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tighernan avatar image
tighernan asked

Recent system install. Can anyone explain the sudden spike in solar battery stage of charge.

On two separate occasions I have noticed a large solar battery spike, roughly 50% battery increase over roughly a one hour period, while the solar panels only making 0.6 KW. These large spikes lead to a low battery voltage, ( the inverters looking to shut down ) while still having in some cases over 50% battery SOC. Our system is. MPPT 250/100, MPPT 150/35, Smart shunt, BMS v2, 2x 25.6v 200AH Smart batteries, 2x 48V Multiplus2. Any help would be gratefully appreciated Screenshot_20230117_112706_Chrome.jpgScreenshot_20230116_235933_Chrome.jpg

battery charging
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2 Answers
Alexandra avatar image
Alexandra answered ·

@Tighernan

It will be the other way around.

The bms on the battery is shutting down or disconnecting, and the production over shoot is the spikes as the power has nowhere to go.

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tighernan avatar image tighernan commented ·

Alexandra

Thank you for the reply. I'm a complete novice here. Could you possibly tell me how I could do a system check on what you have mentioned and maybe a fix for this issue?
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JohnC avatar image
JohnC answered ·

Hi @Tighernan

There's something wrong here. One of your pics shows this..

1674041877811.pngAnd doesn't appear to be registering in the barcharts. Is this charge for real? Or maybe something wrong with the shunt?


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tighernan avatar image tighernan commented ·
We have no idea what's wrong, that screen shot was taken a few seconds after switching the multi's on to charge from inverting and as you can see the percentage went from lets say 60% to 100% and the voltage went from about 49v to as you can see 54.85. This is not the first time it has happened. While monitoring the system via the VRM portal we cant understand do we follow the volts or the battery percentage, and why are they not equal in relation to each other. This is a self install.
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JohnC avatar image JohnC ♦ tighernan commented ·
@Tighernan

Ok, so the charge is real. The shunt has likely prematurely synced to 100% SOC. This is a settings issue in the shunt, and they'd have to be set very poorly to do this at such high current. Can you post a pic of the settings?

Of course this means the SOC is useless until you sort it.

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tighernan avatar image tighernan JohnC ♦ commented ·

screenshot-20230118-123531.jpgscreenshot-20230118-123518.jpgThank you for the speedy reply. I hope I have attached the right information you need.screenshot-20230118-123507.jpg

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JohnC avatar image JohnC ♦ tighernan commented ·
@Tighernan

Look like Lithium batts. Perhaps with an Absorb target of ~56.8V. Try raising the Charged Voltage to just below the charger Absorb setting, say 0.3V lower. That should prevent it recurring.

The other settings are in the ballpark, but the CV may have been set to just below Float, which is ok for Pb's, but not so much Li's, which are usually considered full when they reach Absorb.

As an aside, that 130A charge you showed earlier is pretty aggressive into 200Ah. What's the rush? :)

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