Discover what you can do to keep the integrity of your battery
The loss of electrolyte in a flooded lead acid battery occurs through gassing as hydrogen escapes during charging and discharging. Venting causes the electrolyte to become more concentrated, and the balance must be restored by adding clean water. Do not add electrolyte as this upsets the specific gravity and shortens battery life by promoting corrosion.
Loss of electrolyte in sealed lead acid batteries is a recurring problem that is often caused by overcharging. Careful adjustment of charging and float voltages, as well as operating at moderate temperatures, reduces this failure. In flooded batteries, lost water can be replenished by refilling, but in sealed batteries water loss can lead to dry-out and decline of performance. Replenishing lost liquid in VRLA batteries by adding water has been tried with limited success. Although the lost capacity can often be regained with a catalyst, tampering with the cells turns the stack into a high-maintenance project that needs constant supervision.
Nickel-based batteries can lose electrolyte through repeated venting due to excessive pressure during extreme charge or discharge, as well as from overcharge. Inaccurate full-charge detection and elevated trickle charge can lead to overcharge. This is especially true with aging and faded packs. After recurring venting, the spring-loaded seal of the cells may not seal properly again and the deposit of white powder around the seal opening is evidence of leakage. Sloppy manufacturing can also lead to electrolyte loss. Dry-up conditions result in a “soft” cell, a defect that cannot be corrected. On charge, the voltage of a “dry” cell goes high because the battery has no clamping ability. It is no longer chemically active and does not draw current.
A properly designed and correctly charged lithium-ion cell should not generate gases, nor should it lose electrolyte through venting. In spite of what advocates say, lithium-based cells can build up an internal pressure under certain conditions, and a bloated pouch cell is proof of this. (See BU-301a: Types of Battery Cells) Some cells include an electrical switch that opens if the cell pressure reaches a critical level. Others feature a membrane that releases gases. Many of these safety features are one way only, meaning that once activated, the cell becomes inoperable. This is done for safety reasons. (See BU-304a: Safety Concerns with Li-ion.)
When overcharged, a battery gases, splitting water in the electrolyte into hydrogen and oxygen. A battery becomes a “water-splitting device” by electrolysis. A parallel is the fuel cell but it does the opposite way, turning oxygen and hydrogen into electricity by producing water. Energy is needed to produce oxygen and hydrogen and the battery gets the energy through overcharging.
Last updated 2016-03-07
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