[papped]

Introduction
Hello, I doubt hardly anyone here has a Xperia X1. But since I would wager most of the Mugen batteries are probably pretty similar, this may be of some benefit anyways. This review is for the Mugen 1800mah, OEM sized Xperia X1 battery.

Initial Impressions
There isn't a lot to say here for a battery. The packaging is good, instructions are simple. Manufacturer recommends doing 3-5 full charge/discharges (run the battery until you get a low battery warning, not until it's dead).

The battery fits snugly and hasn't seemed to have any build quality issues.

Longer Term Observations
The battery life seems quite solid on this battery and a slight bump from the OEM (roughly equal to what you would expect going from 1500mah to 1800mah). Nothing major though.

It does seem to generate significantly less heat on high loads than the OEM. This is the primary reason I got the battery in the first place.
Here is a link to another user's experience:
xda-developers - View Single Post - Better Battery X1

I have not encountered any of the "charge level" issues he stated though.

The battery has not had any problems with loose connections, leaking or anything like that, so I would say it has been as reliable as the OEM.

Conclusions
If you want to meet most of these conditions, I would recommend this battery:
-Less heat generation on high loads
-Slight battery increase
-Want a second battery in general
-Want an OEM sized battery and don't want a larger battery door/bulk

If you want serious battery life, I would go for the Mugen 3600mah instead (crazy big).

If you simply want a second battery, I would have no problem recommending this as a second battery purchase.

Pros
-OEM size, can use the same battery door (huge plus for me)
-This battery seems to generate far less heat than the OEM battery, which is the main reason to get this battery

Cons
-Not a tremendous increase in battery life (shouldn't be since it's only 1800mah and OEM size though)
-Price of new battery might not be worth it if you are buying the battery only for the increase in capacity.

More Info/ Purchase Link
Mugen Xperia X1 1800mah Extended Battery