Explore how industrial batteries can be repaired.
Batteries for power tools and other industrial devices can often be repaired by replacing one or all cells. Finding a NiCd and NiMH cell is relatively easy; locating the correct Li-ion cell can be more difficult. Naked Li-ion cells are not readily available off the shelf and a reputable battery manufacturer may only sell to certified pack assemblers. (See BU-305: Building a Lithium-ion Pack) When repairing a Li-ion pack make certain that each cell is properly connected to a protection circuit. (See BU-304: Protection Circuits and BU-304a: Safety Concerns with Li-ion)
If a relatively new pack has only one defective cell, replacing the affected cell makes sense. With an aged battery, it’s best to replace all cells. Adding a new cell to a pack with faded cells causes a cell mismatch and this is often a short term solution. Always replace with the same chemistry cell.
A well-matched battery pack means that all cells have similar capacities. An anomaly can be drawn with a chain in which the weakest link determines the performance of the battery [BU-803 Can Batteries Be Restored?].
When replacing all cells, the rating is less important. The charge time will be a bit longer with higher capacity cells that the charger can handle. If the new cells come at different charge levels, first apply a slow charge first to bring them all to the same level.
Many visitors of BatteryUniversity.com ask if NiCd can be replaced with NiMH? This should be possible but charging may be an issue. NiMH uses a more defined charge algorithm than NiCd [BU-408 Charging Nickel-metal-hydride]. A modern NiMH charger can charge both NiMH and NiCd; the old NiCd charger could overcharge NiMH by not properly detecting full charge state and applying a trickle charge that is too high.
Spot-welding a cell is the only reliable way to get dependable connection. Limit the heat transfer to the cells during welding to prevent damage.
Simple Guidelines when Repairing Battery Packs
Last updated 4/29/2015
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