RAT Electric Bikes

PAS (Pedal Assist System) is a ‘feature’ of most e-bikes on the market, but is optional when building your own bike. With my first e-bike, I did not install PAS and am very satisfied with using the thumb throttle to supplement pedal effort. My second build includes PAS and I have to say I’m not really a fan of PAS. My issue with it is that once you set the PAS level, when you start pedaling, the motor kicks in and depending on the level set, the bike might take off at a speed greater than you anticipated. Not good! I would prefer to modulate my starting-out speed myself.

My objective with this post is NOT to get into the legal implications (which I’ll cover in a future post) of PAS, but to convey my personal experience. I like riding bicycles and having a motor makes riding more enjoyable for me. I’m getting older, and promoting e-bikes for an aging population is a good thing, I think. But the concept and implementation of PAS just doesn’t cut it for me.

On the web, there’s lots of information about the care and feeding of current generation lithium-ion (Li-Ion) batteries (like this or this), but I’m going to boil all this information down into a few digestible points:

1. Invest in a better charger than the one that came with your battery. My favorite (and affordable) charger is the Luna Charger 48V Advanced 300W Ebike Charger for $100, or this one, the 48v 3amp Luna Mini Charger. The Luna allows you to adjust the charging rate and percent charge, both of which are important to the longevity of your battery. You might need to purchase or build an adapter for your battery. The Luna comes with an XT60 connecter, which is not what most batteries use a charging port interface.
2. DON’T charge your battery to 100% and let it sit for a long period of time unused!
3. DON’T leave your e-bike battery out in the cold (or hot)! It likes ‘room-temperature’ like you do, for storage AND charging.
4. DON’T use fast-charging unless absolutely necessary! Charging at 2 amps is better for your battery, but will take longer. Patience – your doing a good thing for your battery.
5. Using the Luna charger, DO charge your battery to 80% (at 2 amps) four times, then to 100% for the fifth charge cycle. This assumes you’re running your battery down to about 20% before each charge. Charging to 80% will increase your battery life considerably (in case you’re interested). Then a periodic 100% charge will ‘re-balance’ the cells to ensure you have maximum charge across all cells. The only thing to note when charging to 80%, is this will reduce your expected range a bit. My experience with the Joyisi 14ah battery is I get about 45 miles on a charge at 80% and 60-65 miles at 100%.

Bottom line: Treat your battery well and it will repay your kindness with improved longevity and range. Just something to think about…

Your new e-bike is built, your battery is charged, and you’re wanting to hit the road. Not so fast, there’s a bit of tuning required to make sure this e-bike is going to be safe to ride. As mentioned previously, having a bike stand or a way to get the bike off the ground will help getting your brakes and derailleurs tuned. So, in just 3 simple steps, you’ll be safely on your way to e-bike bliss!

1. Let’s start with the brakes. Disc or rim, mechanical or hydraulic, make sure your brakes and brake cables are adjusted so a) the brake pads aren’t dragging on the discs or rims, AND that the cables are adjusted so the brake lever travel is correct and doesn’t bottom out on the handlebar.
2. Next are the derailleurs. I adjust rear first, and I adjust it with the front derailleur in the center chain ring. Make sure the rear derailleur shifter travels from high to low settings cleanly and that the derailleur stops are adjusted so the chain doesn’t go past the highest and lowest gear. Once the rear derailleur adjustments are done, we’re going to check chain travel, then adjust the front derailleur. Move the rear derailleur to the smallest cog in the rear (highest gear) and the smallest gear in the front (lowest gear). What you’re looking for is tension on the rear derailleur without the chain touching the rear derailleur mechanism. If there is interference, then links must be removed from the chain. If not, then proceed with front derailleur adjustment. As with the rear derailleur, your looking for clean shifting from low to high chain rings, stop settings that keep the chain from going past the lowest and highest chain rings, and no drag between the front derailleur and the chain in each setting. I usually put the rear derailleur in the middle gear on the rear cluster when tuning the front derailleur. Once all is complete, test the full range on both front and rear an tweak as needed…
3. Test your electronics. First, depending on which kit you purchased, there is usually a way to customize the controller settings. Familiarize yourself with this and dial your settings in as appropriate (here’s a video for the SW900 display used with the Voilamart controller – video). Next, a quick test will determine if you’re actually getting power from the battery to your rear wheel. With the rear wheel elevated, power on the battery and the display. Check you throttle function and if the rear wheel turns in the correct direction, then you have functioning e-bike.

