Battery cuts out too soon

[gordonrjones]

My 52 volt battery( 14 ah, bottle battery) cuts of at 44.5 volts, it is on a bbs02 I bought in October along with the battery, they have almost 300 km on them all cold winter driving, about a month ago it just died and it should have had more miles to go, I did not check the voltage with meter but since then i have been checking every time i go for drive and today it died and it was at 44.5 volts. I got almost 50 km from it which is fine I guess, but should it shut down at such a high voltage?

 

[amberwolf]

If it's not well-balanced, it could cut off like that. typically that sort of problem gets worse over time, so if it started cutting off too early a while ago, and has been getting less and less range, then that's probably why.

Leave it on the charger at least overnight, see if it changes. If so, but still doesnt' have the range it should, leave it on the charger all the time you are not using it, and eventually it will rebalance itself if there are no other issues.

There are other possible problems, but the above is the easiest thing to fix, and doesnt' require opening anything up.

Over time, even this problem will eventually get bad enough to require repair or replacement to maintain the same range. How long that will take depends on what the cause of the problem is (could be weeks, months, or years).

As long as you leave it on the charger whenever it is not in use, it will balance itself as best as it is able, and keep itself as closely balanced as is possible in the given time.

 

[gordonrjones]

Does not sound good, when I first charged it in October it only charged up to 58.4 volts and since then the highest it has reached has been 58.2. I will do as you say and keep my fingers crossed.
Thanks.

 

[Sunder]

58.4v / 14 cells = 4.17v per cell - Most balancers won't start bleeding off overcharged cells until 4.20v. Some won't start until 4.25v. The problem is worse once it only charged to 58.2

14Ah cells are also not small, so overnight might not make a difference. I needed 10 days on the charger 24 x 7 to fix my unbalanced cell problem. However, I'm now getting about 2.5x the range I used to get.

One of the problems that many good eBike vendors make innocently, is that they pair a battery with EXACTLY the same voltage charger. Why is that a problem? Because if the BMS won't balance until 4.25v, then you can have 13 cells at 4.24v and 1 cell at 3.68v, and the pack won't balance. If you paired that battery with a 60v, but with a current lower than the BMS can bleed, what happens is that your charger actually feeds the BMS on the cells that are fully charged, but directly charges low cells.

I'm starting to find that this is such a frequently asked question and misunderstood issue, that I might write a proper article on it.

 

[gordonrjones]

It is up to 58.4 this morning, hope it keeps rising as it should...

 

[999zip999]

I would not ride cutoff as a rule maybe once or twrice a year. Riding to cutoff will unbalance the battery over a short time. Leave on charger for some time.

 

[flat tire]

To avoid the situations of leaving the battery chargin for 10 days you can charge the individual cell using a power supply and header pins into the balance connector. That would take like a couple hours vs 10 days.

 

[gordonrjones]

To avoid the situations of leaving the battery chargin for 10 days you can charge the individual cell using a power supply and header pins into the balance connector. That would take like a couple hours vs 10 days.

I bought the battery from Luna Cycles in October 2016, the frame broke on my old bike after 16 miles and never got it going again till January and been too cold to really notice about the battery or put many miles on it till now, not sure if i should open it up to do that in case there is a warranty on it never thought to see about that, maybe i should get in touch with them before i do any thing like that. Be nice to have it charging properly though.

Thanks...

No warranty. I have no idea what header pins are but I have some knowledge about electronics( lilbit). Maybe you can direct me to a link which will have some visual aids, ( LOL).

 

[gordonrjones]

10 days on the charger 24 x 7

Sunder when you said the above do you mean you did not use it at all during those ten days? It seems like my charger just does not turn back on after the light turns green, I have it where i can hear it as long as I am home and it just does not turn on after the light turns green unless I unplug and plug it back in again...

 

[Sunder]

10 days on the charger 24 x 7

Sunder when you said the above do you mean you did not use it at all during those ten days? It seems like my charger just does not turn back on after the light turns green, I have it where i can hear it as long as I am home and it just does not turn on after the light turns green unless I unplug and plug it back in again...

