Water-proofing, and basic ebike trouble-shooting

October 23, 2015

Sooner or later, even the most expensive ebike can have a minor glitch. The problem is that…right now there aren’t a lot of ebike mechanics out there. If you have a factory turn-key ebike, they might be able to give you some advice from an email, or over the phone. And if you bought it from an ebike store? (and it’s still under warranty), they might even fix it for you. However, for a lot of new ebikers, the emails and phone calls will end with the other side saying that this time…they just don’t know what the problem is.

This article will NOT turn you into an ebike repair expert, but…it might help you identify some common and basic issues, and either fix them, or…maybe even avoid them.


Basic trouble-shooting and also water-proofing of your ebike when the rainy season comes is something we’ve needed to write about for a long time. Well, that time has arrived, and we will expand this article as more information comes in. If this article becomes big enough (over time) we will break it into two parts (trouble-shooting vs water-proofing), but right now we need to get as much of this information out to our readers as soon as possible, instead of waiting until every part is perfect.

The basic trouble-shooting starter kit I am recommending is to have a spare throttle, a small back-up sensorless controller, and a Digital Multi-Meter (DMM). Over time, you will accumulate more tools, but this will give you a good start.


A spare throttle (from the same company as your stock controller, so the plugs are the same), and a small spare 6-FET sensorless controller. Banana for scale (to show how small a 6-FET is), and besides, who doesn’t like bananas?

Spare Throttle

Throttles are cheap, and it just makes sense to have a back-up throttle, since that is one of the components that might give you trouble. Even if you have a warranty on the stock unit, it is annoying to have to wait for the replacement to arrive.

I don’t like full-length grip throttles (similar to what a motorcycle has). I have seen friends start to fall off of an ebike, and they gripped harder on to the hand-grips…then as they fell, they inadvertently pulled the throttle to full power (Wide Open Throttle / WOT). For this reason, I have gravitated over time to the remaining options.

1) Half-grip, which seems to be growing in popularity for off-roaders.

2) Thumb-lever

3) Pedal Assist Sensor / PAS

I recently tried an ebike with both a PAS and a thumb throttle, and I liked the combination very much. That particular controller had the option for both, and when using PAS, my hands (and my mind) were completely free to get on the brakes at a moments notice, without any concern for what I was doing with a hand-throttle (this is the law in many European countries).

Which-ever style appeals to you, I recommend getting a back-up spare throttle from the same supplier as your kit or factory ebike, that way…the connectors will be identical. At the first sign of any issues, you can swap the spare throttle in (with the powered wheel in the air), and see if that fixes the problem. A bad throttle may be unlikely, but it is the fastest and easiest test to do, and besides, they are cheap, and…who doesn’t need a spare throttle?

Spare Sensorless Controller

Inside most ebike hubmotors there are Hall sensors. It is an ON/OFF switch that activates when a magnet is placed near it. Since the stator coils are divided into three groups (which makes it a common 3-phase motor), then there will be three Hall sensors which tell the controller precisely when to power each of the three phase-groups, on and off, each in their turn.

For an ebike that demands the ultimate in reliability, you might eventually go to a sensorless controller, but doing that means you may need to move the pedals a ¼ turn or more so that the controller can sense the position of the rotor before applying power. Some off-road ebikers prefer to have a hand-throttle of some type, when crawling over awkward and difficult technical obstacles…that way they don’t have to stop (while trying to balance themselves) and re-position their feet and pedals for the next nudge.

You are unlikely to ever find an ebike kit hubmotor with no Hall sensors installed, but…if you decide to stop using the Halls by going to a sensorless controller, you simply don’t have to plug-in the Hall wire socket (from the motor) into anything.

And, this brings me to why I am recommending a sensorless controller as a back-up. If your ebike is having problems, it could be any one of several problems. By swapping-in a sensorless controller…if the motor then works fine…you know immediately that the motor phase coil-groups are OK. Even so, once you reach that point…the fact remains that you don’t know if the problem is in the Hall sensors (located inside the motor) or in the stock controller, or…maybe the wires located between the two.

