i forget what i used before, but i'm sure a rolling pin, or similar cylinder-type object would work well. i'm not too sure how safe that is actually, but from what i understand the LI-Ion Polymer is designed to be pliable. i would take very much care not to puncture or damage the covering for sure. perhaps someone else can give some advice regarding the safety of doing this.

UPDATE: BATTERY REPLACEMENT FOUND. Previous issues reported have been solved.

I have successfully replaced the original battery with a battery from http://ebay.to/1IWUAQ6

Two issues with the battery:

1. it's a bit too thick, flatten it a bit (as much as possible to avoid "watermarks" from pressure on the LCD). the best placement is as far to the bottom left as possible (looking at the back, with the device screen facing away from you). try both in the little notch towards the bottom, or to the left more above the notch, where black and red twisted wires run.

2. there's a third wire on original battery, with a contact point on the tablet's motherboard labelled N. the replacement battery has only two wires, but powers the device with yellow N disconnected. i had to connect yellow N to black ground wire to get tablet to charge the battery. (i bridged the contact points). originally i did not think it was charging but after fixing my connections and giving it some time it definitely was working fine.

i ordered the battery and both issues came up. it was too thick, but i flattened it a bit with a rolling pin action. the case i have is missing a few tabs so it doesn't close all the way anyway. i put the battery vertically on the bottom left side (back view). anywhere else it would press and make an impression mark when using the LCD.

i could not get it to charge. the original had a Yellow wire (N), in addition to the Red and Black. i tried leaving Yellow disconnected and it powered on, but when i plugged in USB it showed a lightning bolt and said Not Charging.

next i tried putting Yellow to Black (Ground). it did not react to USB. so i removed Yellow again and this time it said Charging but it still wasn't.

only thing i can think is to tie the Yellow to Red, but i'm hesitant to damage the board, as it's a customer's tablet. if anyone else has any ideas on how to get this to charge, let me know. i can provide some pics of the circuit board and batteries if needed. thanks very much in advance.

so i'm fixing this tablet for a friend. the battery was all puffed up. on the battery is printed "HX 3098126 | 3.7V 4000mAh | 14.10.05" on the battery circuit board it says "HX-704406-01A-2". doing a search for hisense sero 8 battery, i could only find one for the sero 7 lt which is only 3400 mAh, and i hear the battery life is already bad on these. so i found one that looks like the proper power rating, but two issues.

1. the dimensions are listed as 90 x 60 x 6 mm. i measured my sero 8 battery and it seems to be about twice the size (120 x 90 mm). not sure about the thickness, but i'm worried that half size would be double thick, keeping the case from closing on it.

2. the replacement has only red/black wires, the sero has a yellow wire labelled N, which i figure might be ground, though some people suggest it could be something to do with the thermal sensor (not specific to this tablet). most said it wouldn't charge unless you wired it to either ground, or the black wire.

http://ebay.to/1IWUAQ6

there is another ribbon cable not marked in the step 4 picture. i have a pink square around it here: http://i.imgur.com/AMSuP5A.png

also both boards came out together when i removed them.