Ideas needed: Mount downtube battery with a twist

[mohammed]

Hello all,

I got myself an Eskuta SX-250 and want to add an extra battery to increase range.

I had an idea to use a read rack battery but they're out of stock at my usual vendor so was thinking about other ways.

The Eskuta downtube is covered by a plastic panel, see image circled in red. There is a few centimetres gap between the downtube and panel so was looking for some ideas for the best and safest way to mount a downtube battery.

I asked ChatGPT and it said following:

Given the gap between the down tube and the hard plastic panel on your e-bike, here are a few tailored solutions that could help securely mount the battery:

1. Custom Bracket with Spacers​

• Bracket with Spacers: You can create or buy a bracket that spans the gap, using spacers or standoffs to fill the space between the down tube and the battery mount.
• Materials: Aluminum or steel spacers, rubber gaskets (to reduce vibrations), and longer bolts that can reach through the spacers to secure the battery to the down tube.
• Installation: Measure the gap and select the appropriate size spacers to fit between the panel and the down tube. Attach the battery mount over the spacers, ensuring it’s snug.

2. 3D-Printed Spacer or Mount​

• Custom 3D-Printed Mount: You could design a custom spacer or even a complete mount that fits the contour of your e-bike’s plastic panel and down tube. A 3D-printed spacer could fit perfectly in the gap, providing a solid mounting surface for the battery.
• Advantages: This solution would be precise, lightweight, and allow for a seamless fit with the contours of the plastic panel and down tube.

3. Use U-Bolts or Frame Clamps​

• U-Bolts or Frame Clamps: You could use U-bolts or frame clamps that go around the down tube and extend through the gap between the tube and the panel. This would give you a solid anchor point for attaching the battery mount to the frame, bypassing the need to deal with the plastic panel.
• Installation: Ensure you use protective rubber or foam padding to avoid damaging the frame or the plastic panel.

4. Foam or Rubber Padding for the Gap​

• Gap Filler Padding: Use dense foam or rubber strips to fill the gap and create a flush surface for mounting. You could layer the foam between the battery bracket and the down tube to make the mount secure while reducing vibrations.
• Application: Cut the foam or rubber to size and adhere it to either the panel or the battery bracket using adhesive or strong double-sided tape. This will give you a cushioned, snug fit when bolting the battery in place.

5. Flexible Strap or Velcro Solutions​

• Heavy-Duty Straps: Use heavy-duty Velcro or ratchet straps that wrap around both the down tube and the panel. This could work temporarily or as a backup securing method if the battery is already mounted loosely with brackets.
• Custom Padding: Place a thick, non-slip padding (such as rubber or foam) between the battery and the plastic panel to prevent movement and secure the battery snugly using the straps.

6. Rivnuts and Custom Mounts​

• Rivnuts: If you want a permanent solution, you could consider drilling into the plastic panel to install rivnuts. Then, create a custom mounting plate that attaches the battery to the rivnuts, spanning across the gap.
• Advantages: This method would allow you to avoid clamping over the plastic, and create a solid attachment directly to the bike’s frame, without interfering with the plastic panel.

Is there anything the community could add to help me on this journey?

TIA!

 

[6zfshdb]

I used this product from Grin Tech:

Triple Bob

Triple Bob and Hose Clamps for Secure Mounting of Hailong-01, 21700, and Reention Downtube Batteries. See Product Page for More Information

ebikes.ca

I then mounted a Reention battery cradle like this one, but you could use a cradle for other battery types as well:

Battery Cradle, Reention

Spare Reention Downtube Battery Cradle. Use your Reention battery on more than one ebike!

ebikes.ca

You don't have a lot of space to work with though, so check measurements before ordering anything.

 

[mohammed]

I used this product from Grin Tech:

Triple Bob

Triple Bob and Hose Clamps for Secure Mounting of Hailong-01, 21700, and Reention Downtube Batteries. See Product Page for More Information

ebikes.ca

View attachment 184154
I then mounted a Reention battery cradle like this one, but you could use a cradle for other battery types as well:

Battery Cradle, Reention

Spare Reention Downtube Battery Cradle. Use your Reention battery on more than one ebike!

ebikes.ca

View attachment 184155

You don't have a lot of space to work with though, so check measurements before ordering anything.

View attachment 184156 View attachment 184157

Thank you for the suggestion! I've used something like this before but used it to mount to the rear rack, very handy.

My issue would be would the plastic panels be strong enough for the hose clamps as they won't be directly placed on the downtube, definitely worth a try though!

 

[indianajo]

I find hose clamps rather flimsy for structural use.
I cage the battery in a box of 3/4" aluminum angle. I use #10 SS machine screws and elastic stop nuts that don't fall off. Then I can attach the box to any strut with a 1"x8" band of #18 sheet steel with 13/32" holes drilled in it. I cut the sheet of steel out of a dead box fan shell. Again #10 screws are the attachment. If you live in the UK you may want to buy 5 mm machine screws. Use safety glasses when using power tools.

 

[6zfshdb]

Thank you for the suggestion! I've used something like this before but used it to mount to the rear rack, very handy.

My issue would be would the plastic panels be strong enough for the hose clamps as they won't be directly placed on the downtube, definitely worth a try though!

It's hard to see in your pic but you said there were a few CM clearance between the plastic panels and the down tube. You should be able to run the hose clamps through this space. That way, the bottle bob would contact only the downtube.

I use the bottle bob with a 10# Dorado 9C battery, and it hasn't moved a bit in four seasons of fairly rough trail riding.

 

[harryS]

Does the seat lift off to expose a storage spot underneath? I wouldn't put a battery there. Just curious.

Mounting to the plastic panels wouldn't work. You could use several clamps around the downtube to hold a battery bracket. Be creative. There are hose clamps, u-clamps, u-brackets. Use rubber inner tubes, etc, to protect the finish and don't tighten so hard you crush the tube.

Most battery cradles have no integral strength. You really need something like Grin's battery bob, but I've just taken a piece of steel and made my own. I have a drill press, so might as well use it,

Some people, those with experiece, will drill holes in the down tube and add riv-nuts. I bought a whole box of them, but every time I went to install a battery, I went for a non-invasive approach.

 

[mohammed]

It's hard to see in your pic but you said there were a few CM clearance between the plastic panels and the down tube. You should be able to run the hose clamps through this space. That way, the bottle bob would contact only the downtube.

I use the bottle bob with a 10# Dorado 9C battery, and it hasn't moved a bit in four seasons of fairly rough trail riding.

The thing is (might not have been clear in the OP) the plastic panel fits over the downtube.

Preferably I want to fit the bottle bob on top of this, maybe drill some holes though the panel to the downtube then attach some bolts through all this. My issue I think will be it might not be sturdy enough to hold a 5/6kg battery.

Here's a picture of the inside of the downtube panel: