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Installing circuit breaker or fuse, and on/off switch on Wilderness Energy Systems Worksman Port-o-Trike

I need to replace a 36V 600W 35 Max Amp Brushed Motor speed controller. The on/off switch and fuse were built into the controller.  I believe I can replace the controller alone with item SPD 36750A, which appears to have the same 2 prong connector or 36800A if I change connectors. It appears both would work with the thumb throttle THR 1000-2.  I will replace my current throttle since it will not be compatible to the new controller. Please let me know if I am correct in this research.  Which brings me to, how do I install a circuit breaker or fuse, and on/off switch?  I know they need to be attached between the battery and controller, but I do not know which parts to purchase and how and where to attach them, and what connectors to use, etc. since they were previously part of the controller.   I would appreciate any insight and directions you can give me.  Thank you.

Since your old controller is 36V 600W item # SPD-36750A would work as a replacement controller because its Voltage rating is the same and Wattage rating is the same or higher than the controller it is replacing.

Regarding installation of the circuit breaker or fuse, and on/off power switch they are usually mounted into a panel where the wiring is behind the panel and the switch rocker or lever, and circuit breaker reset button or fuse cap is in front of the panel. I believe that Wilderness Energy Systems electric bikes have all of their electronics placed inside of a fabric bag which does not have a solid panel though.

To make things easy I recommend using an inline fuse holder instead of a circuit breaker. That way the fuse holder can be tucked away inside of the fabric bag that the other electrical components are already in.

                       Item # FUS-360

For the power switch, the SPD-36750A requires an on/off power switch with a high Amp load rating, which would be very difficult to mount to wires and tuck inside of the fabric bag. So I would switch over to a different controller such as our item # SPD-36800B which can use a power switch that has a low Amp load rating. That way a handlebar mounted power switch such as item # SWT-21 could be installed and the power could be turned on and off from the handlebars.

             Item # SPD-36800B

                  Item # SWT-21

Please let me know if you have any questions.

Thank you for your response. How do I attach the inline fuse you mentioned?

(The previous controller had a rocker switch embedded in it. I thought the fuse was inside, but could be wrong. In any case it’s long gone.)

I need a compatible system of controller/switch/low battery light thumb throttle.

My current throttle is a 4 wire black red white purple which operated a low battery light. It is important for me to know when the battery is getting low. The 36800B would not allow for this feature to work. I have not been able to find a controller that would fit the 4 wire throttle I have, hence the reason for considering the 36750A or 36800A which uses the matching 5 wire THR 1000-2 thumb throttle I mentioned above, which has the low battery light.  Do you have a controller that would fit my current low battery light thumb throttle or what controller/switch/low battery light thumb throttle combo do you suggest?

Thanks in advance.


It is important to have a fuse or circuit breaker between the battery pack and controller for safety. The fuse holder should go on the positive wire anywhere between the battery pack and controller. The closer the fuse is to the battery pack the better, but if it has to be close to the controller that is okay.

A throttle with battery indicator can be used with the SPD-36800B controller. In fact the existing 4 wire throttle will most likely work with it. The existing 4 wire throttles purple wire would go the SPD-36800B's power light connector red wire. The existing 4 wire throttles remaining three wires would go to the controllers throttle connector with red to red, black to black, and white to blue. If you want to use a new thumb throttle with the new controller item # THR-68 would work, or even better our thumb throttle with power indicator and on/off switch item # THR-138 could be used with the SPD-36800B controller. On request we can install matching connectors on either of the throttles so they will plug into the new controller and work perfectly without any guesswork.



Thank you!  The THR-138 throttle with switch sounds great!  I will order that, the SPD-36800B controller, the  fuse holder and fuse. What determines the correct fuse? 
Also, does the loop on the fuse holder detach so it can be attached to the battery?  Sorry, but I need fuse holder beginner instructions. This is all new territory for me.


The SPD-36800B controller's wiring directions show that is has a maximum power output of 32 Amps so a 35 Amp fuse should be the right size for that controller.

The fuse holder wire loop can be cut anywhere before installing it so that it has two wires to attach. There is no polarity so it does not matter which side of the fuse holder goes to the battery pack or speed controller side. Here is an illustration showing basic electric scooter or bike wiring and where the fuse could go.

All factory made electric bikes have fuses or circuit breakers, and I have never seen one inside the speed controller, so chances are that your battery pack already has a fuse or circuit breaker in or near it. You may want to check for an existing fuse holder or circuit breaker so you don't unnecessarily install a second fuse holder and fuse.

If you do wind up needing to install a fuse holder then, unlike as shown in the illustration above,  the best and easiest place to install it is between two of the batteries as shown in the photo below.

Having high quality connections between the battery pack and controller wires is very important so they do not come apart and short circuit while riding. The downfall of many speed controller installations is poor quality wire connections.

If you would like we could professionally attach (crimp and solder) push-on connectors to the fuse holder wires that clip onto the batteries, and make wire harness adapters to go between the existing battery pack and motor connectors and the new speed controller connectors to make the installation faster and easier. I would need photographs of the existing battery pack and motor connectors in order to make adapters for them, and then I could provide you with a quote for the adapters.

 Here are a series of photos to figure this out.  I have not had any problems with these connectors in the past.  I would like the fuse loop to have connectors put on.  The charger is currently working fine. 

Close up of battery terminal

Close up of wire connector

I have looked all over for the fuse.  Just prior to hurricane Sandy I was following controller testing instructions, but I just can't remember where that fuse was.  Then the trike was stuck in the house for months before any of us were allowed back so getting it going again had to wait.  

Below, where I have purposely detached the battery wire loop, is this where I should put the fuse loop?

