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BMV712 switches back to 100%

When my fridge is on the BMV712 appears to be working fine capacity is going down and the ah is increasing but when the fridge cycles the capacity returns to 100% and the ah shows 0

What am I doing wrong as I’m very new to this

Geoff

Lithium Battery
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thewayes answered ·

Hi John, thanks once again for your help unfortunately I still don’t get it yet with the tail % has to do with charging but I’ve had one win so that’s a start. When the battery is 100% the bluetooth in the battery shows 14v and so does the BMV712. My setting are 14.6v when charging and 13.6v float. I raised the 13.2v setting to 14.1v and charged the battery back to full so everything is showing 100% and had another go with the fridge and at this stage it appears to be working. The fridge is cycling and the BMV712 is doing what it should do and showing 98% and not going back to 100% so I’ll run it for 24hours to see how things go. Now raising it to 14.1v might be too high but I’ve no way of knowing that yet. More learning for me but hopefully I’ll get it.


Geoff

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JohnC answered ·

Hi @Thewayes

The BMV will be 'synchronizing' to 100%. It will do that if battery V is higher than the set Charged Voltage and the charge current is lower that the set Tail Current (for x minutes, the Charged Detection Time).

If not charging, it's likely the CV is set too low, and the batt V is bouncing back when your fridge stops drawing amps.

Please read the manual, the BMV needs you to understand these settings to allow it to produce reliable readings of SOC. Over-and-over if need be.. :)

https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-712-EN-NL-FR-DE-ES-SE.pdf


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Thank you for that and yes I’ve been reading it over and over and unfortunately I sometimes find it hard to understand but I’m trying. You’ve been of great help as I’ve found that the battery voltage is 13.3v at 80% and my charged voltage is set at 13.2v so I’m assuming this is what you mean. Also I’m still trying to find what the charge current is set at but I’ll keep looking


Geoff

@Thewayes

Yes, that's what I mean. If you raise that 13.2V to slightly above the batt standing V, then it shouldn't sync prematurely. If you go too far (especially above Float charge level) then it may not sync at all, so go easy..

The charging current setting is the 'Tail'. It's expressed as a % of charge Amps over set batt capacity of Ah. So a 1A charge to a 100Ah batt is 1% Tail. The default I think is 4%, which is way too high for me, and I use 0.5%.

All batts perform differently, so don't go by my settings. Also, seasonal variations in batt temp can change reactivity markedly, possibly also necessitating adjustments.

Understanding how these great devices work is the key to making them work well. You'll get there.

Just for fun, this is mine today syncing from 99.8% to 100% at 1.1A. Close enough for me..

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1606875228932.png (48.3 KiB)

Hi John, thanks once again for your help unfortunately I still don’t get it yet with the tail % has to do with charging but I’ve had one win so that’s a start. When the battery is 100% the bluetooth in the battery shows 14v and so does the BMV712. My setting are 14.6v when charging and 13.6v float. I raised the 13.2v setting to 14.1v and charged the battery back to full so everything is showing 100% and had another go with the fridge and at this stage it appears to be working. The fridge is cycling and the BMV712 is doing what it should do and showing 98% and not going back to 100% so I’ll run it for 24hours to see how things go. Now raising it to 14.1v might be too high but I’ve no way of knowing that yet. More learning for me but hopefully I’ll get it.


Geoff