Trying to increase my batteries longevity but did i actually destroy it doing so?

valsam

100 mW
Joined
Mar 27, 2018
Messages
36
My first ebike and my first battery(48v 13ah chinese cells) so i was trying to follow what i read on the net for li ion battery longevity,and for 1 year that i have my battery i almost always charged to 90%(53v) except once a month when i charged to 100% and tried never to le the batterey drain beneath 10%( the 90%-10% =80% use!)!
Now my baterry doesnt go above 54v on a 4ah charger and 52v on a 2ah charger and is totally unbalanced even if i leave it on the charger for a whole day ,this is the voltage of the 13s:
1)3,75 V
2) 4,13
3)3,95
4 3,85
5)4,18
6)4,19
7)4,21
8)4,23
9)4,20
10)4,22
11)4,22
12),4,22
13)4,22
I went to a couple of battery techs and both told me that it whas my fault that the battery is like this because charging the way i did i didnt let the BMS do its work balancing the cells and by doing so when i unpluged the charger the first series had charged and the others where lower charged so the first series took all the abuse and that is why they are in this condition and there is nothing i can do about it any more!
I asked them if they can manualy balance the 1,2,3,4 series and they both told me that yes ,it will cost me save your money because it is just a waist of time,the cells might charge fully but again will drop to 3,75v .3,95,....,.....,because the cells are bad!
I asked if they can change the bad cells and they both told me no because by putting in new batteries in the pack the pack will go bad quickly again!
I had the BMS changed with an excact same one i had laying around but again i got the same readings,could it be a problem caused by the BMS and both my BMS are faulty?
Any ideas anyone?
And is it a fact that by charging the way i did i caused the problem to the battery?
And if yes what is the proper way to charge to get the most cycles out of a battery?
 
Your BMS is not balancing your pack. It's only bulk charging

Get a small 12V filament bulb from an auto parts store, solder wires onto it's two contact points, and attach the two wire ends (alligator clips?) To the positive and negative of the cell groups that are 4.22V.

A large bulb (*headlight) will overheat your pack from high current, and a 12V LED bulb will not work under 10V

Drain them down to the lowest cell group, 3.75V. Repeat until all the groups ate at 3.75V

Any cell group that sits at 4.15V or higher for any length of time will lose capacity. I dont know if your cell groups are permanently damaged. It remains to be seen.
 
The battery likely has mismatched cells from the factory, which are the reason it became so disbalanced in the first place.
This is unfortunately very typical for cheap batteries.

The disbalance is probably so intense that it would take multiple days to balance the battery. *if* the balancer works.
Seeing cells at 4.22v indicates you have a poor quality BMS, which may have damaged some of your cells, and may do further damage if you put the battery on a charger for multiple days.

Spinningmagnets' idea of discharging the strong cell groups is a good idea but your pack may have a chronic problem, and manually balancing it may only be a temporary fix. Personally i'd be worried about the safety of this battery and dispose of it; there are way too many problems going on here to consider it safe to use.
 
neptronix said:
The battery likely has mismatched cells from the factory, which are the reason it became so disbalanced in the first place.
This is unfortunately very typical for cheap batteries.

The disbalance is probably so intense that it would take multiple days to balance the battery. *if* the balancer works.
Seeing cells at 4.22v indicates you have a poor quality BMS, which may have damaged some of your cells, and may do further damage if you put the battery on a charger for multiple days.

Spinningmagnets' idea of discharging the strong cell groups is a good idea but your pack may have a chronic problem, and manually balancing it may only be a temporary fix. Personally i'd be worried about the safety of this battery and dispose of it; there are way too many problems going on here to consider it safe to use.

I dont think that the battery had mismatched cells from the factory because after a month of use i took it to this battery guy and he mesured the Voltage at each of the 13s with battery nearly fully charged and all 13s where from 41,5v up to 41,7v max,the battery guy today also told me that up to 42,2-42,3 is ok and that most of his battery packs with branded cells like samsung ,lg,panasonic also show these numbers!
Also today i left the battery to charge for 9 hours on my 4a charger and for the first time in a long while it showed 54,4v charge with charger connected and after disconection from charger it showed 54,2v,is this a good sign that maybe the bms has something to do with the problem and that this one is not perfect but does a slightly better job or maybe even a bad and dangerous thing if the cells that were up to 4,22v may have gone to 4,5v and that is why the increase in voltage and not a case of the 3,75v rising higher?
Should i try to leave the battery on the charger lets say for a whole day to see if any balancing is fixed further more ,is this a safe thing to do?
 
