Waterproof Custom Battery Case

[ShlomiMir]

I am a student of Industrial Design working on a Dahon folding build using a Bafang & Ping 36v 10amp setup. I have access to a vacuum forming machine and am planning on creating a custom streamlined case for the battery and controller that will replace the rear rack. For those who do not know, vacuum forming is a relatively easy way of forming plastic sheeting that is used for rapid prototyping.

I would like to create a waterproof plastic case for these electronics, but I am worried that they might overheat. I was wondering if anyone here had any experience with this sort of setup. How much heat sinking is necessary? Is metal the only way to go, or can it be done with plastic?

Any input welcome.

 

[lifepo4ever]

you can use a carrier case Schwinn like I do my 100volt controller is inside and battery pack also the only thing you can do is to put some vent hole . the controller is monted on the top of the case so you have some place for the battery . I use 2x 36 volt 15 ah ping battery ,one outside and one in the carrier case theses battery is also for sell 300$ each and only 75 cycle on it with a custom plexiglass case to protect from the water and element

 

[amberwolf]

One fairly simple way to work it is to integrate the heatsink(s) of any device(s) (BMS, controller, charger, etc) that will be in the case into the design of the case exterior so that airflow over the case will be guided thru the heatsink(s) as well. The heatsink(s) could be secured to the case so that there is a waterproof gasket or mounting coupling, and only the fins of the heatsink(s) would need to protrude from the case.

Alternately, a ducting setup from front to back that forces air to go around bends that won't allow water from above in would make it rainproof, but might still allow splash from underneath (like from tires) and would definitely allow moisture/humidity in.

 

[lifepo4ever]

Alternately, a ducting setup from front to back that forces air to go around bends that won't allow water from above in would make it rainproof, but might still allow splash from underneath (like from tires) and would definitely allow moisture/humidity in.[/quote]



yes and with this case it work very well and also if you want increase ventilation you can drill hole in the case of the controller like I made the best is outside but for my everyday use like to protect my controller from the element and also i stay stealth with this case , everybody think is a normal bike

 

[veloman]

My battery case is water proof from rain. It was $6 at Lowes, a plastic snap shut Rubbermaid "Handi-box". Bolted through the bottom to my rear rack.

 

[blues]

Assuming that you intend to use one of the "infineon" motor controllers, there are a couple of things to exploit in your thermal design. First, while all the FET's are mounted against the inside of the case, and the case has vestigial fins on the surface, this is actually a pretty poor system for convective heat removal. But, if you look at the cross section of the typical "infineon" controller case, the lower side wall and bottom of the extrusion are thicker than the rest of the walls. In my bike, I have mounted the the controller to a 1/4" thick aluminum heat spreader, sized to fit the bottom of the controller. This is sufficient to project through a hole cut in the bottom of the German "City Box" (vacuum formed ABS) panniers that I use to carry the battery on one side and the controller on the other. I attached a flat plate ( about 5 in. by 8 in. to the bottom on the aluminum heat spreader. This plate sits in the air flow under the pannier to reject the heat to outside air. A similar approach may be suitable for your design

The City Box Panniers have stiffening corrugations molded into the bottom and these serve to channel air past the heat sink plate which has proven to be a very effective thermal solution. I have a 48V 30 amp system and on long hill climbs that has the controller running near it's current limit for extended periods, the temperature of the controller case never exceeds "barely warm". I had intended to put a thermocouple on it and record the temperature but the temperature rise was so small that I never bothered. An additional advantage to this approach is that it is quite stealthy. The big City Box panniers cover the Crystalyte hub motor and the absence of most external visible hardware make it look like I'm just a fat old guy with a gray beard riding his bike to work--which of, of course, I am--with no indication of all the batteries, motor, controller, etc, inside.

blues