By this logic, you might wonder why you simply shouldn’t buy a back-up controller exactly like the stock unit. First of all, it might be a very expensive controller. Secondly, if you have a bad Hall in the motor…the stock controller might only work when using halls (some controllers have a “dual mode”, but most don’t). Ebike hubmotors have proven to be very reliable, but…on the rare occasion that there is an issue, Hall sensors are a top suspect. By having a sensorless controller, you can still ride your ebike while you decide what to do next (maybe file for a warranty claim on the hubmotor or controller?).


Hall Sensors are small and very cheap, but they are buried deep inside of ebike motors.

Although swapping-in a spare controller to give the wheel a spin is another test that is fast and easy, at that point…you wouldn’t know if the problem was one of the Halls, or the stock controller. The next step would be to scroll down to the section of this article on a DMM, and see how to test each Hall sensor wire while you hand-spin the wheel, to see if each one of the Halls are working.

If all three Halls are working, then the stock controller is bad (or possibly the wires between the controller and Halls, so check them for “continuity”). If one of the Halls turns out to be bad, the stock controller is probably OK. If a motor wire is damaged enough from a crash, to cause a separation in the copper strands that “eliminates continuity”, the damaged wires are usually pretty obvious.

Replacing a single Hall sensor is not technically difficult, and it’s easy to get it right the first time, but…it is a huge pain in the neck. You have to dis-assemble the motor, dig out the bad Hall, solder-in the new one (after you waited for it to arrive in the mail), and then re-assemble the motor…all for a tiny $2 part (actually, you should replace all three of them). Some hubmotors are even coming from the factory with a dual set of halls. If one of them in a set goes bad, the customer can simply just plug the controller into the second set.

So…get a spare sensorless controller.

EDIT: Here’s the best hall sensor trouble-shooting video I’ve found. You’ll need to buy a cheap 10-Ohm resistor to go with the multi-meter.

Testing Hall sensors

Here is a 3 minute youtube video on how to test the hall sensors while the wheel is still on the ebike. You shove the DMM negative probe into the negative (black) wire out of the 5 skinny wires coming from the motor (at the plug), and then you shove the DMM positive probe into one of the three signal wires. Spin the wheel, and the DMM should show about 4V on and off as the wheel spins. Then move the positive probe to each of the other two signal wires.

If any of those three wires do not read out an on/off 4V signal when the wheel spins…then that hall sensor is bad. A frequently listed replacement is an authentic Honeywell SS41, buy three and replace all of them as long as you have the motor a part.

Digital Multi Meter / DMM

This is the first and most important diagnostic tool that every ebiker should have, as soon as you get an ebike (whether it’s a kit…or a factory turn-key ebike). The model shown is about the cheapest I would recommend. I also have a $5 unit I got from Harbor Freight that I got when I was almost broke, but…it just feels like it could break at any moment from the slightest shock. This one is $15, and I opted to buy the second pair of test cables with spring-loaded alligator clips on the ends, instead of having only the basic set of needle probes.

Here is a 4-minute video that is a great introduction to the basic features and capabilities of a DMM.


This is a basic $15 Digital Multi Meter (DMM), from Spark Fun. Please pay the extra $5 to get the extra set of test cables with alligator clips, you won’t regret it.

Save the instructions it comes with, and mark the case near the probe cable sockets with a black felt marker and red nail polish (when the probes are removed for storage, it might be a year or so later before you use it again for a simple voltage test, and color-coding the sockets just saves you from needing to look it up again). Also, buy a spare 9V battery for it, and keep it taped to the back of the DMM.

[The black probe is connected to the common socket, which is often labeled “COM”]

I highly recommend also getting a second set of test cables with alligator clips ($5) at the same time. If the clips are not shrouded, paint their outer parts with liquid tape as an insulator. Of course, do not put anything on the teeth of the clamps, they must remain with bare metal exposed.

