With a readily available source of power on an eBike I would have thought manufacturers would provide some way of powering accessories. I’m thinking of something like an electric tyre pump. I suppose you could even go as far as a small kettle to make a drink on the go. Most of my rides are around the 30 to 40 miles mark and I’ve never gone lower than 70% after the ride so there is plenty of spare capacity.
You may find this interesting when compared to the amount of energy you may have left in your battery during a ride:-
Again, heating of 1 litre of water from 20oC 100oC need 330kJ (0.091kWh) of heat. All these method provide the this amount of heat to water. If you...
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Also, assuming that you have a 36 volt battery, a kettle element for 36 volt DC I have personally never seen, so you will need a DC to DC converter, to get to 12 volts for most things, but if you are lucky, there are things around for 24 volt trucks, which might be OK on 36 volts, if the battery "state" can supply the needed current continuously.
My personal take would be to take a meths stove and kettle and a pump with a built in battery.....or possibly a second spare bike battery.....
Remember that bike batteries are generally expensive to buy, and have basically only a certain number of recharges in them, often specified as 2000 or so, but many people count themselves lucky to achieve 500 recharges....
It would be interesting to experiment as a cup of tea or coffee on a long run would appeal to many of us possibly, certainly the idea has some merit.
regards
Andy