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Well, Ive actually been looking into this myself after being caught in the rain. Make sure to also seal up the battery box, it has leaks including along the top that let water in, and that big hole in front as well.

I was going to do a more old fashioned approach for mine until I could find a better way... slip some plastic bags over the parts so they are out of the water but usable. I'd be more concerned with water going down the lines through the hole in front and finding their way into the controller. So I'd find a good rubber grommet or some solid foam to cram in the hole and maybe tape over it with waterproof tape (or just tape over it well enough to keep water out of the bigger holes on the battery case).

Ive seen stuff online that is for electronics that you dip them into that 'waterproofs' the guts but I don't trust that myself. Other option, find yourself 2 clear boxes and mount them over the LCD and throttle so you can see and use but water doesnt get in. Other ideas anyone?

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For those new to Sondors and eBikes in general, or those that haven't found good information, one of the formost sites on the subject is electricbike.com. One of the foremost experts, that posts there goes by the moniker, "Spinning Magnets". He has written this article which although a couple of years old, is still 100% relevant and covers the whole topic of eBikes and moisture. None are waterproof and as he writes, "if you tempt fate sooner or later you'll need this info to help protect or diagnose a water based problem".

"Water-proofing, and basic ebike trouble-shooting

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 throttlefrom 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.


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.


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.

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)." R

Edited by Reddy Kilowatt

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I do the following and so far riding in rain my battery box stays completely dry.  Note this is true even though I have removed my battery cradle and use the resulting open air channel for ventilation.  I do NOT seal the battery box up because then I have created an oven, which is sub optimal for my battery and controller.

Generally, most of the water that will get into a bike and onto you comes up off the ground, not down from the sky (this is not true if you want to try riding in torrential summer downpours, like you get in the American South or during the wet in Australia).   So I concentrate on keeping the water off the bike from the ground and this has so far kept my battery box dry 100% of the time.  Note this is a practical not an aesthetic solution.

'mud' type off road fenders work extremely well for the above and are dirt cheap.  They are easy to install permanently with zip ties and they are easily removed or repositioned by snipping the zip tie and reinstalling.

  1. Front fender.  T'aint Muddy Hard Egghead front fender.  If you have a suspension fork the Egghead fender has slightly different hole positions to fit properly, otherwise its the same fender.
  2. Body Fender: Mucky Nutz Fat Gut fender.  This awesome thing does about 80% of the job all by itself.  In summer months, because I have the open air channel on my gen1 battery box where the cradle used to be, this fender keeps direct airflow - and dustflow - out too.  
  3. Rear fender:  Mucky Nutz Fat Face fender, mounted to the rear chainstay rather than the front fork.  After some experience in the rain I took a flexible black cutting board bought on Amazon for about $4, and using matching black gorilla tape and some heavy scissors, cut the cutting board into a strip that extends the fender forward so it fully covers the rear tire down to the bottom bracket (its cut at a decreasing angle so it isn't massive and tucks neatly behind the seat tube).  Next I went a little insane and did the same thing out back, extending the fender and attaching it to the underside of my rack (more zip ties), going about 6 inches past the back of the rack so its a long tail that keeps water spray from coming up at me from the back.  You do not need to go to this extreme but if you want to get serious about a rear fender thats one hell of a solution.

By the way... if you don't want to see the advertising/logos on the fenders, just install them upside down and the logos are underneath now.

For the front hole in the battery box, I just use a short length of Velcro One Wrap and wrap the wires right in front of the hole, so it makes a sort of big round non-fixed barrier.  Thats plenty to keep water from splashing in.  You could also do the same with rubber mastic or any other thick tape but the velcro is easily attached or removed/repositioned.  Buy a box of 100 of them and they have so many uses you will use the first roll of 50 in no time.


For all of the HIGO plugs and the motor plug on the chainstay... they are waterproof in the first place, but a standard recommendation is to apply dielectric grease to all of the plugs.  It has the consistency of vaseline and it will not hurt the plugs.  Google it or find it on Amazon.  Do not cover the motor plug in, say,  Saran wrap or a similar cling wrap.  I tried that and it turns out it holds onto water which eventually works its way underneath and onto the plug.

Lastly, a plastic sandwich bag covers my LCD with a rubber band holding it snug.  

So far so good riding in all weather conditions.

Edited by MattRobertson
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Also I might add, not sealing the battery box is a good idea. Ive got a fan in my fatty's box to pull air through to be safe.

But in torrential downpours as Matt said, the box is going to leak. From my experience, its the top and top front corner where water comes in. It pools between the frame and box due to molecular cohesion and location and then finds its way to the seam at the top.

You can, if you wish, put a strip of tape along that seam if riding on a day when its going to rain or is so top down stuff doesnt get in. Ive been trying to find a thin rubber or foam piece to put there so when the doors closed it cant get in the top and top corners, esp in front.

I think (and this is me spitballing here), the 2 big holes bottom and front could be "covered" in a way to stop splashing but to allow air in, just be careful of water running along the cables down into it from the bars. Not enough length to make a drip loop there sadly.

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Funny you should mention that.  I do have a drip loop up front but I also have a totally different wiring config thanks to the front motor, custom cables in the box and so on.

The tape on the top seam is a really good idea.  If its looking like a serious rain, not a bad idea to tape up the top of the door seam before you go out.  Simple scotch tape would be plenty for the trip out that afternoon..

Edited by MattRobertson

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Matt, I can totally see you doing a drip loop. You seem like the kind of person who thinks of this stuff for sure. I thought about it but it was passing and when I tried to get some extra cabling via extenders I ran into snags finding the cables.

I personally would avoid scotch/transparent tape due to its difficult removing and if that box flexes a little when biking it could pop that seam possibly. I use a strip of Monster tape that I've folded one end over so I can grab and pull it. I was thinking of trying to figure out how to get back access to charging via the port in the side of the door and then just seal the top w white electric tape or similar.

I do want to put a thermometer inside that tracks temp and saves history so I can see what temps the inside gets in diff places esp near the controller. I had a BBQ grill one that connected to the phone I was going to use and it would easily fit in there but of course I broke it when I grilled last. It stored history of temperatures, alerts at temps you want, timers etc. An alert if its too hot would be nice. And it would help me figure out how to waterproof but still let it breathe.

Ive got some of that Velcro strapping on order BTW. I could use it for cable wrapping too, as well as how you suggested. :D


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6 minutes ago, alienmeatsack said:

I do want to put a thermometer inside

I use this one.  Its dirt cheap and dead nuts accurate.  Plenty of cable length to string anywhere inside the battery box up to the bars.


As for drip loops, in another life my wife and I bred tropical fish in our apartment.  I think we had 9 fish tanks and yeah pretty much thats against the rules.  But drip loops were de rigueur... or else :-)

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