assist cut off ?

[Alm]

Hi There
I'm an old guy from Denmark who could use some help from some wise guys from Britain.
I have a City bike with Bafang components, front motor, which gives me some problems.
The motor assist cut off after I have driven approx. 10-15km when I ride with the bike's max PAS 3. if I go to PAS 1 . the assist will hold a bit longer longer. I can then step back/brake and the assistant will then engage again very briefly and then cut off again
When I start the trip, the battery is fully charged
It is a 36V system and when I measure the battery when the error occurs there is still approx. 40 volts .back
I think it is because too many watts are being used, but is that a fault in the motor or could it be in the controller?
I have tried with a different battery and the error was the same?
Hope someone can help me...

 

[saneagle]

Hi There
I'm an old guy from Denmark who could use some help from some wise guys from Britain.
I have a City bike with Bafang components, front motor, which gives me some problems.
The motor assist cut off after I have driven approx. 10-15km when I ride with the bike's max PAS 3. if I go to PAS 1 . the assist will hold a bit longer longer. I can then step back/brake and the assistant will then engage again very briefly and then cut off again
When I start the trip, the battery is fully charged
It is a 36V system and when I measure the battery when the error occurs there is still approx. 40 volts .back
I think it is because too many watts are being used, but is that a fault in the motor or could it be in the controller?
I have tried with a different battery and the error was the same?
Hope someone can help me...

The problem is that your battery can't provide enough power. That can be because it's worn out or something is wrong with it, like out of balance, bad internal connection, faulty cell or anything like that. Whatever is wrong, you can solve it with a better battery.

For more more detailed advice, you'd have to provide a lot more info about what you have.

 

[Nealh]

If the battery is cutting out with 40v registering then there is an issue as mentioned with battery. It would need an expert or someone with the diy knowledge to be able to check for the issue with the battery.
It can be one of several factors , battery age , balance and cell quality, a balance issue and or a low or weak cell group being a weak link, this is only a guess as one can't tell without the battery being opened .

It may be more helpful if you can tell us the actual voltage hot off the charger and the battery age.

 

[sjpt]

My first thought was battery, but OP did say he'd tried a different battery and it was the same.
Maybe the second one was in bad shape too.

 

[Nealh]

We know a 3 spd/PAS set up usually means a speed type controller so the current in each level will be max or near as a damn.
Battery age/condition and cell spec will all be critcial with such current draw.
One is assuming we are talking max 15a current for an OEM bafang system bike.

From Alm's description the battery voltage is sagging /collapsing at approx or just unde 40v, this indicates at this point the battery can't handle the 15a load asked of it.
The 40v reading will be a rebound voltage reading , ideally one needs a temporary voltage meter wired up to see what actually occurs to the voltage at the point of the cutting out.

 

[Alm]

Thank, for your reply. I Will try to wire it up, so I Can follow the volt ,and se if it drops

 

[Alm]

We know a 3 spd/PAS set up usually means a speed type controller so the current in each level will be max or near as a damn.
Battery age/condition and cell spec will all be critcial with such current draw.
One is assuming we are talking max 15a current for an OEM bafang system bike.

From Alm's description the battery voltage is sagging /collapsing at approx or just unde 40v, this indicates at this point the battery can't handle the 15a load asked of it.
The 40v reading will be a rebound voltage reading , ideally one needs a temporary voltage meter wired up to see what actually occurs to the voltage at the point of the cutting out.

Hi again Nealh
I have now tried to wire it up, battery, fully charged 40,5 V , maybe it wasn't quite correct, but I took my voltmeter and connected it directly to the the battery and drove for a ride, to keep an eye on, when something happened with the voltage
Right at the start of the ride, the assist cut off, but I could re-engage by stepping back on the pedals/brake a little. it happened several times in the first km. but then became more stable and the assist stayed on, I could see on the voltmeter that when the assist engaged, the voltage dropped to approx. 38.5 V and then rose to 40 V. vhen a little more speed came on. After approx. 10km the error started to be more constant,but I could still re-engage the assist, but with a little more difficulty, after the trip the battery was at approx. 40 V.

This is the bike that makes trouble: Kildemoes E-going City bike 2017.
Battery : 36v-14.5Ah 522wh
Front engine Bafang : FM G320.250.R13
Controller Bafang : CR S105.250.SN
Bracket axle sensor: Bafang C8705065-1-124
I hope this can help a little
I my self have a
But thank you very much for all your input, I really appreciate it
Etc. Lars
about the Controller, but am not quite sure whether it can make such an error?

 

[saneagle]

Thye battery should be 42.0V when fully charged. $0.5V indicates a problem. Try leaving it on charge all day to see if the voltage improves and whether the cutting out improves too. If it does, do it again until you get 42.0v hot off the charger.

 

[Alm]

We know a 3 spd/PAS set up usually means a speed type controller so the current in each level will be max or near as a damn.
Battery age/condition and cell spec will all be critcial with such current draw.
One is assuming we are talking max 15a current for an OEM bafang system bike.

