Quick Q re state of charge

[Oldrat]

Even with our winter weather, I would expect my battery to be very close to 100% so I don't understand the disparity?

Van has been parked up for about 3 weeks with everything off, save a small internal camera and of course the control panel.

The state of my Roamer 230ah Lithium battery on the app is 100%

Whilst my Votronic control panel is showing it as 58% ?

 

[Ian_H]

Isn't 13.0V about 50% SOC?
Might be worth measuring voltage with a meter.

 

[Oldrat]

Thanks for the prompt reply

Would the BMS try to keep the state of charge low if it detected a lack of use?

 

[Two on Tour]

I would go by your Voltronic readout as long as everything is wired correctly through the shunt.

 

[Oldrat]

Raul I’d welcome any thoughts Raul?

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[Raul]

Definitely votronic shunt, at 13,01v it can’t be at 100% charged. It will have to be 13.25v or above, to be close to 100% SOC. Give it a full charge ( plug in) so the roamer bms will reset at 100% SOC properly.

 

[Raul]

Thanks for the prompt reply

Would the BMS try to keep the state of charge low if it detected a lack of use?

The bms, can’t detect a smal draw and slowly over time will become out of sync with the stare of charge. BMS can only detect only above a certain amount, like 0,2A. If consumption is lower that that, it will go undetected.
The shunt has a much lower resolution and will pick up almost any draw. Trust the shunt, and the bms will reset on full charge.

 

[Oldrat]

The bms, can’t detect a smal draw and slowly over time will become out of sync with the stare of charge. BMS can only detect only above a certain amount, like 0,2A. If consumption is lower that that, it will go undetected.
The shunt has a much lower resolution and will pick up almost any draw. Trust the shunt, and the bms will reset on full charge.

Thank you Raul

 

[Ian_H]

The bms, can’t detect a smal draw and slowly over time will become out of sync with the stare of charge. BMS can only detect only above a certain amount, like 0,2A. If consumption is lower that that, it will go undetected.
The shunt has a much lower resolution and will pick up almost any draw. Trust the shunt, and the bms will reset on full charge.

I think the Fogstar bms doesn't detect less than 1A draw.

 

[Raul]

I think the Fogstar bms doesn't detect less than 1A draw.

Very possible, hence in the forgstar spec somewhere I came across, says charge with 0.2C, that’s 20a for a 100ah battery; so the bms can account for it. My guess is the bms calibration is done at 0.2 rate ish, so it can cover a wide range of charge/ discharge rates. That makes it less accurate at very low or very high rates. If you calibrate for very low, it will be less accurate in the midd and high rate. So the midd range calibration can miss the very low currents. Just fully charge any now and then, and it will catch up and reset.

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[LithiumConvert]

The state of my Roamer 230Ah Lithium battery on the app is 100%

But the BMS shows a battery of 361Ah

Something is not set up correctly somewhere.