thinkpad battery issues

[seraphin]

I have an old thinkpad - E420, that has been running fine.
The battery is now dead. On the battery, it reads (10.8V, 48W, 25+).
I cannot find the same model but have come across newer battery with higher Watts (10.8V, 57W, 70+)
The new battery fits in the socket but I am not sure if 48W v 57W and 25+ v 70+ would cause any problems.
Specifically, both batteries read "caution: replace with the same type only. Use of another battery may present a fire or explosion".

Any suggestion ?

[Thinkpad4by3]

The 70+ is identical to the 25+ except for having a security chip. It will work no problem with your E420 but it also can work in the E430 as well unlike the 25+ which will not since the laptop will not accept any battery without a security chip. I run 70+ batteries all the time in my T420 and T520. Plus it has the benefit of more capacity .