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How to balance batteries?

marionw said:
The screenshot does not allow me to see all cell voltages. If one or more cells is above 3.45 volts then I should see "Bal" next to the cell voltage. If I blow up the picture it does appear (Although with my old eyes I can't be sure) that some cells might have "Bal" which is good. Hold the charge voltage between 55.2 and 56.0 volts to ensure that one or more cells does not reach 3.6 volts which is Cell Overvoltage Protection. If a cell reaches OVP then the BMS will stop the charge preventing other cells from balancing. Hold it there for a couple of hours and let the battery "soak". The juice (electrolyte) in the cells will become happy happy and hopefully all will be well. You might have to from time to time (hopefully not that often) do this but with all batteries in your bank. Balancing the cells in one battery is not the same as balancing all batteries together. I have one in a rack of six that always discharges first and also charges first. Not necessarily a "bad" battery, just a different batch and I might from time to time have to tweak the charge profile to accommodate this battery
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I didn't make any changes to the parameters but that may be an option in the future after 10 cycles. I am open to any suggestions.

I used 100mA to charge low cells to 3.53 and a 10W 8 ohm resistor to discharge ones in over voltage warning. It is now sitting at 56.3 (on Chargeverter) resting peacefully.

Short recap over the last week it sat on the chargerverter being walked up from 54 to 55.4 and would go into alarm. No matter how long it sat with zero to 100 mA it wouldn't balance. The BMS starts to balance any cell over 3.535 for over a second. The low ones never came up. I waisted a two weekends over a new and 1 year old battery (2 of 6).

I greatly appreciate all the suggesting and help. Nothing was ignored. My wife and I were at the point that if this isn't corrected soo we would be looking for alternative storage device.

30+ years in electronics this was going to end NOW and it did. The gremlins have been put back in the cage.

Issue Resolved.

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The bottom of the screenshot is cut off so I can't see the firmware version.
The "Status:" at the bottom of the screen should indicate something like "BMS: QT-YS00-16SV100A-V3.37". If it does not end with V3.37 then you do not have the latest firmware installed.

Screenshots for the "ParameterSettings" tab would be helpfull. Will take two screenshots to to show the full top and bottom of the Protection/Alarm parameters.

The CELL_OV_Start should be = 3.600
The PACK_OV_Start should be 57.60
The Bal_Start_Volt should be 3.450
The Bal_Start_Diff should be 20 millivolts.

The above screenshot shows the BMS is starting to balance cells and the SOC has reset to 100%. The cell voltage difference is 0.008 volts (8 millivolts which is not bad) and there are no alarms. This does not look to bad....
 
marionw said:
The bottom of the screenshot is cut off so I can't see the firmware version.
The "Status:" at the bottom of the screen should indicate something like "BMS: QT-YS00-16SV100A-V3.37". If it does not end with V3.37 then you do not have the latest firmware installed.

Screenshots for the "ParameterSettings" tab would be helpfull. Will take two screenshots to to show the full top and bottom of the Protection/Alarm parameters.

The CELL_OV_Start should be = 3.600
The PACK_OV_Start should be 57.60
The Bal_Start_Volt should be 3.450
The Bal_Start_Diff should be 20 millivolts.

The above screenshot shows the BMS is starting to balance cells and the SOC has reset to 100%. The cell voltage difference is 0.008 volts (8 millivolts which is not bad) and there are no alarms. This does not look to bad....
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Brett V said:
What a pain in the ass this all is! I’m glad I built my own batteries so I could properly top balance the cells before assembly. It’s so much easier than trying to do it after they’re built.
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It's a little late for me but that thought had crossed my mind. I can work with this now. I know how I can correct the issue myself. The goal of this system is to provide power to my family during a storm event. With the solar it is "Backup with benefits". I'll swap this battery out tomorrow and fix the 2nd one. Fix was EZ but I wanted to ensure I did everything with the BMS first before I did it the old fashion way.
 
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Nicely done.
At a quick glance I would reduce the balance start voltage to 3.4V-3.42V.

I've considered swapping to JK BMS for the active balancing but my JBDs work just fine with top balanced packs.
 
42OhmsPA said:
Nicely done.
At a quick glance I would reduce the balance start voltage to 3.4V-3.42V.

I've considered swapping to JK BMS for the active balancing but my JBDs work just fine with top balanced packs.
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The Heltec active balancer has a solder bridge jumper you can remove and replace with a switch to turn it on and off. I have one with alligator clips I hook up to a pack when needed. Been thinking of getting 3 more and wiring them in permanently, then use relays to turn them on when the voltage goes above 54.4v.
 
