Can someone tell me how a closed loop communication bms will charge the battery's, SOC or voltage

[Magman36]

Hi , im a real dummy when it comes BMS's with closed loop communication, i was questioning myself on how the bms's charge multiple server rack 48 volt battery packs, does anyone know if the Bms's charge equaly the battery packs based on their SOC or voltage when they are connected for closed loop communication with the inverter ? , is there a thread i could read on this forum, please dont be too harsh on me because im still crawling on all four legs when it comes to this.

 

[sunshine_eggo]

Typically the BMS passes a "charged" voltage to the inverter, and the inverter follows a 2 phase (bulk/absorption) charge to that voltage and holds it once attained.

Some systems have additional controls. A cutoff voltage may be set for either SoC or voltage.

For the server rack battery, the master battery aggregates all the data received from all connected batteries and passes control data to the system. The system only sees one battery even if multiple batteries are connected.

 

[Magman36]

Typically the BMS passes a "charged" voltage to the inverter, and the inverter follows a 2 phase (bulk/absorption) charge to that voltage and holds it once attained.

Some systems have additional controls. A cutoff voltage may be set for either SoC or voltage.

For the server rack battery, the master battery aggregates all the data received from all connected batteries and passes control data to the system. The system only sees one battery even if multiple batteries are connected.

Thank You !

 

[n2aws]

To be clear, closed loop communications doesn't change how evenly or uniformly an individual battery pack in a set charges. That is still done the same way. IE, if you put 57v on the bus bar, that means each individual battery pack has the *potential* to reach 57v. but doesn't necessarily mean they'll all be exactly even.

What the closed loop communication generally does is tells the charging equipment that "this stack of batteries can handle up to 100amps of charging right now." and then as packs fill up "This stack of batteries can handle 30amps fo charging right now". As a result, the equipment that handles the charging will ramp up/down the output, to keep from overcharging the batteries or charging them too quickly.

As an example, the BMS in my stack of batteries will allow the charge controllers to do a combined total of 500a of current (my equipment can't provide 500, but thats what the batteries can *handle*, as they start getting near full.. it'll reduce it. down to eventually 15a or so, and then stop. (In my system, it's smart enough to take the "excess" and sell it back to the main panel. so even though the battery isn't able to consume the rest, I'm not losing output. If the stack can handle 50a, and my solar output is doing 100a, the inverter is smart enough to invert the extra 50a, and send it to the main panel/grid. which keeps the batteries at their "50a limit"

 

[dbostoc1]

To be clear, closed loop communications doesn't change how evenly or uniformly an individual battery pack in a set charges. That is still done the same way. IE, if you put 57v on the bus bar, that means each individual battery pack has the *potential* to reach 57v. but doesn't necessarily mean they'll all be exactly even.

What the closed loop communication generally does is tells the charging equipment that "this stack of batteries can handle up to 100amps of charging right now." and then as packs fill up "This stack of batteries can handle 30amps fo charging right now". As a result, the equipment that handles the charging will ramp up/down the output, to keep from overcharging the batteries or charging them too quickly.

As an example, the BMS in my stack of batteries will allow the charge controllers to do a combined total of 500a of current (my equipment can't provide 500, but thats what the batteries can *handle*, as they start getting near full.. it'll reduce it. down to eventually 15a or so, and then stop. (In my system, it's smart enough to take the "excess" and sell it back to the main panel. so even though the battery isn't able to consume the rest, I'm not losing output. If the stack can handle 50a, and my solar output is doing 100a, the inverter is smart enough to invert the extra 50a, and send it to the main panel/grid. which keeps the batteries at their "50a limit"

So I have 6 100ah @ 48v sungold batteries in a stack all on in a eg4 with bus bar cabinet and my sungold inverter will stop charging when one of the batteries hit the max charge limit set @ 56.4v but it's not the top (first) battery but the other 5 batteries will be somewhere between 54.8-55+ so is that normal or can I fix this somehow? I'm not sure if the inverter is seeing the batteries or not though

 

[n2aws]

So I have 6 100ah @ 48v sungold batteries in a stack all on in a eg4 with bus bar cabinet and my sungold inverter will stop charging when one of the batteries hit the max charge limit set @ 56.4v but the other 5 batteries will be somewhere between 54.8-55+ so is that normal or can I fix this somehow? I'm not sure if the inverter is seeing the batteries or not though

Sounds like one of your packs has a cell imbalance, and maybe be hitting a single cell overvoltage. Purely a guess based on your description.

