Has anyone used SE48S70 (48V,70AH) lithium-metal polymer battery (made by Avestor)? These are normally used in outdoor DC power backup cabinets in by telco's such as Bellsouth, Verizon, etc. Very high energy density & long lifetime at all expected operating outdoor temperature (from -40 to +65 deg C) make them ideal for such applications, but I was curious about their prices, availability and actual MTBF (versus theoretical MTBF). Has anyone used hundreds over several years & have some info? Before I consider using them in some of our projects (we build UPS systems for outdoor traffic lights & roadside message boards and actual battery lifetime at 65 deg. C is a VERY IMPORTANT selection criteria).