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Unit shut down suddenly and wont start


Jasonf20
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I was riding around and suddenly my unit shutdown and now when I turn it on it beeps for a second and then turns back off. The charger does not help. I opened it up and the only thing I could find wrong was a very slight dent in the battery because apparently it was loose and banging the walls. 

Any idea whats wrong? Thanks for the help

I was riding around and suddenly my unit shutdown and now when I turn it on it beeps for a second and then turns back off. The charger does not help. I opened it up and the only thing I could find wrong was a very slight dent in the battery because apparently it was loose and banging the walls. 

Any idea whats wrong? Thanks for the help

Edit: I checked the battery with a multi meter and it is currently outputting 58 volts. The sticker says it should be 67. I don't know if this is OK or not

 

Edited by Jasonf20
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It would help if we had a bit more idea what "Unit" it is exactly?

if the voltage states it is 67 (probably 67.2V) that would suggest it is, as is normal, a battery comprising of 16 cells in series and 67.2V is the fully charged voltage. Fully discharged should be between 55 and 50V depending on the wheel's firmware. So battery is low, but not too low to run the wheel. 

That means we next need to know what you mean by:"The charger does not help". Do you mean it says the battery is fully charged all the time or do you mean it seems to keep charging for ever?

if it is the latter then 58V is equivalent to 14 fully charged cells so one possibility is that two of your cells have failed or been damaged. The voltage would never get high enough to turn the charger off. that would certainly be likely to have the effect you describe. This is also more likely if you only have one set of 16 cells, I.e. If the watt hour capacity of the battery is less than 170Wh probably 120-132Wh. 

Edited by Keith
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1 hour ago, Keith said:

It would help if we had a bit more idea what "Unit" it is exactly?

if the voltage states it is 67 (probably 67.2V) that would suggest it is, as is normal, a battery comprising of 16 cells in series and 67.2V is the fully charged voltage. Fully discharged should be between 55 and 50V depending on the wheel's firmware. So battery is low, but not too low to run the wheel. 

That means we next need to know what you mean by:"The charger does not help". Do you mean it says the battery is fully charged all the time or do you mean it seems to keep charging for ever?

if it is the latter then 58V is equivalent to 14 fully charged cells so one possibility is that two of your cells have failed or been damaged. The voltage would never get high enough to turn the charger off. that would certainly be likely to have the effect you describe. This is also more likely if you only have one set of 16 cells, I.e. If the watt hour capacity of the battery is less than 170Wh probably 120-132Wh. 

Thanks for the replay. Some more info which might help according to your post. The wheel is some china wheel ao not sure of the model, can upload a pic if needed. But the battery is a 16s 132w standard cheepo. When I connect the charger the light on it stays green (it usually goes red until charged) and the battery should not be full because I had been riding for a while before. 

 

I've attached a photo of the "dent"  in the battery. I can't tell if this is enough damage to actually cause an issue

IMG_20160804_200201.jpg

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Usually a good assumption is that there is a single fault so the questions become: what single fault could cause these symptoms? Damage to the battery is possible from your picture but it is hard to tell.

Nothing is immediately leaping out at me so, although everything does point to the battery or its BMS (battery Management System) being where the problem is. 

let us start with what I do know. The charger, when the battery is low, starts by supplying a constant current, typically around 2 Amps. The charge LED goes red. The voltage slowly rises until it reaches 67.2V at which point the charger will hold that voltage and the current will start to drop. Eventually the current will drop down to a trickle. The Charger goes green once that current has dropped below a predetermined figure - say 100-200mA Note the charger does not stop charging and it is a good idea to leave it on accasionally for an hour or two longer to help fully balance all the cells to the same voltage.

So, bottom line, assuming the charger itself is not faulty all it takes for it to go green is the current being supplied to be below 1-200mA or, indeed no current at all. So first possibility is the charging lead has become disconnected somewhere.

Where did you read the 58V? Note the charging input is often protected for reverse polarity and short circuits with either a transistor or diode, so voltage may not read correctly across the charging pins, however some quite low voltage can usually be read with a meter - if no voltage can be read it is certainly disconnected.

