How does temperature affect the performance of my batteries?
At higher temperatures (above 77oF) battery capacity generally increases, usually at the cost of battery life. Higher temperatures also increase the self-discharge characteristic. Colder temperatures (below 77oF) will lower battery capacity and prolong battery life. Cooler temperatures will slow self-discharge. Therefore, operating batteries at temperatures at or slightly below 77oF will optimize both performance and life.
How do I determine my battery capacity when it is colder/hotter?
Battery capacity is basically a linear relationship. A good rule of thumb is that for every 15oF above 77oF, capacity is increased by 10% and for every 15oF below 77oF, capacity is reduced by 10%.
How do I account for temperature when taking my gravity readings?
Temperature will affect specific gravity readings. As temperature increases, the electrolyte solution expands and as temperature decreases the electrolyte solution contracts. As a result, it is a good practice to temperature correct specific gravity readings. Here are the relationships Trojan recommends using:
For every ten degrees above 80oF add 3 points to the hydrometer reading.
Example: @ 90oF the hydrometer reads: 1.250 The actual reading: 1.250 + .003 = 1.253
For every ten degrees below 80oF subtract 3 points from the hydrometer reading.
Example: @ 70oF the hydrometer reads: 1.250 The actual reading: 1.250 - .003 = 1.247
How do I account for temperature when taking my voltage readings?
Temperature will affect voltage readings. As temperature increases, voltage decreases. Conversely, as temperature decreases, voltage increases. Here are the relationships Trojan recommends using:
For every 10 degrees below 80oF, add .028 volt per cell to the charger voltage setting.
Example: A 12 volt battery @ 70oF. The recommended charging voltage (@ 80oF) is 14.60 volts. The adjusted charging voltage is 14.60 +(6 cells * .028vpc) = 14.77 volts.
For every 10 degrees above 80oF, subtract .028 volt per cell to the charger voltage setting.
Example: A 12 volt battery @ 90oF. The recommended charging voltage (@ 80oF) is 14.60 volts. The adjusted charging voltage is 14.60 -(6 cells * .028vpc) = 14.43 volts.
Is there a maximum temperature for charging my batteries?
When charging lead acid batteries, the temperature should not exceed 120oF. At this point the battery should be taken off charge and allowed to cool before resuming the charge process.