Rebuilding a 18v battery pack

[tstombaugh]

I just finished up rebuilding my 18v battery pack for my Craftsman 18v cordless drill/driver.

The following are some tips which you might find to be helpful.

The first problem I ran into was removing the screws with the special star slot. I could not find anything in my shop that would fit. In order to get around this I used my screw extractor set to remove them. This worked out pretty well. I replaced the old screw with matching diameter phillips head screws.

I ordered from ebay 15 sub C cells, 1.2 v, with the tabs for $25 including shipping.
As a word of caution, leave the rubber sleaves on until you are ready to solder them. If they touch another cell, they really can get hot in a hurry. I found this out the hard way.

I made a diagram of the old cell layout, showing the solder tab configuration.
Then using a tip I read about, I put the cells together using hot melt glue. It
really save time when you are trying to solder the connection together.

Next I soldered the connections together and using electrical tape, covered
the connections for safety purposes. Use a good grade of solder for good
connections.

In my case the new cells were charged, so all I did was to place the cells back in the case and buttoned it up. My drill has come back to life.

Hope these tips help.
Tom

[sparkeyjames]

Nice. But if your not into soldering you can take it to Batteriesplus and get it done for a nominal charge. I had mine done there just because I don't know battery systems and getting the parts is a hassle. Not only that but if I messed it up and burned up the driver motor I would have been very pissed off at having to buy another driver set. Two 12v packs cost $54 to have redone.

I'm no stranger to the soldering iron having built a few small devices and am in the process of building some guitar effects pedals right now.

[Alex Franke]

So I guess this is instead of reviving them by shocking them? I've seen videos where people bring the batteries back to life with a welder or car battery... I was thinking about looking into how "real" that solution is because my Ryobi 18v batteries are all pretty much dying...

[mpc]

So I guess this is instead of reviving them by shocking them? I've seen videos where people bring the batteries back to life with a welder or car battery... I was thinking about looking into how "real" that solution is because my Ryobi 18v batteries are all pretty much dying...

The "zap" revival technique works only for shorted-out NiCadbattery cells; not for Lithium-ion or other battery technolgies, nor will it do anything for aged NiCad packs. What happens:
1: in a multi-cell battery pack, each cells will be ever so slightly different in capacity... so when the pack is ready for a re-charge, some cells will be a little more discharged than others. If you keep trying to use the power tool, without recharging, eventually the weakest cell reaches zero charge. Meanwhile the other cells, though low on charge, are still generating some current. This current begins to reverse-charge the zero charge cell. For NiCad batteries, that causes fine metal whiskers to form inside the cell... from one plate to another. These whiskers eventually connect, leading to a shorted-out cell.

2: no matter how much you charge the pack, the shorted-out cells remain dead.

3: Connecting a high-amperage direct current (DC) power source, such as a welder or car battery, to a shorted cell basically "blows" those whiskers as though they were itty-bitty fuses. Once fried away, the cell will accept a charge again. It'll have a tad less capacity than it did originally though - since some of the metal plate material is now gone.

The "zap" technique is basically:
1: isolate the shorted cell so you don't do anything to other cells.

2: hook a DC voltmeter to the dead cell. Verify it has no charge. If it shows a few tenths of a volt, it's NOT shorted out so don't try the zap resuscitation technique.

3: Connect the beefy battery to the shorted cell for just a split second, negative to negative, positive to positive (as if you were going to charge it with the beefy battery). You'll probably get a spark/arc when you make the connection - plan on that, don't use your nice alligator clips! Keep the connection time short - just a fraction of a second. If the zap works, the cell will begin to charge while still connected to the beefy battery. It likely is being charged WAY too quickly - and with too many volts (often 12 volts trying to charge a 1.2 volt NiCad cell) so it'll heat up rapidly... potentially explosively. Just tap the connection for a split-second.

4: Look at the voltmeter, if it's reading a few tenths of a volt (or more), put the cell/battery pack into its normal charger and let it go for a full charge. Otherwise jump back to step 3 and zap it again. Try a few times... but give up after 5 or so attempts or if you feel the cell warming up.

NiCad cells, like all rechargeable batteries, have a finite number of charge/discharge cycles. After that, they are simply worn out. I'm not aware of any technique to revive old cells. NiCads have an additional problem, the infamous memory effect: if you partially discharge a pack (but don't discharge it to the regular "it needs to be recharged now" point) and then charge it (top it off basically) a few times in a row, it gets trained to expect a top-off charge and will seem discharged/dead after just a few minutes of tool use. A few deep discharge & recharge cycles will un-train it. Other rechargeable battery types don't have this memory effect - that's one of their big advantages. NiCads also will "self discharge" just sitting unused... again, a characteristic of many battery types. Some battery types/technoligies will self-discharge in a month or two, others can sit many months and still have a full charge. NiCads are some of the shortest shelf-life types out there.

mpc

[leehljp]

I have a PC 14.4V drill/driver that is/was fairly powerful - more so than my 18V Ryobi. Both batteries are dead. The PC was purchased in 2000. I have been debating if I just want to leave it here or take it back and do the same as you did - rewire/replace the internal batteries. I don't care to purchase new batteries because of the price, but if I can replace the parts, I will gladly do that. The PC DD is 10 years old, strongly made and powerful. Just needs new batteries. Your post is giving me the incentive to do this.

