Replacing the Battery in a Sony Clié PEG-TH55

If you’re looking for a new battery for your TH55, the size you’re after is a 503759. These are available as 1300mAh batteries from AliExpress. I specifically got this one, if the listing is still available, making sure you pick the right option from the listing as it is for multiple sizes. They can be bought elsewhere as singles, but I bought 10 because I’ll need them eventually and they’re cheaper in bulk.

To get into the battery compartment you’ll need a tri-wing security bit (basically like a Philips bit, but with only three corners). I have a 2.0mm size one that works well.

You’ll likely need to transfer the connector from the old battery to the new, which should be done by soldering, ideally replacing the cable where it is connected to the protection circuit board on the battery as the fit is tight. If you splice the cable, make sure you cover the joins with heatshrink (remember to put it on the wires before you solder them). Ensure the wires are at least 60mm long.

When fitting the new battery, they tend to catch on ribbon cables in the battery bay, so push a bit of thin paper, such as a receipt, into the opening between the rear case and ribbon cables so that it covers them, and then slide the battery in between the paper and rear case. Then pull the paper out.

It is also advisable to loop some tape around the battery as a tab to pull it out as it is a tight fit.