Help! battery needs repair

[minexplorer]

hi everyone.
Ive not posted on here for ages but have decided to finally try an sort my problem out, an would dearly like some advice.
Last year i posted how the 11 month old 52v batt on my Bbshd (15ah 5p samsung 30Q cells), from Electron Cycles, had suddenly starting cutting out well short of the LVC and had lost somewhat on range. Briefly ,of the 14 series of cells 2 were not charging beyond 4.0v and 4 were 4.1v the rest 4.2v.
i tried trickle charging the low cells with a mobile phone charger. for a short while balance charging settled them all at 4.1v. but it soon started the sagging and early cut outs again.Just as D8veh said it would.
I cant say for sure the cause. i was often in the habit of running the batt to the LVC. but also the charging instructions never mentioned, it had to be switched on to enter balancing mode.consequently for 11 months it was never balanced once.
Anyway several people advised cells were damaged an had to be replaced. Basically the bikes been covered in cobwebs for the last 7 months.
Several months ago i asked a local battery shop if they repaired ebike batteries. Yes they said,they send them away to their specialist it will cost £400 min. After id come to i slinked off home,more cobwebs.
What can i do? the battery was £450 im not paying that again for a repair. Can anyone advise me of a much cheaper repair service? would it be cheaper an better ,to buy a spot welder an cells,an learn the art of self sufficiency?
much thanks to anyone for any advice

 

[wheeliepete]

Try Jimmy at ebikebatteries.co.uk for a price to recell it. Chances are he's the specialist your local battery shop are going to use, then stick their % on top of his price. 70 Samsung 30Q's from Nkon are gonna cost you 346.50 Euros plus postage.

 

[Nealh]

If you were a regular on ES then you will find that the 30Q is a poor choice of cell to use and cycle life isn't very good, 30Q suffers from self discharge after only about 50 cycles. Currently there is a very good thread going on over the other side of the pond and a couple of members are doing cycle testing up to 700 full cycles to see which of the popular best cells are better. LG MJI and M36 are showing to be top of the class, Panasonic /Sanyo bottom of the class. The Samsung 29E is also proving to be a top cell.

 

[minexplorer]

If you were a regular on ES then you will find that the 30Q is a poor choice of cell to use and cycle life isn't very good, 30Q suffers from self discharge after only about 50 cycles. Currently there is a very good thread going on over the other side of the pond and a couple of members are doing cycle testing up to 700 full cycles to see which of the popular best cells are better. LG MJI and M36 are showing to be top of the class, Panasonic /Sanyo bottom of the class. The Samsung 29E is also proving to be a top cell.

hi nealh thanks.you have exchanged enough dialog in posts with me in the past ,when i bought the battery a year an a half ago the 30Q was considered a very good choice. i chose it after much research.
so you think this is just inevitable wear an tear for the 30Q after 1500 miles, rather than damage? because if so, theres no point in me trying to have a few cells replaced. its an expensive lesson in poor battery cell choice and needs to just be used at its reduced range til worn completely out?
ive given it a full balancing charge overnight an this is the result. total 57.1v strings 4.13 ,4.13 ,4.05 ,4.07 ,4.07 ,3.92 ,4.06 ,4.20 ,4.09 ,4.11 ,4.06 ,4.06 ,4.13 ,4.13

 

[minexplorer]

Try Jimmy at ebikebatteries.co.uk for a price to recell it. Chances are he's the specialist your local battery shop are going to use, then stick their % on top of his price. 70 Samsung 30Q's from Nkon are gonna cost you 346.50 Euros plus postage.

hi wheelipete.well a complete re cell wld be pointless may as well buy a fresh new battery. i was hoping just a few cells would need replacing.its only done 1500 miles.you can see from my reply to nealh above the condition the cells are in .do you agree with him this is expected wear from the 30Q. thanks

 

[Nealh]

1500 miles at a guess is 30 odd cycles , whether the imbalance is down to the BMS or with the 3.92v group a bad or dodgy discharging cell is not known.
Have you tried to manually charge the low cell groups at all by disconnecting the BMS and charging thru the balance leads ?
By balancing manually to 4.13v and having all fairly equal you can then leave the battery (with BMS disconnected) for several days to see if the cells self discharge or not.
With several other cell groups quite a bit down voltage wise, more then just a few cells might need replacing, if self cell discharge is the fault then the battery is no good apart from maybe using as torch cells.

 

[Nealh]

One of the cell groups is at 4.2v so it will prevent the others balancing esp as the voltages are so wide a part, discounting the very low group other still vary by 0.15v which is not balanceable in the normal way.
BMS can't cope balancing when cells are even 0.1v out, they are for fine balancing of cells not far out of kilt.

