Swifty Liberte Coppercell ES20 36V 7.26ah battery charger problems

[brackb01]

Hi. I lost the original charger, and purchased a new one, a 42V2A, but it did not work, when I tested it, it was duff. So i bought a new one, the new one is giving out the correct power (multimeter tested), but although it states "Red, charging, green, not charging," when I plug it in, it does not change to red.

I also am unable to get the battery to full charge, so it does appear that the charger isn't doing its job.

does anybody know of a charger they have purchased / used that garuanteed to work please?

thank you

Brian

 

[thelarkbox]

NOT AN EXPERT!!..
Did the battery sit for a long period without a charge? if so something like the bms itself could drain the battery or a single group of cells below the level its considered safe to recharge??

If your battery is at a low voltage you may need to open it up and confirm that all the cells are holding at least a viable voltage? check online for minimum viable voltage iirc its 2.2v??

leaving the battery plugged into the charger for a few hours while keeping an eye on the charger and battery temperatures might allow the bms to trickle balance the cell groups IF cell group imbalance is the problem??

 

[Ghost1951]

Has you battery been stored a long time without use?

This symptom you describe often comes up with bikes that have been left a long time without charging them. In those cases the cause of the no charging e-bike is that the voltage of some of the cells has fallen below the level at which the Battery Management System is prepared to charge them. Over discharged cells can sometimes be recovered and sometimes not.

EDIT:

I see Larkbox has given you a good answer while I was messing about typing and being distracted by other people.

 

[Ghost1951]

Like Larkbox said, try leaving it plugged into the charger for a few hours (supervised) and if no joy, disconnect for a few minutes and do it again, and again. It might come back, or it might not.

Failing the above, you will either need to scrap the battery, or open it up and do some testing of the voltages of the individual groups of cells. My bet is that some of them will be at reasonable voltages like 3 volts and above, and one or more groups will be low - like 2 volts. It is these low groups that are stopping it charging.

There are ways to interact with these low groups but some members do not like that being talked about. Those low cells can be quite damaged. Sometimes though - they are not and will be recoverable.

 

[brackb01]

Thank you, I had considered this possibility, and yes the nike has been in the shed for quite a while, but I wanted to pursue the theory that maybe the chargers are faulty, first. Are cells easy to replace?

 

[Nealh]

If your old charger was a simple generic two wire pin out charger the same as the new one then there is nothing wrong with the new charger if one sees 42v via it's charge lead .
These chargers are dumb chargers and only charge if the battery BMS accepts a charge thus allowing the charger to charge .
It isn't the charger that allows charging to proceed but the BMS which needs to swtich on to allow it to do so.
The BMS is a battery pack safety device and if it reads an anomally with a voltage it simply doesn't allow or accept a full charge.

A red led does indicate charging , where as a green led can indicate charge process finsished , charge process balancing or simply BMS not allowing charge process. Which of the above it is depends on the pack voltage.

If the battery isn't fully charged (a voltage reading would help), it usually means the battery s unbalanced (too far out of balancing for the BMS to act on), a cell fault indicated by non charging or even a wire fault.
If out of balance or there is a low suspect cell group the BMS will stop charging once the majority of cells hit 4.15 - 4.2v.
Practically all BMS top balance however the balance margin is small and any battery likely more then 0.5v out of balance will not balance via the BMS .

Any voltage over 41.4/41.5v can be accepted as a fully charged battery.

 

[thelarkbox]

Thank you, I had considered this possibility, and yes the nike has been in the shed for quite a while, but I wanted to pursue the theory that maybe the chargers are faulty, first. Are cells easy to replace?

Not really, generally bike batteries are 18650 or larger cells spot welded together.
and require SAFE procedures and equipment like a spot welder to work on at the cell level. - also considerations like the fact new cells will not match the charge discharge profile of older cells even if branded exactly the same, so when coupled to the older cells can accelerate the deterioration of the original cells (laymans understanding..) -
Chances are VERY high that if working on your first bike battery YOU WILL make a dumb error and short out the cells in a dangerous way. And that could be VERY BAD!!

Since its a one off situation and depending on just what voltage the battery has left in its cell groups, a recharge of each parallel group to 4.2v to 'reset' the battery might be a viable option, but you would always have your doubts about the battery moving forward..