That doesn't explain the failure to turn on as well, it is possible, but very unlikely,  the wheel won't run below 58V but there would be a fair bit of capacity left.

The more likely cause is that you do have at least one damaged cell, but damaged in such away that it won't supply any current hense the whole pack won't charge and voltage plummets as soon as you turn the wheel on, causing it to turn off again.

Assuming you have good continuity in the charging lead as far as the battery and if you check, carefully, the voltage coming out of the charger it is 67V within less than 1 volt the charger is probably OK, then I think you may find the damage in your picture is a damaged cell. You may have take the heat shrink off of the battery and check the voltage of each and every cell, they should all be the same 3.5 to 4.2V within 0.1V. Be VERY careful as these cells hold a lot of energy an accidental short can burn AND WELD.

Edited by Keith
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From the pic it looks like at least one cell is visibly damaged, which means you shouldn't use it as it may blow up at some point. If you're not familiar with electronics I wouldn't advise wasting time on testing and fixing it. No matter what's busted, there's no easy fix. Best case scenario only 2 cells are busted, and replacing them needs spot welding and mixing new and old batteries in one pack is not very good practice). If I were you I'd try to find a proper 60V power supply to check if the wheel works, and if so, get a new battery.

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3 hours ago, Keith said:

 

20 minutes ago, Keith said:
5 minutes ago, Tomek said:

 

 

 

thanks guys, I might test the cells tomorrow individually but according to the info you provided it sound like atleast a cepl is busted. (I thought if a cell is busted it would break the circuit and I wouldn't get any current but i measured 58 at both the charge and supply connectors). 

 

Do you have any recommendations where to get a replacement from? (international shipping required) 

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28 minutes ago, Jasonf20 said:

Do you have any recommendations where to get a replacement from? (international shipping required) 

If only one cell has been physically damaged it may be possible to solder a replacement in, it will be an 18650 cell and should have its type/size/make written on it they can be found easily, but be careful of fakes. A tagged cell would be needed, they damage easily if soldered to directly.

As @HECsaid @1RadWerkstatt Produce batteries which have a very good reputation on this site and good BMS built into them. As @Pingouin said, cheap wheels can have fairly awful BMS (the circuit board built into the battery) that can shut down, and stay shut down even after a power cycle on low voltage (in use) or high current. The MOSFET transistors controlling this can be shunted to stop it happening. However, they do reset when the battery is charged.

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I've opened the cell wrapping up and am pretty sure I have at least one if not two damaged cells. As you can see in the attached picture.

 

I have a soldering iron (but a cheap one so it won't heat up very fast) and don't plan on buying a welder. Is there an easy method to replace these cells with what I have or should I just buy a new battery?

01fedf9e-b735-4ff0-a540-3e6de33a3a2e.jpg

67e1d421-9171-42c6-9bd0-49fb7be9cb0f.jpg

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Those cells have taken quite a beating, the outermost metal layer on the other one looks like it's at least partially pierced! Good thing they haven't vented / caught fire, but I don't think you should keep on using those...

As for soldering directly on the batteries, I haven't done it, and it isn't recommended, but some people have built entire battery packs with nothing but a soldering iron. Still, it isn't very safe practice, as overheating the cell can easily damage it, even up to point of catching fire or exploding. The "critical temperature" where the thermal runaway (ie. the chain reaction inside the cell starts) is fairly low compared to soldering iron temperatures, something like 120-150 degrees Celsius, if memory serves.

You could try to ask around something like e-bike shops which built batteries, if they could fix it for you. If you choose to go the soldering road, read up on it and be very careful...

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8 minutes ago, esaj said:

You could try to ask around something like e-bike shops which built batteries, if they could fix it for you. If you choose to go the soldering road, read up on it and be very careful...

I Have read about it :) That is why I'm reluctant to try and fix them. I will however try asking around at shops if they are able to repair it. Thanks for the suggestion.

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