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Answers to Frequently Asked Questions

Whether you're an EV novice or expert, questions arise. We believe there are no stupid questions. When it comes to EVs and conversions, answering your questions can avoid mistakes like burning out a controller, or avoid hazards which can injure yourself or others. This is why we are committed to support and sharing as much knowledge as we can. Below you will find answers to many of the basics. If you can't find the answer you're looking for here, just ask in the comments at the bottom of this page and we will try to reply with a thorough answer for you. So let's start this discussion and keep it going!

  • I want to make an EV! How do I start and what do I need?

Start by checking out our How to Videos on YouTube.  Simply put, you need a motorcontrollerbatteries and fuse, contactorthrottlecharger and wire.  Beyond that, you may need or want to have a DC-DC converterbattery management systeminstrumentation or state of charge meterheatsinkprogrammermotor platesprockets and/or gear reduction, and of course a voltmeter and wiring tools.

These kits are still powered by batteries which are DC. The controller is responsible for inverting the power to three-phase AC. We recommend AC systems for high performance or high-efficiency needs.

One side of the adaptor plate bolts directly to your air-cooled VW transmission bell housing while the other side is bolted to the electric motor through a spacer block. The motor shaft has a taper lock bushing that attaches to the flywheel. The spacer block puts the motor and flywheel in the proper position inside the bell housing. The customer is responsible for attaching the bushing to the flywheel and bolting the components together.

There are several variables that will contribute to your decision. How fast and how far do you want to go? A higher voltage vehicle will go faster than a similar lower voltage vehicle. A larger capacity battery pack will last longer than a similar small capacity pack. Also consider how much current you will need to draw and be sure your batteries are capable of that, otherwise it's best to program your controller to only pull the max that the batteries are rated for. See Battery University for more. 

  • What's the difference between series and parallel?

Check out our Understanding EVs page.  There is lots of great info on the free site at Siemens.

  • What is a BMS?  What does that even stand for?

BMS stands for Battery Management System or in some cases, Battery Monitoring System.  In short, this enables communication between the battery and the charger preventing overcharge.  If you need more detail, here is a link to Wikipedia's article

  • Does the type of Charger I use matter?

Your charger should match your battery voltage and chemistry, and may need to be set up for your specific pack in the case of lithium batteries. Most plug right into a stadard outlet; fancier types use either a 220V input, or a J1772 plug.

  • Can my EV recharge it's own batteries with this fancy new secret generator thingy to have infinite range?

Unfortunately, no. Your new secret generator must get it's energy from somewhere. Usually that's in the form of the vehicle moving, which ultimately is powered by your batteries. Remember that energy cannot be created from nothing!

  • How do I know if my Controller is right for my motor?

There are a few basic categories of motor and controllers that we sell. Our Motor Compatibility Chart is a bit out of date now, but on each motor item page we mention which controllers will work.

  • Why don't you sell Kelly controllers?

We only like to sell things that we personally use, and when it comes to controllers, we like something we can count on. Although Kelly controllers work well for plenty of people, the difference in cost between a Kelly and something more robust, and proven effective, is pretty minimal when you consider the time it takes to install and wire a controller. We consistently get mixed reviews about Kelly controllers, even by field professionals.

This is basically a large safety switch (or solenoid) that connects the high power from your batteries to your controller. It is possible to damage some controllers by bypassing the contactor. Don't make that mistake!

  • What is that pre-charge resistor and diode that I see on the contactor drawing for?

On AXE controllers, the pre-charge resistor helps equalize the voltage potential between the batteries and the controller in a gentle way, as opposed to a sudden arc. This is good for longevity. The diode helps prevent any back emf from going to the controller that is caused when a contactor is opened. Sevcon and Curtis controllers handle this internally.

  • Why is there a discrepancy between the voltage rating on my contactor and my battery pack or controller?

Contactors are usually rated on their COIL voltage (also called enable voltage) and their current carrying capacity. Sevcon and Curtis AC controllers have adjustable coil outputs and are typically set up for 24V. In these instances, the controller is responsible for closing the contactor. Alltrax AXE controllers don't have a coil output, so your contactor is closed either by a key switch running directly from your battery pack or through a relay if you want a lower voltage to go through your key switch.

These are used to step down your pack voltage to 12VDC in order to use a vehicles OEM wiring systems' lights, horn, and accessories. Some are also capable of charging a 12V battery.

  • What's the difference between a Sevcon converter with isolated power and the cheaper Green Galaxy converter with a common ground?

The Sevcon has 4 wires: 2 in and 2 out. The Green Galaxy has 3 wires: in a 48V converter there will be 48V+ in, 12+ out, and one wire that shares both 12- out AND 48V- in. Where this matters to you, is that if you're using a 72V converter with common ground on a vehicle with chassis grounded accessories, in essence, you have grounded the battery pack negative to the chassis. It's up to your wiring as to whether or not you consider this a problem.