When I use this DMM, 99% of the time I am using the “0-200 DC Volts range” setting. If I was checking a 5V signal (from a throttle or a Hall sensor), I suppose I could use the “0-20 DC Volts range” setting, but…I am not really looking for the best possible accuracy. A Hall will either have a 0V signal or a 5V signal, and a functioning throttle will slide between 0V and 5V as the handle is rotated.

Don’t worry if you put the red/positive probe onto the black/negative terminal of a fully charged battery, the DMM will not be damaged, it will just read a negative number. Test this on a 1.5V flashlight battery to see what it looks like.

A bad throttle will always read 0V, or…the 5V signal might flash on and off instead of holding steady at WOT. Fortunately, this model of DMM has a fuse just in case of situations where: I have it set on the 0-20V setting, and I accidentally test a 48V battery socket. Although, it might just flash an “over range” indication. I really don’t want to change out a burned fuse, so I’m not going to test that over-range protection feature on my DMM.


Most DMMs have a continuity feature. That just means you want to test if there is a continuous connection between two points in a circuit. On this DMM, there is a buzzer, so if you put the two needle probes onto two ends of an insulated wire, the buzzer tone will indicate that there is no break in the wire underneath its insulation.

Part of the reason DMMs have needle-probes as their basic tool set is that…sharp tips allow a tester to poke through wire insulation and touch the copper wire inside, without needing to strip any insulation away. This is a very handy feature, whether you are testing the electrical systems on cars, motorcycles, or ebikes.

5V Power Supply

It can be useful to have a stand-alone 5V power supply, so you can test the Halls or the throttle…without needing to plug them into the controller (which is where they normally get their 5V supply). Halls can typically take up to 30V DC without being damaged.

1) Four 1.5V disposable AA or AAA batteries (equaling 6V) in a generic cell-holder found on ebay.

2) A cell phone “wall wart” charger.


The generic AA-cell holder on the top left can hold up to six cells, and I soldered the output wires onto the fourth cell terminal to produce 6V. The white “wall wart” phone charger converts 120V AC into 6V DC. Cut off the stock plug, solder 4mm sockets onto the wires, plug it in and test the sockets with the DMM to see which one is positive, and which is negative, then slip on some red/black heat shrink to identify them.

The plugs at the DMM-end of these test cables use a 4mm bullet/banana plug (on this model), and they fit OK into the common Hobby King 4mm bullet sockets (the common XT60 sockets are 3.5mm, and XT90 sockets are 4.5mm, so neither will work for this).

This can be handy, by allowing you to plug the DMM alligator clips onto a 5V power supply for testing. You can solder the 4mm sockets onto the cables from a four-pack cell holder of AA or AAA disposable batteries, and…you could also use a “wall wart” cell phone charger, which typically converts a 120V AC wall socket into 5V DC, in order to be able to charge the 4.2V batteries found in most cell phones.

Recently, almost all smart phones have converted over to using the mini-USB plug and socket in order to reduce the number of proprietary interfaces out there for all the different phone chargers. This means that any of those old 5V phone chargers that are not using a new mini-USB, and can be found for dirt cheap at just about any thrift store (I found the white one for this article for $1). After clipping off the stock plug, (slide on some sections of heat shrink) solder 4mm sockets onto the two wires, test the sockets with the DMM when the charger is plugged in (to identify the positive), then add 6mm red heat-shrink over the positive socket to identify it.

As a side-note, when testing Halls, most of them are known to be able to take up to 30V DC without damage, so an alternate method would be to use a common 9V battery as the power source (I would not use a 12V car battery for testing, since they are capable of very high currents).

Grin Tech Troubleshooting guide

Just found this, its a basic troubleshooting guide for ebikes. Definitely worth looking at.


