Bafang BBS02 keeps turning off

[Yak]

Hi all,

New to this forum and new to ebikes. I have a Nihola cargo tricycle that has had a Bafang conversion done. It is a second hand bike.

It is fitted with a generic 48V lithium battery.

Basically when the battery is charged, everything works, but once it drops to 48-49V, it starts turning off once a bit of load is applied (both with pedal assist and the throttle). If I lift the rear wheel up in the air and use the throttle it does not cut out.

If it cuts out, I have to disconnect the battery and reconnect it to get it to turn on again, but it continues to turn off when any load is applied. I have also noticed that when it has cut out and I have just left the bike in the garage and come back in a few hours it turns back on (without needing to disconnect the battery), but again cuts off after any load is applied.

I have done some trouble shooting and here is some data. Unfortunately I don't have a multimeter.

Fully charged battery voltage
I charged the 48V 20AH battery and when I plugged it in the voltage was 50.9V according to the Bafang display. My googling suggests this should be around 54V. I have now left the charger to charge overnight and will check again. I only waited until the charger light went green the first time.

Connections
I checked all the connections, couldn't see any loose ones. I did notice that the mini-anderson connection from the battery to the motor had some slight black/burnt marks on the pins. I can see the red connector spark a little when I am joining the connectors, but no spark after connecting them.

Configuration settings
I went into the display settings and also went a step further and got a programming cable and checked the motor settings. I was mainly checking the cutoff voltage. I have attached all the screenshots.
Display settings

Motor parameters

So given the charging voltage not being 54V, I am suspecting a battery issue - but thought I would turn to the forums and ask for guidance/help/a fix please.

 

[ElHegpah]

I would ask you to supply some more information, but you won't, so why bother.

You have a seriously defective battery, possibly dangerous. Repair or replace, store away from flammable materials.

Why don't you contact your kit supplier, they are so well known to provide wonderful tech support.

 

[Yak]

I would ask you to supply some more information, but you won't, so why bother.

Relax bud. Happy to provide more information - if I have missed something. Maybe go for a walk and get some fresh air...


I will be talking to the supplier, it is currently the weekend. I would like to be an informed customer and also learn about the system myself. Given all this is completely new to me, I thought I could turn to this forum for some guidance on what I have done and found so far.

Noted regarding the battery - I'll turn off the charger!

Someone let me know if this forum is not meant for beginners. If so please close this thread. I'll go elsewhere

 

[HumanPerson]

Relax bud. Happy to provide more information - if I have missed something. Maybe go for a walk and get some fresh air...


I will be talking to the supplier, it is currently the weekend. I would like to be an informed customer and also learn about the system myself. Given all this is completely new to me, I thought I could turn to this forum for some guidance on what I have done and found so far.

Noted regarding the battery - I'll turn off the charger!

Someone let me know if this forum is not meant for beginners. If so please close this thread. I'll go elsewhere

Yur good mate and Welcome to the forums!

The old ElHegpah is a bit harsh at times but he means well, we hope

Try this, set the: Current Limit (Amps) 30
To: Current Limit (Amps) 25

and drop the Low Voltage cutoff to 41.6

Just for sh hits and giggles to see if that even helps any.
Otherwise i'd say it's a dud battree/BMS

Again,
Welcome to our humble home

 

[ElHegpah]

Start with how old is it? How long have you owned it? What EXACTLY is printed on the charger in terms of voltage? Has the battery been replaced from original installation? Has the controller in the motor been replaced? Has the charger been replaced? Do you still have any contact with the original owner? Are they honest? Has there been any serious, or trivial, impact event which might have affected the battery?

Has anyone reset the display settings from original settings? Did anyone properly setup the display in the first place? How long did it get stored without usage or charge? How many times have YOU charged it? How many times has it gone dead? Do you own a Voltmeter? Does it read two digits past the decimal point? Does it have a fresh battery? Can you go get one RIGHT NOW?

Do you have a BBQ grill or a fireplace?

Also, I have to ask, what POSSIBLY would be the point of dropping the controller LVC a grand total of 0.40V?

Short version is the battery is almost certainly toast, charging it is Dangerous, using it is Dangerous, standing next to it is Dangerous, dispose of as Hazardous materials.

BMS and/or case might be worth saving, if you want a project.

 

[m@Robertson]

Since you can reset the system by merely turning things off and on, that means you are not popping the battery's low-voltage BMS limit. So whatever it tripping the system off is outside of the battery. That does not mean its not the battery that is at fault.

If you have a 48v battery, that means you have a '13S' pack, which is groups of cells are connected together in bundles of 13, with the number of bundles making up the parallel count of the pack. So lets say for the sake of argument you have 5 of those bundles, that would give you a 13S5P pack.

