BMS for lithium battery

Thread Starter

love-ev

Joined Mar 22, 2016
3
i have bought lithium battery pack for my boat.it works without BMS. it seems its high risk for the battery pack without BMS protect.
there are some cells over discharged.
i need BMS inexpensive.

Mod edit: Please do not post your own question in someone else's thread. Now you have your own thread.
 
Last edited by a moderator:

GopherT

Joined Nov 23, 2012
8,012
Are you looking for a device (BMS) or a single chip and you want to build the circuit yourself (and PCB etc) as a DIY project? Please elaborate on your goal and your needs, (battery configuration (number of cells in series (voltage))). Also, any details on the battery mAH (or amp-hour) rating and charging rate (C-6, C30, ...).

cheers. What thread did you post this on originally?
 

Thread Starter

love-ev

Joined Mar 22, 2016
3
thanks for your reply
yes,i am looking for a bms for my diy project.
its a 24v400ah battery pack. lifepo4 battery.
8 400ah cells in series.
my working discharging current is less than 50 A
the charging current is 40A
battery pack is 400ah winston battery like this
http://www.evlithium.com/Winston_Battery.html
i just need a BMS which could cut off discharge when there is a cell over discharged.
so i could charge the battery pack to prevent the battery pack be over discharged.
 
I searched "lithium protection circuit" on Amazon and came up with a bunch of 4s boards for around $13. No 8s boards, but they exist.

Ebay has a lot of them but the 8s boards like this one tend to be for very high currents (40A) for E-bikes and such. Still, the one in the link is only $21 but sizeable.

Ebay has a number of 12V boards... Since you're wiring this up yourself, why not wire in 2x 12V boards?

Here's a 12V board that has 3A of current capability, and sells for 2 for about $10.

All of this is available easily by Googling... "LiFePO4 Protection Circuit"
 
Thinking about your 8s battery pack:

How do you charge this currently? Charging 8 cells in series will be disaster for the cells.

You should take apart the pack, wire in the protection circuit, and bring out all the individual cell (+) wires for balanced charging. You can get a balanced charger, maybe 2 x 4s chargers because I don't know if there are any 8s chargers out there. Or you can get a charge-balancing PCB, but they're harder to find and don't work that well, especially with higher numbers of cells.

If you have a real 8s charger, it will rebalance the cells. If certain cells still run down a lot faster than the others, replace the individual cells to restore your pack to full operation.
 

Thread Starter

love-ev

Joined Mar 22, 2016
3
thanks a lot.

most of the pcb/bms from ebay/Amazon have limited on discharging current.
i hope it works when the battery charged at high current. because the instant discharge current is 0.5C that is around 200Ampere.and last 10-15s.i will order one '8 cells 24V 40A 60A peak balancing LiFePo4 Lithium iron phosphate Protection PCB' to check if it works well with my battery pack
 
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