[ask] how high can chinese pnd battery can be upgraded ?

I got a 5" chinese PND with li-polymer 3.7v 1250 mAh battery, which dimension is 6cm x 3,8cm x 0,4 mm

I'm planning to replace it with a higher capacity battery, what is the max capacity for the replacement ?

Can I just soldering a 3.7v 4000 mAh battery with the same dimension to replace the old one or there are some restrictions on the capacity ?

I'm not a technician, nor I know anything about soldering electronic equipment, I plan to pay a tech repair guy to do that for me xD


Thanks

It's not something I've done but while the voltage is fine and the capacity doesn't matter, the charge rate from the device is important, modern rechargeable batteries need to be charged correctly or damage can result.

Is the charge rate controlled by a pcb in the battery or by a chip in the pnd's pcb ?

There is circuitry in the battery and depending on the device there may be feedback from the battery on charge level, temperature, etc... How many connections is there between the battery and device?

Only 2 wires, red and blue

What I would do here is measure the voltage across the battery, and the current through the battery while it's charging, and compare it with the tech sheet from the new battery, if it falls within range then you're good to go. Batteries are not simple things anymore, they can explode or catch fire if abused, Remember the Dell laptops a while ago?