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rich avatar image
rich asked

BYD BMS low current draw

Hi All,

Can anyone confirm if the low current draw issue on the BYD BMU was resolved? I.E If i current lower than 1A per module was drawn the BMU wouldn't acknowledge it and allow you to drain the batteries with a small load whilst still reporting it as being 100%.


In the comments section of the victron compatibility for the BYD batteries;

https://www.victronenergy.com/live/battery_compatibility:byd_b-box

Guy mentions in a comment that BYD are aware and are hoping they are working on a fix.


Has a fix been found?


I will probably use an external shunt anyway, but Guy mentions that it shouldn't be used to start a generator too based on SOC, which is exactly what i want to do with it.


Thanks

Rich

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Rich.

The good news is that BYD have resolved the problem, the bad news it is only solved in the new range of LVS and LVL Premium batteries. These have recently been tested and approved.

For yourself and others with the B-Box Pro range, your solution to use a shunt, and use that to trigger a generator is a fine one. The only reason I caution it is because depending on ANY State of Charge reading will at some point lead to disappointment.

In the case of a BYD, if a whole module drops out for some reason (eg individual cell failure), the BMV/shunt will have no visibility of that, and carry on just counting Ampere-Hours of a now diminished total battery capacity. If that failure scenario is acceptable/manageable, then you can still use the BMV.

To help, if you can, please also have a secondary battery voltage trigger for your generator. This isn't that easy either with a LiFePO4 battery like the BYD, as they tend to have very flat voltage profile, but something is better than SOC alone.

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rich avatar image rich commented ·

Thanks Guy, all very clear.


I haven't bought the BYD B-Box pro yet, i was weight up between that and the Pylon system. It sounds like it wont be a big deal breaker, but i will also look into the LVS and LVL systems too.


Thanks Guy

Rich

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