Please or Register to create posts and topics.

How to assemble 16 cells to make a 12V battery?

I'm getting ready to upgrade my batteries on my Jeanneau to LiFePo4, and have enough space for a bank of 16 batteries using the EVE 280ah cells.

I've heard great things about your BMS, and plan to use it for my system. Though I'm wondering what you'd recommend for a configuration...

4P4S - where I parallel 4 individual cells (280ah 3.2v) to make a larger 1120 ah 3.2v cell, and then series connect 4 sets of these for a nominal 12.8v 1120 ah bank. I'm wondering if in this configuration, if the BMS can it monitor each individual 280ah 3.2v cell, or if it would just monitor each larger 1120ah 3.2v cell?

4S4P - of course, I understand the alternative is to create 4 banks of 12.8v 280ah and then parallel them together. However, I imagine this may require 4 separate BMS and related equipment such as disconnect relays, etc.

The plan is to have high and low voltage disconnect relays, as well as a CANBUS connection to a Victron monitor and a Wakespeed alternator regulator.

Any help and direction you can provide would be appreciated.

Thank you!

J.

I like simple systems and I would go for a 4P4S configuration (single BMS, shunt, set of contactors...).  The downside, as you say, is that the BMS does not monitor each individual cell, but each group of 4 cells in parallel. 

The cells in parallel in each 4P group will always be balanced between them (as demonstrated in most drop-in batteries that are made with 10's of cells in parallel).  You need to be sure the cells you buy are good quality grade A - meaning that they have certified internal resistance and capacity, like that all the cells will behave about the same way.  If a cell goes bad in a 4P group, the internal resistance of that group will go up and the BMS will warn you with a lower SOH (State of Health) / higher cell resistance.  At that point you will have to put aside the 4 cells from that group and rebuild your battery in a 3P4S configuration - then you have time to investigate which cell is bad...

If you decide to go the 4S4P route (or (2P4S)2P like a client just did), we are extending the CAN application using the OS Energy protocol (same one used by Wakespeed), so that the BMS's will communicate between them and only send one set of data and commands on the CAN bus.  We expect to have it debugged and operational before the end of the year.

Apparently you have Victron equipment and it is a good idea to use their wired remote control feature to have the BMS control them directly in addition to CAN bus (but at slightly different levels so that it can be a safeguard in case the CAN bus is down).  On my boat I have a single relay to isolate the battery in case the CAN commands and the wired remote commands have no effect and the battery is getting in the danger zone.  My thinking: if after giving the command to stop the charge (CAN and wired remote command) the voltage still goes up there must be some wiring problem or other major issue, and I prefer to disconnect the battery entirely to be on the safe side.  But before disconnecting the battery, the BMS commands a relay to place the starter battery in parallel so that power is not lost.

CAN integration with Wakespeed and Victron (CerboGX) is standard.

Philippe

Skokie has reacted to this post.
Skokie