I'd check the cell balance, and if needed.. top balance them. That said, if it's happening to one pack, it's likely that all packs have some level of imbalance, so you likely want to top balance all of them.

 

[dbostoc1]

thanks I will try that

 

[dbostoc1]

Sounds like one of your packs has a cell imbalance, and maybe be hitting a single cell overvoltage. Purely a guess based on your description.

I'd check the cell balance, and if needed.. top balance them. That said, if it's happening to one pack, it's likely that all packs have some level of imbalance, so you likely want to top balance all of them.

so I checked soc at the battery with the bms screen and all are at 100% but voltages were acting the same as before so I isolated each battery from the bus bar by turning off breakers on 5 of them at a time and testing each one that way with a multimeter and all 6 batteries are reading 56.4v like the inverter was set to but the screen on each battery were all over the place like before. any ideas? thanks

 

[n2aws]

so I checked soc at the battery with the bms screen and all are at 100% but voltages were acting the same as before so I isolated each battery from the bus bar by turning off breakers on 5 of them at a time and testing each one that way with a multimeter and all 6 batteries are reading 56.4v like the inverter was set to but the screen on each battery were all over the place like before. any ideas? thanks

SOC doesn't give any indication on cell imbalance.

You'd need to download the BMS utility, and plug into the battery with the BMS cablea to see individual cell voltages

 

[dbostoc1]

SOC doesn't give any indication on cell imbalance.

You'd need to download the BMS utility, and plug into the battery with the BMS cablea to see individual cell voltages

thanks again, is the cable needed for this the same for all batteries?

 

[n2aws]

thanks again, is the cable needed for this the same for all batteries?

It is the same for the EG4 batteries (Lifepower4 and LL, at least). but if by "all batteries" you mean, from all manufacturers, then no. There are posts in this forum about how to make your own, or you can buy one directly from signature solar for the EG4 batteries

 

[dbostoc1]

thank you again

 

[CharliVN]

I recently have 4 of these batteries https://batteryhookup.com/products/51-8v-252ah-13-05kwh-14s-ess-battery-module-with-bms put together, they hookup to Growatt inverters and 9K of the solar panels, first few days I didnt know what protocal I should be setup for after a few tried I end up with protocal #4 when I reboot the BMS send thformation to the inverter and setup the charge amp to 84 amp, change the voltage to 58.1 on both so far I jut let them working together and look fine for 15 charge cycle sofar, I hope I got the right protocal, oh btw the BMS are XDZN-6022-165-100A-LFP not a lot of information you can find out there for this BMS but the price is right, after over 10 yrs messing around with GM Volt and Nissan Leaf battery, now I have 4 of these in my garage and after 10 days, I only use about 20% of the juice, my house is 100% electric I have no gas

 

[Ennis437]

so I checked soc at the battery with the bms screen and all are at 100% but voltages were acting the same as before so I isolated each battery from the bus bar by turning off breakers on 5 of them at a time and testing each one that way with a multimeter and all 6 batteries are reading 56.4v like the inverter was set to but the screen on each battery were all over the place like before. any ideas? thanks

I have SunGold batteries and if you press enter on the “cell voltage” screen you can see all 16 individual cells voltage on the screen without any additional software you can then scroll through and see if you have a cell that has bad voltage or the like.

 

[dbostoc1]

I have SunGold batteries and if you press enter on the “cell voltage” screen you can see all 16 individual cells voltage on the screen without any additional software you can then scroll through and see if you have a cell that has bad voltage or the like.

thanks I did check the individual cell voltage and all were extremely close but it was odd that the overall voltages on screen were so off from each other but I did a bottom balance and now it seems that things are as they should be