4AH @ 40v = 160wh. Figure 15% inversion losses and you're looking at 130wh or so. It's interesting that these batteries all seem to lock into their various tools quite securely, as well as the chargers, but for this inverter it looks like it's barely connected.
Yup, the only way to charge the 40v battery is to buy the charger separately! I have to buy the 40v battery, the inverter and the charger. There is 1 good thing about the about the charger tho, the wire that connects to the charge is detachable. It also has a USB port on the charger! Just detach the wire on the charger, plug in the 40v battery and that's it! Portable USB power!
