Amidst a recent spate of Model S fires, Tesla has upgraded the software on the EV to prevent unsafe charging, according to a tweet from Tesla S owner @ddenboer. If input power fluctuations are outside a safe range, the software will automatically reduce the charging current by 25 percent — from 40 amps to 30, for instance. The change is supposedly a response to a recent Tesla S blaze, which happened in a California garage in November.