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BMW-712 Charged Voltage setting with two stage lithium compatible charger/converter?

We have recently upgraded the batteries in our travel trailer from flooded lead acid to lithium iron phosphate units. The batteries we are using are three Lynac Lithium 12.8V 100Ah – True Series which give us a total Rated Capacity of 360Ah.

To support the new LiFePO4 batteries, we purchased a WFCO WF-8950L2-MBA power converter replacement main board. This is a two stage converter charger with an Absorption Mode (Nominal Voltage) of 13.6V and a Bulk Mode (Quick Charging Voltage) of 14.6V.

To better track and monitor the state of our batteries and how much energy we're using, we purchased a Victron Energy BMV-712 Smart. Now that we have the batteries and monitor installed, we'd like to get the battery settings configured accurately so the monitor is reflecting the current state of the batteries as best possible.

We have referenced section 4.2.1 of the BMV-712 manual and have set up the Battery Capacity (360Ah based on the Rated Capacity spec from Lynac Lithium) and Peukert Exponent (1.05 for LiFePO4 batteries per the manual) settings with no problem, but are a little unsure about a couple of the remaining settings that require adjustment...

  • Charged Voltage: In the BMV-712 manual it states "this parameter should always be slightly below the end of charge voltage of the charger (usually 0.2V or 0.3V below the "float" voltage of the charger)"... given we have a two stage charger without a Float Mode, would the Absorption Mode voltage be what we reference for this setting?
  • Tail Current: We have set this to 2% based on a Charger/Monitor Setting Recommendations page on AM Solar's site.
  • Charge Efficiency Factor: We have set this to 99% based on the above recommendation.

Any input that could be provided would be helpful.

BMV Battery Monitor
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1 Answer
tozz avatar image
tozz answered ·

1: Yes, with lithium batteries float isn't required. You can use adoption voltage as reference.

2: Your tail current is probably fine. If the bmv712 doesn't see your batteries at fully charged, even when they are you can increase the percentage. Tail current in the BMV is used as one of the parameters to detect a full battery bank (voltage and tail current for X minutes). Basically, if the configured voltage has been reached and the tail current is less than what you have configured for a specified time (eg. 30 minutes) the BMV sees the bank as 100% SoC

The lower the percentage, the more full your batteries will be when the BMV says it's full. Too low and the BMV will never see your bank as fully charged.



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