Can you repair an 18v dewalt battery?

Answer 1

Some lithium-ion batteries fail due to excessive low discharge. If discharged below 2.5 volts per cell, the internal safety circuit opens and the battery appears dead. A charge with the original charger is no longer possible. Some battery analyzers (Cadex) feature a boost function that reactivates the protection circuit of a failed battery and enables a recharge.

Generally, the answer is "No." The rechargeable batteries for most cordless tools are made with nickel and cadmium. When these batteries are kept constantly charged, they develop what is called a 'memory', which means that they will not discharge properly. A very brief period under load will cause the battery's voltage to drop, and it will not recover. On the other hand, when NiCD batteries fail it is usually due to internal shorts that can be removed with a process called Battery Resurrection.

Some people have had limited success discharging the battery as fully as possible, recharging it, and discharging it again. By repeating this cycle numerous times, it may be possible to regain some limited life on the battery.

It is best to store nickel cadmium batteries with a partial charge, and only charge them up fully when you know that you will be using them immediately. Discharge them slightly after charging by running the tool for 15 to 30 seconds.