Help! Motor Cutting Out Intermittently

[Radancer]

My first post on this Forum was hoping someone could help or point me in the right direction.

I have a Bafang 500w mid drive with a 36 V Frog Battery that I have only done about 300miles on so all pretty new kit.

Problem is that yesterday the motor was cutting out intermittently and now wont come on at all. When I got on the bike yesterday I travelled about six feet on throttle but when I started to pedal the PAS did not kick in. Cycled on manually for 50 yards or so and the PAS kicked in for a bit then kicked out. Stopped switched off / on and the same thing happened again and then quite a few times on the journey. Took bike home and put it on stand but I am getting nothing in the throttle or PAS departments.

I recall reading on a post here sometime ago that Frog battery holders are not the most robust as the prongs sometimes dont engage into the battery leaf spring connectors tightly. I wondered if that might be the problem but what is confusing me is that power is getting to the controller and the sensor on the wheel blinks red and is working as it is recording mileage and speed. The battery is fully charged and I imagine it is not the motor which as I say has been kicking in intermittently. All the connections look tight so thought it could be ignition switch problem especially as I said the bike started on throttle but when I place my full weight on the saddle the PAS kicks out.

I am not electrically minded so any help would be greatly appreciated about what I can try to resolve the problem.

 

[Andy-Mat]

My first post on this Forum was hoping someone could help or point me in the right direction.

I have a Bafang 500w mid drive with a 36 V Frog Battery that I have only done about 300miles on so all pretty new kit.

Problem is that yesterday the motor was cutting out intermittently and now wont come on at all. When I got on the bike yesterday I travelled about six feet on throttle but when I started to pedal the PAS did not kick in. Cycled on manually for 50 yards or so and the PAS kicked in for a bit then kicked out. Stopped switched off / on and the same thing happened again and then quite a few times on the journey. Took bike home and put it on stand but I am getting nothing in the throttle or PAS departments.

I recall reading on a post here sometime ago that Frog battery holders are not the most robust as the prongs sometimes dont engage into the battery leaf spring connectors tightly. I wondered if that might be the problem but what is confusing me is that power is getting to the controller and the sensor on the wheel blinks red and is working as it is recording mileage and speed. The battery is fully charged and I imagine it is not the motor which as I say has been kicking in intermittently. All the connections look tight so thought it could be ignition switch problem especially as I said the bike started on throttle but when I place my full weight on the saddle the PAS kicks out.

I am not electrically minded so any help would be greatly appreciated about what I can try to resolve the problem.

You say the battery is fully charged, but the only way to know this for certain, is with a reasonably accurate DC Voltmeter. Is that how you checked it?
Or are you going just by the colour of the charging LED? Which can be most misleading.
How old is the battery now? Would also be useful information to add.
See if you can borrow a reasonable meter, and get yourself in a state of knowledge where you can measure the battery voltage, without causing a short!
Do wear safety glasses, just in case.....
regards
Andy

 

[vfr400]

It's quite simple to find the source of the problem. If the LCD goes off when the motor cuts and has to be switched back on, the problem is with the battery or its connection. If the LCD stays on, it's a motor or control system problem.

 

[Radancer]

Hi Guys

Fully charged to two green lights and 5 bars on LCD and got my mate who was a BT engineer to test the voltage and got a reading of 15.29 volts as photo which he says is not good and explained a bit about battery technology. He also by looking at the screws suspected the battery had been opened.

The conversion was done a few months ago and I must confess I was a bit dubious about the age of the battery as it had a name painted on it which was not mine when the bike was returned. The other reason it was Frog battery is that guy said he could not fit a standard battery into the triangle which I agree was tight so I told him to go ahead. In hind-site I now suspect he had the battery lying around and this was a good opportunity to off load it.

I kinda think I know where this is going and told my mate I would report back to the Forum in case there are any further tests that you guys think would be of assistance as although he is pretty knowledgeable he is not familiar with ebikes.

 

[vfr400]

15.29 means either that the BMS is switched off or the meter is faulty. The motor would never have turned at that voltage. 15.29v doesn't tie up with green lights on the charge indicator either!

See if you can measure the voltage on the charge socket.