Rather than almost never charging passed 90%, what would work better with cheap cells is to usually charge to 100% - but only do it right before a ride. That way the cells aren't stressed by sitting for long periods at 100%, but they do get equalized often - assuming, as noted, that your BMS actually does have a proper EQ function...
 
I would get an active balancer, one of the large ones.not the small cheap ones. And have that connected while charging to balance the pack. Sometime thats the only way to balance the pack and then monitor it.

Just because it went out of balance doesnt mean the pack is bad, get it balance and hopefully it will be good to go. If the cells keep going out of balance then you might have several cells that are weak. Even then it won't be a problem if you use the pack right away after charging it, instead of letting sit several days.
4.22 volts is high but its not going to destroy the battery. My foxnovo charger charges to that voltage.

It would be a good idea to get some sort of monitor to use while charging, I use the tenergy cellmeter-6 lipo checker, it will sound an alarm if the cell voltage goes above 4.22 volts, you would need several for you large pack. This meter since its lcd, you can just leave connected all the time and will warn you if a cell starts getting to low from self discharge. You can find on amazon for 11 dollars. I don't trust the bms to stop the charge everytime, I had some cells go almost to 4.30 volts because of a bad bms.

tenergy checker.jpg
 
valsam said:
this is the voltage of the 13s:
1)3,75 V
2) 4,13
3)3,95
4 3,85
5)4,18
6)4,19
7)4,21
8)4,23
9)4,20
10)4,22
11)4,22
12),4,22
13)4,22
Couple of things:
- 4.23V isn't that bad. It isn't great for the cells, but it isn't the end of the world either. Don't stress about it right now.
- Your multimeter might not be that accurate anyway. 0.02V is 0.5% of 4V.

What I would do:
1. Disconnect the BMS, and individually charge each parallel group up to 4.2V using an RC charger or lab PSU.
2. After an hour, measure each group voltage.
3. Wait a couple of days and remeasure voltage of each group. If no group has significantly dropped, they're probably ok. If some groups drop, they probably won't perform very well under load. I would dispose and start again. Alternatively, if you're desperate, then just make sure you use the pack directly after charging.
4. Measure the raw output of your 13S charger. Should be around 4.2x13=54.6V.
5. Reconnect the BMS to the pack.
6. As previously mentioned, you should charge to 100% every charge to start with, to give the BMS enough time to maintain balance.
7. Continue to monitor group voltages regularly, and if they're staying balanced, you can reduce the number of 100% charges.

As mentioned, a pack made of good quality matched cells goes out of balance very slowly. A pack made of cheap unmatched cells goes out of balance quickly. You need to get some data on your pack over time to determine how rigorous your balancing regime needs to be.
 
If the pack you have tends to become unbalanced, consider adding one of these:
https://www.ebay.com/itm/4S-8S-13S-20S-Lithium-Battery-Active-Equalizer-Protection-Board-Balance-Board/383907966158

This is one example out of many such boards that are available.

It will balance the cells whenever an imbalance appears, rather than only at the top charging voltage. It can/should be used in combination with a working BMS board. (Yours isn't working.)

Matching, inherently balanced cells are best. If that's not what you have, you do what you need to do to get the potential that remains in your battery.
 
valsam said:
I dont think that the battery had mismatched cells from the factory because after a month of use i took it to this battery guy and he mesured the Voltage at each of the 13s with battery nearly fully charged and all 13s where from 41,5v up to 41,7v max,the battery guy today also told me that up to 42,2-42,3 is ok and that most of his battery packs with branded cells like samsung ,lg,panasonic also show these numbers!

The only way to properly find out if cells are matched is to run a cycle test.
The ghetto and not exactly accurate, but 'good enough' way to do that is to fully charge your battery until it's balanced, discharge it until it hits LVC, and measure the voltages of each cell when the pack considers itself drained. The differences in the cells' voltages will reveal differences in cell capacity.

Measuring the cells after a full balance charge tells you that they balance charged successfully; not anything about capacity. So your battery guy seems to not have done his homework.

