Short answer, you don't know until you try. 115°F is on the upper-end of the operating range for most batteries, and higher temperatures do tend to wear the battery more quickly.
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Leyden Energy hasn't published any real datasheets for their Lithium Ion batteries (Enertia+ and Empulse), but they list these specs:
Discharge: -30°C to 60°C
Charge: -20°C to 60°C
Valence has published a
datasheet (pdf) for their U-Charge XP batteries used in the Enertia. They list these specs:
Discharge: -10°C to 50°C (122°F)
Charge: 0°C to 45°C (113°F)
Storage: -40°C to 50°C
See below a pair of performances charts for the Valence batteries. First, the lifecycle graph.
At the max temp, a C/2 charge/discharge cycle allows for 1500 cycles before the battery drops to 80% capacity. Brammo charges the batteries slower than C/2 (800w charger, about C/4), but you're likely to discharge closer to 1.5-2.5C while riding. I don't know what impact a lighter charge or heavier discharge rate will have on the battery life.
After 1500 full cycles (or 3000 half cycles), you're looking at around 5-7 years and 45k miles on the bike. The battery has fallen to 80% capacity (typical range 24-26 miles), and barring catastrophic failure should still be useful as long as you're happy with the range.
Second, the temperature graph. Cold temperatures (below freezing) take a heavy toll on useful capacity, and this is at a C/5 discharge rate. The battery looks like it responds better to warmer temperatures, including up to 45 C.