This is one area where I get really angry at the Chinese companies that make almost all of the ebike components that are available. If these parts were water-proofed at the factory, it would cost just pennies-per-unit to do it right. Also, the customer who lives where it rains a lot (or it just sometimes rains unexpectedly) would not need to go through a huge hassle to make their ebike more water-resistant.

Even if you live where it rarely rains, (or you are the kind of ebiker who never rides in the rain), humidity and oxidation (from exposure to the air) can affect any electrical connector…and that can cause lots of problems. Even if your ebike works great when it’s new, just give it time, and…you will be searching for this article again, in a year or two down the road.

Lets get started! To research for this article, I set aside all my previous experience working on old cars, and decided to look at you tube videos to see what the newest info and products are. There are a LOT of youtube videos from RC enthusiasts who operate model boats.

We are fortunate in that most ebike connectors have a very thin plating of actual gold on the contacts. This makes them very resistant to the type of corrosion that results from exposure to air and humidity. The type of corrosion that hurts the connectors becomes bad much more rapidly if you live near the ocean, due to the salt in the beach air.


Apply dielectric grease all over the sockets and pins that insert together, and apply liquid tape at the butt-ends, where the wire inserts into the soldered or crimped joints.

The popular Anderson Power Poles have metal contacts that are made from silver-plated copper. Silver is also very good at resisting corrosion, but for water-proofing they also benefit from using dielectric grease.


These connector blades are likely to be zinc-plated copper. Clean them and apply a generous portion of dielectric grease. The green corrosion at the base of these blades show that they are copper at their cores.

If you are using connectors that are made from bare aluminum or copper, they will degrade from the bright and shiny clean aluminum and copper to a dull color, shown in the pic below. Some battery cases that slide into frame-mounts and have blades and sockets that mesh when the battery case is inserted. If the blades look like aluminum, they are most likely zinc-plated copper to resist corrosion.


Here are examples of bare copper and aluminum that have been exposed to the weather, so the dull side is oxidized. A light sanding is all it takes to improve the connection (on the right side of each example), and a smear of dielectric grease will keep the contacts from oxidizing after that.

Oxidation and humidity will cause corrosion that will reduce the conductivity of the connection, and…when you flow the same amount of amps through less of a connection, that smaller connection that exists will get hotter…MUCH hotter.

If you have an old ebike, you should clean the connectors, and then coat them with something that will seal them away from air (oxygen) and humidity. The smart move is to use “dielectric grease” from an automotive parts store, which is readily available and cheap. An “old skool” alternative is to use petroleum jelly (commonly branded as Vaseline), which does not conduct electricity, but it does easily and cheaply protect electrical connections from exposure to air, humidity, and rain.


Generic clear nail polish and petroleum jelly are the cheap way to protect electrical connections.

There are some parts of electrical components that you will want to coat in something that is waterproof, and also non-conductive. The cheap method is to use clear nail polish. It is made from nitro-cellulose, which is the same plastic that makes up billiard balls and piano keys, and it is dissolved in an ethyl acetate solvent (and cleaned up with an “acetone” based nail polish remover). This is one area where the cheapest stuff (found in a “dollar store”) is actually better than the expensive stuff. The cheapest stuff has the absolute minimum of additives (such as plasticisers and thickeners).

Clear polish also doesn’t have any metallic pigments, which could affect its conductivity. If you want to use red or black nail polish as a marker (in addition to being an insulator), I recommend you coat the item with clear nail polish first, and then the colored polish afterwards, just to be safe. If you use any type of nail polish, paint a a piece of scrap first, and test its conductivity with your DMM (you want there to be NO continuity, because it should NOT conduct electricity).


This is the good stuff for making your ebike water-resistant.

Now, if you want to insulate any electrical part in a professional manner, use a product called “Liquid Tape“. It can be found in the electricians supply section of any large hardware store, and it can be found for about $7 a can in black, red, green, yellow, blue, etc (plus it can be ordered from ebay and Amazon). If you use any insulation product for water-proofing, make sure to avoid coating any LED indicator or also any heat-shedding part. Liquid Tape is rated to maintain its integrity up to 200F / 93C, and your connectors should never get even close to those temps.

