00:00$103. That is the Home Depot price on a DeWalt 4 amp hour pack right now. A Milwaukee M18 in
00:07the same size sits right beside it. A nicer Ryobi 4 amp pack can run about $130. A lot of
00:13the packs
00:14people throw out still have four good cell groups inside. The fifth group dropped too low. A small
00:19board saw that and shut the whole pack off. Today I will show you how to tell a sleeping pack
00:24from
00:24a dead one in about 10 minutes how to wake the board without doing anything reckless. And how
00:29to replace the one group that actually failed for about $8 to $16 instead of buying another $100 pack.
00:35I have brought more than one of these back. I'm not paying full price every time a charger starts
00:40blinking. The blink is a lock, not a death sentence. I will show you the voltage map that proves it,
00:46the winter habit that bricks more packs than any saw, and why that board would rather shut the pack
00:50down than let you charge it. First you need to know what you are holding. An 18 volt Ryobi or
00:57Milwaukee pack and a 20 volt max dewalt are built the same way, with five cell groups in series.
01:02Each lithium cell sits around 3.6 volts, so five in a row give you about 18 volts. A compact
01:092 amp
01:09pack is often five single cells. A 4 amp pack is usually 10 cells, two in parallel in each group.
01:16People say one bad cell killed nine good ones. Close. One bad group killed the other four. On top of
01:22those
01:22cells is a battery management board. It watches every group. If one group falls under about 2.5 to 2
01:29.7
01:29volts, the board opens the circuit. The charger blinks. The tool acts empty. The other groups can
01:35still be sitting at a healthy 3.6. Most of the battery is still there. You just cannot use it.
01:40That cutoff is chemistry. A lithium cell that sits too low starts dissolving copper inside itself.
01:46Charge it hard from that state, and the copper can plate back as thin metal whiskers. Those whiskers can
01:52poke through the separator and short the cell. That is heat you do not want in a garage. The board
01:57refuses to charge a cell that has been under about 2.5 volts because that cell may no longer be
02:03safe to
02:03bring back fast. The blink is the board picking a dead tool over a fire. So the pack is not
02:09dead the
02:09way an alkaline AA is dead. It is locked. Sometimes the cells are fine and the board went into a
02:15deep sleep
02:16after the pack sat too long at a low charge. Sometimes one group really failed. Those are two different
02:22jobs. Mix them up and you either throw away a good pack or you force current into a bad one.
02:27Four things people get wrong. The pack is dead. Measure it. If the terminals still show real voltage
02:33and the case is cool, dry, not cracked, and not swollen, you are usually looking at a lock. If the
02:40whole pack reads near zero, it smells sweet like solvent. The case is hot. Or the plastic is puffed out.
02:46That one goes in the recycle bag. Do not open it. Do not try to wake it. It only happens
02:51to cheap
02:51Ryobi. Dewalt and Milwaukee use the same five-group layout. Different software. Same physics. Name
02:58brand packs shut down in a cold garage the same way the yellow ones do. Jump it with a car
03:03battery.
03:04Do not. A car battery has no useful current limit for these cells. That is how you get a melted
03:09case.
03:10If you wake a group, you do it slow with a voltage cap and a current cap on a surface
03:14that will not burn
03:15and you stay in the room. Anything below the cutoff can always come back. No.
03:20Some cells recover if they only sat low for a short time. Some are already damaged and should never go
03:25back in a tool. The test is simple. Will the group climb under a small, controlled charge?
03:30And will it hold voltage after you take the leads off? If it drops right back, that group is done.
03:35If you are still watching, subscribe. It is free and it helps the channel.
03:40Members get the extra videos I keep off the main upload. Now the map, because that is what tells you
03:45whether this is an eight dollar fix or a trip to the battery bucket. Do this on a workbench.
03:49Glasses on. Pack cool. No cracks. No wet spots. No chemical smell. If it fails that look, stop.
03:56Before you open anything, check the boring stuff. Try a pack you trust on that same charger. Try this
04:02pack on a charger you trust. Wipe the terminals. A lot of dead packs or a charger that stop talking
04:07to them.
04:08If it still blinks, measure the pack at the main terminals and write the number down.
04:11A moderate voltage with no charge light usually means sleep or one week group.