This is the old controller.  I will need a matching connector from the new controller to the blue and green motor wires which I will have to detach from the old controller.   How do I attach the new connector onto the wires? 

Here is a close up of the connector that comes off the battery.  Should you change the controller connector to match this, or should I change this to match the new controller?  This one currently works, but it is a bit worn and I wondered if it's not difficult to change to the new one then maybe I should.

So, those are my thoughts, but please tell me what all my options are.  Easy is better :)  Thank you very much.
Surprisingly I do not see any type of fuse protection in the wiring between the battery pack and controller so you should definitely add a fuse to the battery pack. It does not look like the fuse holder is missing but rather that it never existed. The fourth photo you inserted showing the disconnected red jumper wire is exactly where the fuse holder should go. The fuse holder should replace that entire red jumper wire. We can crimp and solder two CNX-06F battery connectors onto a FUS-360 fuse holder and include a couple of 35 Amp fuses with it for $5.95 parts and labor.

The easiest way to attach the battery pack to the new controller would be to use its existing wiring harness and connector. The battery pack connector in the fifth photo looks to still be in serviceable condition as it does not show any signs of overheating. There are some marks at the end of its terminals from sparking but they are only at the ends and should not effect the connectors ability to work properly.

We can make an adapter to go between the existing battery pack connector shown in the fifth photo and the new controller for $8.95 parts and labor.

We can install connectors on the THR-136 throttle that plug directly into the new SPD-36800B controller free of charge because it will only take us a minute to do.

That just leaves the connection between the motor and the new controller to deal with. I can not tell from the photos if there is a connector between the existing controller and motor?

If there is a connector between the existing controller and motor then we can make an adapter to attach the motor's connector to the new controller if you could insert an image of the connector.

If the wires between the existing controller and motor do not have a connector then you can cut the wires apart and we can make an adapter for the new controller that has two stripped wire ends. These wire ends could be attached to the motor wires with a crimp connector which is unfortunately named a butt connector.

Butt Connector

            Automotive Wire Crimping Tool

If you wind up needing to crimp the motor and controller wires together then a crimping tool should be used. An automotive wire crimping tool is a common tool so you may be able to borrow one, or purchase one if needed.

 The controller unplugs from the motor by the front wheel about 50 inches of wire away from where the battery and controller sit in the rear basket in a case.  You can see the black connectors with green and red wires just barely showing in the middle of this photo

Here is an overall photo showing the rear basket where the battery and controller normally rest and the forward wire connection to the motor by the front wheel.

I accidentally posted the connector to the old controller which for whatever reason is in better shape than the battery connector it was plugged in to, below.  It still works because I can make the motor run by plugging it directly into the motor connector as a test, but it kind of caved in some time ago and I had to pry it open.  What is your opinion?  The charger wire and battery wire are attached in the same terminals which is visible in the battery photo I sent earlier which could complicate replacing it I guess?  Suggestions?

I will be having the work done for the quotes you gave me.  Thank you again. 

Just wondered if you could respond to my comments and questions to the above 3 photos today or tomorrow so I could place my order tomorrow.  I am eager to get this trike up and running again, however I understand if you are having a busy week and cannot get back to me right away. 


The motor to controller connector in the photo above looks okay to me because its plastic is not melted. I would go ahead and use it. It can always be replaced in the future if needed.

I made item numbers for all of the adapters that you will need. All of the parts and adapters are listed below. The THR-138 is the correct throttle, not the THR-136 which I mentioned above. When you add all of the items that you want to purchase into the shopping cart it will add up all of the prices and give the price quote.

Please let me know your order number so I can write a note on the order explaining that connectors need to be installed on the throttle which match the controller.

Throttle, item # THR-138:

Speed controller, item # SPD-36800B:

Fuse holder with connectors, item # FUS-360:

35A fuse, item # FUS-ATO35:

Speed controller to battery pack adapter, item # CNX-2PX1:

Speed controller to motor wires adapter, item # CNX-WF632P:

Speed controller to motor wire crimp connector (2 needed), item # CNX-18:

Crimping tool (if needed), item # CRM-200:

I think that should cover everything needed for the project. Please let me know if you have any questions.

I just placed the order.  So you can write that note concerning the throttle connectors needed, my order number is 88502.  Thank you ever so much for all your help.  I could not have figured it out without your expertise. 
PS  If you happen to notice that 2-  8" tires are on the order and wonder if I ordered the wrong thing, no, I didn't make a mistake; that's just another project I'm working on.
You got it. I just made a note on your order explaining exactly what needs to be done. We will send all of the parts to you already plugged into each other and fully tested so it will be super easy to install.

If you haven't charged the battery pack in a while I would go ahead and charge it now so it is ready to use when the parts arrive.

We need to custom make several of the items on your order so it will take us a little longer than normal to ship the order out. I expect that we will ship it out in around 2-3 business day instead of our usual 1-2 business days.

After you install the crimp connectors that attach the motor wires to the controller wires, I recommend pulling hard on the attached wires to make sure that they are firmly crimped into the connector and can not come apart. Also be careful not to strip too much insulation off of the wires so that after they are inserted into the connector there is no exposed copper wire. If too much insulation has been stripped off the wire then cut a little bit off of the copper wire so it is not exposed after inserting into the crimp connector.

Thanks for letting me know about the two 8" tires on your order. However I notice that there are two 8" tubes instead of 8" tires on the order though. Probably just a typo, but just to confirm so that we send you the right parts: Do you need two 8" tubes or 8" tires?
LOL, yes tubes, not tires.  Just a typo.  Thank you for the crimp connector instructions.  Batteries charged and ready :)

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