Battery dies quickly, next stop scrappy ?

[egroover]

Hi all,

I have a 5 year old 36v 10ah Hailong battery (Yosepower LG M1 cells) that I very rarely use now I have higher capacity batteries.
I top up the charge on it every couple of months as I do for all batteries if not used often. The last time I used it on the bike a few months ago it was working fine.
Now when used it starts off as showing fully charged 41.6v on my display but as soon as I start riding it drops down very quickly 38,36,34,32 ect volts within a minute or two of riding, and after about 3 mins it's turned itself off.
When I then start charging it it doesnt charge at the full rate which for my charger is about 100w...it starts off at about 60w and drops down quickly and within 20 mins or so the charger thinks it's fully charged and stops charging.
The display is showing 41.6v or so as soon as I start charging .
I read somewhere that it could be a bank of cells has been shutdown by the bms ? At the moment I'm trying to charge again but this time with a rechargeable fan plugged into the display usb port and the display set to always on to try and extend the charge time in the hope that it brings the cells back up to voltage.
If that fails, I think its off to the tip with it, I don't fancy taking it apart, it's old ish and low capacity so I don't think worth saving by unsoldering cells,testing, bms replacement etc
Anything else anyone can suggest I can try ?





Thanks all

 

[guerney]

I'm curous about what your Yose battery pack looks like, opened up... but I'm not suggesting you do so, risking being zapped.

 

[Tony1951]

This might or might not help, but could the battery be badly out of balance in the voltage between the series cell groups?

I have a battery which went way out of balance one winter when I left it alone because the overall voltage was about 38 volts. I didn't just leave it in the garage unloved and unattended. I checked the overall voltage about once a month. Come the better weather, I charged it up to about 41 volts (the charger cut off after a short period of charging and I set off on a nice long ride. After about two miles, the thing switched off. Overall, the battery had a decent voltage, but it just would not go.

I took off the battery cover and measured the voltages of each group of cells. Most were at about 4.1 or 4.2 volts. One of them was at about 3.2volts.

I had to manually intervene with that group and take it up to a full charge and then I could ride the bike about thirty miles and it was still going well.

There is something wrong with a cell in that group, or the BMS which is draining away charge from that group over time. About once a month, I leave it charging for many hours after the green light comes on and that group gets charged up the same as the others. The BMS can re-balance the battery because they are all not too far from one another in voltage.

May help. May not, but you won't know unless you or someone else opens the case and measures the voltage of each parallel group of cells, to see if they are reasonably close to one another.

In my case, the BMS stopped charging when the highest group of cells reached 4.2 volts. That is what it is supposed to do. It was also cutting off the battery current to the motor when the lowest group of cells reached about 3.2v. Again - that's what it is supposed to do.

The only practical solution for me was to solder some wires to the + and -ve end of the lowest charged group and connect a small lithium charger to that group and leave it to charge for about 12 hours, until it was the same as the other groups. I didn't like having to do this but it was the only way to sort it out because that group had got so far out of wack in comparison to the others.

I have no idea how technically adept you are - sorry about that, but do take care if you attempt this. You probably know to do that, but since I don't know where you are at, I feel obliged to give the safety warning.

 

[saneagle]

This might or might not help, but could the battery be badly out of balance in the voltage between the series cell groups? I have a battery which went way out of balance one winter when I left it alone because the overall voltage was about 38 volts. I didn't just leave it ion the garage, I checked the overall voltage about once a month. Come the better weather, I charged it up to about 1 volts (the charger cut off after c short period of charging and I set off on a nice long ride. After about two miles, the thing switched off. Overall, the battery had a decent voltage, v=but it just would not go.

I took off the battery cover and measured the voltages of each group of cells. Most were at about 4.1 volts; one was at about 3.2volts.

I had to manually intervene with that group and take it up to a full charge and then I could ride the bike about thirty miles and it was still going well.

There is something wrong with that group or the BMS which is draining away charge from that group over time. About once a month, I leave it charging for many hours after the green light comes on and that group gets charged up the same as the others.

May help. May not, but you won't know unless you or someone else opens the case and measures the voltage of each parallel group of cells, to see if they are reasonably close to one another.

In my case, the BMS stopped charging when the highest group of cells reached 4.2 volts. That is what it is supposed to do. It was also cutting off the battery current to the motor when the lowest group of cells reached about 3.2v. The only practical solution for me was to solder some wires to the + and -ve end of the lowest charged group and connect a small lithium charger to that group and leave it to charge for about 12 hours. I didn't like having to do this but it was the only way to sort it out because that group had got so far out of wack in comparison to the others.

It's a good logical analysis except for one point: If the battery were out of balance, like yours was, the total voltage when charged would not reach 41.6v. Only 0.4v is missing, so the worst case should be that one cell or only reaching 3.8v; however, OP doesn't say when the voltage was measured. If it were hot off the charger, the bleed balancing system wouldn't have time to bleed down the high cells, so one could be much lower, in which case you're correct.

