High temperature is the most dangerous enemy of batteries, even for lead-acid batteries as well. It is stated that compensating temperature levels of a lead-acid charger to make temperature modifications can prolong the battery life by 15 %. For every degree of temperature rise, the suggested compensation is a 3 mV drop per battery. In case the floating voltage is set to 2.30 V for a battery at 25 degrees C (77 degrees F), the voltage must be at 2.27 V at 35 degrees C (95 degrees F). If it is cooler, the voltage must be 2.33 V for a battery at 15 degrees C (59 degrees F). These ten degrees C modifications indicate 30 mV changes.
Lithium ions (including the famous LiPo batteries) perform well at high-temperature levels, however extended exposure to heat sources could prolong their life span. Discharging and charging at high temperatures produces gas, which might cause the pouch battery to swell and the cylindrical battery to vent. Numerous manufacturers of chargers forbid users to charge over 50 degrees C (122 degrees F).
A few lithium based bundles are heated for some time up to high-temperature levels. This is applicable for batteries in surgical tools, which are disinfected at 137 degrees C (280 degrees F) for as much as twenty mins during autoclaving. As a part of the fracturing method, gas and oil drilling further increases the exposure of the battery to heat.
The capacity reduction at high-temperature levels is directly linked with the state of charge (SoC). LiCoO2 (Li-cobalt) cycling at room temperature level usually doesn‘t cause a substantial capacity loss. At 20 % SoC and 130 degrees C, ten cycles can cause a slight loss in capacity. This loss is greater at 50 % SoC and 130 degrees C which indicates a disastrous consequence when completely charged.
Charging nickel-based batteries (like the NiMH battery) at a high-temperature level decreases the production of oxygen gas, which lowers the charge acceptance. The heat causes the charger to incorrectly assume that the battery isn‘t completely charged.
Above 30 degrees C (86 degrees F), the charging effectiveness lowers substantially. At 45 degrees C (113 degrees F), the battery can just be at 70 % of its full capacity; at 60 degrees C (140 degrees F), the charge acceptance rate lowers down to around 45 %. The NDV used for complete charge detection ends up being not dependable at higher temperature levels, and temperature level sensing is necessary for backup.
The following table displays the very best peak voltage at different temperature levels while charging lead-acid batteries. While in standby mode, the table also incorporates the suggested float voltage.
Table 1: Suggested voltage limits for preserving and charging fixed lead-acid batteries during floating charge. While working under severe temperature levels, voltage compensation can prolong a battery‘s life.