E-Bike shuts down shortly after being under power.

[deronmoped]

I have a 36VDC brushed motor, Lithium battery with BMS and 36VDC controller.

This bike is not stock. I installed the controller and battery pack. The combination has worked great for probably a year now. Just recently the bike started shutting down when applying power. At first it would happen randomly, now it shuts down fairly consistently only after using power for a minute or two. The only way to get the power back on is to disconnect the battery pack/BMS combination from the controller. Then the bike powers up normally, until it does the same thing all over, that is, shuts down after being under power for a minute or two. It shuts down when I reapply the throttle after backing off to brake or shift gears.

What I tested so far:
I pulled the battery pack/BMS out of it's case and checked individual battery voltages and total voltage. They looked good. I looked for burned parts on the BMS and did not see any. I tried loading the battery pack up with automobile car headlights, but that was inconclusive.

I also took a look at the controller and did not see any burned parts or loose wires. All the other functions on the controller work, that is, power switch, brake switches and power indicator.

If I was to guess, the controller is sensing a over-current condition and is shutting down wrongly. What have experienced in the function of the bike is, the shutdown does not occur because of too much load. It shuts down without getting to full throttle or the bike being loaded heavily.

It could be the BMS too, sensing a overload.

I would hate to start throwing parts at it and I'm not set up to bench test 36VDC items, to determine if it's the battery pack or controller.

Anyone got any ideas?

Thanks, Deron.

 

[dnmun]

most likely it is sag on one of the cells that drops it below LVC. you should put some cellogs on the pack and if you get the recording type cellogs then you can just use the bike to get the data but if not use a bench test of the battery at 30A or so to see which is hitting LVC first. then check capacity and internal resistance.

 

[NeilP]

If pack is a year old, sounds like BMS is doing its job correctly and protecting low/dodgy cells.

Have you tried leaving the pack permanently connected on charge for two or three days?
if you have a cell that is very much out of balance, it could take that long for the BMS to balance the cells properly.

If, up till now you have always charged the pack leaving it on charge for 12 hrs or so , then this is unlikely to help....but if you have regularly over the past year only left the pack on charge till the ligth has gone green, then disconnected, you have not been allowing the BMS time to balance the pack at the top end..so one cell has got progressively worse over the past year, till now when it keeps tripping the BMS

 

[dnmun]

he said he checked individual cell voltages, but never listed them here. if you put some cellogs on the pack then it will show you if the pack is balancing when it charges.

 

[NeilP]

he said he checked individual cell voltages, but never listed them here. if you put some cellogs on the pack then it will show you if the pack is balancing when it charges.

If you want to go to the hassle of building the balance lead T- adapter that you would need to connect the cell logs and the BMS.

but just measuring the cell voltages won't be of great use..yes it will give you an idea of gross out of balance ..but as you say ride with a load of celllogs..that will then show a cell with large sag due to higher IR.

but for now, just leaving the thing on charge for a few days on end to give BMS a good chance to do its thing. Saves building up adapters for the cell logs just yet. if it works..problem solved and we can deduce it was a Balance issue..without having to make up the adapters.

If 3 days on charge and there is no difference.then yes fit the celllogs.

 

[deronmoped]

Cool, I will put the pack on charge for a few days and see what I see.

These are the big cylindrical cells, like 1.25"X4.75"s.

The voltages were, using my digital volt meter:
1) 3.3
2) 6.6
3) 10
4) 13.3
5) 16.6
6) 20.0
7) 23.3
8) 26.6
9) 30.0
10) 33.3
11) 36.6
12) 39.8 This voltage was measured at the output terminals.

I'm guessing my volt meter rounded up the voltages when it got close to 10, 20 and 30. Otherwise it seemed to be accurate.

One other thing, I bought this pack used off of EndlessSphere. So I don't know the history of it.

 

[dnmun]

it should charge up to more than that. your BMS will not force them to balance until you can get the cell voltage over the 3.6V for the shunt transistor to turn on.

 

[deronmoped]

At 3.6 volts, that comes out to 43.2 volts for the entire pack. The charger says 36 volts on it and that is the charger that was supplied with the battery pack. I will measure the output of the charger to see what it goes to under charging conditions.

 

[NeilP]

1) 3.3
2) 3.4
3) 3.3
4) 3.3
5) 3.4
6) 3.3
7) 3.3
8) 3.4
9) 3.3
10) 3.3
11) 3.3
12) 3.2

One other thing, I bought this pack used off of EndlessSphere. So I don't know the history of it.

And used as well...ahh..so yo have had it one year on top of the original age.

