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#75327 - 02/23/07 12:54 AM Nicads wearing out  
trollog  Offline
Member
Joined: Oct 2004
Posts: 276
San Diego California USA
So what's the consensus here? Rebuild or buy new when the nicads in drill battery packs die? I have been looking around the net for individual cells to rebuild some dead batteries I have, but it seems that for the
time and labor plus the cost of the cells + shipping, I still can't find a cheaper scenario that just buying a complete generic replacement from these guys-
http://www.camera-battery.net/power-tools-battery/DEWALT/DW9091-DW9094-3000.htm

I know it is a no-name pack with no-name generic cells inside, but I am tempted to click "buy". Anyone had experience with generic packs? I bought a genuine dewalt pack for ~$70 just to get me by in the short term, but could still use 2 more to round off my collection, but the price on the generic packs is so enticing.. almost half the
price..


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#75328 - 02/23/07 01:51 AM Re: Nicads wearing out  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
The question begging to be asked Ryan, is why did the cells die in the first place?.
Sure Ni-Cad packs do get a "memory effect" if not charged at the right time.
Trying to charge a Ni-Cad bank is like pushing s*it up hill if it has the memory effect.
From the start, you have to fully discharge NC cells and then charge them from there.
My Panasonic gear uses Lithium Ion batteries, never had a problem with them before.
Only 12V too.


#75329 - 02/23/07 01:54 AM Re: Nicads wearing out  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,142
Estero,Fl,usa
If they are dead anyway you can try to zap them. The safest way is with a big capacitor but some folks use a car charger. Stand back! Wear your PPE


Greg Fretwell

#75330 - 02/23/07 09:36 AM Re: Nicads wearing out  
trollog  Offline
Member
Joined: Oct 2004
Posts: 276
San Diego California USA
I assume it was just age and normal use that wore them out. They are 4 years old and were used almost daily. I have heard the tricks for reinvigorating them, but I am not sure how these tricks would work in the case of individual dead cells in a pack, which was the case in one of them I disassembled.


#75331 - 02/23/07 09:44 AM Re: Nicads wearing out  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
Batteries are both a blessing and a curse.

First, there is a definite difference in batteries. Even, staying within the same parent company, and using the correct chargers, I didn't get near the life from "Firestorm" as I do from "DeWalt." In a similar manner, those who have tried the very cheap imports have noted an almost 'one time use' to the batteries.

As for "new" vs. "rebuilt," the batteries I had rebuilt at Batteries Plus seem to hold up nearly as well as new batteries ... and at half the cost.
Some of this difference may be the thermocouples some batteries have built into them. Even more of the difference is likely to be in the chargers.

Twice, with different makes, I have had batteries ruined by faulty chargers. Chargers do fail. Sometimes they fail in a spectacular and obvious way, with smoke and glowing contacts. Other times, they simply cook a few batteries until you notice a pattern...

Last, I am beginning to wonder if the reduced life I seem to be getting is the fault of the tool itself. Bad bearings or worn brushes? I can't really say.

What I can say is that I have become more aware of the limits to cordless tools - and have returned to corded tools, saving the batteries for special circumstances. I've certainly canceled plans to purchase additional types of cordless tools.

Batteries may be fine for vacuums and drills ... but I'm sticking with my corded angle grinder and band saw. Even with the drill and vacuum, I am keeping corded tools on hand.

[This message has been edited by renosteinke (edited 02-23-2007).]


#75332 - 02/23/07 11:17 AM Re: Nicads wearing out  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
An important caution on the 'Memory Effect'.

For NiCd cells, the premature voltage drop caused by partial discharge and recharge can be corrected by fully discharging the cell. When a NiCd reaches this premature voltage drop point, it still has significant energy stored, and with proper design can be discharged further, however this voltage drop point looks a lot like an end of discharge knee, and will often trigger low battery warnings.

However there is a significant risk if you are dealing with _batteries_ of cells, meaning multiple cells in series. The direction of current flow associated with discharging a cell is the same as the current flow that would 'reverse charge' the cell. Reverse charging a NiCd cell will cause significant damage to the cell.

When you discharge a _battery_ of cells, there is always going to be one cell that discharges first. The other cells will continue to push current though this cell, reverse charging it and damaging it.

So if you elect to discharge a battery 'all the way', be sure to limit 'all the way' to a reasonable value, or you _will_ damage the battery.

A good charger is critical to battery life. I'd recommend investing in a good general purpose 'smart charger' such as sold for RC car use. Use this periodically to evaluate the condition of your batteries, even if you use your normal tool charger most of the time.

-Jon


#75333 - 02/23/07 11:20 AM Re: Nicads wearing out  
NORCAL  Offline
Member
Joined: Sep 2002
Posts: 874
"As for "new" vs. "rebuilt," the batteries I had rebuilt at Batteries Plus seem to hold up nearly as well as new batteries ... and at half the cost."

I had the samething done, the cost for rebuild was $45.00 VS $60.00 for a new Milwaukee,plus 7.25% sales tax. Where is the saving when it requires being dropped off and picked up?( I should say it was a Mil. 14.4 V batttery.)



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