The benefit of using this over a $1 bottle of generic clear nail polish is that…nail polish will become hard and brittle, while “liquid tape” will remain pliable, flexible, and waterproof across a wide temperature range (below zero in a North Dakota winter, above 100F in a hot Texas summer)

If you have a battery bag (maybe a triangle bag from Luna Cycle?), you might also want to consider spraying the outside of the bag with “Scotchguard” or some similar water-proofing spray. Also, any wires or cables that are routed into any bag should have a drip-loop (just like a hubmotor cable) so any water that splashes onto it will run down and away from going into the bag. If a wire or cable enters a battery bag at the top, rain (or any splashed water) could run down into it, possibly causing an electrical short.

One example of this is the common Hall-based throttle. It has three tiny wires going into it. One is the positive/red wire, one is the negative/black wire…and one is the variable voltage signal wire (a signal between 0V and 5V). If water gets down inside the throttle, and bridges the positive wire and the signal wire…the signal wire will be getting a full 5V Wide Open Throttle (WOT) signal…not good!

Dis-assemble the throttle, and use clear nail polish or liquid tape to seal off the soldered ends on the wires from the cable bundle…and then coat everything with either Vaseline or Di-electric grease.

Here is a youtube video showing a test between clear nail polish and potting compound (it also tested silicone, but…he concluded…don’t use silicone because its messy, and has no benefit over clear nail polish.

Water-proofing spray, and water-proofing tape

There may be applications where you would like to spray an electronics-safe spray to make them waterproof. I was just informed about ACF50 spray, which is a common product for aircraft maintenance and repair. Its positive effect is rated to last a couple of years before needing re-application. I have also seen videos of RC model builders using “Corrosion-X” and also “Neverwet”

Also, many ebike kits put the connectors for the battery-to-controller…the three motor phase wires, and also the Hall sensor plug/socket…and they end up located on the bicycle frame, and exposed to rain and splashed water. Another method to waterproof these joints in a way that can be reversed without causing any mess, is to use silicone self-fusing tape.  It is very stretchy, and its surface “feels” sticky, but leaves no residue when removed.

There are many brands, but here is a video that shows what this product is capable of.

Mechanical throttle with a remote potentiometer

For the absolute most water-proof throttle, one idea is… don’t run electricity up to the handlebars and back! ES member gwhy! is an off-road ebike enthusiast, and frequently rides in wet conditions. His major concern wasn’t waterproofing (common ebike throttles can be easily waterproofed), but…he didn’t like the feel or limited selection of ebike throttles.

He was already familiar with gasoline off-road motorcycles in the trials competitions. Once he got used to the most popular trials throttles, he wanted the same quality for his ebikes. Why not use a gasoline trials bike throttle, and just have the cable actuate a generic potentiometer that is hidden inside a waterproof battery enclosure?

I am still assembling pics and specs, but if this idea appeals to you, check out this discussion thread here, and also the discussion here.

Marine-Grade, adhesive-lined, heat-shrink wire insulation

That was a long title to a simple suggestion.

I have a pile of various heat-shrink insulation in many different colors from Hobby King. Occasionally, I would buy something from them, and the check-out features informed me of the shipping weight, plus how much weight I could add without any additional shipping charges for a box that size. I almost always added some heat shrink, because it is dirt cheap from China, and several meters’ length is still very light.

Of course at first I bought a few meters of red and black in many different diameters/sizes, and then, after a while…I started also also getting some blue/green/yellow too (why not?).

Now? I have more than I will ever need, so I have started buying water-proof marine grade (designed for boats) heat-shrink wire-insulation that is “adhesive lined”. When it is heated in order to shrink it onto a soldered wire connection (I use a butane flame for its portability), the dry glue on the inside bubbles up and creates a water-proof seal.

