"Switch" ebike, battery with one bad cell

[darth_elevator]

This is a general battery question that's quite a bit off topic, but I thought I'd ask you guys here first before starting a thread in the general battery forum. I picked up a non-functioning Switch ebike (formerly sold at Target) for practically nothing ($50). I figured it was worth more than that for the frame and parts, even if I can't fix it. Last night I took the 36v lithium pack apart and found that it has ten cells.



Based on what I found on a battery FAQ -- http://endless-sphere.com/forums//viewtopic.php?f=14&t=26621 -- it looks like this is a LiMn/LiCo pack, since there are 10 cells. It also looks like there is one bad cell. That cell reads 1.8 volts, while the other nine cells read 4.0 or 4.1 volts.

Anyone have any suggestions on where I should start looking to try to find a replacement cell? Am I even correct in concluding that this is a LiMn/LiCo pack?

 

[0utrider]

Anyone have any suggestions on where I should start looking to try to find a replacement cell? Am I even correct in concluding that this is a LiMn/LiCo pack?

They look like LiFePO4 prismatic cells. The 4.1 resting voltage throws me. I would expect 3.2. From the photo it looks like BMS wire leads?

 

[darth_elevator]

Yep, it has a BMS.

 

[0utrider]

Yep, it has a BMS.

I suppose you can separate that one cell and try to revive and charge it with your RC hobby chargers see if it can take and hold the voltage well. If so, perhaps the BMS is the problem. I can see where you made the deduction that they are Lithium Manganese or Lithium Cobalt because of the voltage.
I also see the difficulty you are having finding them! Google is not showing much of anything.

For curiosity’s sake, I'd sure like to see pics of the rest of the bike.

 

[darth_elevator]

...separate that one cell and try to revive and charge it with your RC hobby chargers...

Good idea. I'll try that. Not sure if this will mean anything to you, but before I disassembled the battery, the BMS was outputting 24 volts. Not sure if this is because it's a 24-volt motor -- in that case, then the controller's probably dead. But your guess that it's the BMS might be right. Before disassembly, the battery's voltage meter wasn't working. There's a button you push on the top of the battery casing that is next to an LED battery level display. But nothing happens when I push the button. Seems strange that the BMS would not output anything to the battery meter, while outputting 24 volts to the controller.

For curiosity’s sake, I'd sure like to see pics of the rest of the bike.

Here you go. It's a pretty decent cruiser with a nice elongated frame to fit a battery. The bike is in nearly perfect condition. I've had several ideas of what I could do with the frame if I end up not being able to get it going as currently set up. I guess if all else fails, I can build a 10Ah lipo pack for it. Or there's some good components that could be salvaged, like a sweet handlebar twist throttle. I'm amazed that someone would pay $1100 bucks for this. I sure wouldn't. LOL

 

[darth_elevator]

...separate that one cell and try to revive and charge it...

I put the low cell on a slow trickle charge until it got up to the same voltage as the other cells. Amazingly, after a couple days, it's still holding steady at that voltage. I suppose there's a chance it could tank again under load, but I think this is a good sign that it's holding it's voltage. I'll reassemble the pack and try it on the bike again. If it still doesn't work, then the BMS is a likely suspect.

 

[darth_elevator]

I reassembled the pack last night. Output voltage is now 40 volts, as it should be. Powered the system up, but I get clicking noises from the speed controller whenever I initiate throttle. So my next step will be to swap in a different controller.

 

[0utrider]

I reassembled the pack last night. Output voltage is now 40 volts, as it should be. Powered the system up, but I get clicking noises from the speed controller whenever I initiate throttle. So my next step will be to swap in a different controller.

That's very good news. If it's a bad BMS, the pack won't charge properly through it and will go out of ballance again. The good news is that it might be easier to find a BMS for a S10 40volt pack. So, with which controller are you going to replace the existing possibly damaged unit?

 

[darth_elevator]

So, with which controller are you going to replace the existing possibly damaged unit?

That's a GREAT question! LOL. I need to do some forum reading to get up to speed on what controllers are available for a 36 volt rear hub motor. Any recommendations? I haven't even looked at the controller yet. It's mounted in the frame, beneath the battery casing. I'm sure it won't be difficult accessing it. If there are any markings on it, I'll post a pic.

