On the battery charging aspect, I picked up a really cheap microprocessor controlled microUSB 2 amp charger off 'that auction site' (under £4 including postage if I remember right), sold as suitable for a Nexus 7 (by a seller with a huge number of sales and a good reputation score).
It definitely seems to prevent any risk of over charging, as the most it will let the battery get to, is a 99% charge.
I don't let the battery get too low at the moment (30% ish for a bit, due to it having run down too far when in transit, but after the weekend I'll start letting it discharge progressively more until it gets to an automatic switch off), and using the Teclast P85 (which charges through the USB port) with it plugged in, doesn't get anything heated up (everything, including the charger, stays nice and cool - I don't do any graphics intensive gaming with it though).
I think an intelligent charger like this might be a good investment to keep the batteries in good condition for a long time (available for dedicated charging ports as well, as I have one for my Nokia phone, which can also charge through the USB port as well as the charge port).
Can you post a link about the charger?