Thanks for the post!

QUESTION: Where or from whom do your order? Any recommendation would be appreciated.

[woodturner]

NiCads have an additional problem, the infamous memory effect:

Good information on NiCads, except for the "memory effect" - it's a myth.

The origin of this myth is a NASA study that appeared to show the "memory effect". NASA soon found the errors, corrected them, and published the correction, but it was too late - the myth had taken on a life of its own.

What people think is the "memory effect" is usually just the cells wearing out. Nicads are generally good for 200 or so recharge cycles, but lose capacity beyond that point. They don't immediately and completely die, however, so people continue to use them and attribute the decreased capacity to the "memory effect".

Here is a link with more information, including discussion of the controversy:
http://www.repairfaq.org/ELE/F_NiCd_...ICDBATTERY_014


This report says the memory effect does exist, but has a different cause than the usual attributions:
http://www.reconditionbatteries.com/...nditioning.pdf

[leehljp]

Memory effect or not, we still need them . . . at least for now.

I am going to need 24 of the 1.2V for the PC. I am kinda excited to be able to use that again. But it will be at least late January before I can unpack my tools Stateside and work on the batteries. I just checked Amazon and they want $84 for one!. There is a cheaper generic replacement battery for about $50, but it got bad reviews.

[tstombaugh]

Hank,
I found the vendor on ebay. His ID is battery-geek. I did a general search for rechargeable
batteries and found several vendors. The battery-geek vendor has some of his items
listed with free freight.

Hope this helps.

Tom

[leehljp]

Hank,
I found the vendor on ebay. His ID is battery-geek. I did a general search for rechargeable
batteries and found several vendors. The battery-geek vendor has some of his items
listed with free freight.

Hope this helps.

Tom

Thanks, I appreciate the response. I will not order until January but I will need them soon after that.

[Alex Franke]

The "zap" revival technique works only for...

Wow -- great info! Thanks! :thumbsup:

[parnelli]

The first problem I ran into was removing the screws with the special star slot. I could not find anything in my shop that would fit.

One of these security bit sets are great to have around the house. I bought the smaller one for a single project about 5 years ago, and have ended up using them about 3 times since then.

http://www.harborfreight.com/33-piec...set-93388.html

http://www.harborfreight.com/100-pie...set-91310.html

[Thalermade]

Interstate Batteries can also rebuild battery packs. They are opening many retail places, pretty much in direct competition with Batteries Plus. My BIL had a couple of Craftsman 18volt (I believe) rebuilt and was happy, no make that ecstatic, about the work, price and results. Better than new he claims. As like most folks he really liked his drill set, and didn't want to buy a new one.

[LCHIEN]

MPC made a nice post detailing the zap technipqe for restroring Nicads.

Two important things are that it works to restore shorted cells, a common but not 100% reason for pack failures. If you can get to your cells after trying to charge them and some have voltage around a volt or so and see 0.0 volts across one or more cells they (the 0.0 volts ones) are shorted.

MPC says that running them down too far causing the least capacity cells to reverse charge is the cause, I think its just a failure of the chemistry in older cells.

MPC suggests isolating the cell and zapping that cell. That will surely work, but I usually just zap the whole pack (much easier - don't have to disassemble it)... use a powerful power supply or lacking that something like a 12V Lead acid or two in series as long as its got several more volts than the pack volt rating being zapped. The burst of current is in the charging direction (i.e. put the plus lead of the charging source to the plus lead of the battery being zapped) so the net result on other cells is to charge them. Ten amps for a second is only .003 A hours of charge - way much less than a full charge (~1.5A hrs) - it'll either add to the charge of a partially charged cell or heat it up a tiny bit.
I'd say 2-10 or more amps would burn off the shorting whiskers and not damage good cells, I usually tap the leads several times - maybe a little more dwell time than a tap - tenth of a second or so.

This has revived a pack or two, but i have to say the problems that lead to the shorting will likely occur again in the same or other cells (of the same age and construction) in the pack. BUT, if you need it now and considering the pack is otherwise worthless, then its worth a shot. There's more than just a little science behind this.

[lago]

The first problem I ran into was removing the screws with the special star slot. I could not find anything in my shop that would fit.

I have a dead DeWalt 18v nicad and reading this, I checked it to see what it would take. It had the Torx screws and a T10 driver worked fine.

This is my first looksee at a rechargeable battery. I pulled the cells out and am wondering what the single cell was that is above the battery pack.

Ken

[LCHIEN]

Lago, if its a single cell just like the others they just put it in a different position, means nothing to the battery where it is. All the batteries will be in series.