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zed-must asked

Color control/BMV 700 showing incorrect battery charge %age

Hi, my color control is incorrectly showing batteries at 100% when they are only at 13.7V. I have another monitor which correctly shows the real %age charge at around 89%. Any ideas?

BMV Battery Monitor
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1 Answer
JohnC avatar image
JohnC answered ·

Hi Zed. I know the figures on the GX can 'flick about' a bit as it samples, but drawing 11W and holding V in Float means they're 100%. Your batts aren't pocket sized (from memory), so up to you which meter you trust.

Fine to trust V or A on a meter, but SOC needs user input to calibrate. Any brand. And if that other one can't be tweaked, it's landfill. Perhaps it's just converting V directly to SOC? - definite landfill..

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zed-must avatar image zed-must commented ·

Tanks John, I hear you on that, except I know that they In a few days they will get up to 14.7v. They are a bank of 4x120ah ages by the way. So are you saying that they actually are 100% charged even though they are at 13.7v and won't be any more charged in a few days by which time they will show 14.7v?

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JohnC avatar image JohnC ♦ zed-must commented ·

Yeh, pretty much. Consider a fully charged Pb batt standing for 24 hours, no load or charge applied. It may settle to (say) 12.6V. Apply a heavy load or charge to it, and V can vary widely - but it's still 100%.

Victron's BMV doesn't actually use V to determine SOC, but it may 'drift' a little under varying conditions. So it needs to 'sync' regularly to 100% by looking at a min V and the 'tail' current under charge. That tail is the 11W (0.8A) your pic shows, and if your batts are > 100Ah in size, then it's easily 100% done for all practical intents & purposes.

And oh, didn't mean to offend by the 'landfill' comments, at very least it's a pretty Voltmeter, and if it's tunable to supply an accurate SOC, then go for it. It will likely have a connected shunt if it's of any real use for SOC.

Unfortunately there's plenty cheap pretenders out there that actually state %, when all they do is convert V to %, and even label it SOC. Market fraud.

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zed-must avatar image zed-must JohnC ♦ commented ·

Super thanks John!

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