Brett V said:
The Heltec active balancer has a solder bridge jumper you can remove and replace with a switch to turn it on and off. I have one with alligator clips I hook up to a pack when needed. Been thinking of getting 3 more and wiring them in permanently, then use relays to turn them on when the voltage goes above 54.4v.
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Only problem is, my worst pack rarely goes above .012 delta, the rest usually hang around .003 - .006 so while it would be a cool project, it’s not really worth it.
 
Brett V said:
Only problem is, my worst pack rarely goes above .012 delta, the rest usually hang around .003 - .006 so while it would be a cool project, it’s not really worth it.
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I agree. My worst pack is the Envision cells I didn't top balance, I'm going to properly top balance them when I add my 4th pack.
My EVE LF230s have very similar deltas to what you are seeing, they were properly top balanced.
 
I can tell you some issues I have with the EG4 LifePower4 (QT-YS00-16SV100A) Narada BMS

>Only 6 balances going on at any time, maximum shunting current is ~300mA or 10-12 ohms.

>It will stay balancing on a cell while another cell are at a much higher in voltage, software needs to jump around more. I would press the reset button and the BAL would go to the highest 6 cells. I shouldn't have had to do this. those Transistors should be bouncing all over the place. There is a minimum hold time or V drop but High V has priority.

>The lower V cells take forever (days) to come up. With more active shunts with higher current the low cell get more of the source voltage & current and would be able to charge faster. The MOSFETS are on the board with I/O attached so why not use them. Unless they are multiplexed and can only use 6 at a time.

It seems most of this can be corrected with a firmware update.
 
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Also doing it with small power supply. ChargVerter excellent for large current. Small one that can do small constant current will do it but take a long time. The top set voltage of 56.2 @ 25mA, it will slowly walk up as it balanced. This was suggested by GXMnow. I already tried this with CV but I couldn't control the current at the low level.

Not preferred method because it will take a very very long time. Monitoring separately with Solar Assistant.
 

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25 ma is really low. I would hope the balancer can bleed a bit more than that. My weakest BMS balancer appears to be about 60 ma. If you try to raise the current does the top cell start to run away? What are the top and bottom cell voltages at now?
 
GXMnow said:
25 ma is really low. I would hope the balancer can bleed a bit more than that. My weakest BMS balancer appears to be about 60 ma. If you try to raise the current does the top cell start to run away? What are the top and bottom cell voltages at now?
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I started at 55.11V 100mA and I would come back in and check on it and it was 0mA, charge MOSFET open. Turned down to 25mA and reset over night. This morning I put it on 50mA. Differential 217mV

My previous method as a human BMS worked great but takes way to much effort. I was hoping that leaving it on a constant current supply for 48hr would do it but not looking good so far. This is pack #3 of 6 with issues. All the other 5 in the cabinet are working great after my intervention.

I have spent many hours working on this. At this point I feel someone owes me a spare battery as there will be on on the bench getting a super balancing procedure every now and then. If this was billable hours then the cost for each one of these packs it is 150% over retail.

The pack was on MPPT at 56.2V when I noticed it went into protection mode. Pulled it and put it on bench.
Started charging with 100ma 5:21pm yesterday. Reset to 25ma all night and now 9:00am set for 60mA.

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BarracudaBob said:
I started at 55.11V 100mA and I would come back in and check on it and it was 0mA, charge MOSFET open. Turned down to 25mA and reset over night. This morning I put it on 50mA. Differential 217mV

My previous method as a human BMS worked great but takes way to much effort. I was hoping that leaving it on a constant current supply for 48hr would do it but not looking good so far. This is pack #3 of 6 with issues. All the other 5 in the cabinet are working great after my intervention.

I have spent many hours working on this. At this point I feel someone owes me a spare battery as there will be on on the bench getting a super balancing procedure every now and then. If this was billable hours then the cost for each one of these packs it is 150% over retail.

So in short, how to bring up the low cells with out taking the cover off?

View attachment 219871
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This is not the full display. What is the charge current? Are there any alarms or protections active that stopped the charge (bottom of the screen)?
3.60 is Cell OVP. If you use around 55.5 constant voltage (3.5 X 16 = 56.0) and still get a cell OVP and the Charge "CMOS" is off the "Limiter" will cycle on and off. When the "Limiter" turns on you will see current increase, when the "Limiter" turns off current will go to 0.

I often find that at this point stopping the charge and placing a slight load on the battery will bring the "Max Diff" back down to one or two millivolts.
 
marionw said:
This is not the full display. What is the charge current? Are there any alarms or protections active that stopped the charge (bottom of the screen)?
3.60 is Cell OVP. If you use around 55.5 constant voltage (3.5 X 16 = 56.0) and still get a cell OVP and the Charge "CMOS" is off the "Limiter" will cycle on and off. When the "Limiter" turns on you will see current increase, when the "Limiter" turns off current will go to 0.

