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Strange ebike problem , BMS problem ?  

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Tuna
 Tuna
(@tuna)
Street cred = 10 mAh
Joined:2 years  ago
Posts: 14
14/11/2017 10:34 pm  

Hi.
I finally managed to get my bike together ūüôā

Yesterday I was out on a short test ride. I drove both fast and slow and everything worked perfectly and I was really happy.
But today when I took the bike out of the garage to go for a ride, it did not work well anymore.
it starts up and indicates that the battery is fully charged. It's no problem to ride away and everything works as it should until I throttle quickly the power cuts off If I go easy on the throttle the bike will power up to full speed. 
The power don't die completely,What happens is that the power disappears and the battery icon starts flashing like the battery was out. it also losing the contact
to the temp sensor,and the temp value just flashes. After about 3-5 seconds, everything returns to normal, until i I throttle quickly next time. 

I recharged the battery again to 58.8v and plugged it in and everything worked perfectly again ūüôā
I went for a short ride to my parents' house, I turned off the bike and went in and visited them for about 10 minutes. 
After the visit i I turned on the bike and drove home (5 min) everything still worked prefect.

Then it became the same problem again after standing in the garage overnight.
S
omething happens when standing overnight even though the bike is completely off .

Feels almost like something wrong happens with the battery when it is not used for a few hours.


strange error, anyone have any idea ?  BMS ?

This is my setup:

Battery is : 52v 14s 7p Panasonic NCR18650PF 2900mAh - 10A

BMS:

51.8V lithium ion battery bms 3.7V 14S 30A BMS with the balance function Different charge and discharge port
Brand Name:ANN
Model Number:14M30AFK
Size:L108*W60*T11mm
Voltage:51.8VNominal 
Capacity:10-50Ah
Weight:0.1KG
Application:Lithium ion battery
Type:Lithium ion battery BMS
Product name:14S 51.8V 30A lithium ion battery BMS
Rated Voltage:51.8V
Charging voltage:58.8V
Continuous working current:30A
Over-Current Discharging Protection:100A
Maximum charging current:15A
Balanced Current:50mA
Charge and discharge:Different charge and discharge port
Dimensions:L108*W60*T11mm
Composed Type:14S

And This kit from :  https://www.aliexpress.com/item/PASI...311.0.0.fvh3Oq

Kind regards
Johan 


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Micah (Vruzend Rep)
(@admin)
Street cred = 5 Ah Admin
Joined:2 years  ago
Posts: 433
18/11/2017 12:55 am  

Hi Johan,

One immediate culprit that is jumping out at me is the cold. In the winter if your battery is left outside or in an unheated garage, the cold will really decrease the performance. The voltage will drop and it will cut out much sooner. I made a video about this here:  https://www.youtube.com/watch?v=9W-lOxQL7QU

This could also explain why your battery works during the day and immediately after a trip, because its still warm. But when you use it after a cold night, it senses low battery.

There are other pack construction issues that can make this worse, such as including only one point of connection for discharge wires on the pack and other things like that which increase resistance and decrease the amount of usable battery you have.


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Tuna
 Tuna
(@tuna)
Street cred = 10 mAh
Joined:2 years  ago
Posts: 14
18/11/2017 6:48 am  

Hi !

Thank you very much for the answers .

I have had the bike in a heated garage, I do not think the temperature  have been below 10 C at any time .

Do you still believe that it may have affected the battery that much ? I only drove the bike for about 10 minutes in total.

I have tried to connect as you do in this video :  https://www.youtube.com/watch?v=m4DGDkwFr54

How do you think the battery looks ? something that does not look right? 

 


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Tuna
 Tuna
(@tuna)
Street cred = 10 mAh
Joined:2 years  ago
Posts: 14
18/11/2017 6:49 am  

One more pics ūüôā¬†


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Simoc
(@simoc)
Street cred = 10 mAh
Joined:1 year  ago
Posts: 8
19/11/2017 7:34 pm  

Johan . What is your battery Volt reading after your ride? Is it the same in the morning? It sounds like the battery is draining like something has been left on.


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Tuna
 Tuna
(@tuna)
Street cred = 10 mAh
Joined:2 years  ago
Posts: 14
21/11/2017 6:28 am  

Hi I'm back ūüôā

Now I have charged the battery for 12 hours. 

when I use the volt meter to view the battery it shows 56v 

As usual, the bike worked well on my first 10 minute ride after full battery charge. I measured the battery after the ride and it showed 55.3v
I took the battery from the garage to make sure that the cold temparature (+10c) would not be a factor.

