Battery & charger advice please?

[Nealh]

4.2v per cell is fine for charging and using a battery , the damage occurs when you charge to 4.2v per cell and leave it sitting there for weeks and months on end. Like lipo use a storage charge 50 - 80% SOC when not being used regularly.
Lion is a bit more tolerant then lipo and has wider discharge range, unlike lipo they don't go off the cliff below 3.6/3.5v.

 

[superjonnyboy]

4.2v per cell is fine for charging and using a battery , the damage occurs when you charge to 4.2v per cell and leave it sitting there for weeks and months on end. Like lipo use a storage charge 50 - 80% SOC when not being used regularly.
Lion is a bit more tolerant then lipo and has wider discharge range, unlike lipo they don't go off the cliff below 3.6/3.5v.

Yes, I was surprised to see minimum volts for Li ion cells listed as low as 2.7V/cell in several places.

 

[superjonnyboy]

OK, challenge #1. No voltage at charger plug when not connected to battery. My guess is the 3rd pin needs some sort of signal to start the charge?

Any ideas?

EDIT: Scratch that, multimeter cable was loose. Got 70.6Volts!

 

[Nealh]

Yes, I was surprised to see minimum volts for Li ion cells listed as low as 2.7V/cell in several places.

3.2v is about the lowest most bms will go, no use in actually killing the cell out right.
There is little in the way of mah to gain going lower.

 

[superjonnyboy]

And we're back in the game....

 

[Nealh]

If the reading is correct then your battery has an unbalanced cell group if it does not balance /charge.
Your only option is to open the pack check the 17 group voltages and manually balance the low cell group.
If you have been short charging to a lower voltage purposely to extend cell life, then you will have caused your self a headache which needn't have happened. Simply managing lion by top full charge and using with in a few hours and using a storage SOC when not in use is all that is needed to keep cells healthy, forget about your manual lipo charge days.
KISS is all that is needed nothing technical or hard to manage.

 

[superjonnyboy]

If the reading is correct then your battery has an unbalanced cell group if it does not balance /charge.
Your only option is to open the pack check the 17 group voltages and manually balance the low cell group.
If you have been short charging to a lower voltage purposely to extend cell life, then you will have caused your self a headache which needn't have happened. Simply managing lion by top full charge and using with in a few hours and using a storage SOC when not in use is all that is needed to keep cells healthy, forget about your manual lipo charge days.
KISS is all that is needed nothing technical or hard to manage.

I haven't been purposely under charging at all Neal. I guess I'll find out if it's balancing now the charger is adjusted back to the correct voltage.

 

[Nealh]

I haven't been purposely under charging at all Neal. I guess I'll find out if it's balancing now the charger is adjusted back to the correct voltage.

OK you have realigned the output voltage, It wasn't clear earlier you had done this as you mentioned faulty/loose MM cable.
No reason then why bms shouldn't balance better then with correct input voltage, complete balance might not happen first time round and may take a couple of discharges/charges to get it right or within 0.2/0.3v.

Let us know how it goes as the info is useful for others with a similar issue.

 

[superjonnyboy]

Sorry, probably wasn't particularly clear. Bike is on charge now, fingers crossed.

 

[Nealh]

You should be ok now.

 

[superjonnyboy]

Things seem to be heading in the right direction. Battery is now balancing and sitting at 69.9V, up from 69.2V previously. Probably needs a few charge cycles to get back to full charge.

 

[Nealh]

A little above 4.11v, so yes heading the right way.

 

[superjonnyboy]

I left the battery overnight and it was still balancing this morning. Disconnected the charger and battery was holding 70.0V solid, haven't seen 70 on the display for a good while! Rode to work again today so battery will get another charge before the weekend. Hopefully it'll pick up a bit with each charge.

 

[Nealh]

Indications are that likely a cell group or more are out of balance, depending on how much the BMS might eventually realign them all. A BMS balances at a very low rate something like 100ma so any large imbalance would take along time.
Once a cell group reaches 4.2v then the bms stops balancing, If voltages are too far apart. It is not unusual to have 0.1/0.2v variation, any greater then balancing is to great.
They are good at keeping all cells in check when imbalance voltages differences are small but not so good when they are wider.
All you can do is discharge and charge a few times to see if the imbalance improves, probably pointless recharging if discharge is only slight. I would be inclined to discharge down to about 63v /64v and then carry out a good charge cycle.

 

[superjonnyboy]

I would be inclined to discharge down to about 63v /64v and then carry out a good charge cycle.

Will do. I'm down to 66V just from the ride in to work so should be closer to 61/62V by the time I get home up a few BIG hills!

 

[superjonnyboy]

A bit more follow up information - After some investigation in to the manufacturer of the charger, I found out it is made by "YEWY", mine is the model "UY360".

I also found a direct contact e-mail address and asked which potentiometers control which functions. To my surprise, I received a reply today, so I can confirm the following.

VR1 adjusts charge current.
VR2 adjusts cut-off voltage.
VR3 adjust cut-off current.

 

[Nealh]

Tinkle time then .

 

[vfr400]

I can't see that changing the currents will solve anything. The balancing current is controlled by the BMS and depends on how many bleed transistors are open, though mostly it's shut off by the charge MOSFET while the high cells are bleeding. Changing the trickle current will only change how quickly the BMS shuts off the charge MOSFET, which will shut when the first cell reaches 4.25V. Everything is controlled by the BMS, not the charger. The only thing you need to adjust in the charger is the charge voltage.

 

[superjonnyboy]

Yes. the BMS controls what goes in to the battery, but the charger also has it's set limits.

Apparently, the charger can cut the charge short if the current demanded by the BMS to balance is lower than the charger current cut-off set-point (during the CV phase). It's not unknown for the poti value to drift, in the same way my cut-off voltage has.

It's detailed in the link I posted at the start of the thread. I've yet to see if