Even though battery capacity at high temperatures is higher, battery life is shortened. Battery capacity is reduced by 50% at -22 degrees F – but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures – for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of lead-acid battery, whether sealed, Gel, AGM, industrial or whatever. This is actually not as bad as it seems, as the battery will tend to average out the good and bad times.
One last note on temperatures – in some places that have extremely cold or hot conditions, batteries may be sold locally that are NOT standard electrolyte (acid) strengths. The electrolyte may be stronger (for cold) or weaker (for very hot) climates. In such cases, the specific gravity and the voltages may vary from what we show.