It is most always beneficial, but not always necessary. A cool controller will run more efficiently, and will be more robust. A cool controller also benefits the batteries and motor. If you are drag racing your controller probably won't get too hot from a 10 second burst but if you hope to have a 100 mile range, your controller most likely will get significantly hotter.

Properly installed instrumentation is better than occassionally using a voltmeter. How much did you spend on those batteries?? Besides, you'll want to brag about how far you can go, and how much current your drag car pulls, right?

  • How do I get my motor to spin my wheels?

We like chain drive for motorcycles and karts as they're relatively cheap and interchangeable. Don't forget to have a way of taking up chain slack like a slotted motor plate or slotted wheel stays. We use belts on our boat kit gear reductions as customers prefer them to be as quiet as possible. With cars you'll need to make or buy an adaptor plate to bolt the motor to the transmission, with or without a clutch. Occassionally we've seen them bolted directly to a differential.

  • What gearing should I use?

Check out our Gear Ratio Calculator.

  • Do I have to have a programmer for my controller?

Alltrax AXE controllers work at 100% output right out of the box. If you want to make changes, like to your low and high voltage settings or throttle ramp, you can download free programming software at Alltraxinc.com.

The Curtis AC kits also are sold as full functioning units and we will inquire as to your application before shipping so that we can set up your controller to work for you. If you want or need a programmer you should be prepared to invest some time learning the interface as it's not exactly a mass-produced, streamlined tool. The handheld unit is much easier to use, and is recommended for simple changes.

The Sevcon Gen4 controllers are typically set up and bench tested in house before shipping, and thus should not require any programming. If you decide you want to change a throttle type for instance, you can use either the handheld (for purchase or rental) or you may choose to invest in the pc based software, which is not very straightforward and involves a good deal of time to learn the ins and outs of. The handheld is simple to use, although not all of the more complex parameters are accessible. Sevcon does not provide a manual for the handheld, and you should expect to spend some time getting to know the unit.

Your controller will require a certain throttle type. Alltrax AXE has a default setup to use a 0-5K ohm potentiometer like the Magura twist throttle or Curtis PB-8. They can also be set up to use a 5K-0 pot or 5V source. These throttles can also be used on Sevcon and Curtis controllers as long as they are set up as such. Curtis AC controllers are usually set up for a PB-8 from the factory. Sevcon controllers are set up per the customers request for a small fee.  Thi is complimentary with the purchase of a kit.

Call us at 707-578-7973 M-F 9-5pm PST and speak with a specialist who can help you!  There are many variables that affect your speed and many find it helpful to speak with someone that has converted a similar size sailboat to get some real life performance stats. You're likely to find someone that can share their experience through the yahoo sailboat page or another Online Forum. You'll find lots of valuable information there from sailboat owners just like yourself.  Of course, we are also happy to assist you and answer any and all of your questions, so give us a call anytime!

  • Can I use a sailboat kit to power my go-kart?

It depends. You should probably let us know when you're ordering so we can be sure to help you choose the best components and features. There may be a better kit at the same or lower cost. 

  • Why are your sailboat kits so much cheaper than your competitors?

We largely use the same components (motor and controller) as some of our competition. We make our own gear reduction in-house which allows us to keep your cost low and quality high. Additionally, our gear reduction is optional.  Most other companies include the gear reduction in the price of their kits.  Not only are the gear reductions not optional, since theirs are not made in house they are more costly as their prices are dictated by their supplier.  Please also note that our kits are not a drop-in box.  The customer is responsible for proper mounting. This allows us to keep prices affordable and makes the kit more versatile for the large variety of boats out there.

  • What else do I need in addition to a sailboat kit to get me out of the docks and into the water?

We bench test the controller and harness of all the sailboat kits we sell to confirm that it's set up according to your needs. You'll need to get batteries and a charger. You will also need cables to put your batteries in series, and some way to hold your batteries in place.

Purchasing a heatsink for the controller is a good idea, but not always necessary. Keep in mind, how you mount your controller might change if you get one. Having air circulate through the engine compartment is beneficial, and may be necessary.

How you mount your motor depends on whether or not you install one of our gear reductions. If you decide not to employ a gear reduction, you'll need a thrust bearing somewhere in line with the prop shaft because most motors are not rated for axial/thrust loads on the shaft. The gear reduction can eliminate the need for that, and comes with a coupler for joining the two shafts. You'll likely need some large lag bolts to mount the reduction plate to your old engine mounts. Depending on your throttle type, you may choose to keep your existing throttle lever and run a connecting rod to the ET-134 or PB-8 throttle for convenience.