Some batteries use one cell to power the BMS, so if you don't use the battery for a long time, one cell can go right down. Occasional charging is not enough. The balancing system works on the principle of a little and often, which is why you shouldn't adopt the bad practice of only charging to 80%.

The logical thing to do is open the battery and check the voltage of the individual cells. It may well be scrap, but should have plenty of good cells to harvest for powerbanks.

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[Tony1951]

It's a good logical analysis except for one point: If the battery were out of balance, like yours was, the total voltage when charged would not reach 41.6v. Only 0.4v is missing, so the worst case should be that one cell or only reaching 3.8v; however, OP doesn't say when the voltage was measured. If it were hot off the charger, the bleed balancing system wouldn't have time to bleed down the high cells, so one could be much lower, in which case you're correct.

Some batteries use one cell to power the BMS, so if you don't use the battery for a long time, one cell can go right down. Occasional charging is not enough. The balancing system works on the principle of a little and often, which is why you shouldn't adopt the bad practice of only charging to 80%.

The logical thing to do is open the battery and check the voltage of the individual cells. It may well be scrap, but should have plenty of good cells to harvest for powerbanks.

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Thanks.

I can't swear to the exact accuracy of my account of the overall battery voltage or the low point I found. I made the comment from memory the best I can. This was a couple of years ago, so you are probably right on the your remark above in the first paragraph of your response.

Your point about some BMS boards using one cell group to power the BMS may very well explain how my problem came about and continues. I am also unsure of whether the battery was always left with its on board power switch off or on, and / or whether that might effect the draining of one cell group if the BMS is connected as you mention.

I modified things a bit (I don't recommend this, but it is what I did) by taking the two thin wires I soldered to the bad group via two small value fuses to the outside of the case where I have two insulated contacts so I can measure the voltage of the bad group easily. This means I can also rectify a badly out of balance situation if I need to, without stripping the battery case down or even taking it off the bike.

 

[guerney]

@egroover - To measure cell bank voltages, I got needle probes because it's all so darn tiny.








My eyesight is awful, and I almost crossed the probes at one stage... so I covered all but the tips of the proves with heatshrink...




...then bought a big magnifying glass with LED ringlight for next time! Thanks largely ongoing AliExpress Winter sale...

 

[Nealh]

Check the cell voltages via the bms multi pin connector , though my guess is the batteries life is over for general use. As it charges to 41.6v then collapes in ues is a good indication of a knackered battery when used, what you don't mention is how much current is being drawn when it collapses.

I have an two old Woosh (8 y/o)14.5ah dolphin case batteries that only charges to 41.4v which will sag a lot above 6a draw but below that still can get 20 - 25miles or so, all cell groups register 41.4v . I don't use them now for my bikes but do use them for other 36v DC gadgets where the current load is only 4a or less, for which they still give sterling service.

 

[egroover]

Hi all

Thanks very much for all of the suggestions, I think @Tony1951 you are most likely bang on the money with your explanation, I think I have the same issue as you did.

I've had the battery on 'charge' as explained earlier for most of the day, it now reads 41.8v hot off the charger, I'll see in the morning what this has dropped down to rule in/out @saneagle prognosis

As mentioned, I don't fancy taking the battery apart, with my sausage fingers I'll end up shorting something out requiring new boxers, I'll leave that stuff to the more adventurous (and more capable) amongst us. But I do appreciate the advice, I now know that the only way to tell for sure is to measure each bank of cells (thanks @Nealh and @guerney It does sound like though it's a lost cause and it's off to the tip with it.

I'm happy to take the hit on losing this one, it's my own fault, the temptation of new 17/20ah Hailongs from Aliexpress for £200 or less got the better of me over the last couple of years, hence why my older batteries got neglected (not neglected as ion not charged up regularly, but not used in anger on the bike)

Cheers all

 

[egroover]

Voltage down to 41.3 when powered on this morning, so 0.5v drop compared to when hot off the charger. I always see a difference of about 0.2 or 0.3v I think on any of my batteries when just off the charger and a day or so later, Im guessing this is normal ?
When the weather improves will head off for a ride to test, and will try lower power setting as well, but not too hopeful

Cheers

 

[Nealh]

If one gets a better range and less sag in lower power/PAS modes then one can ascertain that the battery is worn but useable however one may only see this if the controller uses current control where current is incrimental with PAS selection. If speed control is used then current will be much the same in all PAS selections and one will not see much difference in volatge sag.

With my pair of Woosh dolphins I could still manage nearly 40 miles in PAS 1 or 24/25 in PAS 2 , using PAS 3 would soon dip to 15 miles and a throttle use would cause cut out once the voltage was below 60/70% . If I lived in a hilly locale then then the batteries would have been of little use .

