CYC Stealth Downhill Build - Need Ideas/Advice for Battery

[Marjoriefinnegan]

that is the cleanest cyc motor setup i have seen on the net. any wobbles of the battery or is secured well enough for hard rocky descents? what is the total weight of the bike? have u had a conventional ebike before that you can compare this build with?

Not my bike so can't help, it's someone on the cyc Facebook group.
Stealth and battery will add approx 8 to 10 kilos to your bike depending on battery choice.
2021 meta am around 16kgs so not particularly light.
I haven't heard of anyone having much trouble with wobbly batteries.

 

[mikethebikeguy]

Have you guys seen this from EBC?

52v 50amp 10Ah Mini-Max Samsung 21700-50S E-bike Battery

52V 50 amp 10Ah Mini-Max Lithium-Ion Ebike Battery with genuine Samsung 50S Cells. This battery is ultra-light (4.6 lbs), ultra-compact (3.75" X 3" X 6.75"), and versatile. Delivers 50 amps in a tiny package and was designed to fit perfectly in its saddle bag tucked under your seat. This 52v...

www.electrifybike.com

That’s really tempting to throw under the frame. I could probably get a metal case made for it and strap it under the frame with hose clamps. The bike would probably be sub 60 lbs then but with not so much range.

 

[Marjoriefinnegan]

Have you guys seen this from EBC?

52v 50amp 10Ah Mini-Max Samsung 21700-50S E-bike Battery

52V 50 amp 10Ah Mini-Max Lithium-Ion Ebike Battery with genuine Samsung 50S Cells. This battery is ultra-light (4.6 lbs), ultra-compact (3.75" X 3" X 6.75"), and versatile. Delivers 50 amps in a tiny package and was designed to fit perfectly in its saddle bag tucked under your seat. This 52v...

www.electrifybike.com

That’s really tempting to throw under the frame. I could probably get a metal case made for it and strap it under the frame with hose clamps. The bike would probably be sub 60 lbs then but with not so much range.

It'll give you decent range if you're not using loads of power

 

[mikethebikeguy]

It'll give you decent range if you're not using loads of power

Thank you, I wonder if it would actually give me similar range to my cr*ppy chinese-celled 52v 15ah that I max out constantly at its ~25A continuous ability

 

[mikethebikeguy]

I should update anyone following my project: I am scrapping the battery backpack idea altogether. Despite its many pros, my doctor says there's a high chance my back injury is directly correlated to bouncing around a cr*ppy 12lb battery backpack on my back for hours on end. Whatever solution I go with now is going to be mounted on the bike

 

[Marjoriefinnegan]

How about a custom pack?
Molicel p45b cells

 

[mikethebikeguy]

How about a custom pack?
Molicel p45b cells

Wow those cells have some impressive specs... and impressive price! I've found some equally impressive battery packs from Electrify Bike Co and Bicycle Motor Works that have swayed me away from thinking about making my own.

 

[mikethebikeguy]

Electrify Bike Co's Minimax 52V 10ah battery with their hard case inside an aluminum cage hose clamped to the frame and butted up against the motor... what do we think? Lightweight and powerful.

 

[mikethebikeguy]

Is it customary to start a new thread for install?
I’m planning to install the motor and test run the bike this coming Thursday with a cheap battery I have lying around. Thank you to everyone who has responded with opinions and information so far; you have really helped me through the thinking/drafting process.

 

[mikethebikeguy]

Motor install and first tests with temporary wiring and battery:

Problems to be addressed:

• The controller extension wires were great but the controller mount for mounting it elsewhere on the frame is plastic garbage (I just strapped it into the triangle). I will be making my own controller mount eventually.
• There is no extension wire for the speed sensor so I have no speed reading yet because I moved the controller forward on the bike. I need to buy more wire for that.
• I don't have the battery I want yet but I am saving up to buy it and saving up to get that custom aluminum mount made. It looks like there will be more than enough room to fit it under the frame with ease.
• I have a 7 speed cassette and I bought a KMC e8 chain and it's too thick to shift properly so I'm stuck on first gear for testing.
• The 48V 10ah 25A BMS battery I'm using to test the motor overheats after a few minutes of gunning it and it shuts off. Better battery is high priority.
• All the wiring/strapping is temporary and for testing!

It works though! It's super fun. I'm still healing from my back injury but I was able to take it up and down some stairs with its incredible ground clearance. I also rolled over some big rocks and stumps and dropped off a 2 foot drop. It has soooo much potential to be the most fun bike I'll own.

 

[mikethebikeguy]

It’s been two weeks since I logged in so quick update I’m just grinding away at work and saving up $$$ for the next steps of the build: battery, custom aluminum case, etc.

 

[ebikehound]

Hello mikethebikeguy,

I’m interested in the Minimax too and am interested in how you plan to get your aluminum case made. I spoke with the owner of Electrify Bike last week who told me the battery doesn’t have a hard case, only shrink-wrap, so given your mounting location, a sealed external case is important to protect it from impacts and water.

