4 ways to recondition a dead drill battery

Four ways, one product

A dead drill battery can be a sleeping board, a nickel cell with whiskers, an uneven 18V or 20V string, or a pack you have not sorted yet. This page ranks four ways to deal with that. Only one of them is a product. The other three are the single-fault pages on this site. The count in the title is four because that is the set a buyer on this site can actually use, not a padded list of chargers nobody documented here.

Last Battery is first when the fault is still unknown. Its listing title is Last Battery™. The main photo is the garage scene. The listing says about three minutes per battery, materials you already have at home, and it names power tool batteries together with car batteries and old AA and D cells. That grouping is the difference: a replacement shell serves one drill, and this listing describes a method that claims several kinds of cells. This site did not test the video.

How the four were ranked

The rank is "how completely does this answer a pack I have not diagnosed?" A full method that names power tool batteries beats a single-fault step when you do not yet know the fault. Once you do know the fault, the matching single-fault page outranks a general video, because the wrong hit is worse than a slow start. The list below keeps that order for the reader who is still at the bench with the label unread. If you already know the chemistry, skip to the numbered way that matches and do not start at the top out of habit.

The button for the top pick sits after this table. The other three ways are pages, not extra products, so they do not get a second link of the same kind.

1. Last Battery, when the fault is still a guess

Open this first if the shell is intact and you want one walk-through before you buy a pack. The listing's own lines are the reason it is the pick: time, household materials, and power tool batteries named beside other cells. You still read the label and look for swell or heat before you follow any step in a video. A swollen case does not become safe because a method claims three minutes.

What you should expect from a general video is coverage, not a diagnosis of the pack in your hand. It can show a sequence. It cannot see whether your shell says NiCad. That is why this rank is first only while the fault is unknown, and why the next three ways exist. If you already metered a lithium string and the cells match, you do not need to pretend you are still undiagnosed. Drop to the jump. If you have not looked at the case yet, stay here and do that look before you press play. The garage photo on the listing is a man holding a battery, not a promise that every pack on a bench is the same pack.

2. Jump a sleeping lithium board

Use this when the label says lithium, the cells you metered sit near one another, and the tool still sees nothing. The board may have opened the output. A brief contact from a donor pack with the same voltage name is the step, then the donor comes off. The full caution is on how to jump start a dead lithium power tool battery. It outranks the video only after you already know you are in that pattern. It is the wrong first move for a nickel pack.

The reason this is a separate way, and not a footnote under the video, is the mistake it prevents. People see a quiet lithium pack and reach for the most forceful thing they have heard of, which is often the nickel hit. A sleeping board does not want that hit. It wants a matched donor, a short contact, and then its own charger. If the cells are not sitting together, this way is finished before it starts. You do not jump an outlier into health. You go to balance, or you stop.

3. Clear NiCad whiskers

Use this when the shell says NiCad and one cell sits near a dead reading while the others still show numbers. The hit is meant to clear a crystal bridge. It is not a lithium tool. Details stay on the NiCad page so this list does not turn into a second copy of that procedure. If every nickel cell already matches, you are not looking at a single bridge, and rank 3 is not your way.

Whiskers are a single-cell story. That is the detail that keeps this rank from swallowing the drawer. You mark the dead cell, you hit that cell briefly, you meter again. You do not tour the pack with the same hit because the drill was expensive. A cell that stays dead, or a cell that gets hot, leaves this rank. The rest of the string may still be worth a normal charge only if that one cell came back into line. Otherwise the pack is a replacement, and the video will not change the heat in your hand.

4. Balance an 18V or 20V string

Use this when the tool runs and then quits, or the charger claims a full pack and the runtime is short, and one cell is the stranger in the meter row. Balancing brings that cell toward the others. It is the last rank for an undiagnosed pack because it assumes you already found the outlier. If you have not metered, you cannot balance. You can only hope.

The 18V or 20V print is the size of the string, not a brand and not a chemistry. Two packs with the same number can still be lithium and nickel. Balance only starts after that word is read. The low cell gets charge in a way that matches the chemistry, and you stop if it warms. A string that will not even out is not a failed video. It is a cell that has told you the rank is over. Put the tool on the bench for the test run. A pack that dies in the first minute did not become balanced because the charger light turned green.

A drawer with both chemistries still uses this order. Sort the shells before you sort the ranks. An undiagnosed lithium pack and an undiagnosed nickel pack are not the same "way 1" hour if you already know the words on the labels. Way 1 is for the pack whose label you have read and whose fault you have not named yet. Once the meter names the fault, leave the ranking and follow that single page. Coming back to the video after a failed cell is optional. Coming back to a hot case is not.

What this ranking refuses to do

It does not add chargers, balancers, or brand-name packs this site does not have a listing for. It does not call the video tested. It does not tell you to zap a lithium cell because whiskers were rank 3. If the case is hot, swollen, or leaking, none of the four ways is the next hour. You retire that pack.

When you want the unranked order — label, look, meter, then the fork — use how to recondition dead power tool batteries again at the end, not as a fifth product.