Can I seal the battery compartment?

In order to make my E-bike (FUTR Alpha frame, Qs motor) waterproof I was thinking of sealing the battery compartment. But then I thought maybe that's not a good idea? After all there is this thing called condensation. My plan was to first seal the two holes in the back of the frame where the cables come in. To prevent any water or similar to ender from the rear wheel. Then I was going to seal the side panels by putting a good silicon sealant around the panels. Is this a terrible idea?

My observation from years of working on bicycles is that you can't reasonably expect to keep water out, but you can very easily keep it in while trying to keep it out. Drains are even more important than seals, it seems. Go nuts with the sealant if you like, but put a hole at the lowest point where water might tend to collect.

Just about every drowned controller I've seen was from people that tried to seal them. I would always recommend leaving a route for water to get out. By all means try and prevent the water getting in from the top, but never seal the bottom.

I don't believe that condensation is a problem, but damp salty air could cause some long-term connector issues.

A dry box that still lets some air in and has a drain would be best. The battery will be warm when you run it, so it will tend to dry itself. And do try to park under a cover, you really can't just park out in the rain 24-7. When you must park in the rain, like at work or whatever, cover critical stuff like the bars, the battery, the controller.

Some kind of pipe fitting with an elbow, open end down, will do for the air vent IMO. The big deal is not having something that directs water into the box, or motor, or whatever. This is called a drip loop, a small dip in the wires so water running down the wiring drips off before it enters the box, motor, etc.

And then, fenders. Dirt motorcycles have em, street motorcycles have em. Why are they left off electric dirt and street bikes? Weight of course if pedaling, but you are not pedaling at slow speeds.

Thanks for the great replies! I'll keep all of this in mind

Chalo said:

My observation from years of working on bicycles is that you can't reasonably expect to keep water out, but you can very easily keep it in while trying to keep it out. Drains are even more important than seals, it seems. Go nuts with the sealant if you like, but put a hole at the lowest point where water might tend to collect.

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Ditto on that--all my cargo boxes I've used or made over the years have had to have a hole at the lowest corner(s). Doesnt' rain much here but when it does it can be quite a drowning, and it'll get into anything it can, flowing up and back thru cover adn door edges, hinges, etc., even if there are seals on them...then it pools in the bottom of the pod if it has nowhere to go.