From Alm's description the battery voltage is sagging /collapsing at approx or just unde 40v, this indicates at this point the battery can't handle the 15a load asked of it.
The 40v reading will be a rebound voltage reading , ideally one needs a temporary voltage meter wired up to see what actually occurs to the voltage at the point of the cutting out.

Hi again Nealh
I have now tried to wire it up, battery, fully charged 40,5 V , maybe it wasn't quite correct, but I took my voltmeter and connected it directly to the the battery and drove for a ride, to keep an eye on, when something happened with the voltage
Right at the start of the ride, the assist cut off, but I could re-engage by stepping back on the pedals/brake a little. it happened several times in the first km. but then became more stable and the assist stayed on, I could see on the voltmeter that when the assist engaged, the voltage dropped to approx. 38.5 V and then rase to 40 V. after that a little more speed came on, after approx. 10km the error started to be more constant but I could still re-engage the assist, but with a little more difficulty, after the trip the battery was at approx. 40 V.

 

[Alm]

Hi
I will make a recharge , and hope I will reach the 42V.
The battery is from March 2021, has not been driven that much and is otherwise stored indoors
I wonder if the controller or the motor could make that kind of problem ?
Because the error will come and go, but it becomes more visible when the voltage drops on the battery
Just for info, I have replaced the bracket axel sensor because I was told that was the issue.but it makes no difference ?? Sorry for my English it could be better

 

[Nealh]

As an example my 14.5ah dophin /09 case batteries using Sam 29E cells were fine at Pas 1 drawing a meagre 1.5a or so , I would get some range of 64km.
PAS 2 drawing approx. 3.5a or so I would get 40km of range and in PAS3 drawing 7a Iwould get 12- 15km, this was with 6 year old aging cells in the batteries .

I stopped using the batteries some 3 years ago and now they are used in other uses for DC power where they work faultlessly at a lower power draw.

As cells age they sag voltage wise, my batteries have lost some capacity but were still charging to 41.4v.

 

[Nealh]

Your battery charge of 40.5v is low and indicates an imbalance or a weak cell group.
Be very careful leaving a battery on charge for extended periods , one should be able to monitor them in case of an issue. Don't leave on charge over night whilst you are a sleep unless the battery is isolated safely out side some where.

 

[Nealh]

Hi
I will make a recharge , and hope I will reach the 42V.
The battery is from March 2021, has not been driven that much and is otherwise stored indoors
I wonder if the controller or the motor could make that kind of problem ?
Because the error will come and go, but it becomes more visible when the voltage drops on the battery
Just for info, I have replaced the bracket axel sensor because I was told that was the issue.but it makes no difference ?? Sorry for my English it could be better

Your fault/issue is most certainly likely in the battery , though you could have a look at the phase wire connections at the controller end . Look to see if they are melted or have become warm and show discolouration at all.

 

[saneagle]

Hi
I will make a recharge , and hope I will reach the 42V.
The battery is from March 2021, has not been driven that much and is otherwise stored indoors
I wonder if the controller or the motor could make that kind of problem ?
Because the error will come and go, but it becomes more visible when the voltage drops on the battery
Just for info, I have replaced the bracket axel sensor because I was told that was the issue.but it makes no difference ?? Sorry for my English it could be better

Your battery only charging to 40.5v indicates a problrm, assuming that your meter reads correctly. You can check your meter by measuring the charger jack, which should be 42.0v.

If you do don't use a battery much, it can go out of balance. that's a comm on problem. You can re-balance it by leaving it on charge for a long time. If it is out of balance, it will slowly increase to 42.0v.

There are other possible causes of your problem, but it's best to eliminate one at a time.

 

[Alm]

Okay , thanks for all your replies , I Think I Will find someone who can test the battery ,so I Can eliminate that

 

[saneagle]

Okay , thanks for all your replies , I Think I Will find someone who can test the battery ,so I Can eliminate that

Putting it on charge for a long time costs nothing, and there's a chance that it will fix your problem.

 

[Alm]

Hi again
I have now had my 14amh battery tested, and the test says that the battery is ok? So now I see there should only be 2 possibilities left, the motor which can have intermittent faults or the controller which has a periodic fault?
The funny thing is when I pedal the bike up to approx. 20km/h I can get the engine to pull, naturally the battery will not perform that much, and quite naturally you will see that the fault should lie there.
But if test says OK then what ????
hope for good answers

 

[joelectric]

Did you ever measure the voltage coming out your charger to make sure you are getting 42v?
This is the first place to check and i dont think you confirmed this.

 

[Alm]

No, I haven’t try that, I Will try to measure it thanks

 

[Nealh]

The battery has been tested ?
What did they test ?
Did they give you any facts or figures ?
If not then any test to you is meaninless.

For us guys who know batteries and build them we at least would need to know the very basics but for this one needs figures and reading to have an idea .