How can I stop a belt brake (band brake) from squealing? One of our bikes is an electric bike.  It's an older iZip HG 1000, and although we got it through the American "manufacturer" (Currie Technologies), like most of the low-end ebikes it's made in China of heavy steel and uses cheap, cheap, cheap components.

The rear brake is called a belt brake or band brake.  When I was researching this a bit, I came across a discussion that said this type of brake is something like 20 cents cheaper than V-Brakes to manufacture in bulk, which is why it shows up on this type of bike.

Here's a couple pics: just the brake and then one mounted on a bike (not our bike):

 


Actually, now that I look closely at the pictures, I can see part of why it's cheap - no special frame fittings needed.  The donut-shaped "drum" mounts to the hub, the other piece just fits over that drum and is clamped to the seat stay.

My problem is that the thing squeals like a banshee.  There's no pad adjustment as there would be for cantilevers, the only adjustment is how tight the belt starts.  If I loosen it enough to stop the squealing, there's not enough pull to actually stop the bike.

Is there any adjustment I could do to get rid of the squealing?
That style of drum brake relies on friction between steel and leather. If it is setup to stop reasonably well, they will always make some noise. Quite often, when new, they do indeed howl like Baoine Sidhe. 

This will get better with use. From the photos, it appears your brakes are fairly new? Assuming that they are actual photos of your bike...

Rubbing talcum powder into the leather strap will help quiet the brake, but it may also have an adverse effect on your braking performance. Best to let it work out naturally, with time and use. 

I hope that helps.