SOC going up “percentage by percentage” possible?

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mike5fant asked Nov 12, '22

SOC going up “percentage by percentage” possible?

Hi! I have a 24v 110ah lithium battery which supply my 220v appliances in my van. With this I have a SmartSolar Charger MPPT 75/15 from Victron which that handles the power from the solar panels on the roof and connects to the 24v lithium battery and lastly I have a SmartShunt 500A/50mV from Victron to be able to se the status of the lithium battery.

My issue is that even though I receive sun on the solar panels and the voltage is rising the SOC on the Smartshunt doesn’t change before synchronization, so I don’t know how much more capacity I have before I destroy the battery.

I’m wondering if there is a way to calibrate the Smartshunt so the percentage goes up “percentage by percentage” (e.g. 64%,65%,66%} or can I safely continue to use the electricity if the voltage is high enough (e.g. over 26v) even though the SOC says I’m going lower than 10-20%?

Thank you!

Best regards, Mikael

Lithium Battery SmartShunt SOC

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mike5fant commented · Nov 12, 2022 at 09:38 AM

@JohnC since you answered one of my questions before, maybe you have an answer to this?

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pwfarnell answered · Nov 12, 2022 at 10:05 AM

It sounds like the solar charger negative is connected to the batteries not to the system/load side of the shunt. If the solar negative is connected to the batteries they get charged but the shunt does not see the current so it can not count it back in. However, when the voltage goes above the "charged voltage" setting in the shunt it synchronises to 100%. Therefore you probably need to move your solar negative to the load/system side of the shunt.

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mike5fant commented · Nov 12, 2022 at 10:53 AM

Thank you for the response! I still don’t fully understand, maybe if I send a picture you could clarify it further:

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81e8f3fc-2428-4c72-a58d-9d685ebb51b1.jpeg (4.2 MiB)

image.jpg (2.9 MiB)

mike5fant commented · Nov 12, 2022 at 11:58 AM

I think I understand now, thank you for the explanation!

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pwfarnell mike5fant commented · Nov 12, 2022 at 06:54 PM

Been busy and others have confirmed. The symptoms are easy to diagnose even without the photos. Let us know how it goes after you move the solar negative to the shunt.

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christern answered · Nov 12, 2022 at 11:45 AM

Difficult to see from your pictures but think of it this way:

All power that goes to or from your batteries should be on the “load” side of the shunt. On the “battery” side there should be ONLY the battery!

This way the shunt will know what is taken from and what is sent to the battery.

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mike5fant commented · Nov 12, 2022 at 11:58 AM

I think I understand now, thank you for the explanation!

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Modifications Space

Node Red Space

Answer 1 · 2022-11-12T12:29:12Z

JohnC answered · Nov 12, 2022 at 12:29 PM

Hi @Mike5fant

I spoke to you before about much the same thing, but mainly regarding premature syncing at a low Voltage. It seems your shunt is probably wired incorrectly, as the mppt's BATT negative wire doesn't go anywhere near the shunt. I'm unfamiliar with that battery, with what appears to be auxiliary charge terminals, but you'll need to sort that out before the shunt will register a charge. As Christern described.

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mike5fant commented · Nov 12, 2022 at 05:34 PM

Thank you for the response and the great explanations I’ve recieved from all of you, I have now moved the cable and it seems to be working correctly now, thanks again!

Best regards,

Mikael

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