I just pulled my LiPolys out today to check them before installation in one of my planes. These were brand new units never used. I have had them for about 5 months and checked their voltage every three weeks per the manufacturer. Last test was 2 weeks ago. All was well. Then today both units were dead and I mean no voltage at all!!! This is very very strange?? both units dead as hell and never have been used???? Manufacturer was notified.they will replace both units with newer and safer Li-Man units at no cost.
The point is battries can go bad at any time so make sure you check before EACH flight not just before a day of flying. Use a good quailty load tester.... the don't cost much. But they can save your plane.