Bad news is if the battery is unrecoverable, its a loss..

 

[Nealh]

What the Op hasn't done is told us the battery final voltage, as always someone likes ot blame the charger without knowing how a BMS works or it's limitations in enabling balancing.

Balancing typically is carried out at approx. 100mv so any cell out of balance can take several hours if it is within balance voltage range , that balance range may be quite small and 0.1 - 0.2v may be typical .

Anything out of balance of a greater margin then 0.4v ususally requires manaul intervention and often means opening the battery to investigate.
A series of ten cell group voltage readings will give one an idea or the answer to the issue.

Often if a battery after long standing is out of balance then it is down to weak cell group or the BMS draining one or two cell groups below or near LVC.

 

[Nealh]

Working on a battery with most tools one shouldn't do much damage unless one leaves the cell group ends unprotected.
Even then most thin buss material or thin bits of wire which can cause shorting will soon burn thru or glow quite bright even go bang but can be removed quite quickly.

One shouldn't be useing metal tooling at if all if possible, wooden lolly sticks are good as are wooden kebab type skewers, other wise plastic tools. If any metal tools are used they should b epalced well away form the work area.
Any metal jewellery needs discarding , so rings , wathches , bracelets neck laces and even earings.

 

[thelarkbox]

However IF the battery is just below the voltage the bms registers as too low? then a recharge should be fine.. the red flag is finding a group of cells with a significantly lower voltage than the others in the battery,, and it the group has dropped way too low.. thats bad news..

 

[Nealh]

Repairing batteries is only worthwhile as a learning process and to physically see how the process works.
Building repairing doesn't save money as typically a good arduino type controlled spot welder will cost around £200 - £300 without the battery power source required.
One can buy cheap spot welders to do the odd spot weld here and there but they have no control over power/intensity od weld delivered.

Typically before spot welding one should test on old cells or use craft knife blades to test spot weld intensity for burn thru and weld strength.

 

[Nealh]

However IF the battery is just below the voltage the bms registers as too low? then a recharge should be fine.. the red flag is finding a group of cells with a significantly lower voltage than the others in the battery,, and it the group has dropped way too low.. thats bad news..

The only voltage the BMS will use for charging indication is only at cell level and not pack level in case anyone doesn't understand the reason why.

BMS have an upper voltage (HVC) of 4.2 v - 4.25v where above 4.2v any voltage usually will be bled off .
It is the lower voltage level (LVC) where most issues occur of non charging and this is nothing what so ever to do with two wire generic chargers.
BMS's LVC will vary some may allow charge from 2.9v others will vary from 3v - 3.2v even 3.3v.
Vary often only batteyr surgery may giv eone the real answer to the issue.

 

[Ghost1951]

If the OP is careful and is technically competent to examine the cells in the opened battery, he may find the low cell group or groups are just below the 2.2v sort of level which would cause the BMS to refuse the charge. If the bad groups are very low or totally dead, there is no point in going further. The cells are ruined.

If the bad group is about 2 volts near as dammit, and the rest of the groups are reasonably similar to one another, he could carefully charge the low group with a 4.2volt lithium charger, until it is at the same voltage as the other groups and then he will likely find the ordinary charging process will work. Lifting a cell group voltage with a small charger will take some hours.

I bought a small lithium charger of the wall wart type on ebay, and it cost about £7. It only gives slow charge - maybe 400mA, but it has worked well for me.

You can tag the charger wires onto the nickel strips of the affected cell group. DO NOT LINGER with the soldering iron on the nickel. You don't want to heat up the cells, just tag the wires onto the nickel with a quick dab of the fluxed iron. Choose a bit of nickel in between the cell welds so it is just the nickel strip you are BRIEFLY heating. It only takes a moment with an iron of about 30 watts or a bit more.

TAKE SERIOUS CARE not to cause a short circuit while the battery is open. You REALLY don't want to do that. Approach everything as if it was High Voltage. It isn't of course, but the battery can put out a very large current of you do something daft. This might cause a fire or other harm.

 

[Nealh]

From my experience 2.2v is far too low for any BMS to consider charging (unless a smart BMS where one has some input in the parameter settings ).
My LG BMS on the swizzbee allowed charging at 2.9v but typically most generic china ones I have had need to be in the 3v - 3.3v range.