As I mentioned they now provide power where I have no AC power and can provide the DC power I need for other items in the garden at low current of approx. 4a. At 8/9 years old they still have good usable power for my other needs so certainly am getting good value out of them. Cells are the excellant Sam 29E's which are quite good in 5p configuration, in larger batteries with more parallels they are £4£ the best 18650 on the market.

 

[egroover]

So just got back from a 45 min ride (dodged the showers) and started off on lower level assist at about 100w. After 10 mins Increased it to about 150w assist. I could see that.under.load the voltage reading would sag by 2-3v and then recover when freewheeling. When I increased assistance to 200w the voltage reading dropped quickly, so I switched vack to 100/150 w assistance. So managed to get about 45mins on variable assistance at lower levels. A final little hill finished off what I had left when hovering around 31.5 or so volts.
Just popped it back on charge, and the charger is drawing 110w as normal. The display showed at 36v when I plugged in the charger (to get the battery back on, and after I removed the charger again) so it would seem it's not able to use all the charge in the battery as it's starting off at 36v ?
Once it's finished charging today, I will see from my smart plug with energy monitoring how much the flat battery takes to fully charge. I think the battery is not going to be that useful to me if it collapses under heavy load or can only have available, say 5ah of the 10ah capacity ..
But certainly progress since yesterday, maybe a few discharge, recharge cycles may help recover it....




Cheers all

 

[saneagle]

You have two choices: Open it to diagnose and fix it or chuck it. There isn't much you can do from the outside. There is nothing on the inside that can zap you.

 

[Nealh]

One needs to measure the ten cell voltages at both charged and discharged levels to see what is occuring, one way or another one should give an idea as to what is wrong.

 

[egroover]

You have two choices: Open it to diagnose and fix it or chuck it. There isn't much you can do from the outside. There is nothing on the inside that can zap you.

Well yes, those were my 2 choices yesterday, and as I didn't think it was worthwhile trying to fix even if I had the expertise, spot welder and replacement cells/bms for an old low capacity battery it was gonna be dropped off at the tip today, but today it would seem I now have a third choice in that the battery can be usable for up to 10.mile rides at 100-150w assist levels, which maybe may improve slightly after a few charge cycles...will probably still ditch it anyway as have other newer high capacity batteries, but if nothing else, it's been an educating experience.
Cheers all

 

[Nealh]

Before I dispose of a battery , I try and find out the reason for the poor performance but in most cases I already know the batteries short comings from past use and diagnosis.

 

[guerney]

@egroover - does your battery manual say anything about how balance charge is activated? Perhaps balancing could occur after a series of charge/discharge cycles plus a long balance charge? I say take it off! Show us your bits! (sorry, force of habit) but don't do it in an old pub with one of the nekkid nickel stripped sides of your unpeeled battery making direct contact with the conductive surface of a copper table.

 

[Tony1951]

Before I dispose of a battery , I try and find out the reason for the poor performance but in most cases I already know the batteries short comings from past use and diagnosis.

Give that man ten gold stars! )

I could never just 'chuck' a battery or anything else without trying to find out exactly what went wrong with it, and whether I could fix it. Then, I would have a think about what else it could do for me.

The battery may be improving, so I would give it a number of charge discharge cycles. I would also make sure it wasn't just way out of balance (like mine was). Failing all else, I would take it to bits and re-use any cells that were still good (of which there will be many).

I use old cells in led torches. If you have a torch with those little alkaline battery holders which take about three AAA alkalines, all you need do (if the torch is the right size) is to wrap your salvaged battery in a bit of old plastic bag, and stick in your 4v lithium battery. Being a really tight old git, I love to find a way to re-use a half good battery or whatever. The other thing of course, as someone mentioned earlier, you can use them in those USB power banks.

Lithium is a rare and very valuable material. It should not be just chucked away.

 

[Nealh]

Same here all old batteries have cells dismantled for torch use or other smaller 12v packs .
My pair of dolphin batteries and an old Sam 22f pack (all 36v) still hold good voltage but sag with heavier current draw so are used as DC supplies for my beekeeping electric centrafuge extracator which only demands 4a max.
Some 8/9 years later my 36v Sam 26f packs still provide sterling service, now reconfigured to two 12v 3s 6p packs they provide power for a diy beevac using a fermenting bin and my vapouriser pans to administer treatments via vaping organics acids .

To much stuff is thrown away when it still has plenty of life left .

 

[egroover]

Thanks all. Had the battery on charge for 8 hrs today, my energy monitoring smart plug tells me it took 0.2kwh during that time, so about half of the original capacity it would seem is now usable.

Will try a few discharge and recharge cycles to see if it improves

Cheers

 

[Lily-YOSEPOWER]

Hello, as lithium batteries age, they may experience reduced mileage over time. After 5 years, its lifespan is likely coming to an end. To identify any issues, you would need to test the voltage of each battery cell, but this might not be something you want to do. Therefore, I suggest replacing the battery with a new one for continued use.