On Monday, October 17, 2016 at 10:12:15 AM UTC+1, wrote:
The battery in my Hannspree SN14T71 13.3" tablet is damaged but I can't
find a supplier for a replacement. The battery looks like two taped
together, one is marked 3.7V 4000mAh and the other is unmarked. There
are 3 wires going to pads marked + - and T,

T is temp sensor

the charging voltage across
+/- is about 7.8V.

LiPo nominally 3.7V MT 4.2V full.

There's a picture of the battery on eBay:
http://www.ebay.com/itm/GENUINE-HANN...-/112044599739

I haven't had anything to do with LiPo batteries before. Am I correct
that there will be two in series?

yup

Mr Google has suggested that LiPo batteries are sold by size (as well as
voltage and capacity) but I can't find anything that is about
4x160x145mm - any suggestions?

Neither could Hanspree, look for 4mm thick Lipos that might fit, voltage is a constant , capacity rises with size, you`ll still need 2 in series

http://www.ebay.com/itm/3-7V-4000mAh...AOSwbsBXlt7 a

Hannspree don't sell them and, with hindsight, their UK repair
contractor (RepairTech Ltd) were the people who damaged it in the first
place when they did a warranty repair so I don't want to pay them to
replace it.

If I can't find a battery I'll remove the duff one and run on mains as a
digital photo frame (uses about 6W, so not too bad to leave on).