Hi. I have setup with Victron 12V 200ah LiFePO4 smart batteries and a BMV712 (and other components).
I am unsure if I have the maximum discharge and maximum charge voltages set properly.
I found a range for these of 2.85 V – 3.15 V and 3.3 V - 3.75 V per cell, respectively. The low and high of those seem to represent extremes that should be avoided. That is an 11.2V floor for a 12V battery, which is directly from the spec sheet. Are these ranges accurate?
Also, I have seen voltage tables for other batteries that represent %-charge, such as here:
Is that universal to LiFePO4 batteries or specific to a particular manufacturer? I would like to configure the BMV range to ~ 20% floor and ~100% ceiling (possibly 90%).
You’ll find the vast majority of lifepo4 have very similar specs, it more so comes down to how you intend to use the battery that has the most effect on your settings.
If you use the system regularly and are undersized on the battery bank, yes you will want to push your limits to the extreme ends of the scale to utilize max AH at the sacrifice of battery lifespan. In the case of an oversized bank/light use it would be ideal to keep the battery more in its middle/upper soc%, without trying to get it to 100% soc every charge cycle and not drawing it down below 20% will help prolong its life.
Charging to ~80% soc is ideal if you want to try to get the most life out of them, but you gotta go with what’s practical too. They aren’t cheap and if you’re only using 50% of its capacity and shorting yourself on run time by doing so you may as well have gone with lead acid batteries
This is a lightly used RV application. We chose the LiFePO4 for mounting (interior), lifespan, size, and weight and the range of discharge. but, understood.
I thought that the BMV controlled the limits; maybe it is just the programming and UI for the BMS, which is a VE.Bus BMS (v1 IIUC). I thought that it controlled the shunt too, but maybe that is the BMS. It has been years since I wired all of this. The system also has a buckboost, MPPT, and multiplus-II.
We’ve had the gear for a while. But, it has twice turned off at what the CGX claimed to be 70 and 80% charge. Since, I have found that there were pending fw updates for the BMV, batteries, and MPPT, that 2 cells were not completely balanced, and that I had a few settings wrong.
Here is a FAQ dealing with the critical settings in the BMV battery monitor. If these are wrong, the SOC displayed can be over optimistic and result in shutdowns when the monitor says SOC is high but the batteries are in fact empty. The VE Bus BMS sets the min and max voltages and as far as I am aware, these are not user configurable. They certainly are not on my Victron Lynx BMS.
