I don't think the batteries in most mods or vanilla game provide enough power to move cars and trains. The batteries simply have too small a capacity for that.

I suggest introducing a new game option of StartUp level, a fractional number, to specify the ratio of energy conversion when pulling it from charged batteries on the vehicle grid. This will default to 1 for compatibility.
The logic is as follows: [Energy gained for fuel] := [Energy taken from battery] * [Coefficient entered with this option].

So it simply multiplies the energy when it is converted into virtual fuel. And everyone can customize it to the mod set they play with.

Looks good to me, but it has been a long while since I worked with Lua or Factorio modding and I kinda don't remember how to do it lol.

Do u know how to program it ? I be glad to 'merge' your code and give you credit.

ok, I will take a look at the weekend

Thank u :)

lol :)
things dragged on, and then 2.0 came out - I don't even play now, just testing mods when they get ported to the new version ;-)