Try measuring all cell voltages immediately the bike cuts out. Guessing one cell is getting low...or maybe they all are ..
And if you can measure per cell like above, rather than cumulative that makes it easier to instantly see a low cell

 

[deronmoped]

Thanks guys.

Yeah, I would usually unplug the charger as soon as I saw that the charging light had turned green. I just assumed the charger new what was best for the battery pack.

Leaving my battery pack charging for several days did a good job of recovering the low cell(s). The charging light did not cycle between red (needs charging) and green (charged), but the charger held the voltage at almost 42 volts, for a 36 volt pack. The individual cell voltage did not show any change with the additional charging. They were anywhere from 3.4 to 3.7.

The bike ran with renewed power, stronger then it has in a long time.

I wish I would of known this before I tore the battery pack and controller apart twice

 

[NeilP]

Yeah, I would usually unplug the charger as soon as I saw that the charging light had turned green. I just assumed the charger knew what was best for the battery pack.

It know does, to a degree.
Having re thought what I said..the light may still stay green and the BMS could still be cycling on/off.

The green light (generally ) merely indicates that the charge current has dropped below a certain set point..probably 10% of charge current..so a 10 amp charger..once current drops below 1amp..light will change, but there will still be a small trickle charge running in to the battery.

It could well be that your charger and BMS are not 'tuned' to each other as well as they could be..so charger is going green before ANY cells on the pack have reached the BMS individual cell HVC point.
If this happens, then balancing is never occurring.


Did pack and charger come from same supplier...as a kit? ...and component values do drift over time.

Save me some work of re -reading the thread..what is the chemistry again? how many cells?

Maybe you could tweak the upper voltage set point of the charger by a few tenths of a volt...show us pic of charger...if it is easy to open, the insides too..it may be easy to identify if there are adjustment potentiometers to increase the voltage a bit.... Be really helpful and label the potentiometers in the picture...1, 2,3 so we an say..adjust number 2 etc

 

[deronmoped]

The battery pack I purchased used off of this site. It's 18650 cells, not sure of the chemistry. The charger came with the pack. It's one of those really cheap looking chargers, I pulled one apart before and did not see any adjustments. 12 cells. The BMS looks really well built, so I'm assuming the pack is of good quality.

I'm going to just change my charging style, from unplugging the charger after the green light comes on to, leaving the charger plugged in for extended periods of time. This worked to get the battery pack functioning really well again. If I start to have problems with this method I will look into what your recommending.

 

[DAND214]

Cool, I will put the pack on charge for a few days and see what I see.

These are the big cylindrical cells, like 1.25"X4.75"s.

The voltages were, using my digital volt meter:
1) 3.3
2) 6.6
3) 10
4) 13.3
5) 16.6
6) 20.0
7) 23.3
8) 26.6
9) 30.0
10) 33.3
11) 36.6
12) 39.8 This voltage was measured at the output terminals.

I'm guessing my volt meter rounded up the voltages when it got close to 10, 20 and 30. Otherwise it seemed to be accurate.

One other thing, I bought this pack used off of EndlessSphere. So I don't know the history of it.

The battery pack I purchased used off of this site. It's 18650 cells, not sure of the chemistry.

18650s are real small 18mm x 65mm and it would be 100s.

More like headways.

Dan

 

[deronmoped]

Your right, I just looked at the shape and that it was rechargeable and figured that the number meant the shape not the size.

Could never figure why cells are still manufactured in a cylinder form. I guess manufacturing ease is more important then capacity. Lots of wasted space between cells.

Is Headway the only maker of this larger size cell? Mine are the 10Ah cells, 36V pack.

This used pack cost me $250.00 with the charger. Looking at Headway's prices, $414.00, seems kinda pricy, it that the going rate?

 

[d8veh]

Your right, I just looked at the shape and that it was rechargeable and figured that the number meant the shape not the size.

Could never figure why cells are still manufactured in a cylinder form. I guess manufacturing ease is more important then capacity. Lots of wasted space between cells.

Is Headway the only maker of this larger size cell? Mine are the 10Ah cells, 36V pack.

This used pack cost me $250.00 with the charger. Looking at Headway's prices, $414.00, seems kinda pricy, it that the going rate?

$250 is a good price for a headway pack. They're LiFePO4, so will last a long time, and they can give very high current. I have a 10aH 36v Headway pack that keeps cutting out when I go over 20 amps, so I added a bit of solder to the shunt in the BMS, which fixed it.

 

[deronmoped]

So I found the problem. I did a load test and checked individual battery voltages and they seemed fine. I took a better look at the BMS and found the ground plug coming from the battery to be getting really hot, to the point that the plastic part of the plug was starting to melt. I got rid of the connectors and soldered the wires directly to the board. Next time, I will cut to the chase and just get rid of any connectors before they cause any problems.