Depends on the BMS and charger. You are correct that badly paired chargers and BMSes will never turn back on by themselves. One work around without voiding warranty is to charge through the discharge port if they use the same adaptor, or using a constant voltage power supply set a tiny bit higher than the charger, if you have one.

I did not touch mine for 10 days, but I had a constant voltage power supply plugged in on the discharge port set at about 155v on a BMS that "should" have started balancing at like 149v (forgot the exact maths by now). If I plugged it into the charging port side, the BMS would keep disconnecting the charger while it bled down a single high cell. (1 of 43!) By plugging it into the discharge port, no such protection existed, and almost all cells were mildly overcharged and being bled off at the same time - not enough to significantly shorten the life of the cell, and not more than the balancing part of the BMS could handle, but enough to make the process a lot quicker.

 

[Animalector]

others have talked about BMS and balancing. That's all good and true. But it's worth mentioning that if you have a 13S4P pack (for example), and the welds on any end of just one of these cells in the pack comes loose, your 4P becomes a 3P for that bank and it will trigger the bms cut off at 3/4 capacity... Whammo!! instant reduction, and no amount of balance charging will fix it.

Solution is to Open the pack, measure the Series increments at the BMS to establish which bank is lower than the others.. Identify this set of cells, then start gently lifting the nickel until you find your culprit, then re-weld it.

Good luck. if you're in Cairns Australia, I'll do it for you but not many people in the world live in Cairns Australia.!!! 0.0026% of the worlds population live near me..

 

[neptronix]

Do you have a device that can display wattage, total amp hours drawn over a ride, amps, volts etc?

I would guess that your battery is sagging and cannot handle the load properly. If so, it wouldn't have given the amp hours you expected from the factory... and also it would give even less capacity in the cold.

That is a common problem that gets misdiagnosed as a battery cell balance issue or BMS issue. What cells are inside? we can imply some information based on that.

 

[gordonrjones]

Do you have a device that can display wattage, total amp hours drawn over a ride, amps, volts etc?

I would guess that your battery is sagging and cannot handle the load properly. If so, it wouldn't have given the amp hours you expected from the factory... and also it would give even less capacity in the cold.

That is a common problem that gets misdiagnosed as a battery cell balance issue or BMS issue. What cells are inside? we can imply some information based on that.

I ordered a cheap watt meter not here yet though. I have been measuring the voltage before and after each ride and this is what I have:

58.2 volts, April 26
50.9 volts 28.35 km
--------------------------------
58.1 volts, April 13
57.5 volts 3.1 km
56.5 volts 5.53 km = 8.63 km
55.7 volts 3.14 km = 11.77 km
53.2 volts 12.8 km = 24.57 km
48.6 volts 15.0 km = 39.57 km
44.5 volts 7.9 km = 47.7 km at cutoff
= 3.5 km/volt

________________
58.2 volts, April 12
57.5 volts 3.77 km
57.0 volts 5.95 km = 9.720 km
55.3 volts 6.07 km = 15.79 km
54.7 volts 3.11 km = 18.90 km
53.5 volts 4.75 km = 23.65 km
= 5.032 km/volt

--------------------------
58.1 volts, April 10
56 volts 12 .03 km
55.5 volts 1.57 km = 13.60 km
53.3 volts 10.1 km = 23.60 km
50.1 volts 17.3 km = 40.90 km
= 5.113 km/volt
--------------------------------
58.1 volts , April 4
57 volts 8.8 km
56.4 volts 5.71 km = 14.51 km
55.5 volts 5.79 km = 20.30 km
55. volts 3.36 km = 23.66 km
54. Volts 3.87 km = 27.53 km
53.3 volts 3.28 km = 30.81 km
52.7 volts 3.74 km = 34.55 km
52.1 volts 3.72 km = 38.27 km
= 6.378 km/volt

I bought the battery from Luna cycles in October 2016, it was listed as: PANASONIC battery: Bottle 52v GA 14ah, that is all I know about the battery, it has never charged above 58.4 volts since I got it I never worried about it I figured it would come around but frame broke on bicycle and never got another going till middle of Jan did not realize the warranty was only for 90 days.

 

[gordonrjones]

Solution is to Open the pack, measure the Series increments at the BMS to establish which bank is lower than the others.. Identify this set of cells, then start gently lifting the nickel until you find your culprit, then re-weld it.