Edit: Something weird about that meter or the measurement. The selector is pointing at current, not volts. Are you sure he was a BT engineer?

 

[Radancer]

Sorry guys I am not electronically versed but I have arranged to meet my friend tomorrow night and we will re-check your suggestions and revert which got me thinking that I need to be doing this for myself so can you suggest a reasonably priced meter that would cover ebike things. I want to be safe and learn at the same time.

 

[vfr400]

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[Radancer]

Mate got back to me and says you are absolutely correct but said that he could not get a reading (error code or over limits or something like that) on the V DC but I will take round tomorrow and he says he will check meter readings and get reference voltages from other sources and buzz out the rest of bike electrics and I will get back to you.

 

[Radancer]

That meter looks a steal for 5 quid and will probably order just to learn against reference objects however I have some reservation as I purchased a chinese digital caliper for a one off job which worked for a bit but now after a couple of months is complete naff and gives erratic readings

 

[vfr400]

That meter looks a steal for 5 quid and will probably order just to learn against reference objects however I have some reservation as I purchased a chinese digital caliper for a one off job which worked for a bit but now after a couple of months is complete naff and gives erratic readings

You probably damaged it by trying to measure voltage with it set to current.

 

[Radancer]

Yeah good one ! lol. I did not see that coming but will revert tomorrow with our findings

 

[vfr400]

Yeah good one ! lol. I did not see that coming but will revert tomorrow with our findings

No, I mean it. That one that you used above has automatic current measurements, so is probably protected. The cheaper ones, like I suggested you buy, have different sockets to connect the probes depending whether you're measuring current or voltage/resistance. If you have it in the voltage one and try to measure current, it will quickly develop a terminal fizz. Cheaper meters don't even have the socket for measuring current, but you can measure very small currents if you do it right; however, if you set it to that scale and try to measure voltage, it's a dead short, so goes fizz!.

 

[Andy-Mat]

That meter looks a steal for 5 quid and will probably order just to learn against reference objects however I have some reservation as I purchased a chinese digital caliper for a one off job which worked for a bit but now after a couple of months is complete naff and gives erratic readings

Replace the battery in the Caliper.
If that doesn't help, remove the battery and short out the contacts on the unit where the battery would normally fit.
Press all buttons (all done to fully discharge any caps).
Check the new battery voltage is within range for (usually) button cell used. They get sold sometimes already well down!
Replace battery and see if it works correctly now.
If not, sadly, it is probably defective, assuming the new battery is within range.
The last test is to remove the battery, press all buttons, give it a week with no power, and see if the fault is corrected then.......the last chance saloon, so to say!
The reason that some of these problems arise, is storing the caliper with the battery installed, and they cause the battery to self discharge, putting the (cheapo) electronics into a state that it was never designed for.....
I myself have two cheapo electronic Calipers, (and a few without electronics as backups!) always stored with the battery removed, and they must be 10 years old now (guessing!), and still work fine.
Best of luck.
By the way, the same problem can happen with electronic calculators too....but as such electronics nowadays is so cheap to replace, its really not a big deal.....just annoying.
regards
Andy

 

[Radancer]

No, I mean it. That one that you used above has automatic current measurements, so is probably protected. The cheaper ones, like I suggested you buy, have different sockets to connect the probes depending whether you're measuring current or voltage/resistance. If you have it in the voltage one and try to measure current, it will quickly develop a terminal fizz. Cheaper meters don't even have the socket for measuring current, but you can measure very small currents if you do it right; however, if you set it to that scale and try to measure voltage, it's a dead short, so goes fizz!.

No, I mean it. That one that you used above has automatic current measurements, so is probably protected. The cheaper ones, like I suggested you buy, have different sockets to connect the probes depending whether you're measuring current or voltage/resistance. If you have it in the voltage one and try to measure current, it will quickly develop a terminal fizz. Cheaper meters don't even have the socket for measuring current, but you can measure very small currents if you do it right; however, if you set it to that scale and try to measure voltage, it's a dead short, so goes fizz!.

Sorry I was talking cross purpose as not familiar with electrical terms. When I was talking about digital calipers I was referring to the the measuring kind for taking internal and external measurements .