 

[minexplorer]

1500 miles at a guess is 30 odd cycles , whether the imbalance is down to the BMS or with the 3.92v group a bad or dodgy discharging cell is not known.
Have you tried to manually charge the low cell groups at all by disconnecting the BMS and charging thru the balance leads ?
By balancing manually to 4.13v and having all fairly equal you can then leave the battery (with BMS disconnected) for several days to see if the cells self discharge or not.
With several other cell groups quite a bit down voltage wise, more then just a few cells might need replacing, if self cell discharge is the fault then the battery is no good apart from maybe using as torch cells.

hi nealh. with the mileage id get on the bbshd i reckon id charged it 70 times. im charging that 3.92 cell group now with a mob phone charger. i tried in the past to get them all manually equal. it worked for a bit with the battery going down to the 42v LVC with no sagging even pulling high amps. but it didnt last long before playing up again and cutting out at 47-48v.
i will try that disconnect bms an see if the 3.92 cell group takes charge then self discharges.then repeat with all the cell groups evened up.
when i was last using the bike (with battery in this condition) i cld still go 18miles with reasonable amount of high power.used to get 24-28 miles.thanks

 

[Nealh]

If cells hold up and don't self discharge might be worth trying another 14s BMS.

 

[wheeliepete]

hi wheelipete.well a complete re cell wld be pointless may as well buy a fresh new battery. i was hoping just a few cells would need replacing.its only done 1500 miles.you can see from my reply to nealh above the condition the cells are in .do you agree with him this is expected wear from the 30Q. thanks

I agree, no point recelling your pack, although the cells Jimmy uses may be of a higher grade than the ones in your pack from Francis. Do yours look genuine? I only threw out the price of the 30Q to give you an idea for building your own pack. Your balance issues are certaianly interesting, I guess, as Neal has said, if they are prone to self discharging, this could explain the problem. One other thing worth checking is the welds, esp. on the string that has charged to 4.2v. If you have a weak parallel weld there, it would explain why those cells charge quicker. I say this because I had this problem on a pack I built a couple of years ago. Finding and replacing bad cells in those shark packs is a pita because the cells are all glued together, so unless you are doing it for yourself, it's far too time consuming. As has been said, try bringing the pack back in balance and maybe look for a new 40 amp BMS that will fit in your case.

 

[minexplorer]

I agree, no point recelling your pack, although the cells Jimmy uses may be of a higher grade than the ones in your pack from Francis. Do yours look genuine? I only threw out the price of the 30Q to give you an idea for building your own pack. Your balance issues are certaianly interesting, I guess, as Neal has said, if they are prone to self discharging, this could explain the problem. One other thing worth checking is the welds, esp. on the string that has charged to 4.2v. If you have a weak parallel weld there, it would explain why those cells charge quicker. I say this because I had this problem on a pack I built a couple of years ago. Finding and replacing bad cells in those shark packs is a pita because the cells are all glued together, so unless you are doing it for yourself, it's far too time consuming. As has been said, try bringing the pack back in balance and maybe look for a new 40 amp BMS that will fit in your case.

the firm electron cycles seem reputable.they say they use genuine cells and they look so.
the 3.92 group charged to 4.08 and no higher.after a few hrs reading 4.05. i decided to see how many can reach 4.20. left the first too long.it went to 4.40 but after a few hrs dropped to 4.35. gonna have to ride round the block tomorrow an start again. thought would automatically stop taking charge beyond 4.20.

 

[Nealh]

Manual charging with a 5v phone charger needs very careful monitoring to prevent over charge, not really sure how much damage the cells may have suffered as it is above there max threshold. I would leave the battery some where very safe tonight as there is a chance of internal thermal runaway and a fire starting is a risk.

 

[minexplorer]

Manual charging with a 5v phone charger needs very careful monitoring to prevent over charge, not really sue how much damage the cells may have suffered as it is above there max threshold. I would leave the battery some where very safe tonight as there is a chance of internal thermal runaway and a fire starting is a risk.

cheers nealh. still alive. ive made a bit of a mess of things.the 3.92 group refused to budge above 4.08. but i then tried the 5v phone charger on it again.not thinking it would ever get to 4.2 and didnt moniter it.was surprised to find it too has reached 4.4 this 2nd time,damn! dropped overnight to 4.35 and seems steady there.whats going on.seems likely all the groups will charge to 4.20. ineed to lower the two overcharged groups (other is 4.33)will it be safe to ride a mile or two to lower them ?

