Large voltage swings

[Withered+Flame]

I am getting massive, volt large voltage swings with my overkill solar 48v bms when charging 25a from my chargeverter.

I am charging with 57v 25a from my chargeverter.

Bms:

16s BMS 100a for LifePo4 with 12″ 8ga Wires

Comes with 12 inch long 8ga wires soldered to the board as shown. BMS For 16 cell, 48v volt Lithium-iron-phosphate DIY batteries 100 amp continuous charge or discharge current Low Temperature Charg…

overkillsolar.com

Chargeverter:

EG4 Chargeverter 48V 100A Battery Charger | Current Connected

Revolutionize the way you charge your batteries with the EG4 Chargeverter - a cutting-edge 48V charger boasting a charging capacity of 100A or over 5kW!

www.currentconnected.com

Ring terminals:

https://www.amazon.com/dp/B09QKM178Z?ref=ppx_yo2ov_dt_b_product_details&th=1

Cells:

https://www.amazon.com/gp/product/B0BJJN9HJQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Buss bars:

https://www.amazon.com/gp/product/B0BMXJ26R2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

See attached. Mainly the last 2.
I can't imagine this being good for my battery or bms.

I did top balance the cells.

Any ideas on how to stop?


Edit: Is there a way to slow down the current? I think if the current came gradually and not all at once this would not happen

 

[Quattrohead]

There is something drastically wrong with that battery, double check all of your connections and confirm individual cell voltages with a multimeter. You either have really extremely very bad cells indeed or bad connections.

 

[Brett V]

Did you ever top balance the cells?

A photo of the battery showing connections would help too.

 

[DIYrich]

My guess is the BMS is cutting off the battery when cells 11 or 14 exceed 3.65v. That can lead to wild charging fluctuations.

Section 2.3 of the manual: "Before the battery pack is assembled, lithium battery cells must be top-balanced,"\

My guess it will take forever (months) for the BMS to balance the cells. 280ah

 

[Quattrohead]

This is quite clearly not a top balance issue, there's over half a volt difference between the top cell and the bottom cell when the BMS finally cuts off due to the top cell over voltage.
Also the BMS thinks the battery is at a low state of charge at 55 volts but completely full at 51 volts, are the balance leads even in the right places? I guess they are because each cell is in the 3 volt range.

 

[Withered+Flame]

Did you ever top balance the cells?

A photo of the battery showing connections would help too.

See attached. I did top balance and added pic of battery and bus bar specs

 

[Withered+Flame]

This is quite clearly not a top balance issue, there's over half a volt difference between the top cell and the bottom cell when the BMS finally cuts off due to the top cell over voltage.
Also the BMS thinks the battery is at a low state of charge at 55 volts but completely full at 51 volts, are the balance leads even in the right places? I guess they are because each cell is in the 3 volt range.

Cell voltages checked at rest, all good, and connections were all solid. Could not pull anything out with slight tug.

 

[Quattrohead]

That last picture you put up, is it just me or do those nuts really not look tight. I know it's not something you can see but they just look wrong. Can you take your multimeter and step through each individual cell and make sure that you're getting each cell voltage and adding them up to make sure that part of the math works so that we can see whether the cells are bad or the BMS is getting wrong information.
Looking at your link to those cells they had hardly any reviews and two of them were copy and paste, I don't like the look of that either.
But regardless by the looks of things the BMS just does not understand what is going on.

 

[Withered+Flame]

That last picture you put up, is it just me or do those nuts really not look tight. I know it's not something you can see but they just look wrong. Can you take your multimeter and step through each individual cell and make sure that you're getting each cell voltage and adding them up to make sure that part of the math works so that we can see whether the cells are bad or the BMS is getting wrong information.
Looking at your link to those cells they had hardly any reviews and two of them were copy and paste, I don't like the look of that either.
But regardless by the looks of things the BMS just does not understand what is going on.

The bolts are on with as much torque as my hands can produce without struggle or pain, maybe thats the issue. No voltage mismatches either, i doubled checked with multimeter, maybe it only shows problems with high charge and discharge?

 

[Brett V]

Did you top balance by putting all the cells in parallel and charging to 3.65 volts? I really think you have an assembly error and the cells are all out of whack now. I'd take everything apart and top balance them again to 3.65. Be sure the connection surfaces of the cells and bus bars are cleaned, I use 600 grit sandpaper and then clean with alcohol. Some use Scotch-Brite pads but the metal needs to free of oxidation and oils. Not sure what cells you have but there are torque specs available and they need to be followed. Double check your crimps on the BMS leads at the ring terminals. I really don't see the current assembly as salvageable, you'll be better off taking it all apart and starting over.

 

[DIYrich]

Set the Chargeverter to 54.0 volts.
Hold 54.0 until the cells get relatively closely balanced.
Increase voltage by 0.5v, and repeat.
Keep doing it until you get to 56.0 volts.

Make sure bms is set to balance at 53.90 volts or lower.

 

[740GLE]

Is this the first time you’ve charged this battery set up or have you had it in service without issues for a while?

Have you ever been able to charge the battery so all cells were with in 0.010v of each other at say 3.4v?

Also why is the BMS trying to balance when cells are under 3.4v as is shown in the first picture?

 

[42OhmsPA]

The bolts are on with as much torque as my hands can produce without struggle or pain, maybe thats the issue. No voltage mismatches either, i doubled checked with multimeter, maybe it only shows problems with high charge and discharge?

You were using a wrench and not just your fingers, correct? Sorry for the semi insulting question...

 

[Withered+Flame]

You were using a wrench and not just your fingers, correct? Sorry for the semi insulting question...

Bare hands

 

[Withered+Flame]

Is this the first time you’ve charged this battery set up or have you had it in service without issues for a while?

Have you ever been able to charge the battery so all cells were with in 0.010v of each other at say 3.4v?

Also why is the BMS trying to balance when cells are under 3.4v as is shown in the first picture?

This is the first time ive had a load this big, no issues for awhile.

Yes. 3.3 and 3.2

That must be an error, i have balance set to 3.45

 

[42OhmsPA]

Bare hands

I really hope you're joking.
I got a good laugh either way.
Good luck.
Abort mission and start over.
Insulated tools are highly recommend, wrap standard in electrical tape if needed.

 

[740GLE]

This is the first time ive had a load this big, no issues for awhile.

Yes. 3.3 and 3.2

That must be an error, i have balance set to 3.45

3.2 and 3.3 isn’t close to fully charged.

Seems like you have some things to work out with your settings and hopefully a top balance will help you out.

 

[DIYrich]

This is the first time ive had a load this big, no issues for awhile.

Have you been fully charging (55.0v or higher) on a regular basis? If not, the cells could have become unbalanced.

Assuming it worked originally, you need to top balance. Either give the BMS voltage and time to do it, or take it apart and do it manually. If you take it apart, buy a torque wrench to put it back together. I can't, with my bare hands, unscrew a torqued nut on my battery.