Will it work? 3P4S @ 690ah


  • Working on upgrading the house bank on a 42\' sailboat for full time cruising. Currently set up with 1200 watts of solar with Victron mppts for each panel then everything else is the original Heart Interface system and FLA batteries. I am planning on building a 600 - 700 ah battery bank using CALB 180 or 230 cells, Victron 3k inverter, Cerbo GX and a WS500. Will the REC Active handle a 3P4S @ 690ah 12v battery bank? The other scenario is the Master/Slave config but that will add several thousand to the cost. Which will be close to using all Victron including batteries and lynx BMS. I am trying to avoid going 24v since all components are currently 12v.


  • Sounds like a great config and yes, the Active BMS is good to about 1,000Ah of well behaved \"A\" grade cells like CALBs. FYI, for large scale 12V projects there is a Master/Slave solution but you won\'t likely need it. If you would like help building your system we now handle both Victron and CALB and can build you a fairly complete solution.  Just contact us at tech@offgridsoftwaresolutions.com

  • and here is a 2P4S wiring diagram from the REC BMS North America site you can use as a starting point https://rec-bms-na.com/download/31/rec-active-bms-sketches/1290/rec-active-bms-wiring-diagram-rec-active-bms-2p4s-1-relay-precharge_3_0.pdf  

  • I have a 4p4s 1120ah system working perfectly for 24 months now. Eve grade A cells. My system hardly ever (never?) has to blance, cells stay in sync. Very very happy with my settup. Go for it with good cells. I paid close attention to making sure all cables were the same length, and my topology was such that every cell had the same "distance" as eachother. Everything is staying balanced.


  • @Cedar Are you running the REC Active? Any issues exceeding the 1000ah recommendation? I ask because I was considering a 3P4S set up in a van build using the EVE LF304K cells, but the space the batteries are going in could just about perfectly accommodate a 4P4S system that would add up to over 1200ah, and am wondering if the REC Active would work for that application or if I'd need to move on to something else. 


  • Hey Chris,

     The Active BMS is designed to active balance up to 2A loads and we have actually seen installations with almost 2,000 Ah systems.


  • @Chris yes, REC Active BMS. My system is 1120 ah, so only slightly over the recommended amount, but I have seen absolutely no issues. My feeling is that limit would only really be a factor if you had poor quality cells, or your wiring was poorly conceived/constructed which was causing balance issues. Mine hardly need any balancing at all, and I imagine it could do bigger even than mine. I do wish there was a 24v active BMS. I may have still gone 12v but it would have made it more of a decision.  


Please login to reply this topic!