4.22v per cell should only be seen during charging. They should settle to 4.18ish. A cell that remains at 4.22v ~15 minutes after being charged is one that was overcharged and will have tiny bits of it's life shaved off each time you charge it that high. You don't want to see that. That's a sign of a BMS that's not doing it's job.

Your cells are SUPER disbalanced and putting the pack on a charger for multiple days may help if the BMS works, albiet slowly.
 
I am starting to beleive that maybe my problem is not bad cell or cells but more a matter of a very unbalanced battery pack!
As i wrote in my post once a month i charged to 100% but did i actually do so?
I charged until the green light on the charger had turned green ,that is what i thought was 100% and except for a couple of times that i forgot the charger still on after green but that was only for a couple of hours at the most!
So have i ever balanced my battery ever charging this way for a year?
I will leave the charger on for 10-12 hours and tomorow i will measure the 13s voltage again to see if this 54,4 that i get now is a result of that the low voltage series 3,75,3,85 and 3,95v have risen and have closed the gap between them and the 4,22v charged series or is it because the 4,22v series have gone to 4,5V and that is why i have a 54,4v pack reading?
Someone posted this at EBR forum :Some batteries don't balance. Those that do will take a long time. It might take a week if you really had cells that were 1/2 volt apart. Usually, the cells in a new, healthy battery are within .10 volt of each other.
Mine are 1/2 volt apart ,so tomorow when i open the case and messure and if i see that the 3,75V sereis has risen should i leave it on the charger for a week ?
 
sometimes it can take weeks

60-80mA isn't much energy dissipation

especially poorly balanced series strings

and you also need charger that

restarts charging after bleeding down

and bms resumes charging

not all chargers do this
 
A charger of a lower than ideal voltage could prevent a BMS from beginning to balance.

So many things could be going wrong here.
 
Opened the battery again after 4 times 10-12 hour chargings and the result whas not what i was hopping for ,the new VOLTAGE COMPARED TO THE OLD READINGS ARE:
OLD NEW
1)3,75 V 1)3,90V
2) 4,13 2)4,19
3)3,95 3)4,00
4 3,85 4)3,95
5)4,18 5)4,22
6)4,19 6)4,22
7)4,21 7)4,23
8)4,23 8)4,24
9)4,20 9)4,23
10)4,22 10)4,24
11)4,22 11)4,24
12),4,22 12)4,24
13)4,22 13)4,24
So what does this look like ,bad cells or a bad bms?
In a couple of days a friend of mine is waiting for a 13S 50A BMS so should i hook that up to my battery to see if anything changes or is it hopeless ?
The battery tech guy told me that we should try the new BMS and if that dont work then a solution is to disasamble the battery and messure each cell find the bad ones and make smaller battery with the good ones 13s 4p or 13s 3p depending on how many bad cells there are!
Is it worth it?
Already i spent about 20 euros on voltage testings and BMS changes ,will spend another 10(very very friendly prices!) for the new bms installation and if that dont work that the tech told me for the dismantle of the pack testing the batteries and rebuild about another 60 so that makes a total of 90 euros and if i ad a BMS that is over 100,or is probably better to just buy a pack like this one: https://www.aliexpress.com/item/4000290976528.html?spm=a2g0o.detail.100009.2.60e86bef7AIXjA&gps-id=pcDetailLeftTopSell&scm=1007.13482.95643.0&scm_id=1007.13482.95643.0&scm-url=1007.13482.95643.0&pvid=869c83b0-edb6-46f1-8f40-b7b315d75bb1&_t=gps-id:pcDetailLeftTopSell,scm-url:1007.13482.95643.0,pvid:869c83b0-edb6-46f1-8f40-b7b315d75bb1,tpp_buckets:668%230%23131923%2331_668%230%23131923%2331_668%23888%233325%239_668%23888%233325%239_668%232846%238111%231996_668%232717%237559%231_668%231000022185%231000066059%230_668%233480%2315683%2339_668%232846%238111%231996_668%232717%237559%231_668%233164%239976%2347_668%233480%2315683%2339 that is 48v 12,4ah that costs € 149,45 and has samsung brand cells and BMS and just throw it in the case i already have ?
 