I also asked the owner for a template or detailed dimensions, but he didn’t have that info 🫤. So if I want to design a case I’ll need to buy the battery first. Frankly I would have expected better, but the Minimax with its 2P14S configuration of Samsung’s 50S cells is pretty impressive. So I’m willing to work a little harder!

I’m doing this because I need to update my wife’s XS ebike (pictured below). Its batteries are the (discontinued) Luna Cycle Wolf Pups. They’re each 4Ah and 52V (with Samsung 40T cells in a 1P14S configuration), and together these easily took her 16 miles. Unfortunately the lower battery went bad due to water intrusion or a bad motor, so I need to replace it. And doing so with the Minimax will increase her distance by 75%, which will be fantastic!

BTY I’m an engineer who’s been designing with SolidWorks 3D CAD for decades. I consider building a battery case via 3D printing, although I’ve never done that before. Maybe someone else on this forum might have suggestions as to material, shrinkage issues etc.? If I do design something I’d be happy to share it with you and others. I also had planned on a 2P14S battery (like the Minimax), but in a trapezoidal configuration as shown in the second image below. Doing this from scratch would take a lot of work though, and thus my interest in the Minimax. I’m also a little paranoid of blowing up my garage! Any ideas are welcome though, as I’ve been thinking about this for so long my brain hurts!

 

[mikethebikeguy]

I’ve been thinking about this for so long my brain hurts!

Me too man. Me. Too.

Thanks for your reply, I was going to buy it and have a metal shop make a case for me with one open side so I could remove it as needed with a plate and rubber gasket and hinge and screws. This is all just in my head as of now. Seems completely doable though. The build is still on pause for now. I hope to make progress before fall but we’ll see. Life is a rollercoaster!

Have you considered getting her a new bike that’s more battery friendly? You have a short travel bike there and I know many frames that could get a larger battery working… but I understand that may not be an option. Did you look into the saddle bag that electrify bike co sells too? Nice remote location for a battery with minimal design/fabrication needs.

 

[ebikehound]

My wife is Asian American and 5'0" tall, so this XS bike was the only size that would fit her. Even then I had to jump through hoops to dial in the geometry. She loves it though, with its low center of gravity, etc. I'm amazed with what she can do with it (although it freaks me out sometimes!). So after much consideration, it seems the bike stays. And unfortunately the saddlebag won't work, since with her 2.8" x 27.5" tires there's no clearance below the saddle.

So do you have a metal shop in mind? Most shops don't do design work so I'm curious what you have in mind.

I actually just joined this forum, so I also consider posting my battery idea(s) on one of the threads that might be more focused on the subject (?).

 

[mikethebikeguy]

My wife is Asian American and 5'0" tall, so this XS bike was the only size that would fit her. Even then I had to jump through hoops to dial in the geometry. She loves it though, with its low center of gravity, etc. I'm amazed with what she can do with it (although it freaks me out sometimes!). So after much consideration, it seems the bike stays. And unfortunately the saddlebag won't work, since with her 2.8" x 27.5" tires there's no clearance below the saddle.

So do you have a metal shop in mind? Most shops don't do design work so I'm curious what you have in mind.

I actually just joined this forum, so I also consider posting my battery idea(s) on one of the threads that might be more focused on the subject (?).

You can also throw a battery on the top tube (although I personally avoid this). I was going to design it in detail and take my design to a local metal shop and tell them to weld it! We’ll see though. I’m prepared for a “sorry we don’t do that.” Hahaha

Definitely make your own post! This is a wonderful community with many members MUCH smarter than me.

 

[ebikehound]

I'd thought about a top-tube mount, but she needs all the stand-over height she can get.

And thanks, I will consider making my own post (after doing a little homework). I think metal 3D printing is also possible -which would be sturdier, but of course the devil is in the details!

 

[ebikehound]

I meant to say metal 3D printing would be sturdier than plastic 3D printing (I assume?).

 

[mikethebikeguy]

Surprise! I sold the bike.

Now looking for another downhill bike to mount the stealth to. I really want a battery in the main triangle. I couldn’t get comfortable with the plan of having the battery under the downtube. Between build complications and me wanting a bigger sized bike I just decided I’ll go another route.

 

[Plummet]

Full credit to you for giving it a go. But why make it hard for yourself by getting a fame that didn't have an internal front triangle space?

I'd sell the bike and buy a different one that had a more battery friendly front triangle.
Here's one as an example.

 

[mikethebikeguy]

No way you chose that example I’ve been hunting for a mondraker summum for like a month now xD I bought the intense m16 when I was still planning on using a backpack battery…

If y’all see a listing for an XL Mondraker Summum 2016-2020 drop the link!!!

 

[annehemm]

A CYC Stealth Downhill Build sounds like an exciting project. When it comes to battery ideas and advice, it's all about finding the right balance between power and weight. Look for high-capacity, lightweight options to keep your downhill biking experience as smooth as possible.

You might also want to explore Bicycling Land for some valuable insights and tips on building your dream setup. They often have great articles that can guide you through the process.