 

[vfr400]

Sorry I was talking cross purpose as not familiar with electrical terms. When I was talking about digital calipers I was referring to the the measuring kind for taking internal and external measurements .

Sorry, I didn’t read properly.

 

[Radancer]

Replace the battery in the Caliper.
If that doesn't help, remove the battery and short out the contacts on the unit where the battery would normally fit.
Press all buttons (all done to fully discharge any caps).
Check the new battery voltage is within range for (usually) button cell used. They get sold sometimes already well down!
Replace battery and see if it works correctly now.
If not, sadly, it is probably defective, assuming the new battery is within range.
The last test is to remove the battery, press all buttons, give it a week with no power, and see if the fault is corrected then.......the last chance saloon, so to say!
The reason that some of these problems arise, is storing the caliper with the battery installed, and they cause the battery to self discharge, putting the (cheapo) electronics into a state that it was never designed for.....
I myself have two cheapo electronic Calipers, (and a few without electronics as backups!) always stored with the battery removed, and they must be 10 years old now (guessing!), and still work fine.
Best of luck.
By the way, the same problem can happen with electronic calculators too....but as such electronics nowadays is so cheap to replace, its really not a big deal.....just annoying.
regards
Andy

Hi

Update on our findings this afternoon :-

1. Throttle and PAS again and motor worked intermittently then cut out.
2. Battery is fine as it was giving a reading of 41.9 V
3. Prongs and internal +/- on battery all look sound.
4. LCD display is working fine recording speed / mileage
5. Throttle working intermittently but was giving a reading of 4.8 V between the pins
6. Speed sensor is blinking red and appears to be functioning.
7. Main cable appears on visual inspection to be fine.
8. All the main connectors are tight

So that brings us to the Controller and PAS sensor in the motor. Did not open it up as it was getting dark and because I was at my mates did not have my crank puller and I wanted to speak to you guys first to possibly offer some advice as we have tentatively pencilled in to do it on Wednesday coming.

Incidentally to explain yesterdays multimeter reading my friend explained when he set the dial to V he was getting an error reading as he forgot to press the little black button in middle that changes the decimal point position. What he then did was measure 15.3 amps and used the formula P = I X V using a theoretical 36 volt to get wattage. I think I picked it up incorrectly we are happy that battery is sound.

 

[Nealh]

Have a look at the much over looked motor to controller connector and that it is properly and firmly all the way to the raised line on on the motor side.

 

[vfr400]

What he then did was measure 15.3 amps and used the formula P = I X V using a theoretical 36 volt to get wattage. I think I picked it up incorrectly we are happy that battery is sound.

Get a voltmeter and measure the voltage.

It's quite simple to find the source of the problem. If the LCD goes off when the motor cuts and has to be switched back on, the problem is with the battery or its connection. If the LCD stays on, it's a motor or control system problem.

 

[Andy-Mat]

Hi

Update on our findings this afternoon :-

1. Throttle and PAS again and motor worked intermittently then cut out.
2. Battery is fine as it was giving a reading of 41.9 V
3. Prongs and internal +/- on battery all look sound.
4. LCD display is working fine recording speed / mileage
5. Throttle working intermittently but was giving a reading of 4.8 V between the pins
6. Speed sensor is blinking red and appears to be functioning.
7. Main cable appears on visual inspection to be fine.
8. All the main connectors are tight

So that brings us to the Controller and PAS sensor in the motor. Did not open it up as it was getting dark and because I was at my mates did not have my crank puller and I wanted to speak to you guys first to possibly offer some advice as we have tentatively pencilled in to do it on Wednesday coming.

Incidentally to explain yesterdays multimeter reading my friend explained when he set the dial to V he was getting an error reading as he forgot to press the little black button in middle that changes the decimal point position. What he then did was measure 15.3 amps and used the formula P = I X V using a theoretical 36 volt to get wattage. I think I picked it up incorrectly we are happy that battery is sound.

My post was for possibly fixing the Vernier Calipers.....you mentioned that they were not working correctly, its a not uncommon problem!
Andy

 

[Radancer]

My post was for possibly fixing the Vernier Calipers.....you mentioned that they were not working correctly, its a not uncommon problem!
Andy

Right Andy I think we are on the same wavelegth now and I will give what you suggest a try