4x12.8V 200Ah LiFePO4 with their own 100A BMS + Growatt SPF6000ES inverter + PV panels

[vapi]

Hi. I have created the PV system described in the title and it seams I have a charging issue.
Note I have series connected 4 LiFePO4 batteries, each one has its own internal BMS.
Since there is no BMS communication with the inverter I used USER2 settings for Growatt and specified the charging curent 40A (0.2C), charging and floating voltage to 4x14,4V (57.6V), cut off voltage to 44V.
Before connecting the batteries to the inverter I have connected all 4 in parallel for 24h to balance them as much as possible when each one had 13.4V.
Finally, I have connect them in series to the inverter and start charging base on the USER2 settings.
After sometime, the charging stopped when the battery system has about 75% (displayed in mobile app). Actually, each about 20 sec the inverter tries to start charging then stops. I see that on the inverter display and on the clamp ampermeter connected to the battery DC cables (reading sometimes ~5A then drop to 0A).

Since the inverter displays 75% battery SoC I guess it estimates this based on the sum of the voltages and starts charging but something (maybe one of a BMSs) stops it. I have disconneted all 4 batteries and measure after some rest these values:
* 13.91V,
* 13.91V,
* 13.40V,
* 13.53V

I suppose the BMS of one of the 13.91V battery disconnects while the inverter starts charging.

Is that correct my assumption? Can someone please explain what happens? Any luck to fix that or a solution?
Regards.

 

[vapi]

Here are the battery specs for charging. Note Over Voltage Dosconnect is 15V

 

[AshleyL]

Hi. I have created the PV system described in the title and it seams I have a charging issue.
Note I have series connected 4 LiFePO4 batteries, each one has its own internal BMS.
Since there is no BMS communication with the inverter I used USER2 settings for Growatt and specified the charging curent 40A (0.2C), charging and floating voltage to 4x14,4V (57.6V), cut off voltage to 44V.

Wrong settings other than the charging current.

Before connecting the batteries to the inverter I have connected all 4 in parallel for 24h to balance them as much as possible when each one had 13.4V.
Finally, I have connect them in series to the inverter and start charging base on the USER2 settings.

Wrong voltage to balance....and wrong method as well since you have four separate battery packs.

After sometime, the charging stopped when the battery system has about 75% (displayed in mobile app). Actually, each about 20 sec the inverter tries to start charging then stops. I see that on the inverter display and on the clamp ampermeter connected to the battery DC cables (reading sometimes ~5A then drop to 0A).

Since the inverter displays 75% battery SoC I guess it estimates this based on the sum of the voltages and starts charging but something (maybe one of a BMSs) stops it. I have disconneted all 4 batteries and measure after some rest these values:
* 13.91V,
* 13.91V,
* 13.40V,
* 13.53V

Yup. Caused by improper and incorrect balancing method.

I suppose the BMS of one of the 13.91V battery disconnects while the inverter starts charging.

Is that correct my assumption? Can someone please explain what happens? Any luck to fix that or a solution?
Regards.

Go to resources section, find the guide and read it.

View attachment 227716
Here are the battery specs for charging. Note Over Voltage Dosconnect is 15V

Do not use that 14.4v or 14.6v if you want balance the cell inside each battery packs.
Charge each battery pack individually at 13.6v, wait until the current taper off, then increase it to 13.7v, wait till current taper off and finally increase it to 13.8v. You better pray whatever cheap battery you paid for has active balancer inside instead of dumb/useless resistive 150ma balancer.

 

[Brucey]

Hi. I have created the PV system described in the title and it seams I have a charging issue.
Note I have series connected 4 LiFePO4 batteries, each one has its own internal BMS.
Since there is no BMS communication with the inverter I used USER2 settings for Growatt and specified the charging curent 40A (0.2C), charging and floating voltage to 4x14,4V (57.6V), cut off voltage to 44V.
Before connecting the batteries to the inverter I have connected all 4 in parallel for 24h to balance them as much as possible when each one had 13.4V.
Finally, I have connect them in series to the inverter and start charging base on the USER2 settings.
After sometime, the charging stopped when the battery system has about 75% (displayed in mobile app). Actually, each about 20 sec the inverter tries to start charging then stops. I see that on the inverter display and on the clamp ampermeter connected to the battery DC cables (reading sometimes ~5A then drop to 0A).

Since the inverter displays 75% battery SoC I guess it estimates this based on the sum of the voltages and starts charging but something (maybe one of a BMSs) stops it. I have disconneted all 4 batteries and measure after some rest these values:
* 13.91V,
* 13.91V,
* 13.40V,
* 13.53V

I suppose the BMS of one of the 13.91V battery disconnects while the inverter starts charging.

Is that correct my assumption? Can someone please explain what happens? Any luck to fix that or a solution?
Regards.

Yes. Get a balancer, I like this one, 10A so gets the job done fast

https://www.amazon.com/gp/aw/d/B0CLTZ2XQX

 

[vapi]

Thanks for your answers guys.
I have 4 x Redodo (12.8V 200Ah - 100A BMS) batteries almost like @Brucey posted picture above.
I read about these balancers and it looks like they solved a similar issue to the others. Actually, they make sense since internal BMS is taking care of the internal cells balance but there is no balance between battery packs. It is like a higher level BMS

The balancer is on the way and I'll be back with a feedback after I will connect it to my system. Thanks again.

 

[Bananaman321]

https://www.aliexpress.us/item/3256806122793618.html?spm=a2g0o.detail.pcDetailBottomMoreOtherSeller.3.618bmoa0moa0lo&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.40000.326746.0&scm_id=1007.40000.326746.0&scm-url=1007.40000.326746.0&pvid=ced3414a-fc6a-4dd6-8a22-5f9ddca6b20a&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.40000.326746.0,pvid:ced3414a-fc6a-4dd6-8a22-5f9ddca6b20a,tpp_buckets:668%232846%238112%23589&pdp_npi=4%40dis%21USD%2171.68%2125.26%21%21%21520.16%21183.27%21%402103244817200655640118525ea1a4%2112000036705582701%21rec%21US%21%21AB&utparam-url=scene%3ApcDetailBottomMoreOtherSeller%7Cquery_from%3A

Parallel your battery's charge to 14.5 hold at least 4-5hrs series connect with 5-10a active balancer set balance start to 13.5v no need to balance before this, set inverter bulk charge to 57v, float 54v

 

[vapi]

@AshleyL what would be the right settings regarding charging from Growatt SPF6000ES and why:
* charging voltage: ?
* float voltage: ?
* cut off voltage: ?

Based on the values specified in their docs I have multiply them with 4.
Besides that, the values have been confirmed by Redodo service/support team.\
Thanks.

 

[AshleyL]

@AshleyL what would be the right settings regarding charging from Growatt SPF6000ES and why:
* charging voltage: ?
* float voltage: ?
* cut off voltage: ?

Based on the values specified in their docs I have multiply them with 4.
Besides that, the values have been confirmed by Redodo service/support team.\
Thanks.

Play it safe. Fully balance your 4 battery packs first.

Don't use USER2. Utilize the normal USE instead.
CV = 55.2V (3.45v each cell is roughly 95% charged)
Float = 53.6V (Growatt will switch to float mode after the current taper off)
Cut off = 49.6V (3.1v or 3.0v, pick one and x16)