04:17A. Reading near zero is a bad sign. Then, only if the pack is out of warranty and you are
04:22fine
04:23voiding what is left, open it. Most of these cases hide a security torx under a sticker. The board sits
04:29on top of the cells. Do not pry on the nickel strips. Do not short them with a screwdriver. You
04:34will see
04:34five groups. On a four amp pack, each group is a pair. Measure across each group and write the voltages
04:40on tape.
04:41Four groups at 3.6 and one at 0.2 means one group failed. Five groups all low and even
04:48means the
04:48pack went to sleep together. Four healthy and one at zero that will not climb means replace that group.
04:54All of them near nothing, or one that gets hot while you measure, means recycle.
04:58The sleep case is the free win. All the groups are close to each other just under the line the
05:03board likes.
05:04You do not bypass the board. You do not feed the whole pack from a car. You trickle the low
05:09group,
05:10one group at a time, with a bench supply or a small USB lithium module set to about 4.1
05:16volts,
05:17and a low current. 50 to 200 milliamps. Not 3 amps. Voltage limit first, current limit second.
05:23When that group is back above about 3.5 volts, stop. Close the case. Put it on the official charger
05:30and
05:31stand there for the first 10 minutes. If it takes the charge and stays cool, you got the pack back.
05:36The one dead group case is the cheaper pair. Replace that group with cells of the same size,
05:41same chemistry, and a similar age and capacity. High drain 1865s. That can actually run a saw cost
05:47about 5 to 10 dollars each. A parallel pair is 10 to 20. The 8 dollar number is the low
05:52end of a single
05:53cell. Match them. Do not put a tired laptop cell next to a fresh high drain cell. Spot welded nickel
06:00is the
06:00right way. Saldering on a cell body dumps heat into the can. If you cannot do it clean, recycle the
06:06pack.
06:07After swap, first charge while you are standing there. Then test it in a light tool, not a circular saw.
06:13If the pack dies in a few minutes, the other groups were tired too. That still taught you the map.
06:18It does not earn a second teardown. A Dewalt 4 amp pack is $103.50 at Home Depot. Milwaukee 4
06:26amp packs
06:27sit in the same range. Three dead packs in a crate is about $300 of batteries you already own. If
06:33two
06:33of those are a sleep case or a single bad group, you need a meter you may already have and
06:37maybe $16
06:38in cells. One revived pack pays for the meter and the bits. A household that buys one new pack a
06:44year
06:44because it died over winter is spending $100 to $130 to skip a 10 minute voltage check. Do that for
06:51three
06:51years and you have paid for a decent drill. What this will not do. It will not make a swollen
06:57pack
06:58safe. It will not save a pack that cooked in a truck in July. It will not turn leftover junk
07:03cells
07:03into a Milwaukee forge. If the pack is still under warranty, use the warranty. And do not leave a
07:08homemade charger on a pack and walk away. Here is the part that stops the next pack from dying the
07:13same
07:13way. The board does not only trip because you ran a saw until it's sagged. It trips because one group
07:18is weaker and then you leave the pack clicked into a tool in a cold garage for three months.
07:23The tool draws a little current. The pack loses charge on its own. The weak group crosses the line
07:28first. The other four are still fine. The pack set empty on a tool near freezing. Store them off the
07:35tool. Not empty. Not full for six months on a shelf. Somewhere in the middle cool and dry. If you
07:41only use
07:41the brad nailer at Christmas, check the pack in October. Five minutes on the charger in the fall is
07:46cheaper than a $100 replacement in December. The lights on the pack are not the full story. They
07:51show what the board is willing to report. The pack that shows empty and then runs a drill for 20
07:56seconds was not empty. It was locked. Or one group was already too low. Trust the meter over the lights.
08:02If you pull good but tired groups out of a pack you do not trust in a saw, they can
08:06go in a low drain
08:07work light or a USB pack with its own protection. They should not go back into a tool that pulls
08:13high
08:13current. Tired cells in a high drain pack is how you get the heat you were trying to avoid.
08:17I keep a meter in the same drawer as the charger. Any pack that blinks gets a look, a terminal
08:23reading,
08:23and the group map before it gets thrown out. If this keeps a $100 pack out of the crate,
08:28send it to whoever in your house keeps a pile of dead yellow and red batteries and tap the like
08:34button if you learned something. Thanks and see you in the next one.
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