I did some checking, because I have a Pocketbook 360 in perfect working condition and with a fine battery, one that I was attempting to do something with. (I can't say more, due to violating our Posting Guidelines.)
Here's a website that offers some helpful information:
On the right in drawing the accumulator of electronic books Pocketbook 360, 360+ and 360+ New, 301+. It also was installing in e-book readers Orsio. Marks on the battery H503456 1000 mAh HC T0076. Dimensions: 57 x 34 x 4.8 mm. The controller is located on the top part of the battery, but at the same time on an exit only two pins (plus and a minus). You can replace such battery on Nokia BL-6U, having removed a factory's socket with wires from the old battery and having soldered to the new battery. This battery is a bit less on capacity, but well approaches in the sizes NOKIA BL-4C. NOKIA BL-5C - on millimetre thicker than the native battery, but many users of electronic books Pocketbook 301 + successfully replaced accumulator H50345 with this model. At such replacement controller pin on batteries NOKIA, marked by an empty circle, remains not soldered.
Although the English is mangled, it appears that this is the battery inside our Pocketbook 360:
H503456 1000 mAh HC T0076
Dimensions: 57 x 34 x 4.8 mm
The battery in the Pocketbook 360 can (apparently) be replaced with the
Nokia BL-6U, although it is a bit less in capacity.
Here's the website where I gathered my information:
http://e-ink-reader.ru/batt_en.php
You've gotten me very interested in this subject, and I'll do some further research.
DISCLAIMER:
My post is for information purposes only, and I will not be responsible for any damage to any ebook or person if any mishaps or accidents occur.