Bruno,

I have an ASW-27 also. I use 2 tenenergy 10ah LiFePo4 batteries... Kickass

They have special cicuitry that allows them to be charged via regular 12V SLA charger (so if you forget your charger on a trip...WalMart!)

I run a Cambridge 302, ClearNav, Radio (of course) and PowerFlarm. I have yet to have a single battery drain to the point of switching. That includes an 8 hour long out and return this past year.

Also... The other folks here are right... LiPo are the dangerous battery. LiFePo4 are quite safe. The chance of an oxygen pocket being formed are damn near zero.

Terry