  • Why should I buy my parts, kits and components from ThunderStruck and not the other guys?

Find out why here!

  • What if I lose the manual to one of my components?

We keep our Manuals and Data Sheets up to date so you can refer back to them when you need them.

  • Can I return something I purchase if I don't like it?

We want you to be satisfied with your purchase and most items are returnable.  For quality and safety reasons, some items such as batteries are not returnable.  See our Return Policy for more information.

  • Help! I don't understand electrical theory!

Check out Battery Univeristy or our Understanding EVs See diyelectriccar for others who may have converted your same vehicle? You may also find this FAQ by Plugin America or The Endless Sphere forum helpful. Check them out!

  • I want to see more photos and videos of all of the great things you guys are doing!

That's great!  We try to showcase neat things we do and share what others in the industry are doing via our social networks.  Check them out below!  By adding us on Google+, Liking us on Facebook, Following us on Twitter or Subscribing to our YouTube Channel, you will be kept up to date on all our latest mischief PLUS you'll receive special discount coupon codes when available.

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  • Haven't found the answer to your question here? Ask us your question in the comments section below and we will do our best to answer it for you.


When starting a new project and considering ac or dc motors what should govern my decision.

The DC motors that we stock tend to be more simple and cost effective for smaller, or lower power projects. The AC induction kits we sell cost a bit more, but tend to be rated for higher power or for larger vehicles. There's no reason you can't use an AC drive in a smaller vehicle if there is space for it, and it's within your budget. If you want to fine tune the drive characteristics, consider a very simple DC controller like the Alltrax, or the highly flexible AC drives with Curtis controllers. -TSM
Gear reduction....all your data seems to be from diesel motors I have an Atomic 4 and need some info on if I need it.. Do you have any history for converting an Atomic 4 to Electric? Motor is out and Im ready to go once I have all the data

Absolutely you can convert a boat with an Atomic 4, in fact it's probably the most common engine to be replaced with an electric drive. Give us a call or email and we'll try to answer any other questions you have. -TSM
I have a house boat that we had to remove the motors on. I was impressed by your video on the sailboat motor.

The boat has a ton of room for batteries so it seems like it would be a good application to convert the boat to electric.
the boat only needs to got 5 MPH or max10. it is light . and has lots of room for solar panels and generator.

I would love to know what you have that would fit this application.

Hey Scott, what size engines were on it originally. We could find a motors with similar power outputs for you. -TSM
Hi there, I was told if I unhook my speed controller, my golf cart would go faster. Any input on this would be a great help!

I don't know what kind of motor and controller you have, but without the speed controller, hooking the motor directly to the battery is both dangerous and difficult to regulate motor rpm. This might be funny on an rc car but it's a bad idea on something this big. It may be possible to tune your controller for higher output though. -TSM
I am thinking about converting a simplicity 3316h hydrostatic tractor. I am thinking I can control rpms by battery voltage but I look to you for your knowledge. What would I need to make this garden tractor run well? I'm not too concerned about efficiency as I will add more batteries as needed. I plan on 4 group 31 bAtteries on the tractor and 4 more on a trailer or roller I will be pulling as I mow. Mowing with a 50" deck and snow blowing are going to be the main chores for what I use this tractor for. Let me know your suggestions and thoughts please. Thank you very much

Hi Darryl! The safest and most efficient way to vary the motor rpm is through a speed controller. This allows for a slow start with no giant sparks at your switches. Do you already have a motor picked out?
In your FAQ you say: If you decide not to employ a gear reduction, you'll need a thrust bearing somewhere in line with the prop shaft because most motors are not rated for axial/thrust loads on the shaft.
Can you please explain axial/thrust loads on the shaft.
I am planning to order 2800 RPM at 48v, (AC-20 w/1238-5601 if I use gear reduction, my RPM drops a lot. So please advise.
I have a 15ton sail boat.
Also interested in shipping costs to 'Belize, Central America.A
Thanks, Gale P

Hi Gale! That's an excellent question. The thrust bearing is to protect the motor from the forces of the prop. Imagine that the propeller is pushing the boat, so all of that forces to move the boat is pushing on the end of the motor. Most motors are designed around having a chain or belt on them, which has a different force, one that pulls sideways on the motor shaft, not directly into it. What kind of boat do you have? We are releasing a new stainless steel AC motor that is manufactured specifically for the marine industry. -Michael
Planning to install a Sevcon Brushless Sailboat Kit - 10.5KW with the TS Gear Reduction and would appreciate for my final plans the dimensions, specially of the gear reduction system.


Hi Carlos! We have dimensions of the motor and controller on our specs page found here:
The reduction plate is approximately 8"x13" with a shaft that is almost 10" from the plate. -TSM
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