I would still use the cheap Hobby King heat-shrink on indoor jobs (a battery charger adapter?), but…on my ebike, I now use black marine-grade heat-shrink wire insulation over soldered joints. If I want to color-code a certain wire (red/black/green/blue/yellow), I put some cheap Hobby King heat-shrink over the black water-proof stuff. Buy the “assorted sizes” box on ebay, specify marine and also  a 3:1 shrink ratio (2:1 heat-shrink is OK, but after you try 3:1…you’ll never go back).


Go to ebay, and buy an assortment of marine-grade, adhesive-lined, 3:1 heat shrink insulation for all outdoor ebike electrical connections. It’s cheap, do it. Use the cheap Hobby King heat shrink for color-coding and indoor wiring jobs.

Sealing the Motor internals for severe humidity

The endless-sphere member “dogman dan” lives in a very hot and dry desert, and the many times he has dis-assembled a hubmotor, he hasn’t had a problem with rust. However our other friend “Kingfish” lives in Washington, and even though his hubmotors have seemed to be reasonably sealed from the factory, when a hot motor cools down…it draws in humid air that will condense into liquid inside the motor case.


As a hot motor cools down, humid air can be drawn in through the bearing and cables. This is the type of rust that can occur.

Attempts at improving sealing of the motor have failed, and for extremely humid locations…we recommend adding small drain holes, and also coating the insides of the motor with a product that is designed for exactly that job. Experiments have suggested that humid air can be drawn in through the bearings and wire-cables.


This stator was being used on a purposefully ventilated motor, with holes drilled into the sideplates to allow excess heat out. This method is growing in popularity for racing ebikes, and the stator was coated in a motor sealant to prevent rust and corrosion.

Potting electrical components

High-end electrical components are “potted” which means that after they are assembled and function-tested, they are completely covered and filled with a water-proof goo that hardens. Not only does this provide the most extreme water-proofing possible, it also supports all of the individual parts against severe shocks (from dropping or a crash).

The Luna Wolf battery pack, fully potted



The rear hubmotor and controller from a Stromer ST1 ebike.

In the pic above, a Stromer rear hubmotor has been popped open to show the controller that is normally mounted in the center of the hubmotor. You can see that the Stromer controller is fully potted in black plastic. The wires in the coils of the stator look like they are bare copper, but each strand is coated with a clear varnish. The factory doesn’t allow pictures like this to be published, so don’t ask how we got this picture…we know a guy…(*wink).


The controller from the popular Bafang BBS02, shown here with the electronics fully potted in a gray waterproof compound.

Since potting makes it nearly impossible to repair anything on a controller, it is usually reserved for components from very high quality and reliable vendors (which are unlikely to ever need any repairs). And…this is the way that the best designs have waterproofed their components.

I have seen general-purpose epoxy used as electrical potting material with success, but…if you have no product preference…Scotch-Weld DP-270 is specifically made to be used as electrical potting (though I am sure there are many other quality potting products).

The cheap way to pot electrical components has been to use a common and cheap hot glue gun. I haven’t tried this, but it has worked well for many posters on the internet.

This article is NOT done!

Normally I would never publish any article until I felt it had been researched enough and all the required info was complete, however…the rainy weather will soon be here, and each winter I hear sad tales from ebikers who experienced catastrophic damage from water issues.

I will keep adding pics and info to this article as I find and verify them. If you have any tips that would be helpful as water-proofing advice, post them in this endless-sphere discussion for consideration.

Written by Ron/spinningmagnets, October 2015

Grew up in Los Angeles California, US Navy submarine mechanic from 1977-81/SanDiego. Hydraulic mechanic in the 1980's/Los Angeles. Heavy equipment operator in the 1990's/traveled to various locations. Dump truck driver in the 2000's/SW Utah. Currently a water plant operator since 2010/NW Kansas


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