Help with new battery build

[klempak]

I am putting together battery with four CATL 302Ah Grade B cells and Muller Energy BMS (JBD 12v 250A BMS with 5A active balancer). This battery will be used for my camper, only for few DC loads ( lights, fridge, water pump, Webasto heater, Max Air fan and charging outlets) I have been told by Muller Energy that I can build the battery and charge it with my Victron ip22 30A charger and active balancer will take care of cell balancing. However I am not sure about setting up my BMS in Xiaoxiang app. Is there any guide how to do this? Also my charger is currently preset to charge the cells at 14.40V not sure if I should change it or keep it this way.
Thank you.

 

[HRTKD]

See this thread for recommended charge profiles:

Recommended Charge Profile for DIY LiFePO4 Batteries *Sticky Post*

12V 4S LiFePO4 Battery w/ BMS: Absorption: 14.5V Float: 13.6V Inverter Cut-off: 10.7V-12V (depending on size of load and voltage drop etc) 24V 8S LiFePO4 Battery w/ BMS Absorption: 29V Float: 27.2V Inverter Cut-off: 21.4V-24V 48V 16S LiFePO4 Battery w/ BMS Absorption: 58V Float: 54.4V...

diysolarforum.com

There are quite a few threads on the forum about setting up the BMS from the app. They're mostly in the DIY LiFePO4 and BMS subforums.

The Overkill Solar website has a nice manual for their BMS, which is the JBD BMS.

 

[klempak]

Thank you! I have check the Overkill Solar web manual and I am having trouble finding the correct wire size between the cells and BMS / battery terminal. My BMS is 250A however I will be using this battery only for DC loads no inverter. Based on Blue Sea Systems web calculator I should be using 0 AWG wire for 250A.

 

[HRTKD]

As long as your distance is short, 0 gauge should work. It's under 3% voltage drop.

I use a voltage drop calculator instead of the charts.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

 

[klempak]

I am just worried about the stress on cell negative / positive stud, 0awg is quite thick.

 

[HRTKD]

Add strain relief so the cable isn't a problem. Sometimes you have to get a bit creative and think in more than just two dimensions.

 

[littleharbor2]

I am just worried about the stress on cell negative / positive stud, 0awg is quite thick.

Fine strand cable is quite pliable compared to the lower strand count cable varieties.

 

[klempak]

I have finally build my battery (See photos). Thank you all for your help! As I mentioned above I have JBD 250a bms with active balancer and discharge switch. Can you please check my BMS settings? This battery will be charged by Victron smart solar charge controller 100/30 and Victron blue smart charge 30a. My loads are only 12v, no inverter. Thank you.

 

[klempak]

Attaching few pictures of my battery in stainless steel group 27 battery box.The BMS as well as Victron BMV-712 smart battery monitor is attached to the lid of the box. My goal was to make the whole system removable therefore I am using Anderson powerpole connectors.

 

[HRTKD]

It looks like you have the Balance Only When Charging option turned off. This means that the BMS will be balancing all the time. Most of us have that option turned ON and balance only when the cell voltage hits 3.4 volts.

 

[klempak]

HRTKD thank you. I missed that one. Do you happened to know where to find correct settings for Victron MPPT solar charge controller?

 

[HRTKD]

The Victron factory settings are pretty good. When my RV is actively being used, that's what I use. I lower the settings when I have it parked at the storage lot.

 

[klempak]

The Victron factory settings are pretty good. When my RV is actively being used, that's what I use. I lower the settings when I have it parked at the storage lot.

Thank you!!

 

[klempak]

I have just tried to charge my battery with Victron IP22 charger and everything went well until I hit 91%, my bms is showing alarm “cell over voltage protection” cell vent out of balance. BMS is showing 100% but victron shut is showing 91%. Prior hitting 91% shut and bms were showing similar state of change, also cells were balanced nicely……Not sure what to think.

 

[HRTKD]

Your cells are imbalanced. This can often happen once the cells come close to or hit the knee. Your BMS can balance only so much. If you can change your charger to charge with fewer amps and/or fewer volts, it will allow the BMS more time to balance.

 

[klempak]

Your cells are imbalanced. This can often happen once the cells come close to or hit the knee. Your BMS can balance only so much. If you can change your charger to charge with fewer amps and/or fewer volts, it will allow the BMS more time to balance.

I have my charger set to 14V and 30A…also I have 5A active balancer therefore I thought it will be able to keep up with my charger. What would you recommend to change the charger setting to? Thank you

 

[littleharbor2]

Sounds like your shunt monitor settings need to be adjusted. The shunt "full" voltage settings should be slightly lower than your charge setting top bulk/absorb voltage. Also, try to verify all voltage readings from the different components with a known good multimeter.

 

[HRTKD]

I have my charger set to 14V and 30A…also I have 5A active balancer therefore I thought it will be able to keep up with my charger. What would you recommend to change the charger setting to? Thank you

The screenshot of your BMS agrees with your charger's volt/amp setting. This issue could be a poor connection on cell #3. Check all the connections, making sure the contact surfaces are clean and the clamping force is good and tight.

I agree with what @littleharbor2 said about your shunt monitor. The settings are either off or it just hasn't seen a full charge, enough to get it to understand that the battery is fully charged.

What cell voltage does your active balancer start balancing at?

 

[klempak]

The screenshot of your BMS agrees with your charger's volt/amp setting. This issue could be a poor connection on cell #3. Check all the connections, making sure the contact surfaces are clean and the clamping force is good and tight.

I agree with what @littleharbor2 said about your shunt monitor. The settings are either off or it just hasn't seen a full charge, enough to get it to understand that the battery is fully charged.

What cell voltage does your active balancer start balancing at?

Thank you. I checked all connection and it is tight and all was cleaned with rubbing alcohol. I connected my battery to victron MPPT and was closely watching what is going. Attaching screen shots. It looks like all cells are very well balanced until 300.5Ah once it got to 302ah in went all over. I tried twice always same result. Perhaps my actual battery capacity is not 302ah but only 300.5ah???? …..my bms ballancer configuration is se to 3.4V but I am not sure if this setting is for active balancer or the internal bms balancer.
Thank you

 

[HRTKD]

I thought I read that if you have an active (external) balancer then the BMS (internal) balancer should be disabled. The BMS balancer works fine for my two batteries, so I haven't considered using an active balancer.

If you have known Grade B cells, it's probably better to assume a lower capacity than if they were Grade A.