low voltage

Last week i bought my first Vstrom, a 2007 DL650. I bought it used with about 20k miles on it. Was out riding the bike around (about 200 miles), then when i was climbing a hill the engine died. I still had power and the dash was on. Initially i tried to restart the engine, but to no avail...

2004 DL100. Newer battery which seems to hold a charge well. I have a volt meter on the bike. When I start riding the voltage output is 14-14.9 volts but as things get hot as in 80 degree weather/stop and go traffic, the voltage rapidly drops off 13...13.5...12.0....11.8... eventually to a dead...