from your batteries.

Go through the synchronisation process (section 2.2) before looking at battery replacement. The gist of the process is that you have to have to tell the BMV when the battery is full so the SOC starts at the right place.

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tom-bell avatar image tom-bell kai ♦ commented ·

thanks for the insight.

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tom-bell avatar image tom-bell tom-bell commented ·

BTW, my batteries are 5 years old

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JohnC avatar image JohnC ♦ commented ·

Yeh, SOC is a calculated figure, and while the BMV is a very accurate device, you need to tell it how to allow for some things. Your Pb batts (and mine) are surprisingly inefficient, so power in may well equate to less than 80% out. Such is the real world. And you need to tell the BMV how bad your world is.

Peukert factor is related to how fast you charge/discharge, and is a major inefficiency with Pb's. On top of an inherent loss with round-trip-efficiency. You have to tell it those things, to suit your own batts. And you'll never get it quite right, hence the need for regular SOC syncing.

Frankly, once you realize how SOC is calculated, and how much you can influence it yourself, perhaps your reliance upon it might be seriously diminished. Useful once understood, but not really as a primary indicator of Pb batt health.

And oh, Pb's will always accept some charge. Doesn't mean they're bad,

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tom-bell avatar image tom-bell JohnC ♦ commented ·

Thnks again for your knowledge. I will re-synch.

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