This is time for celebration! Congratulations… you did it!

This could be a really LONG post, because my builds take a lot of time to complete, but it’s not going to be. I’m in no hurry to complete a build, and I think it’s fun solving problems as I go, ordering a different part for an application (which takes time), learning something new, etc. So to make this post as short as possible, I’m just going to review my thought process and mention some places where I had issues that took time to resolve. So here goes:

1. You have your bicycle, e-bike kit, tools, and parts obtained from your inventory assessment – good start!
2. Strip ‘er down! Remove the parts you’re not going to use in your final build, check your head and crank bearings (replace as needed). Check your cables (replace as needed).
3. I start my rebuild with the wheels and brakes (assumes crank, fork and derailleurs are in good shape). On both of my rear-drive builds, I needed to add a shim to the derailleur side axle so the gear cluster provided by Voilamart would clear the chain stay. A washer obtained from the local hardware store did the trick.
4. Next, install shifters, brake levers, and throttle (I prefer a thumb throttle over the one provided by Voilamart, though you’ll need to do some soldering for this mod) – helpful video. Install you new cables and cable guides as needed. Brake and derailleur tuning will happen later, so this is just to get things routed and arranged properly. Make sure you have an appropriate amount of play in you cable guides forward of the handlebars so the bars rotate freely.
5. Figure out where you want to mount your controller box. My first build allowed me to locate the box below the top tube and above the battery. My second build required me to put the controlled on the luggage rack since there was insufficient space for it above the battery. Sort this out BEFORE you start routing wires (of which there are many).
6. Route and secure all wires. This is a bit of an art since you want the wires to be out of sight, out of mind, but compromises must be made. Here’s a close-up of my rat’s nest (hence my reasoning behind the name for this website):

Assuming everything is connected the way it needs to be, it’s time for testing and tuning. You’ll want your battery to be charged and ready to go for the next step…

You now have a ‘donor’ bicycle, a rear-hub kit, and a battery with mounting hardware. What’s next? Taking inventory, that’s next. What parts on the bicycle can be salvaged and what can’t? Using my ‘budget’ Trek 4500 as an example NOTHING WAS SALVAGABLE! Here’s my inventory list and parts cost. If you’re able to get a bike with more salvage value, then just subtract from the list below the things you DON’T need to buy, and that will be a fair estimate of your build cost. Case in point, the parts list below add up to just over $600, and that’s AFTER you just put out $600 for the e-bike kit! Are you sure you want to do this? You can stop now and buy that RadCity 4 for $1600 and be done with it. Sounds tempting…

Even though I tried to capture all the major build expenses, add another 10% for other stuff like a bell, lights, mirror, cell phone mount, thumb throttle mod – that sort of thing.

I didn’t say this build would be cheap, but there are ways to control your final cost. For example, my next (mid-drive) build will not be using disc brakes. I like the brakes and wheels that bike has, so other than the mid-drive kit cost, my other rehab expenses should be minimal…

Without getting into a rear-hub versus mid-drive debate for the moment, I’m just going to focus on rear-drive kits. My experience so far is with a rear-hub system sold under the name ‘Voilamart’. I learned about Voilamart through some YouTube videos and thought it would be a good place to start. Here’s the kit I used for my first build (and should have bought for my second build):

Voilamart Electric Bicycle Kit 26″ Rear Wheel 48V 1000W E-Bike Conversion Kit with Controller and LCD Display ($290 on Amazon)

The other expensive component you’ll need to get your e-bike on the road is a compatible battery. The one I chose, and am very happy with so far, is the Joyisi 48v 14ah battery

48V 14.5AH A Grade Cell (200W-1000W) ($310 on Amazon)

There are many other rear-hub systems you might want to consider. Bafang makes a nice 48 volt 500 watt kit for several different wheel sizes (here). Again, my experience (so far) is with the Voilamart rear-hub units, but you’ll find many of the commercial e-bike builders use Bafang parts, so I expect Bafang’s reliability is quite high considering that these builders need to stand behind their product.