The next day I took a trip again, The bike worked well for about 1 min, then the usual fault returned.
Then i used a clamp meter to see how much current the bike would like to pull from the battery. I noticed that it cuts every time it pulls 37.5 Amp for about 2-3 sec.

It makes me start wondering if the BMS is to weak , could that be the problem ? it is specified to Continuous working current: 30A

It appears like that we could rule out a cold temperature problem and voltage drain overnight.

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Micah (Vruzend Rep)
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Posts: 433
27/11/2017 7:12 pm  

Yes it could be that you're having over current cutout issues from pulling high current. The clamp meters often have a bit of a lag as well so you might be pulling more current than you think before it cuts out. I didn't think about that as a culprit at first because most people aren't pulling as much power as that!


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Tuna
 Tuna
(@tuna)
Street cred = 10 mAh
Joined:2 years  ago
Posts: 14
03/02/2018 1:19 am  

Hello again Micah!

Now I have started from the beginning with a new Bluetooth BMS .

I disassembled the battery again,and measured each cell. I found one cell that had no contact.

I connected  one side, and measured all cells again, I had some trouble getting contact  with all cells . When I solved one contact problem, I got a new one, but finally i got contact with all cells. However I can not help feeling that the  connections feels a bit unstable.

is there any way to check if all cells have contact when the battery is assembled ?

During the troubleshooting process, there have also been a number of thoughts that you may bring some clarity to ?

what volt should a fully charged "52v" battery have?  is it 58,8v (4.2 x 14 = 58.8) or is it 52v (3.7x14 =51.8) ?

My battery shows 56v where all 14 cell groups are between 3.98 and 4.00, does it indicate a problem? 
should I not get 4.2 in each cell group and a total of about 58v full charged?

Micah I'm following your YouTube channel, and I think it's very good and you're doing an outstanding job. A video about troubleshooting a finished battery would probably be appreciated by many, how to measure, which measurement values that are ok and so on. 

Kind regards
Johan 

 


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Micah (Vruzend Rep)
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Joined:2 years  ago
Posts: 433
08/02/2018 2:02 pm  

Hi Johan, you definitely want 58.8V for a 52V battery, if you are going to 100% full charge. The 51.8V is just the nominal voltage, which is rounded up to 52V since its easier to say than 51.8V.

Unfortunately I haven't found a good way to confirm all cells are connected after the battery is already finished being built. That's why its a good idea to confirm it before the second side's bus bars on, then mount the battery between plates or something else like pieces of wood if it will be in a moving or vibrating environment.


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Tuna
 Tuna
(@tuna)
Street cred = 10 mAh
Joined:2 years  ago
Posts: 14
08/02/2018 6:12 pm  

Thank you for taking the time to respond.

ok so the fact that I only get 56v after 12 hours of charging indicates that something is wrong ? , and I did not get it right this time either .

so there is a lack of 2.8V on the battery pack,do you have any idea what the error may be?

If one or a few cells would not have contact,would it affect the total volt?

As you can see in the picture, the cell packages appear to be quite balanced between 3.98 and 4.0, would that be the case if some cell has lost contact?

I noticed that I only got 56v last time as well. Now I have switched all cables and switched to a new BMS, is not that a bit strange? , could there be something else wrong? problem with the charger?

Kind regards
Johan 

 

 

 


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Milomilam
(@milomilam)
Street cred = 10 mAh Customer
Joined:3 months  ago
Posts: 2
16/11/2018 10:30 pm  

Im having the exact same problem. Dont know what to do but im not giving up till i find an answer. Ill post when i do


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Milomilam
(@milomilam)
Street cred = 10 mAh Customer
Joined:3 months  ago
Posts: 2
23/11/2018 2:32 pm  

The control module has a cutout that notices when voltage drops below a certain point. So add one more battery in a series to each parallel. That should fix it. Thats what i had to do


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moonlamps007
(@moonlamps007)
New Member
Joined:3 weeks  ago
Posts: 1
26/11/2018 7:22 am  

Truly it may be the case that you're having overcurrent pattern issues from pulling a high current. The clasp meters frequently have somewhat of a slack too so you may pull more present (LED Moon Lamps) than you might suspect before it removes. I didn't consider that an offender at first on the grounds that the vast majority aren't pulling as much power like that.


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