I talked to Torqeedo tech support earlier this week to get some guidance on their warning to not store the Torqeedo battery "at high temperature." Based on that warning, I had been taking the battery from my Torqeedo home after each day of sailing in fear that leaving it in the boat could subject it to "high temperature" in the middle of the summer. Here is what I learned.
The battery storage temperature limit is 110 to 120 F, and this is a battery life issue, not a safety issue.
You should NOT leave the battery mounted on the motor for extended periods of time when it is not in use. The sun beating down on the battery case could raise the temperature above 120 F.
You should NOT leave the battery in a closed, parked car in the summer sun for extended periods of time, as that could also raise the temperature to about 120 F. (Years ago, I measured a temperature of 150 F in a black VW Beetle parked in the Maryland sun in the summer.)
However, you CAN leave the battery in the cabin or covered cockpit of an Ensign, even in the summer sun, as the temperature is unlikely to get higher than 110 F.
In addition, the support tech recommended that the battery NOT be recharged if it has dropped only to 80 to 90 %. (Taking the battery home after each day of sailing encourages this behavior.) However, going out with a battery charged to 80% instead of 100% creates "range anxiety," so you need to make your own decision. Again, this is a battery life issue, not a safety issue. This also impacts on-board charging, though I don't know if any of us are doing that yet.
Finally, he recommended that the battery be charged to 50% to 60% for winter storage, instead of 100%.
Vic Roberts
#2032