Why won’t the e-bike turn on?

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The main part of electric bicycles on the Russian market, as you know, is made in China, and those that are inexpensive are in most cases assembled from low-quality components, and not by the most qualified assemblers.

In this regard, problems with the operation of such bicycles occur quite often. Fortunately, our people are savvy, and almost everyone can replace, for example, a throttle knob that was broken during a fall.

But where to start troubleshooting if everything worked fine, and at some point the electric bike just stopped turning on? I will try to consider all possible options in as much detail as possible, and I sincerely hope this article will be useful to someone. It is always nice to know that you are not doing something in vain, it gives life more meaning and inspires new work.

The very first and most important question: is the bike under warranty? If so, then first of all you need to contact the seller and voice the problem. Quite often, everything is decided at the stage of consultation and interaction with a responsible specialist.

Otherwise, as well as if you want or need to figure it out yourself, let’s go further!

Before disassembling something (which I love very much), you need to make sure that the power source — the battery — is working.

At first

Secondly

Thirdly

If there is no indicator, connect the charger. If charging does not start, the following reasons are possible:

By the way, some chargers require you to first insert the connector into the battery, and only then turn on the charger itself, otherwise charging will not start. This should be borne in mind if this is the first time you are trying to charge the battery without reading the instructions.

Thirdly

If visual inspection does not reveal the cause, you can measure the voltage at the controller power connector with the battery connected. If the voltage is the same as the output of the disconnected battery, the reason is not in the connector, but in something else.

If the voltage has dropped strongly or close to zero — the reason is either in a faulty connector (bad contact), or in a faulty battery (BMS board), or in a controller malfunction — see the section on the controller below.

As a rule, the factory version of the electric bike is turned on either by long pressing a button on the display (remote control from the display), or by a switch (button, turning the key) on the extended-functionality throttle grip, about a similar one.

In the case of a switch, you can disassemble the handle and «ring» it with a multimeter. Let me remind you that in this case (in the photo below) the battery power comes through the yellow wire, and when the switch is turned on, it goes to the voltage indicator (red wire) and returns back to the controller (blue wire) giving it a turn-on signal.

If you turn on the electric bike with a button on the display, you can try to replace the display with a similar one. If you don’t have one, you can try to find another owner of an electric bike with a similar display in your city (for example, through the forum

If everything worked when replacing the display, obviously the problem is in it. Later, I plan to write an article about repairing a KT-LCD3 (or just LCD3) display that has stopped turning on. So subscribe. 😉

On cheap bicycles, as a rule, low-quality materials are used — this is noticeable even when faced with low-current wires: copper conductors are very thin and there are few of them, the insulation is not heat-resistant and melts when the wire is tinned.

In this regard, quite often the cause of a malfunction is a frayed or broken wire. For example, in the case of hidden wiring inside the frame, the weak point is where the wires exit, since they are stationary inside the frame, and outside they bend when the steering wheel is turned.

If the manufacturer did not leave wires of sufficient length on the steering wheel, then when the steering wheel is turned 90 degrees or more (for example, when falling), the wire may be torn out of the display or throttle grip.

To exclude this cause of the malfunction, you should carefully inspect the wiring from the power button (from the display) to the controller.

If you are using a bicycle

If this connector was disconnected, and then unsuccessfully connected (with a bias), then one or more contacts could be bent.

You need to disconnect the connector and make sure that all 5 pins are in order, and then carefully connect.

If the integration cable is not used, and all wires from the steering wheel go directly to the controller, the malfunction may be in the controller connectors — either oxidation of the contacts in a humid environment, or disconnection of the connectors due to vibration.

Despite the presence of latches, the cause of the malfunction often lies not even in the connection of two mating connectors, but in the quality of crimping the wires and fixing the contacts inside the connector — if the antennae on the contact is not bent enough, the contact may pop out.

So to check the quality of the connections, you can slightly tug the wires on the connectors. If any pops up, it is likely that this is the cause of the malfunction. In this case, you need to bend the antenna more and insert the contact back into the connector. But before that, do not forget to de-energize the system so that it does not turn out like in the joke: «The autopsy showed that the patient can learn from the autopsy.»

It is better to start checking the controller by checking for a short circuit (short circuit) at the input. To do this, of course, first disconnect the battery from the controller. Now it is necessary to discharge the capacitors that are inside the controller and retain their charge after turning off the power.

This can be done by short-circuiting the contacts of the power connector through a resistance. It is possible and directly, but then micro-fireworks will happen, as a result of which traces may remain on the contacts.

Now we connect the multimeter and measure

So, if, as a result of the measurement, a resistance value of several ohms is obtained, then this is the reason — most likely, one or more power transistors burned out and the controller needs repair — I will make a separate article about this, so subscribe.

But I met another reason for the malfunction: as a result

If you look into the KT36 / 48 controller, then the turn-on signal equal to the battery voltage comes from the display (or switch) along the blue wire. The soldering point is marked with «DM».

And yet, I sincerely hope that in your case it did not come to the repair of the controller, and you solved the problem before reaching this paragraph.

If you do not want to understand the electric bike yourself, I recommend contacting a qualified specialist or an organization that provides service for electric bicycles. There are such organizations in most large cities (for example, in Samara —

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Thank you for being with me, and see you! There will be many more interesting things ahead!

P.S. Today there are already 300 of us! You have no idea how happy it is! 😊

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