Milwaukee 18v Power Plus NiCad Battery Problem

I've got some OLD 14.4 batteries that died but I still charge & use them. Mt technique; put two 12 volt car batteries in series to get 24 volts, and put the 24vdc across the battery terminals +to+ & - to- for a short time, maybe 10 seconds. Check battery voltage and if it isn't over 14.4 (in my case) do it again for a longer time. When the battery gets to FULL voltage put it on the charger and charge normally.

What I'm doing is zapping the batteries with a heavy current surge to melt the dendrill crystals that are shorting some of the cells; with the shorting crystals gone and a small charge on every cell it will charge normally and hold a charge for a few days. It will eventually short out again since there is a hole in the electrolite where the crystals were and new crystals will form there as the charge disappears. Works well for occasional use if you have an hour or 2 to prep the battery for use.

Just go get one or two replacement battery packs, and toss the old ones in the "Ni-Cad Recycling" bin at the home store - they go bad just from old age, and it isn't worth the hassle to constantly be reviving them.

Get one pack for now, and keep your eyes open - around Christmas they often sell two-packs of power tool batteries at deep discounted prices. The DeWalt 18V XRP battery packs go from $75 each to "Two for $99" for the big sales periods.

And it isn't worth the effort to build new cell packs from loose cells unless the drill is obsolete and the battery packs are not available new at a reasonable price - your time is money.

If they sell pre-clustered and welded replacement cell packs for that particular drill battery pack, then it may be worth the effort to open the pack case and solder the lead wires on.

And from now on don't let the battery packs set for long periods between uses and NEVER let them set totally dead for very long - get them into a battery charger the minute you get a chance.

Ni-Cad's will self discharge just from sitting around, and even unused you have to charge them every month or two or they go bad.

As Nick says, once they sit dead they develop internal shorts, and the end is inevitable. You can blow that short clear and get a few more cycles out of the battery, but it won't last long.

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Why not jump start it from your car battery?

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

The problen is that the chargers are built to recharge fast and if you leave the batteries on them it will overcharge them and cook them. Especially if you have a power glitch that restarts the charge cycle all over again.

Only if the charger is defective or designed by the brain-dead. That third terminal on the pack goes to a temperature sensor inside the pack, it's supposed to signal the charger to cut the current if the pack gets hot. Most multi-cell packs(and chargers) that cost more than $20 are designed this way these days. If the sensor goes bad, the pack can be cooked, I suppose, or just not activate the charger.

With any of these rechargeables, you're lucky to get 5 years use out of them. If you use them heavily, you run up against the max number of charges they can take, if you don't use them at all, they self-discharge. The various technologies have different limits, but they're all chemical systems and slowly turn to toxic junk over time, used or not.

Stan

Stan,

Which terminal is which? Pos., Neg., Temp Sens.?

Thanks,

Tom Haughton

A problem arises when the battery is completely charged and there is a power glitch. Cheap chargers will restart the charge cycle until the battery gets hot again. This is not good.

Most multi-cell packs(and chargers) that cost more than

My problem is I seldom use the rechargable, but occasionally really need it (on a farm). 5 years is too short a life for what they cost. I need something that lasts longer to keep my cost per use down. Maybe someone will come out with a supercap 'battery' that I can recharge quickly in the field off my tractor battery so it's shorter in-use cycle is no problem.

I'm waiting with bated breath for the new Lithium-Iron Phosphate batteries to hit the general-use market. Shoprider uses them on their Scootie(TM) power chair right now. The batteries' producers are starting to make noises about entering other markets.

These batteries seem to be outperforming most other technologies in Amp-hour capacity for unit size, durability, and recharge time and cycles. The last I read on them claims 1/3 to 1/4 size for a given Amp-hour capacity, up to five years service life, and up to 5000 charge cycles at only 2 hours per charge.

The typical sealed lead acid or gel electrolyte wheelchair batteries last anywhere from 1-3 years, with some exceptions, usually last through about 500 charge cycles, and take up to 12 hours to recharge.

Apparently the iron phosphate formula allows this type of Li batteries to tolerate far higher current draw than other Li-ion technologies, most of which don't allow discharge at much more than fractional Amp draws.

The chemistry allowed them to choose a great marketing name for them too: LiFe Batteries.

Of course, they cost 4 times as much as lead-acid right now, but that will change with widespread use, if there ever is widespread use.

I've done that using a wooden plug in the battery hole. Works fine within the reach of the cord, not too well on top of an extension ladder. Extension cords rob power ;)

I notice my rechargable shaver does not have these problems. IT stays on the charger forever and does not get cooked and lasts a lot longer than 5 years. I need to find a drill with this technology; I don't need fast recharge and I don't need extreme endurance, but it sure would be nice to have a cordless availiable when I need it for small jobs.

