I believe most of us understand that LifePO4
is best to have a regulated 14v or 28v as a happy SOC. The BMS is "Protection" so it does not go over a max 28.8v (14.v) if your cells are 3.6v as a max... some cells are 3.8v, but the majority I see here are 3.6v max.
I have 8 cells, and have set the main SOC to be at 28v for the solar charger
and alternator. 28v and no more... the BMS is my own "personal Jesus" to protect the cells. That means the BMS has a "warning alarm HVC trigger", and a "system max HVC trigger". Two different voltages and 2 different methods to cut all power to the cells...
Warning Level HVC = 28.4v
System Max HVC = 28.8v
These are the protection voltages of the BMS... this is NOT saying to continuously maintain your bank at these voltages. It is the protection voltages of the BMS that most of us are talking about. BMS cut off voltages.
I have relays on both the warning voltages, and should they fail, then the system MAX will trigger the relays and cut off any charge to isolate the bank completely.
On my House Power BMS, I have a Yellow strobe and siren alarm that also goes off at the warning voltage levels with the relays... so if the bank that is normally sitting happy at 28v, and it would for some crazy reason reach 28.4v, I have lights, sirens, and relays cutting off charge, and I go see why it is not at 28v.
I have a battery isolator off my port engine
24v alternator, and one output goes to a voltage regulator just for the LifePO4 bank, and the other out goes to the emergency
back up house bank... and should the HVC relays cut any charge (disconnecting the load) if something is amiss, the alternator is still under load with the emergency
Lead Acid bank, all managed by the alternator voltage regulator for a Lead Acid bank. I still have the siren and lights grabbing my attention from the LFP bank, and then even the Lead Acid is safe.
I know some of my replies have been a bit lacking in the full details, but I hope the drawing of my BMS fills in some blanks where I have missed.
One thing that is not in the drawing, is the Cell-Log-8. I have the LVC alarm of that wired into the inverter
, so if the LVC relay of the House Power BMS does not function, then the Cell-Log-8 is the back up. Note: The Cell-Log-8 is powered on the USB input.
As I have 12v on the Genset start and for all NAV gear
, 32v on each Detroit Diesel
(I know I should change over to 24v), and the 24v house banks. I monitor
all of them with the Victron Blue Power Panel, with a VE.Net Battery controller at each bank to monitor
all banks from one location at my main breaker panel. I also have alarms from that....
I live on my vessel, so I am truly a man of redundancy !