Like all chemical processes, lead acid battery performance is temperature dependent.

The available capacity and maximum current both fall at low temperature, and increase, although to a lesser degree, at raised temperatures. For example, both are approximately halved at -20ºC compared with +20ºC, and raised by around 20% at +60ºC. The risk of freezing is also real for a fully discharged battery at temperatures not so far below zero. The chemistry slows down as temperature falls; this applies equally to well charging as discharge. To optimise performance over a wide temperature range, it is important to recognise the temperature related factors in both the charging arrangement and any low voltage disconnection scheme that may be employed. The charging voltage needs to be raised as temperature falls to ensure that the battery continues to accept charge, although it may be necessary to provide an upper limit on this raised voltage to ensure that any load equipment that remains connected during charging is not operated outside of its specified range. The appropriate temperature coefficient for the raised voltage is around 4mV per degree C per cell. So for a 12 volt battery, the charging voltage should be raised by 24millivolts for every degree C that the temperature falls. Similarly, at higher temperature, the charging voltage needs to be reduced to prevent excessive gassing due to overcharge. Overcharge consumes electrolyte and can dramatically reduce the life of some types of battery, in particular recombinant types (so called sealed batteries).

Any system using voltage measurement to ascertain battery state of charge that does not take into account these effects will give poor charging characteristics and take decisions either too early or too late. (It is one reason why crude voltage LED ladders indicating state of charge can be very misleading).