boring photo of a 36v 15Ah battery in a Granite Gear Armored Pocket

DIY battery box for electric Yuba Mundo

I’m trying out a new battery box for our electric Yuba Mundo.

I used the weather-resistant compact file tote from OfficeMax. Inside I’ve placed our 36V 15Ah battery from, which has first been padded in Granite Gear armored pocket. The padded battery fits snugly at the bottom of the box. Perfect!

The box has small handles, and I used this area to cut a small hole with a utility knife for the battery wire to come through. This placement means water would have to be going up to get into the box, so I’m expecting no rain and very little road spray could make in it there. ( Adding drain holes to the bottom could also be a good idea, just in case. )

DIY electric Yuba Mundo battery box: side viewbox is accessible, removable, water-resistant, and easy to add a wire-hole to.

On top of the battery is just the right amount of room left over in the box to carry all of our standard gear– bike repair stuff, spare bungees and a couple of bike locks.

The handle of the box also includes a small loop where a travel-sized lock could be used to secure the box. Perhaps this is useful to prevent some kinds of malice, but considering the box is plastic and the whole box could be easily removed, it might not have practical value as a security feature.

Previously we had kept most of this standard gear in the Go Getter bag. This was problematic when combined with the “Peanut Shell” seat. I could not prevent the Go Getter from sagging off the running boards, putting the weight of the electric battery and a heavy bike chain farther from the center of gravity. Besides being poor for handling, it made the battery connection less reliable– once after going over a bump, the battery disconnected– not good!

DIY electric Yuba Mundo battery box: inside detail.detail of the wiring hole cut with a utility knife.

Now everything is in a small, secure package held reliably close to the bike. It’s an added plus that the whole thing is easy to disconnect and take with us if security demands it. (Although between the battery and bike lock, the box must weigh more than 15 pounds! ) The size and clasp system of the Go Getter bag make it not a practical option to remove, especially when combined with the Peanut Shell seat.

I’ve just put on the battery box today. Now I’ll have to see if it works as well in practice as I expect. Any others out there with electric cargo bikes want to add how you protect and secure your batteries?

UPDATE 2/26/11 The setup in the photo suffered some from vertical bounce. To solve that, I bought a 4 foot cam strap and wrapped it around the box. That stops the bounce, and it’s easy to loosen the strap when I need to get in the box. If I stand up and crank the pedals hard, there is still a unnatural sway, which I think is due to the weight in the box and the location. Having the battery weight centered would be ideal, but isn’t so practical when the child seat in place. This works well enough.