Voltage question 2p16s battery bank of 32 280ah cells

[cgccpres98]

I assembled a large battery bank of 32 280ah cells. It is configured in 2p16s. I have an ANT BMS rated for 300 amp 180 continuously. According to the BMS I have a total voltage of 52.6v, but if I put and actually volt meter in the total + and - terminal I get about 115v. Shouldn't the total voltage at the end terminals be the same as the BMS about 52.6v? The inverter is a Deye 8kw. I haven't connected it yet because I don't want to exceed the maximum voltage of about 56v. I included pictures of they diagram I was trying to accomplish and how its actually connected. I also included a screen shot of the BMS report. The most important question is this okay to connect to the Deye inverter in the current setup? Thanks for the support!

 

[snoobler]

Welcome to the forum.

Place your VM probes on a single cell. What do you get? Continue walking one probe and confirm the voltage increase of 3.3V/cell.

Does your VM need new batteries?

Confirm with another meter?

Remember to use a resistor when connecting the inverter to pre-charge the capacitors.

 

[Steve_S]

Welcome to the forum.
Your configuration looks fine although had to strain to see your busbars (darn black shrink wrap LOL).
The BMS is showing Voltage 1 as 52.6V so that is correct as well.
The voltage range is 2.50 per cell = 40.00V to 3.65V per cell = 58.4V with 51.2V being Nominal (3.200 per cell).
Cells in Parallel are still counted as "One Cell" you have 2 cells in parallel x 16 sets in Series, so you still calculate that as 16 for the math. The same would apply if you had 3 or 4 cells in parallel.

The ANT BMS may have a precharge circuit to handle the surge demand on the Inverter when it starts up but I do not know, you will have to check the docs for the specific BMS model you have. Be certain the inverter is OFF and the battery is OFF (either by DC Disconnect Switch which is preferable or with BMS set to off) then connect your wiring, turn on battery then Inverter at which time the Inverter will have a large momentary draw to fill it's Capacitors before it fully starts. THAT Surge Demand can trip a BMS if it does not have a precharge circuit OR if it does not have the capacity to dole out the amps required for that momentary demand hit.

NOTE:
From the BMS readings, these cells were not Top Charged or Top Balanced and appear to be at the standard storage voltage as shipped. If this is indeed the case, you will have issues with cell deviations and divergence at both the top & bottom of the voltage curve. So below 3.00 and above 3.400 cells will wander off and likely cause premature LVD/HVD (Lo & Hi Volt Disconnects). These cells and most especially any of the Bulk/Commodity cells should be bottom to top balanced and allowed to fully saturate till they take less than 1A charge to get the best performance out of them.

BTW: Nice to see that the Lyuan Tech Doc was helpful to you..
Hope the info helps, Good Luck
Steve

 

[cgccpres98]

You folk on this forum are AMAZING! Thanks for all the help so far! I assembled the battery quickly so I could test the inverter, the ANT BMS, and to see how everything goes together. I guess I am a glutten for punishment knowing I would have to reassemble everything! Last night I took the battery down and will be following the bottom/top balancing procedures. I'm sure I will have more questions in the near future, so thanks again in advance!

 

[Steve_S]

FYI, The 280AH cells can take a 140A Charge Rate.
It took me 14 hours per cell to charge from 2.700 +/- 0.100 to full 3.650 and saturated till they took only 1A charge, using a 40A Benchtop Power Supply, a TekPower TP1540E.

I first Top Charged each cell to 3.65 and left them to settle, once all cells were top charged to 3.65 and taking less than 1A, I allowed them to all settle (averaged to 3.450 after 12 hours) then set the cells up in parallel and then top balanced then to 3.650V and taking < 1.0A. Allowed to settle in parallel for 12 hours & then assembled battery pack.

The charging only requires CC/CV (Constant Current/Constant Voltage).
More amps that can be pushed the faster they will charge.
Between 3.000-3.450 (The Powercurve) charging is Slowwww.
Above 3.450 it gets fast and can reach 3.65 quickly - This is where if you do not Watch Dog the Charger and ensure the voltage matches what is at Power Supply terminals and Battery Cell terminals that overcharging can happen and FAST. NEVER TRUST THE Powersupply Display as that only shows the voltage at ITS terminals, not the Target Object.

