well you can just look at the specs from an official supplier of replacement batteries like ifixit https://www.ifixit.com/products/steam-deck-battery https://ww

well you can just look at the specs from an official supplier of replacement batteries like ifixit https://www.ifixit.com/products/steam-deck-battery https://www.ifixit.com/products/steam-deck-battery this will give you specs for the old old battery, I'm sure valve would've gone with a bigger battery that runs at the sameish voltage for simplicity Watt Hours: 40 Wh Voltage: 7.7 V Milliamp Hours: 5200 mAh