The 1800 mAh removable battery held within is a decent, but not overwhelmingly impressive performer. With moderate use – email and messaging, web browsing, and basic app usage – the Lumia 810 can solidly get through a day on a full charge with some battery life to spare.
Add in streaming video, lengthy game sessions, or considerable surfing and you might see the message warning you to plug in the charger before your head hits the pillow. That's expected, though, and you can always carry around and pop in a battery if you're a regular heavy user – assuming you can get the back cover off.
Luckily, Windows Phone 8 has an optional Battery Saver feature for users worried about draining the charge before the day is through. With it enabled, calls and texts still come through, but apps won't run in the background and push is disabled for email, which can eke out a bit more time from the battery.
T-Mobile's 3G HSPA+ network finds itself between plain old 3G and the much better 4G LTE, which is decent but hardly show stopping. In Chicago, where we tested the device, our best download speed was 7.75 Mbps, paired with 1.5 Mbps up.
If 3G isn't available, expect to crawl along on the 2G EDGE network instead. The Lumia 810 also connects to Wi-Fi a/b/g/n, and supports Bluetooth 3.0 and NFC.