Reporting back. Bought a no-name 9Ah Makita battery. It is a little bit lighter than the OEM battery, for what ever that is worth. Suspect that means those 9Ah may be in the imagination of the manufacturer. It does have a charge indicator, which shows in %, the OEM battery has nothing. The new battery seems to work fine in the pump, and fits in the OEM battery charger. So should be good for a while. The only thing that is weird is the button to turn on the charge indicator is covered by the input air filter. Now I need to find some carry tote, or bag. Something compact with a decent handle or strap.Liking the compressor, definitely makes things easier.