Having said that, you have already figured out your 48v/13S pack is supposed to be charging up to 54 volts or so - the exact amount is 54.6v, and you can follow how that math works by clicking on the 48v chart here. The charts illustrate the calc method in addition to showing the levels.

Li-Ion Ebike Battery Charge Charts

Whats an 80% charge on a 48v battery? These charts give answers to questions like this on common ebike battery voltages: 36v, 48v, 52v, 60v and 72v.

talesontwowheels.com

So going back to that 'P' count above. What happens when one of those 'bundles' is lost? Maybe a weld gives way and one of your bundles goes away from the pack's capacity? Now you have a 12S pack. What is the voltage level of a 12S pack at 100% charge? 50.4v. Which is within the margin of error on many displys (maybe yours as well). My KT-LCD4 display shows voltage about a half-volt low, and my Bafang DPC-18 on another bike shows about 0.75v high, so you don't want to treat a display as gospel.

Your battery pack may be damaged and thats why its showing a lower voltage. Also, while you are using it, it may be sagging hard thanks to the loss of capacity, which in turn trips the motor's low voltage cutoff, which is the one that will let you reset the system just by turning it off and on.

Even if the loss of a parallel cell group is not the source of your problem, most likely its the battery. The controller or the motor is MUCH less likely to cause behavior like this. Especially with what sounds like a pretty clear pattern.

 

[Yak]

Start with how old is it? How long have you owned it? What EXACTLY is printed on the charger in terms of voltage? Has the battery been replaced from original installation? Has the controller in the motor been replaced? Has the charger been replaced? Do you still have any contact with the original owner? Are they honest? Has there been any serious, or trivial, impact event which might have affected the battery?

Has anyone reset the display settings from original settings? Did anyone properly setup the display in the first place? How long did it get stored without usage or charge? How many times have YOU charged it? How many times has it gone dead? Do you own a Voltmeter? Does it read two digits past the decimal point? Does it have a fresh battery? Can you go get one RIGHT NOW?

Do you have a BBQ grill or a fireplace?

Also, I have to ask, what POSSIBLY would be the point of dropping the controller LVC a grand total of 0.40V?

Short version is the battery is almost certainly toast, charging it is Dangerous, using it is Dangerous, standing next to it is Dangerous, dispose of as Hazardous materials.

BMS and/or case might be worth saving, if you want a project.

Battery is 4 years old.

I have owned it 3 days now.

Charger says 54.6V at 2.5A

I believe it is the charger and battery from the original install, unfortunately it is from a deceased estate and no one in the family knows much about it, it has not been used for the past 5 months.

I'd guess and say the controller in the motor has not been replaced.

I have charged it twice and ridden it for 15mins both times, when the voltage gets to ~48V it starts to shut off, unless the wheel is in the air.

Unfortunately don't have a multimeter, but will invest in one. On Monday I will head to the local ebike shop and get a new battery and also ask them to check the existing one.

I think I'll eliminate the battery - then report back my findings.

A couple of questions:

Is it worth resetting the display? The only setting I am interested in playing around with is the PAS 3. Want to have a decent ride in its current configuration to get a feel for the current PAS levels before I tinker.

Is the motor controller something that needs to be replaced every X period or km?

 

[ElHegpah]

You have probably lost a parallel group due to long-term storage. The battery is almost certainly in a VERY dangerous state, charging a cell which has gone down very low is how most lithium fires start. Remember to dispose of as hazardous materials, get it out of the house immediately.

No harm in resetting the display, just beware you are riding with a fire hazard, which is ticking away.

Controllers usually last a long time, as long as they are not driven beyond their capabilities. Make sure it has good airflow for cooling.

Best effort at providing answers to diagnostic questions I have yet seen on this site. Most folks answer one or none, many flat-out lie, which becomes obvious eventually. Kudos.

Note: Research and become aware of long-term storage and charging issues. Sitting 5 months with no charge, and/or being stored with a full charge, and/or no maintenance charge during a multi-month period, plus being 4 yrs old to start with, is almost certainly the cause of the current problem.

 

[Yak]

Appreciate all the information and guidance! Will definitely dispose of the battery in a safe way. I'll do some reading into battery storage and maintenance.

I'll report back if the issue has not gone away.

 

[Chuy]

Some things I would do before discarding the battery:
- get a multimeter - every household should have one, imo. (They are not pricey.) A multimeter will reveal/confirm the battery voltage in the event the charger is defective and/or the display is inaccurate.
- clean off the Andersen plugs. The burnt marks are from arcing, caused by current jumping across the connections when joined. The burnt marks create resistance. Excessive resistance can explain the reduced voltage readings. If the plugs are too corroded, you can splice in new ones. Maybe change/upgrade to anti-spark XT90’s.