I think I pretty much covered all the necessities in the Luyuan Doc, unfortunately, beyond that, the specifics vary a lot depending on people, cells and equipment / methods which vary a lot and can't be documented really (unless I was going to write a huge book and that ain't happening). It's ALL Voluntary.

 

[hipringles]

I thought these cells must always be operated in a verticle operentation

 

[HRTKD]

I thought these cells must always be operated in a verticle operentation

It depends on the manufacturer. Some allow different orientations, some don't. Consult your documenation.

 

[hansesolar]

I assembled a large battery bank of 32 280ah cells. It is configured in 2p16s. I have an ANT BMS rated for 300 amp 180 continuously. According to the BMS I have a total voltage of 52.6v, but if I put and actually volt meter in the total + and - terminal I get about 115v. Shouldn't the total voltage at the end terminals be the same as the BMS about 52.6v? The inverter is a Deye 8kw. I haven't connected it yet because I don't want to exceed the maximum voltage of about 56v. I included pictures of they diagram I was trying to accomplish and how its actually connected. I also included a screen shot of the BMS report. The most important question is this okay to connect to the Deye inverter in the current setup? Thanks for the support!

Good day,
a) I would be interested to know what the balancing looks like after one year? In the picture of the cells I see that the BMS balancer cables are all attached to the first cell of the 4 by 1 busbars.
b) Is it still the design you would recommend?
c) Have you connected the BMS balancer cables differently?
d) How does the voltage distribution look after one year?

thanks for an answer , greetings

 

[MisterSandals]

a) I would be interested to know what the balancing looks like after one year? In the picture of the cells I see that the BMS balancer cables are all attached to the first cell of the 4 by 1 busbars.

Are you referring to the big blue wires? If so, those are not balance wires, rather the main negative wires to the BMS.

 

[hansesolar]

Are you referring to the big blue wires? If so, those are not balance wires, rather the main negative wires to the BMS.

View attachment 122610

No, i referring to the BMS wires. The white once.. Its comes perhaps to miss balance between the parallel cells ?

 

[MisterSandals]

Ah, I see what mean. Yea, the tiny balance current spread between 2P cells probably does very little if anything.

 

[Delphinus]

NOTE:
From the BMS readings, these cells were not Top Charged or Top Balanced and appear to be at the standard storage voltage as shipped. If this is indeed the case, you will have issues with cell deviations and divergence at both the top & bottom of the voltage curve. So below 3.00 and above 3.400 cells will wander off and likely cause premature LVD/HVD (Lo & Hi Volt Disconnects). These cells and most especially any of the Bulk/Commodity cells should be bottom to top balanced and allowed to fully saturate till they take less than 1A charge to get the best performance out of them.

Steve_S
First sorry for intrude, I'm also building one 2P16 with LF105 I was going to top balance cells but they are EVE brand new same batch and voltage 3,286V each so I cycle 2 to confirm capacity and charge them to 3,286V and let them all in parallel during night to equalize charge and I was going to build battery, do you recommend that I still top balance them?

 

[Delphinus]

if I put and actually volt meter in the total + and - terminal I get about 115v

That is odd you should get the value of the BMS.

Is you battery negative grounded?

 

[MisterSandals]

let them all in parallel during night to equalize charge a

Letting the sit connected in parallel does nothing.

do you recommend that I still top balance them?

I think the consensus here is to always top balance. Those that believe otherwise mostly use active balancers or BMSs with balance capability (though that is often very very low balance current).

You have the cells in parallel, its never going to be easier to top balance. At 3.28V you are just over 50% charge so plan the amount of time this takes accordingly with the capability of your charger.

 

[Delphinus]

Letting the sit connected in parallel does nothing.


I think the consensus here is to always top balance. Those that believe otherwise mostly use active balancers or BMSs with balance capability (though that is often very very low balance current).

You have the cells in parallel, its never going to be easier to top balance. At 3.28V you are just over 50% charge so plan the amount of time this takes accordingly with the capability of your charger.

You are right parallel did nothing because was late I put one cell with 3,284 in parallel before wait for the 3,286V, today it was still with with same voltage, I'm charging it now.

The BMS should arrive next week it's a JK 150A active with 2A.

Thanks, I will top balance.