 

[Ghost1951]

From my experience 2.2v is far too low for any BMS to consider charging (unless a smart BMS where one has some input in the parameter settings ).
My LG BMS on the swizzbee allowed charging at 2.9v but typically most generic china ones I have had need to be in the 3v - 3.3v range.

That is entirely correct. The BMS won't charge it.

I was suggesting he do what I did which was to attach a small, wall wart LITHIUM charger to the low cell group, and raise the voltage with that, until it is the same level as the other cell groups. Then, the BMS will allow the whole pack to charge.

Recently, I was doing an extreme range test on my 3 year old 36V, 13Ahr battery. It has a cell group which sometimes goes lower than the others and gets out of balance.

As I was climbing a hill after a 43 mile range check, the pack voltage was dropping to 33 volts (LCD screen reading) and then the bike suddenly shut down and I had to pedal home under my own steam. I examined the pack and the dodgy group was down at 2.7 volts, so I attached my small 4.2 volt lithium charger to it and lifted the voltage to the same as the rest which were at around 3.5v off load.

This sorted it. Probably one cell in the group is weak and I need to often re-balance the pack, but overall, the range is pretty good for what I need so I just work around the problem now and again. I did once think my out of balance issues with that battery might be down to the BMS drawing micro amps from one cell group while out of use, but even if I balance the pack so they are all the same, that group rapidly drops a wee bit lower than the other cell groups. It will happen in ten miles of riding that this group drops 0.1 volts lower than the others even when they started out identical. I think most likely, one group has a lower cell capacity cell in it, so it soon drags the others in the group lower.

 

[brackb01]

Blimey, thats some responses!!!!

I think I will probably not tamper, even if i only get to 50% charge its enough for my needs at the moment. i'll try and run the battery down and see if that makes a difference, if not, i'll have to invest in a new battery.

this is an astounding forum!!

 

[Ghost1951]

Blimey, thats some responses!!!!

I think I will probably not tamper, even if i only get to 50% charge its enough for my needs at the moment. i'll try and run the battery down and see if that makes a difference, if not, i'll have to invest in a new battery.

this is an astounding forum!!

I hope you will let us know what happens when you try to use the bike. From what you said, I think it won't charge up at all.

You did not respond to Neilh's question about the overall voltage of the battery pack at the output terminals.

 

[thelarkbox]

I also am unable to get the battery to full charge, so it does appear that the charger isn't doing its job.

Missed this in the OP, it charges, but not Fully!! DOH!

if only charging upto 50% @brackb01 ? I take it thats going by the bike display or battery leds? use a multimeter on the battery output terminals for a real reading..
could be a dodgy led circuit board ??

but if the charger is stopping charging and your battery has a low voltage afterwards? 50% you say? its probably just down hill from here for you with that battery and it will continue to charge up with less and less capacity.

you need a new battery..

 

[thelarkbox]

How old is the battery?? if bought from a uk dealer its probably got 12-24months of warranty?

Whats the bikes history?

 

[Ghost1951]

Missed this in the OP, it charges, but not Fully!! DOH!

if only charging upto 50% @brackb01 ? I take it thats going by the bike display or battery leds? use a multimeter on the battery output terminals for a real reading..
could be a dodgy led circuit board ??

but if the charger is stopping charging and your battery has a low voltage afterwards? 50% you say? its probably just down hill from here for you with that battery and it will continue to charge up with less and less capacity.

you need a new battery..

Might be, but this can also happen when the battery is out of balance. What happens is that the fullest cells groups reach 4.2 volts, while the weakest ones or the most out of balance ones are still well down. Then the BMS ceases charging all the cells, but the difference between the full ones and the half full ones is so big that the balance function on the BMS is never going to catch up and balance them all at 4.2v.

My battery did that the first winter I had it. I had left it at about 36 volts in November, and checked it now and then but didn't charge it up. Over the winter, one cell group went low and when I charged it up in the spring, I set off riding and the bloody thing switched off about three miles later. 9 groups of cells were up around 4.0 v and one was down at something like 3.2v. My only solution was to spend hours and hours charging that group up slowly with a small charger to 4.2v.

I can still get 43 mile range out of that pack, though the weak cell group does need some attention now and then.