Question on Valence Batteries low voltage

[ericgrand]

Hi!

Thanks for all the valuable information we can find here!

I have managed to purchased two small electrical cars (Courb C-Zen) which have been left uncharged for 2 to 3 years. I have for the time being take delivery of the first one, second should arrive sometimes next week.

These cars are equipped with 7 U27-12XP batteries, connected in serie, under the supervision of a Valence U-BMS.

All batteries are located below the car, in a large box. It is therefore not possible to access them nor the BMS once everything is installed.
Previous Owner reinstalled all batteries but without any connection (communication or power) so anyway, no diagnostic was possible without removing the batteries.

So now, I have all 7 batteries in my garage. 6 of them were at 2,7V (!) and 1 was at 9,8...

I have charged each battery individually at 1A but the batteries didn't reached 2,3V/cell quickly enough, so I have 2 flags:
-Under 2,3V
-under 2,3V w/ Chg Curr.

The first flag rest itself while reaching 3,3V/cell, but the other one did not reset and the batteries are still blinking red...

Is it a latched" flag? Is there a way to reset it?

I have limited charging means, 1 capable of 5A, 1 of 7A, and one of 3,5A...So I can charge slowly 3 batteries at a time.

My plan was to charge each battery up to 25%, and reinstall everything in the car to take benefit of the inboard charging system (22A)...but i'm concerned the flag may not reset and it could become problematic.
Once reinstalled, I can access to the RS485 plug, but that means a disconnection from the BMS, managing the charger through CAN Bus...

Also, do you think batteries may have been severly damaged from being left uncharged for such a long time?

Edit: while waiting my internet access to resume before posting this message, I discivered one of the battery has one toasted cell...not moving from 1.30V...
I think I will have to investigate replacement or rebuilt!
If you have any idea where to find such battery in Europe and more precisely in France, that would be great!

Thanks in advance for all your inputs or advices on this situation!

Hopefully, I will learn for the second car!

 

[snoobler]

I can't say about your situation, but this is my experience:

10kWh series pack used in an aftermarket Gen2 Prius plug-in hybrid system. 58 CALB 40Ah cells (+5 loose cells).

Owner removed the system when he sold the car and put it in his garage. Unfortunately, he left the BMS boards installed, and while they're supposed to cut off below a certain point, they apparently still have a microamp draw. By the time I got them, many months later, all cells were around 0.6V.

After many hours of low current (about an amp) series charging of all the cells, they eventually returned to the working voltage range. The average capacity once individually tested at 20A discharge was 24Ah vs. 40Ah rated; HOWEVER, these values were consistent with 5 loose cells that had been stored without BMS boards installed and had >3.2V. IMHO, their condition is more likely associated with their use as a plug-in-hybrid battery pack in Phoenix, where no cooling was provided rather than the result of the deep discharge.

I currently have two of those cells sitting on my desk a year after their last charge sitting at 3.30V.

 

[ericgrand]

Thanks for your feedback, which give me hope for at least 6 batteries. It seems they are charging normally with very low spread over the cells, even without active balancing.
Theses batteries have pushed "only" 77 kWh each, so more or less 45 cycles...

Unfortunately, as said in my first message, one battery exhibit a cell at 0V this morning. The Valence tool report 1V, but this is inaccurate, direct measurement at the internal BMS plug show 0V... I'm trying to charge this cell at 1A directly from the plug, but voltage is raising very slowly (currently 0.24V...) and decrease as soon I unplug the power supply.
So I believe this battery is dead.

I will have to check my options:
-once receiving the second car, check the 7 batteries and build a new pack if they are Ok...Is there any risk in mixing batteries in serie with different age?
-find new battery, but Valence/Lithium Werk didn't answer any of my request
-locate second hand batteries, which I don't know where to search in France or in Europe. Buying from USA would be too expensive!

Depending on the condition of the second pack, I may consider retrofitting one of the car with LFP cells from Alibaba...
Do you know if the capacity of the cells is limited by the U-BMS? If I install 150 or even 176 Ah cells, reusing internal batteries BMS to keep the Valence system, would I be limited to 138Ah (nominal capacity of the U27-12XP battery), or is the BMS calculate the SOC only based on cells voltage?
This is could be cheap option to get both car running!

 

[ericgrand]

Ok, one battery confirmed dead. Cells are leaking and smelling bad...Opening the case is a nightmare, after trying to do it as clean as possible, I finally destroy it...

 

[WinnieVan]

How is that top portion held on? Glue? I was thinking of taking a heat gun to mine to try and disassemble it nicely. Are there any screws in the lid either?

 

[WinnieVan]

Wish you were in USA -- I'd buy a set of cells from you and see if I could rebuild my battery

 

[ericgrand]

No screw at all! The top cover is glued but it is a U shape over the bottom, so glued inside/outside! I have managed to crack the ouside glue, but was not able to break the inside joint.
I had heated to over 200° the cover with a hotgun with a small nozzle but I was unable to get anything except the plastic bubbling!

Cells are spotwelded on copper/nickel plate...also a tricky process to get them removed!

 

[WinnieVan]

Yeah I see what you're saying. Did you see the video online where the guy hung his upside down and then heat gunned it? I imagine the gravity helps -- but that was on the old version of these batteries.

Probably easier to just destroy the case and extract the good cells... I don't really have a need for small battery packs -- but I assume they're worth something to somebody!

Anyway to save the copper/nickel plate to rebuild the cell? I don't have a spot welder -- but if I could revive this battery with a new set of valence cells, I might consider trying to do it.

 

[ericgrand]

An update on my situation!
I have received the second car and batteries were all showing above 13.2 volts! But previous Owner has mixed batteries of the 2 car to rebuilt a pack, but just forgetting to get them balanced before connected in serie! No need to say the BMS was cutting the charge as the highest battery was hitting 3,8V per cell, while the others were only at 25% charge...Not working at all.
I had all 7 batteries balanced and voilà! the car is running, giving around 100 km of autonomy, which is in line with original spec!

Regarding the 6 remaining batteries (left uncharged at 2,8V per battery), I have charged them and balanced them.
Just running capacity test by discharging at 14A (1/10C). THe first 3 batteries gave 140Ah, for a nominal at 138!
I don't know how they will behave under high load, but at least they does not seem to be damaged at all!
It maybe I will need only one spare battery to get both car running!

This Valence batteries are very tolerant and I have to admit that I'm really surprised how good they are!