I often find that at this point stopping the charge and placing a slight load on the battery will bring the "Max Diff" back down to one or two millivolts.
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Here are the latest images
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My goal was to come up with a simple procedure that owners of this product can easily get out of this failure mode. I appreciate the help but lets keep it real.
 
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I think I see part of the issue.
Cell 14 in your last pic is the highest, but it's not balancing. I remember reading about a limitation on some BMS units. The balance resistors and FETs get too hot, so they can't run the ones right next to each other at the same time. But I doubt this is your case. It's odd to see 2 groups of 3 together, but then the highest cell not balancing. Unless the layout of th parts has a different limitation. In any case, that is a lousy balancer.

I did end up buying a "100Balance" stand alone 16S Active Balancer for like $30 on Amazon. It works great and pulled my way out of balance E-Bike batteries back to within 20 mv in a day. I tried it on my newer 180 AH banks as well, but the cheapo Daly BMS is good enough that they are both within the 20 mv so the 100Balance BMS shuts down as that is "good enough". My older 360 AH bank has a JK BMS with 2 amp active balance. It has not turned on balancing in about 2 years, those cells sit at just 1 to 3 mv max to min at any charge state. I am still amazed how well those cells hold balance. Of course NMC cells are kind of cheating compared to LFP when it comes to the balance issue. The flat discharge curve of LFP is great for many things, but keeping the pack balanced and estimating state of charge are two problems that it causes.
 
At least one cell had to hit 3.60 volts which is the setting for CELL_OV_Start. The Protection fault goes away once the cell drops below CELL_OV_Stop which is set at 3.40 volts.

CMOS On is black/off. If you watch does the "Limiter" Off periodically change to On.

If you stop the charge and place a load (even small one) on the battery you will see the "Max Diff" becomes rather small (hopefully only a couple of millivolts) and cells will be balanced. In other words the cells are probably balanced.
 
BarracudaBob said:
1717614819855.png
GXMnow said:
I think I see part of the issue.
Cell 14 in your last pic is the highest, but it's not balancing. I remember reading about a limitation on some BMS units. The balance resistors and FETs get too hot, so they can't run the ones right next to each other at the same time. But I doubt this is your case. It's odd to see 2 groups of 3 together, but then the highest cell not balancing. Unless the layout of th parts has a different limitation. In any case, that is a lousy balancer.

I did end up buying a "100Balance" stand alone 16S Active Balancer for like $30 on Amazon. It works great and pulled my way out of balance E-Bike batteries back to within 20 mv in a day. I tried it on my newer 180 AH banks as well, but the cheapo Daly BMS is good enough that they are both within the 20 mv so the 100Balance BMS shuts down as that is "good enough". My older 360 AH bank has a JK BMS with 2 amp active balance. It has not turned on balancing in about 2 years, those cells sit at just 1 to 3 mv max to min at any charge state. I am still amazed how well those cells hold balance. Of course NMC cells are kind of cheating compared to LFP when it comes to the balance issue. The flat discharge curve of LFP is great for many things, but keeping the pack balanced and estimating state of charge are two problems that it causes.
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Well that is what I was looking for. Some truth behind the curtain. I am not familiar with these stand alone balancers but would like to try one. New subject for me to binge you tube and forums about 😁

I like the plastic encloser of the 100Balance 16S 1A Balancer
 
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marionw said:
At least one cell had to hit 3.60 volts which is the setting for CELL_OV_Start. The Protection fault goes away once the cell drops below CELL_OV_Stop which is set at 3.40 volts.

CMOS On is black/off. If you watch does the "Limiter" Off periodically change to On.

If you stop the charge and place a load (even small one) on the battery you will see the "Max Diff" becomes rather small (hopefully only a couple of millivolts) and cells will be balanced. In other words the cells are probably balanced.
Click to expand...
I know how to get in there to make it work, plan was to come up with something I can put on it and walk away, go asleep, and wake up with a happy battery. not opposed to a timer, relay, and load. Many people with this type of battery would buy such a device or build it if some drew it up. Two step forward charging, one step back discharge..

Note this is an EG4 Battery on an EG4 Inverter. Fact remains that there is either going to require external active balancing, internal augmentation, or a firmware update that takes care of it. End result is I own a bunch of expensive batteries and I want them to work as well as many other people. I am here to help.
 
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Brucey said:
Honestly for the price being charged for these batteries, having active balancing capability in the BMS (or separate) should be included.
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Agreed, buying a plug-n-pray consumer grade system. My challenge now is I have 6 and have others that bought many more. Need to come up with a good safe fix.
 
GXMnow said:
that is a lousy balancer
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6 of 16S 300mA balancer that doesn't bounce around and lets other cells get way to hi while it is stuck on a cell until it is way down. Yep, no way to candy coat this however that is an issue that is fixable in the firmware.
 
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