Battery? Controller? ...no... Jimmy Wu's dodgy BMS.

[oddjones]

Hi - was riding to work the other morning and I noticed a lack of power for a couple of seconds... "Hmm, funny" I thought. Then it happened again... "Must have a look at that when I get to work" I thought - "maybe my dodgy soldering/crimping inside the motor has come undone".

Then the lights went out on my throttle and everything stopped working.

Thing is, I've tried connecting the phase wires together and turning the wheel backwards as per last time and there's resistance there - it doesn't appear that the motor wire has come loose at all - I will take the cover off the motor but I don't think that's my problem - The fact that there are no lights on at all kinda points in the direction of the controller - where do I start diagnosing that?

I've looked inside my battery/controller box and I can't see anything obvious...( no broken/loose connections)... bah.

On a brighter note - I have a brand spanking new set of Shimano Deore Disc brakes waiting for me at the post office and another 36v 10ah LiFePO4 chugging its way very slowly from China.

Maybe next time I should add a £0.50 fuse to the £40 controller...

[oddjones]

Err - OK - so it wasn't the motor. It appears to be the battery - as it's no longer giving out any voltage whatsoever (I've tested it both sides of the BMS and there's nothing - there doesn't appear to be any sign of damage to the BMS circuit board or components)... What can go wrong with a battery?



I wasn't pushing the bike at all hard when this happened either - indeed I was going downhill when it stopped working - might a cell somehow have come disconnected inside the Duct-Tape Pack?

(What have I done this time!!!)

It's another Chinese purchase and the thought of being without bike for 2 months while I send the battery back and have it replaced is really depressing - where do I start guys?

[marty]

Try charging battery? If that don't work? Unwrap the duct tape. Is there a fuse in there? Don't work on a metal table. Take off all jewelry. Careful with any metal tools. Sparks and Smoke are bad.

[oddjones]

Try charging battery? If that don't work? Unwrap the duct tape. Is there a fuse in there? Don't work on a metal table. Take off all jewelry. Careful with any metal tools. Sparks and Smoke are bad.

Battery fully charged - is there usually a fuse in these things? Want to see how likely it is before I start unwrapping - It'll be hard to send it back once I've unwrapped it!

(BTW I am a motivated website designer)

[Johnbear]

I have unwrapped my battery and there is no fuse inside. Yours may be different. It is very likely that a cell tab is detached from your description. If it is a bad cell maybe you can find it and your vendor will send you a replacement? Check with them and see what they have to say. I had a bad cell on a Yesa pack and he sent me a replacement right away.

[fechter]

Try measuring voltage on the small wires coming from each cell. It sounds like maybe a connection between cells broke. By measuring the small wires, you might be able to figure out which cell connection broke without unwrapping the duct tape.

[oddjones]

Try measuring voltage on the small wires coming from each cell. It sounds like maybe a connection between cells broke. By measuring the small wires, you might be able to figure out which cell connection broke without unwrapping the duct tape.

Umm - I don't seem to be getting a voltage across any of 'em?

Oh fer Chrissakes!!! >>note to self - "Make Sure your meter is working before you trust it"<<

There's nothing wrong with the battery at all - I had a broken wire on my meter.

However - that doesn't solve my actual problem of course... doesn't seem to be the motor, and I now know it's not my battery soooo -- by a process of elimination, the creeping finger of blame is edging towards my controller - what do I test?

The thing that's really bugging me about this whole episode is that I can't think of anything I've actually done to cause it - I wasn't crashing the bike around, I wasn't using the motor to pull my fat a** up hill...I got the two "semi-cut-outs" when I was riding along the flat - incidentally, everything seemed to keep going at this point - I just lost power for a second or so - which is what suggested a loose connection to me, then everything cut off about 5 minutes later as I was coasting down a hill (although I did have the throttle applied)

[dogman]

never mind, that was a dumb comment.

[John in CR]

Sounds like another wiring problem somewhere. At least you know it's not a phase wire again, and not your expensive battery. You can't rule out your controller though, because I don't like the sound of a "battery/controller box". The controller casing is typically an aluminum heat sink, so they need to breath. Check your power and on/off switch wires first, since if you have no lights you know it's not a motor wire, so that narrows the field considerably. Since you didn't kill the controller with that first torture test, you'd think it could handle normal riding unless it overheated in an enclosed box.

John

[fechter]

What controller are you using? Does it have a LED indicator?

[oddjones]

What controller are you using? Does it have a LED indicator?

Ecrazyman PIC based 36v controller - I didn't see a LED when I took the lid off.

[fechter]

It's got one burried in the middle of the board. If you take the end plate off and it's sort of dark, you should be able to see it light up when you turn on the controller. It's green. The number of blinks will tell you the status. If the LED does not light up, then it could be the orange wire is not getting power or something went bad in the regulator.

[oddjones]

It's got one burried in the middle of the board. If you take the end plate off and it's sort of dark, you should be able to see it light up when you turn on the controller. It's green. The number of blinks will tell you the status. If the LED does not light up, then it could be the orange wire is not getting power or something went bad in the regulator.

Well - it looks like the controller to me -this LED doesn't light up at all. I've checked the connections and switches leading into the controller and they're all good - I get 36v into the contoller. When I connect the controller up and measure across it I get 1v - bizarre.

However - not the end of the world as I was buying a new controller anyway - unless there's a magic button I can press

[fechter]

If you are sure the orange wire is getting power but the LED is dark, I would check the voltage regulator parts. There are a couple of big power resistors that would be prime suspects. The LM78xx regulator chips next to them would also be suspect. Could be something as simple as a bad solder joint. If you can hang a test hook on the resistors, you can see if they are passing voltage.

Voltage regulator parts.jpg (80.72 KiB) Viewed 656 times

72v Shenzhen Voltage Regulator.jpg (13.95 KiB) Viewed 657 times

[oddjones]

If you are sure the orange wire is getting power but the LED is dark, I would check the voltage regulator parts. There are a couple of big power resistors that would be prime suspects. The LM78xx regulator chips next to them would also be suspect. Could be something as simple as a bad solder joint. If you can hang a test hook on the resistors, you can see if they are passing voltage.

Voltage regulator parts.jpg

72v Shenzhen Voltage Regulator.jpg

OK you crazy engineering God - you have me hooked - I've got a few days while my new controller's being delivered anyway so - where am I looking? - I remember resistors from A level physics - they're the blue guys right? -- when you say they're prime suspects - what am I looking for? resistance across 'em?

LM78xx regulator chips - they're the big guys with three legs - what am I checking with them? - Bring it on!