PS – Later on, I’ll talk about mid-drive options, but until I install my Bafang mid-drive kit, I just don’t have enough experience yet to share. Stay tuned…

So, you have your bicycle and you’re ready to get started. Of course you’re going to need to think about e-bike DIY kits, but first, invest in some essential tools. Here are most of tools I use:

From left to right;

Star nut setting tool

Bottom bracket extractor

Cable cutter

Crank puller

Bicycle tire levers – 3 work, 4’s better

Crescent wrench and assorted open-end/box wrenches

Screw drivers

Chain breaker

Assorted Allen keys

Assorted sockets, socket wrench

(Optional) Headset press-in tool (I had a bicycle shop do the bearing race extraction, but made this $8 press-in tool to insert the new races)

(Optional) Lockring Removal Wrench & Chain Whip with Cassette/Bicycle Flywheel/Sprocket Remover

(Optional) Bicycle Chain Master Link Pliers Tool for Quick Link Removal

And of course, surgical gloves to keep your hands from getting grimy.

I’m sure there are a few other tools I forgot. And for my builds, a soldering iron, lead solder, electrical tape, assorted Zip ties, drill and drill bits, vice grips, etc. also have a role to play.

Bottom line: I helps to have a fairly well stocked workshop when building e-bikes! Also, even though I don’t own a bike stand, I do use a hoist system to elevate the bike when I’m working on different parts or tuning the derailleurs. This is very handy…

Being a Gary Fisher and Trek brand fan, my search is a bit easier than most, but let me reiterate what’s most important when considering using your existing bike or purchasing a used bike for your e-bike build.

1. Look for sufficient space between the horizontal (top) and down (between the headtube and bottom bracket) tubes for your battery. And while you’re here, it’s a good idea to know the bicycle size (measured from the center of the crank axle to the top of the seat tube) so you know the frame’s not too short or tall for you.
2. Look for usable/reusable components. The better the bike’s condition, it makes sense that your build should cost less to complete. Also, be sure you’re buying a bike that you e-bike kit will work with. My builds have all been on bikes with 26″ wheels. Be sure your kit matches the specs of the bike you’re going to use.
3. Consider what upgrades you’ll want to invest in and how much that will cost above the bike’s purchase price. On the average, your e-bike kit will add 20 lbs or more to the overall weight of the bicycle. Add your weight, and consider that you might be riding at speeds slightly higher than you would without a motor, and now you might need to think about installing better brakes. I prefer disc brakes on my builds, so I make sure the bike either has disc brakes installed, OR has the fork and frame hardware that makes a conversion to disc brakes possible.
4. Once you have made your bicycle choice and have a rough idea what you want to do and how much it’s going to set you back, it’s time to start preparing for your build. Next, I’m going to talk about some tools you’ll definitely want to invest in to help make your e-bike dream come true.

PS – I just went through the exercise of locating a suitable e-bike on Facebook Marketplace (my favorite place to shop for used bicycles). Here’s what I found (date 1/9/2022) for example:

Mens Trek 820 26″ Mountain bike 21 speed 19.5″ ($125)

I spent about this much just for a replacement front fork for my 4500 build, so at this price point, this could be a good platform to start with if the frame is straight and the bike has been taken care of. I would definitely check this bike out if I was in the market for another rear-hub build…

Whether you intended to or not, you just connected with my new website which speaks to DIY (do it yourself) electronic bicycle builders everywhere. In the ‘About’ section of this site, I’ll explain what this is ‘all about’, but for the moment, Welcome! I’m glad you’re here and I hope you’ll be able to learn something new before leaving to go to the site you had originally planned on visiting. Thanks again, and bye for now…