Ebike power cuts out under load
 

I am having trouble with my e-bike. The power completely cuts out under load. The LCD goes blank and a key reset is required to get going again. The cut out happens very fast, after only about 15 seconds. The bike has been going well for about a year, and after reading these forums I made sure that I bought higher quality specced equipment. It is a 26" MTB based e-bike with a 1000W rear wheel kit bought from Dillenger electric bike in Australia. I have recently replaced the controller and the LCD screen.

Specs: 30Amp - 48V - 12 MOSFET Upgraded Wiring Controller, Brushless 1000W motor, Li-ion 10Ah 48V (upgraded wiring and LCD).

I looked inside the motor, and all looked fine. Smelled normal. When it cuts out there is no heat on the motor or controller or battery. I plugged in my spare controller and the same behaviour. Motor spins fine indefinitely off the ground. I examined all the connectors and plugs and connectors and all seem strong and secure and of good quality workmanship. All the posts about cutting out pointed to the battery being out of balance, and so I charged it for 4 days and the same thing happens. Photos of charger attached. The "charged" green light comes on and then stays on, I am not sure about how good the charger (and BMS) is at balancing the pack?


I pulled the battery apart last night hoping to find something obvious amiss, but all the connections and solder looked good. Smelled good. The key mechanism looked good, the wires were solidly connected. I looked into the BMS and it looked fine too. Images attached. I measured the voltage of the whole pack after charging for 4 days, 54.2v - is this too high for a 48v battery?


I couldn't get to the individual cells, but I measured across all the pins on the BMS (must be the cell groups?): 0v, 4.16, 8.35, 12.52, 16.70, 20.8, 25.0, 29.2, 33.3, 37.5, 41.6, 45.8, 50.0, 54.2. This means the groups? are (I think): 4.16, 4.19, 4.17, 4.18, 4.1, 4.2, 4.2, 4.1, 4.2, 4.1, 4.2, 4.2, 4.2. Charger says output +48v 2A.

<I am having troubles adding images>

I had a similar problem and the battery was the culprit. The system operated well for about a year, then had the characteristics you describe.

I agree that's what it sounds like.
Just because under no load the battery voltages look fine does not mean that under load the voltage will not sag enough to trip the LVC on the BMS and/or controller.

Thanks for this input. It is very helpful. I am very keen to do the next step in diagnosis. Can you please give me a hint (or provide a link) on how I measure the voltage under load? Especially if it is required to monitor each cell-group?
Thanks again!

You state that you recently replaced the controller and LCD. WHY? Did anything unusual, anything at all, happen around this time, and exactly WHEN was "recently" in relation to when this problem occurred?

Battery sag past LVC is what you are describing is happening. This can happen because the entire battery is low, this can happen because a single cell is too low, OR it can happen with a controller, like a recently replaced one, has an LVC which is too high.

Unless it shows on the LCD screen, I do not know of a way to check most controllers for what their LVC actually is.

Do you still have the original controller? Or can you borrow one?

The supplied BMS tends to be a weak link, mine blew in both batteries before long and i spent 90 quid on a good quality pair.

The only reservation i have is that you're getting complete shutdown. If the battery wasn't giving enough, and your controller triggered safety cut-out for lack of power, the capacitors in the controller would keep the system and display alive, cutting only the motor. So i'm thinking the battery isn't your main suspect.

I have no idea how to test the controller, but as the display is only a reflection of it's state, the problem points to that. An external wiring fault would expose itself between components but your No1 factor here is the controller going full shutdown.

Can you ride the bike on its lowest power setting?

I haven't been riding an E-Bike, but it sounds a lot like battery headlights that blink off :P

What I would do is get a simple multimeter.
Wire it directly to the main +/- terminals of your battery and add enough wire to get it to the handlebars.

Then ride your bike and watch the voltage (DC).

I'd anticipate that you'll see significant battery sag before it cuts off.

Thanks for the info and questions. The LCD was replaced because of a crash. The LCD was damaged. That was 6 months ago, and as you correctly surmise, it was about that time I started getting the issue. I still have the old controller and switching it in gives the very same problems. I bought the new controller because I was getting an error on the LCD (error 6 I believe) which suggested that the controller was at fault.

Your questions have picqued my interest to wonder if they are related. This post has my photos - ww w.pedelecs.co.uk/forum/threads/e-bike-power-cuts-out-under-load.32134/#post-451014

This video shows the behaviour. It cuts out at 1m20s and 2m20s into the video. Not that the voltage doesnt drop noticably before the cutout. Then I notice something funny, it still shows voltage at the battery terminals after key is turned off. Must be voltage coming back from capacitors in the controller??? Or key mechanism problem?

ht tps://photos.app.goo.gl/Amw3Tx8BuyUjEJkGA

Your battery was down to 48V when it shut down. I call that a noticeable drop if it started fulled charged around 54V and all it has to do is spin the motor with no load. Your earlier data does not show any of the cell groups to be off on voltage. All I would say is that maybe the battery is tired out.

You can, if you wish, look at LVC on that LCD3 display. It will will the C12 setting. If it was set too low, like at 0 which lowers LVC to 40V, that would have been harder on the battery.

I had the same thing happen. As others have said, I suspect the battery.

My commuters symptoms were almost the same, it would just turn off when I tried to pull power out of it. I replaced the battery and it is now fine.

RC, Like you, I replaced the battery and the problem was resolved.

That information should have been your very first post, it boggles my mind that you left it out.

Some additional information that might be useful is roughly how long you have had this bike, how many miles total, and a description of your general usage pattern.

Any more details about the battery itself might be useful, such as shrink wrap or hard-shell case? Where mounted? Type of power connectors? Any info on cells? How much did it cost? What color is it, and what kind of climate do you live in?

Couple of things I would do. Run the battery down for a while, Then test and report all cell voltages.

Use a strong light, magnifying glass, flashlight, AND a second pair of eyes, and go over every wire, every connector, and every individual pin in those connectors, start front to back, take a break, have a beer or whatever, compare notes, and then do it AGAIN back to front. After doing all EXTERNAL to the battery, then do the same thing INTERNAL. Take your time, you have several hundred dollars riding (get it?) on this.

It could be bad cell or cells, they JUST MIGHT have suddenly gone bad at the very same time you had your crash, it is possible, but...... IF, Repeat IF, the timing is as you report, I would have to call that Extremely Unlikely.