100% SOC while connected to BMV-712 and SCC?

[Petroffski]

I've just replaced 2 6V AGMs with 1 200A LiFePo4 Chinese special and was wondering how to figure the 100% SOC (resting voltage - and charged voltage now that I think of it) while it's s-l-o-w-l-y being depleted with required Victron equipment. Do I need to disconnect it from everything to get this info? Am I missing something important even asking this question? THX
Peter

 

[mikefitz]

At rest battery SOC,

BMV settings, set charged voltage to 0.1 or 0.2 below charger setting. Although the value shown below is set to 14.4 implying a charger voltage of 14.6, in many cases this voltage is too high and will cause cell overvolt BMS protection. Suggest a charger voltage of 14.2 and a BMV charged voltage of 14.0.
You can set the SOC manually based on the resting voltage chart, or wait till the BMV auto sync when charged.
You can set the discharge floor to your desired level, I use 80%. With 'battery starts sync' switch if 'off' retains SOC if power lost.

 

[Petroffski]

Thanks muchly for the useful info. I somehow thought that 100% SOC varied between all batteries and I needed to actually find out what mine is. Settings have been set and all is well. Thanks again.
Peter

 

[RCinFLA]

BMV 712 only gets total stack voltage so it cannot judge balance between cells in the battery array. BMV 712 resets to 100% when charger raises absorb voltage to what is set in BMV 712 for 100% full voltage and a current taper value and duration. Usually you want BMV 712 set just slightly below your absorb voltage level.

You can help ensure getting true full Columb counter reset by allowing some absorb time. The BMV 712 does have a value of absorb current drop off before it declares a full 100% state of charge to reset Columb counter. Some caution is needed in using this feature.

This can have a problem if you have PV doing the charging with a running inverter randomly dragging down absorb voltage preventing the current taper down on full charge. Most PV charge controllers have a time out timer to abort an absorb cycle if this happens to prevent too much time at or near full absorb charge voltage that is stressful on battery. If SCC times out before 712 detects charge current taper down value, and its required time duration, it will not reset Columb counter.

Sometimes it is better to just allow BMV 712 to reset based on achieving just below absorb voltage with a high value of taper current Columb counter reset. It is usually better to have a premature Columb counter reset than an overly restrictive reset that rarely occurs resulting in large errors accumulating in Columb count. If BMV 712 resets Columb counter to 100%, and charger keeps voltage above 712 trip voltage, the 712 will stay at 100% until battery voltage drops below the 712 reset trigger voltage.

BMS's SoC indicator have access to individual cell voltages so it can make full charge Columb counter reset to 100% based on lowest cell voltage.