 

[wheeliepete]

Glad to hear you and battery still intact. If the cells you over charged look OK and don't show any signs of venting/leaking, then it's prob. a good idea to bring the voltage down with a ride if you have no other way to discharge. Those cells are likely to suffer further left at that voltage.

 

[Nealh]

Yes ride a round the block, the voltage should come down quite quickly.
Should they vent then you will smell the electrolyte and if they leak you will notice the wrap discolour.
Tbh honest I give you kudos for trying to save or get some use out of the battery pack but think it is damaged and you need to think of where you charge and keep it safely in case of an internal issue in the future.
You will need to note the cells final voltage and how the balance is then ideally let them sit somewhere safe for a good few days to see if any self discharge occurs.
I wouldn't leave them in the house or in any adjoining annexe/building.
Maybe an outside chiminare or a covered Barbeque, wrap battery in bubble wrap to prevent frost or cold to the cells.

 

[wheeliepete]

Currently there is a very good thread going on

Thanks for the heads up on this Neal, been researching emopeds and motorcycles lately, so much to read on ES, missed this one somehow.

 

[minexplorer]

Glad to hear you and battery still intact. If the cells you over charged look OK and don't show any signs of venting/leaking, then it's prob. a good idea to bring the voltage down with a ride if you have no other way to discharge. Those cells are likely to suffer further left at that voltage.

thanks wheeliepete an nealh.i ran them down with the throttle an the wheel off the ground.the overall voltage of the battery fully charged as it is, hasnt budged a spec over 3 days from the display readings. i had tried trickle charging another random 4.05 cell group but it wouldnt budge above 4.08.
im tuning up the bike for a ride today. intend running the battery down .
now assuming i manually even them before putting it on a charge, what will happen if A i just charge with battery off ,and B with it switched on? i know now when on, it goes into balance mode because i hear the cooling fan in the charger going on and off multiple times after full charge reached.
If some cant charge above say 4.08 will they all even out at that in balance mode.or will some continue on to 4.20 and it just wont be able to balance due to too large a diff between the lowest and highest?
After this charge i will leave for a week and note any discharge from each cell group.
ive already thought i can always use it knowing the lowest cells will cause it to cut out at something like 47v instead of the LVC of 42v. better than nothing.i cant see any leaks/swelling damage to any cells.thanks

 

[Nealh]

After running battery voltage down and on recharging, the BMS won't fully balance charge if cells are out by more then 01- 03v per cell. As soon as the first cell group reaches between 4.15v - 4.2v then the BMS will attempt to balance by opening the high cell bleed resistors then will attempt to try and balance the cell groups. Balance can takes hours as the balance voltage is <100mv.
The fact that a cell group won't manually trickle charge above 4.08v suggests that a cell/cells in that particular group are poor.

The low cell groups will stay low and the high cell groups will stay high, so your battery will remain unbalanced, you could try just charging to 4.05 - 4.08v if you can adjust the charger voltage trim pot and see if the cells will maintain self balance without the higher balance voltage being used.
Pointless in charging to 4.2v per cell as the battery won't use the extra voltage/capacity stored, the new base voltage for the battery is the charge level of the weakest cell group.

 

[minexplorer]

After running battery voltage down and on recharging, the BMS won't fully balance charge if cells are out by more then 01- 03v per cell. As soon as the first cell group reaches between 4.15v - 4.2v then the BMS will attempt to balance by opening the high cell bleed resistors then will attempt to try and balance the cell groups. Balance can takes hours as the balance voltage is <100mv.
The fact that a cell group won't manually trickle charge above 4.08v suggests that a cell/cells in that particular group are poor.

The low cell groups will stay low and the high cell groups will stay high, so your battery will remain unbalanced, you could try just charging to 4.05 - 4.08v if you can adjust the charger voltage trim pot and see if the cells will maintain self balance without the higher balance voltage being used.
Pointless in charging to 4.2v per cell as the battery won't use the extra voltage/capacity stored, the new base voltage for the battery is the charge level of the weakest cell group.

thanks for the clear explanation nealh.do chargers all have this adjustable voltage trim pot feature? mine is YEWY model UY180-D5 seems nothing inside or out adjustable.
as with another low group it may take a higher trickle charge 2nd time around. ill post results. charging all to the lowest group voltage sounds a great idea

 

[Nealh]

No not all chargers have adjustable pots inside , my Sans chargers and another similar one has the pot but a couple of others I have don't.
My Meanwell HLG has external pots for current and voltage adjustment, and are very good.