low temp actually the batt are better at storing charge not self discharge la
it's too cold for the chemicals inside the batteries to react and produce charge, that's why you cant get it much power out from it

car batteries run on sulfuric acid..when temp drop below 0 deg....the water freeze la..how to have charge?

that is for storing la. not for using!
at that low temperatures, the chemical have a hard time reacting so it's good for storage but when in use will keep saying low battery!