question

I have contacted you via email for this specific situation.

Hi, from what you say I thinks it’s very unlikely, for both those values (Ah and SOC) to come from the BMV.

More likely you are looking at Ah from the BMV and then SOC of the BYD.

I recommend to verify that first: don’t look at the aggregate (and especially not in the soon-to-be-replaced-with-something-better VRM-app), but look on VRM and then download the excel sheet and check the columns pertaining to the BMV.

hi. thx for your effort!!!

@mvader: no its not the BYD SoC. BMV 700 doesnt show the correct value. see pics attached. BMV is set as the SoC monitoring unit. XLS shows incorrect SoC valued for instance 260 = BMV.

history of the BMV shows strange values. -201 Ah is impossible.

are those values taken into consideration when the BMV calculates ists SOC?

I haven't looked closely here yet, but perhaps a consequence of an incorrect Peukert co-efficient/exponent setting for that battery type.

If the current drawn is very low, the battery will appear to have more usable capacity.

If the current drawn is very high, it will have less.

The Ah value will be the same, but 'capacity' will be different relative to the rate at which it was charged or discharged.

This is quite true for lead acid batteries (and the default configuration). However in batteries with very low internal resistance (like your lithium) and very different charge or discharge profiles, you might get a distortion like you are setting in the readings.

Normally, when batteries get a full recharge regularly, this is not a major issue. But if they go a long time without a 'recalibration' at 100%, then this miscount will add up.

This is only one possible explanation. Try setting the BMV battery setting for Peukert exponent to 1 and see if that behaves closer to your expectation.