Thanks for the info JK Labs...
Bri (and others), the charging and protection circuitry is included in the Wally battery, the meters are reasonably accurate. And as related by others, you'd likely get 6+ hours on the V3 with it. Just watch the lights. The battery should disconnect before becoming completely discharged, or the wahoo's that run it down to zero would be returning them in droves. Since aside from us gearslut-technophile-tapertypes, the REST of the consumer world is pretty fucking IGNORANT when it comes to these things.
I wouldn't recal the battery lite on the V3, so it stays "virgin" for SLA's in case you need to run those in a pinch. I just ordered 2 more JB3 batts, and picked up another Wally 9v - so even for festi's I've got 10-12 hours of light-weight power now - thank GOD - hauling 2 EC-90's was wearing me the fuck out, not to mention having them hand-checked at every TSA checkpoint...
Rick