This is a project I worked on for a friend. He wanted to use several batteries he already had, as a rechargeable power source for his E-Bike upgrade. The bike upgrade kit was available with a proprietary rechargeable Lithium-ion battery, but since he had quite a few rechargeable batteries already, we thought we might try and use them instead. The object was to use 6 Ryobi 18V batteries, without permanently altering the batteries. This would allow for dual purpose use, plug them all together and operate your bike, or remove one and power your cordless Ryobi drill.
Step 1: Create a Removerable Battery Cap
We started off by reverse engineering the Ryobi battery dimensionally. Doing so would allow us to accurately 3D model a removable terminal cap for the top side of the battery. We sourced a couple of spring clips, meant for the negative contact side of a AAA battery from an online electronics distributor. The size and shape of these clips fit the bill perfectly for our battery contacts. After creating the 3d model in Solidworks, we uploaded it to Shapeways.com, and had them print 6 plastic caps.
Step 2: Finish Battery Terminals
After receiving the 3D printed parts, it was just a matter of pushing the contact clips onto each battery cap, and soldering the wires to the terminals. We needed 50V, so we connected 3 batteries in series, 2 times. The three 18V batteries in series provided 54volts, then we wired two of these battery sets together in parallel to increase the amp hours.
Step 3: Button It Up
The batteries fit nicely into a small nylon bag, that gets strapped to the back of the bike. Each battery gets charged individually on a standard Ryobi battery charger, we have three of them. All 6 batteries are recharged in about 4-5 hours. This power supply provides enough power to get the E-Bike up to 30mph, with a range of 20 mileages.
We thought we'd share this project incase anyone else might like to repurpose their Ryobi batteries. The Plastic terminal cap is available to anyone who would like one, on Shapeways, search for Ryobi battery cap. The spring clips were ordered online, Keystone part # BK-204.