 

[sagi]

Hi everyone,
i had the exact same issue and i try to charge the battery for 1.5 days and saw no improvements.

think i should try to plug it for longer period? i am a bit afraid that it will cause damages. Also, can someone please explain to me how charging should fix anything? from what i know, the charger stop charging after light has gone green...

thank you!

 

[amberwolf]

If your battery has a BMS that does balancing, and the charger is designed to restart charging when the BMS lets it and has a high enough voltage to do balancing, then if a pack is not balanced (low cell(s)), the charger may sbe hut off and turned on repeatedly by teh BMS until the cells are all balanced at teh same voltage.

On a new pack, or an older one that's badly out of balance, this could take days (potentially weeks, if it's really bad and the BMS has very low balancing current).

 

[dnmun]

Hi everyone,
i had the exact same issue and i try to charge the battery for 1.5 days and saw no improvements.

can you take pictures of your battery and charger so we can see what you have? do you have a voltmeter?

 

[sagi]

Hi everyone,
i had the exact same issue and i try to charge the battery for 1.5 days and saw no improvements.

can you take pictures of your battery and charger so we can see what you have? do you have a voltmeter?

please have a look

 

[dnmun]

so you checked the fuse on the battery and it was ok? can you open the end and pull the battery out of the case and take pictures of the BMS so we can tell you where to measure.

 

[sagi]

hi, i don't' know what you mean.. what is and where is the BMS? i didn't check any fuse i simply charged the battery for 1.5 days and saw no iimprovement

 

[d8veh]

There's several common possibilities that can cause your problem:

Connectors on the bottom worn or dirty
Faulty solder joint on the key switch
Worn out cell-pack
Faulty cell in cell-pack

Start by charging up the battery. Measure the voltage between the outer two terminals under the battery immediately after disconnecting from the charger. It should be close to 42v. If it's below 41v, you can suspect something wrong with your cell-pack. The further below 41v, the more likely the problem. Below 40v, it's a certainty.

Have a look at those terminals. Compare them with the inner two, which are not normally used so should be virgin. If the outer ones are spread, burnt or tarnished, you should take the bottom off the battery (switched off), take them out and squish them down a bit with thin pliers, or unsolder them and swap them for the inner ones.

If you have above 41v and the bottom terminals are OK, you have to take the top off the battery. Wiggle the wires soldered to the key switch to see if there's any sign of movement to indicate bad soldering. If that's OK, you need to get to the BMS.

If you have less than 41v, you need to get to the BMSW. Take the top and bottom off the battery (4 screws each), turn the bottom piece sideways on ans use it to push the cell-pack up by pulling down on the case and pressing against it. You only have to raise the cell pack a couple of inches, but if you pull down until that base piece disappears inside the case, you can stand up the battery while you work on it. The BMS is a circuit board on top of the cell-pack under the shrink wrap. You have to cut the corners of the shrink wrap and peal ir back a bit to expose the BMS, There you'll see a multi-pin connector in one edge. You need to pull that out and check the voltage of each pin with your other voltmeter probe on the thick black wire that comes from the cell-pack, where it's soldered to the BMs. You can stick a pin in one hole at a time of the multipin connector to make connection to your meter easy, or you can use the slots on the side of the connector, where you can see shiny contact points,

This photo shows one that has white covering. It's normally blue or black. You can see the BMS on the end with its ribbon cable to the multi-pin connector.

 

[dnmun]

hi, i don't' know what you mean.. what is and where is the BMS? i didn't check any fuse i simply charged the battery for 1.5 days and saw no improvement

you can measure continuity across the fuse with your voltmeter. if it is not burned open then put it back in and then measure the battery voltage on the charging plug on the battery.

you can measure the battery voltage first and if there is voltage on the charging plug then the fuse is ok.

what is output voltage of the charger? measured at the plug.

 

[Rocko]

If pack is a year old, sounds like BMS is doing its job correctly and protecting low/dodgy cells.

Have you tried leaving the pack permanently connected on charge for two or three days?
if you have a cell that is very much out of balance, it could take that long for the BMS to balance the cells properly.

If, up till now you have always charged the pack leaving it on charge for 12 hrs or so , then this is unlikely to help....but if you have regularly over the past year only left the pack on charge till the ligth has gone green, then disconnected, you have not been allowing the BMS time to balance the pack at the top end..so one cell has got progressively worse over the past year, till now when it keeps tripping the BMS

How would leave garter on battery that turns offvwhen fully charge you can not