lxpanel missing plugins

[badfish]

I've installed Arch on a WM8650 tablet - one of the little cheap Chinese tablets that you can get on ebay.

Most things are working fine, but I've noticed several of the plugin applets in lxpanel fail to appear. The menu, pager, cpu monitor and clock all work OK, but the battery monitor and volume control don't appear. Has anyone else got these working?