 

[0utrider]

So, with which controller are you going to replace the existing possibly damaged unit?

That's a GREAT question! LOL. I need to do some forum reading to get up to speed on what controllers are available for a 36 volt rear hub motor. Any recommendations? I haven't even looked at the controller yet. It's mounted in the frame, beneath the battery casing. I'm sure it won't be difficult accessing it. If there are any markings on it, I'll post a pic.

A knee-jerk reaction would be to suggest looking at a programmable controller from Lyen once we accept the fact that it’ll be more expensive than you have paid for the whole bike. However, I'm sure there are salvaged and other replacement parts out there for less. One thing I do recommend is making a separate thread for this bike. With the new topic, more people who can provide help could be brought into the thread.

 

[0utrider]

Oh! I forgot to mention this:
Would one of those ebike-system testers be of use? I've seen them listed at some sources for parts and kits.

From EM3EV
http://em3ev.com/store/index.php?route=product/product&product_id=87

 

[darth_elevator]

I tested the speed controller and the lower side mosfet on the green phase is blown. That will be a very easy fix! If I trouble determining the specs of the mosfet, I'll start a new thread over in the technical section. What a bargain! An ebike for $50 + 1 mosfet.

 

[0utrider]

I tested the speed controller and the lower side mosfet on the green phase is blown. That will be a very easy fix! If I trouble determining the specs of the mosfet, I'll start a new thread over in the technical section. What a bargain! An ebike for $50 + 1 mosfet.

Your knowledge and ability are of value too! You have to pay for your services. That makes the bike terribly expensive! Ha ha!

 

[dnmun]

if that cell goes low again you can check the operation of the BMS to evaluate it. it is easy enuff to test to see if the channel is shorted.

 

[Ykick]

Good solid find. I see very similar eBikes all over NYC for delivery riders and they hold up well.

You may very well get lucky if merely a shorted bleed balance channel pulled that cell down. It looks like a ruggedly designed pack.

 

[darth_elevator]

if that cell goes low again you can check the operation of the BMS to evaluate it. it is easy enuff to test to see if the channel is shorted.

Are there any online guides that show how to do this test?

 

[dnmun]

nope, nothing online to tell you how to do it except where i walked people through it before.

 

[0utrider]

nope, nothing online to tell you how to do it except where i walked people through it before.

Interesting! I'd like to hear how this turns out. Any opportunity to learn is eagerly sought!

 

[darth_elevator]

So it is simply checking to make sure there is continuity in the wire that goes from the cell to the BMS?

 

[dnmun]

no, if you wish to determine if the mosfet is shorted then you have to measure the current going through the mosfet when it is turned off.

it is turned off when the cell voltage is below the balancing voltage.

you can measure the current by measuring the voltage across the shunt resistor.

if you put one probe on the end of the shunt resistor connected to the drain of the mosfet and the other probe on the other end connected to the sense wire, then you can tell if there is current going through the resistor from the voltage across the resistor.

if the mosfet is turned off, there is no current so you see no voltage. does that make sense to you?

 

[d8veh]

They're Phylion cells. I can almost guarantee that the battery will need replacing. Phylion cells lose their capacity over time. Everything can look normal; they'll charge to 4.2v, but as soon as you draw any current, they sag right down. If you check them with a voltmeter afterwards, they've bounced right back, so it's very difficult to figure out what the problem is. You need a real-time voltmeter to see what's happening. I've had about 10 of those batteries to repair, and not been able to save one yet. Now as soon as I see those block-shaped Phylion cells, I cut off the BMS for spares and chuck the cell-pack. It's not worth wasting time on them.

I hope I'm wrong in your case, but I know which way I'd bet if my life depended on it.

 

[dnmun]

nothing like the voice of experience.

this is what makes this place work. not the censorship of free speech and stupid rules implemented from on high by insiders.

 

[999zip999]

The battery is the heart of an ebike. It pays to start with a good heart even if you pay for it so you can go ride.
Oh still have to find if motor and controller work, plus throttle.

 

[darth_elevator]

I tested the speed controller and the lower side mosfet on the green phase is blown.

I sent controller to Edward Lyen and replaced the blown mosfet for an extremely reasonable price.