If this was measured not during charging, your BMS is not working, and has overcharged some of your cells into the danger zone.

I would absolutely run this bike around the block a few times to drain the cells, as a cell resting at 4.24v for a long time could explode. Do this immediately.

A full charge and discharge graph of the cells capacity would tell you the state of the cells. However, this pack has been damaged now and is a liability. I would not bother doing these tests. This pack is likely a fire waiting to happen from past and current abuse via the non-functioning BMS.
 
This was measured half hour after charging and yes i took the bike out until the battery droped from 54,1 54,2 down to 52,0v.
And why may i ask is the battery a liability,all BMS"s have Over-charge protect voltage at : 4.25V so the cells wont damage, am i wrong?
 
Okay, that's bad and means the cells were at even higher voltages under charging, and had settled to 'above the rating'.

I don't know of any cells that are happy to sit at 4.25v except hobbyking HV's. Over-charge protection should always be lower than 4.25v, since 4.2v is the absolute max safe voltage for 99.9% of any ~3.6v nominal chemistry... and once you go beyond that, damage can happen that leads to internal changes and eventually explosion from an internal short.

If you can tell me what cells are inside your pack, we can look up the spec sheet and find the maximum charged voltage. But i really doubt it's 4.25v.
 
They are these Chinese cells my friend https://www.aliexpress.com/item/4000189097525.html?spm=2114.12010612.8148356.2.7594530eO9FfdX .
 
Ok so somebody correct me if i am wrong but do'nt all 18650s or most have a Standard specifications of 4.20v, +- .05v if so and to say that my BMS dose'nt work then is'nt it normall that my batteries reached 4,23-4,24V (even if they had reached 4,25v it would still be in the batteries standard specification range)?
As i said before there is also the statement of the battery tech here in my city that has over 10 years experience with ebikes and batteries that told me that up to 42,2-42,3 is ok and it"s normal and also that most of his battery packs with branded cells like samsung ,lg,panasonic also show these numbers ,what do you make of this?
 
Yeah, .05v is probably acceptable without having a measurable effect on battery life.

it is somewhat normal for batteries to reach those voltages while charging for a short period of time.. it's not normal for them to be sitting at that voltage. This tells us that under charge, the battery is at an even higher voltage, maybe 4.3v.

4.25 is the battery life shortening zone. Beyond that, you're entering the 'splodey zone.

People who ran RC cars competitively found this out when they started overcharging their batteries for a competitive edge. Turned out that the batteries become significantly more dangerous and their lifespans shrink like crazy even if they don't blow up.

Your 'battery management system' sounds a lot like a 'battery murdering system'.
 
And i had 2 of these,to have both BMS'S not working properly what are the odds?
So i will change the BMS again once the new one arives and see if all cells will balance below 4,20v(after 100+ full cycles is it normall for batteries to still reach 4,20v?)if that dont work then can i still ride my bike by charging up to lets say 52-53V or will it be still dangerous ?
Will by doing this i will kill all the good cells in the pack in a short time?
Is it better to salvage all good batteries out of this pack and make a smaller one (65 batterries so i have 13 batteries to spare lets say if i have bad batteries in the pack) a 13S 4a 48v 10,4ah pack?
 
Probably a design issue. Cheap chinese batteries with no-name cells ain't gonna come with nice, properly designed BMSes. Many of these BMSes actually end up killing the pack, since they do crap like draw all their power from 1 cell, don't limit voltage correctly, etc etc.

Your cells have probably taken lots of damage already if this BMS has been doing this. Limiting further damage by installing a nice, well designed BMS is probably the only thing you can do at this point.

Honestly i consider this pack a fire risk given that it's probably been over charging those cells this whole time.
All the parallel groups which have been overcharged would need to be chucked if you want to salvage the battery.
You'd need to pull them all out and cycle test them with an RC charger if you wanted to build something solid out of the remnants.

The cells themselves are cheap and on the weak side, so you likely couldn't get away with significantly less in parallel. I wouldn't even bother doing that myself.

Sorry to break your heart but your experience is very typical for those who buy these really cheap batteries. At least you bothered to inspect the voltages, rather than having no clue why things went bad.
 
only shoddy , poor quality cells in series need balancing
I cannot imagine such voltage differences on my Chevy Volt 11S pack.
 
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