Mm, - Gunner (who posted on this) is Basically Correct. And I will offer the following comment based on working with the things (ie, Ni Cads)

1. You need a multimeter to check the polarity - even a el cheapo digital one will do. Useful thing to have in your toolbox, anyway.
2. Once youve worked out the pos and neg on the packs, use jumper leads to connect to your 12 car battery - BUT put a tail light globe in series with it - this will limit any peak current and not destroy things. A few minutes is all it needs - the globe should intitially glow brightly, then dim. It does not matter that the car battery is

12v and your packs are 14v, you only want to kick enough charge into the things to get your pack charger to recognise them.....

1. Once you can get a charge into them, then see how long they last under load - yes, NICADS do die with useage as described in others posts, BUT you get what you pay for - the reason (one of em) that Dewalt tools are expensive is they use GOOD QUALITY Nicads in their packs. The elcheapo Chines ones dont, and consequently have a short life. Add to this, the Dewalt chargers are more sophisticated (again, you get what you pay for) and so get the most life out of the barttery packs.
2. If the battery packs are stuffed, get them rebuilt. Cheaper than buying new ones, and the Dewalt drills etc are worth keeping on the road. Would like to have them here, but cant justify the cost to the Ministry of Domestic Affairs.....

Have fixed a few Dewalt "Builders Boom Boxes" now (the building site radios with the chargers in them) - a nice unit, designed by someone who realised that it would, someday, need to be fixed and so made them fixable by human hands. Wish more things were built like that.....

And even buying premium Japanes NICADS, the packs were worth rebuilding

- a mechanical process more than an electrical one....

Andrew VK3BFA.

Bugger. Brain wasnt working on the last post - somehow, thought it was a Dewalt. My comments stand re testing etc, but rebuilding battery packs MIGHT be dubious if its a cheap import drill. (Remember when brand names meant something, and were a guide to quality...)

Andrew VK3BFA.

You should be able to locate a battery supplier that will spot weld new cells together, in the correct configuration that fits into your battery case. Some battery suppliers will offer a choice of battery grades and capacities.

There are several sources of high quality cells for use in power tools (and other specific uses), although high quality cells are fairly expensive. The best cells, as far as I know, are produced by manufacturers in Japan.. Panasonic and Sanyo, for example. Higher quality tools generally include good chargers and appropriately-rated cells in the original battery packs. Replacement packs from other sources might be filled with cheap under-rated cells.

If you examine the Panasonic cell's specifications, you'll discover that there are cells that are specifically designed/rated to be capable of being left on charge continuously, fast charging, ultra-fast charging, rapid discharge, and other types of uses/parameters.

The shop tech should've suggested that your cells were probably dead from non-use or end-of-life. If he was offering opinions, he should've been able to analyze the battery packs to confirm if they were dead or serviceable.

Neglected cells will die from internal shorts. Neglect is probably the greatest contributor to early battery death. Since they self-discharge, it is neccessary to remember to apply refresh charges periodically. Packs that are used until they're near-dead, then not charged, will most likely not charge.

Chargers vary a lot in design, and cheap chargers will often contribute to short battery life. Using a simple lamp/appliance timer with chargers (cheap or well-designed types), will prevent overcharging and unwanted restarts of charging cycles.

Many power tool packs can be opened by removing screws, or glued cases can be cracked along the glue line by exerting pressure at the seams (at a certain point, the glue snaps free). The separate cells can be checked with a voltmeter and ohm meter. Cells that show 0.0V will likely measure 0 ohms, indicating shorted cells. The practicality of zapping shorted cells will vary, but if the user's livelyhood depends on his power tools, it would be a good decision to replace the batteries completely with fresh new cells, or fresh new packs. The practice of zapping new or used cells, includes discharging a voltage surge from a large capacitor.

I would not recommend connecting any batteries to a high current source such as car batteries, if the condition of the cells is unknown. Cells can explode, and used cells can have faults that would increase the likelyhood of injury. A friend experienced a new nimh cell expolsion a few weeks ago (using the correct charger). Charger parts and one cell were scattered throughout the room, although no one was in the room at the time.

Battery packs often include several other components besides battery cells. It's common to include a self-resetting thermal limit switch, but some packs include circuits for other purposes.

If rebuilding battery packs is favorable, it would be best to choose quality cells, with fresh date codes to insure that you're not getting old stock. I've seen some online suppliers that will assure that their stock is fresh. Some suppliers offer free welding of custom configurations to fit battery packs.

WB metalwork> I have a Milwaukee power tool with 3 18v Power Plus Batteries (NiCad) that

Without having to take out the battery that was fully charged when I put it in last week and put in the one that has been on the charger for the same interval Gerry :-)} London, Canada

All the suggestions about re-building the batteries? Check out eBay. You should be able to pick up a Pair of those batteries, for under $100. Including shipping. That is the 18V Milwaukee battery packs.

They are buying them for about $40 each, and re-selling them on eBay. Oh, in bulk from Amazon.com Now The secret is out.

Pete

What's that Lassie? You say that Tom Haughton fell down the old rec.crafts.metalworking mine and will die if we don't mount a rescue by Sun, 24 Sep 2006 23:33:01 -0700:

you can get the packs 're-celled' at

I have used them twice with good results.

Dan H.