Batteries are a lot more complicated than I thought, I guess I will have to attempt to open the pack up and see what is inside . Thanks...

 

[neptronix]

Yeah the important thing you wanna do is measure the voltage drop under load.. that's more useful than measuring the battery before, after, or during a ride since you don't know the discharge curve and how it relates to the amp hours.

Ah, you have the "14AH" battery. That's a 4P pack. The cells actually contain about 3.4ah x 4 = 13.6AH at a 0.2C draw per the spec sheet.

https://www.nkon.nl/sk/k/ncr18650ga.pdf

Since this cell gives more like 3.2ah under a constant 1.25-1.5C load that the BBS02 will draw, once you hook up that amp meter, you should be able to get 12.8AH out of it if it was brand new with zero cycles and the cells were matched.

That's your baseline. Let's see what the watt meter says. Then we can start looking at individual cells.

 

[gordonrjones]

Yeah the important thing you wanna do is measure the voltage drop under load.. that's more useful than measuring the battery before, after, or during a ride since you don't know the discharge curve and how it relates to the amp hours.

Ah, you have the "14AH" battery. That's a 4P pack. The cells actually contain about 3.4ah x 4 = 13.6AH at a 0.2C draw per the spec sheet.

https://www.nkon.nl/sk/k/ncr18650ga.pdf

Since this cell gives more like 3.2ah under a constant 1.25-1.5C load that the BBS02 will draw, once you hook up that amp meter, you should be able to get 12.8AH out of it if it was brand new with zero cycles and the cells were matched.

That's your baseline. Let's see what the watt meter says. Then we can start looking at individual cells.

It has almost 500 km on it, hopefully the watt meter will be here soon, hope it is ok if I keep using it, I have bad hip and arthritis so walking is painful and the bike is my only method of transportation.

Thanks all for your comments...

 

[neptronix]

Dang.
Have you checked for heat emanating from the battery after a long ride by chance?

It shouldn't be more than say 20 degrees hotter than ambient at the case. Otherwise it's sagging a lot.

Heat is a basic way to find out if some component is creating a lot of waste power from resistance. Controllers, batteries, and motors that are too hot are a sign of something working really hard. To put it in really basic terms..

 

[gordonrjones]

Dang.
Have you checked for heat emanating from the battery after a long ride by chance?

It shouldn't be more than say 20 degrees hotter than ambient at the case. Otherwise it's sagging a lot.

Heat is a basic way to find out if some component is creating a lot of waste power from resistance. Controllers, batteries, and motors that are too hot are a sign of something working really hard. To put it in really basic terms..

Yes I do and there is not much heat from the battery , i drove it to get some food today and the motor gets a little hot but the battery was pretty much a couple degrees warmer than the ambient temp, was sunny I drove almost 30 km.

 

[Laplandlarry]

I had a similar Luna pack doing the same thing. I contacted them, they helped me troubleshoot the problem, but these guys here are steering you the right direction. I open my pack and found the cells all balanced, it's a 14 x 4 pack all the voltages were right. With a watt meter I found the voltage sagged and tripped the BMS voltage cutoff. I found if I was easy on the throttle it wouldn't trip and I would get more mileage.

I added a Grin.ca Cycle Analyst so I could limit the amps, and watts. I changed the ramp up time on the throttle and last charge I went 38 miles on 8 amp/hr with some light pedaling. The CA is great. It's complex for what I'm doing now, you can change 60 parameters, but it keeps the BMS from tripping and I think I will get a good useful life out of the pack.

The charged voltage on my pack has decreased in the 1.5 years I've had it. I'm at 57.9 now, I think 58.8 is the best it ever was. I was told this is how 18650's age. I'm 63 and know even when I'm fully charged I'm not as good as when I was 18.

 

[gordonrjones]

The good people from Lunacycles sent me a newer model of my charger and I hooked it up and it charged my battery up to where a 52 volt battery is supposed to be 58.8 volts which pleases me greatly. Thanks for all the helpful comments and praise for the people from luna...

I think if my battery is not balancing to 58.8 it is just not working as it should...