I bought a 6S LiFe for mine a couple of years ago. LiFe is MUCH safer. And in this case, I didn't really care about the slightly less volts than a LiPo provides. I crafted together a tray to hold the battery just under the starter, with access to allow using a standard electric plane plug, for charging. I was teaching weekly with a glow plane at my club, and usually did 10 flights a day, starting a .40 glow engine. The 20v spun that (and every othe when I loaned it out, including 50cc engines) with ease. Two charges lasted the entire summer.