# leaving cordless tools on the charger for long periods of time



## Ed ke6bnl (Aug 8, 2017)

whats the thought on leaving your lithium ion or ni/cad batteries on the charger for long periods like several days to several weeks. Can the battery be ruined by doing this. Right now I have my chargers on timers that go off at night and start in the mourning.


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## chandler48 (Jun 5, 2017)

There is really no need to do that with lithium batteries. They will hold a charge for quite a long while. LIon and Ni/cads will depend on the manufacturer. I charged my two Milwaukee lithium batteries 4 weeks ago and the charging status lights still are peaked out. I think your idea of timers is good, but I don't think the batteries will know the difference.

The main thing I have found, using battery tools every day is that you need to use them and charge them. Leaving them unused and uncharged can only harm them. Often homeowners are warned against buying battery anything, and are referred to corded drills, etc. If you need a battery drill, chances are the battery will be dead.

To answer your question more directly, many manufacturers build in an "idle" mode that trickles the charge so as not to over charge and damage the batteries.


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## Windows on Wash (Aug 30, 2011)

The newer batteries are supposed to have circuitry in them to prevent any damage. 

The same cannot be said for the older batteries.


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## Mike Milam (Mar 3, 2017)

Thoughts on whether or not to run the batteries down completely before charging? I have heard this over the years. Theory is the batteries have memory?


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## Ed ke6bnl (Aug 8, 2017)

Mike Milam said:


> Thoughts on whether or not to run the batteries down completely before charging? I have heard this over the years. Theory is the batteries have memory?


my understanding is the new lithium ion battery have no memory like the NiCads do. The big no no to lithium ion is to drain them way down, too far and they may not take a charge.


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## Drachenfire (Jun 6, 2017)

With most modern charging systems, you can leave the battery on the charger. For instance the instructions for my Porter-Cable 20v cordless drill states;
_
*Leaving the Battery in the Charger* 
The charger and battery pack can be left connected with the LED glowing indefinitely. The charger will keep the battery pack fresh and fully charged. This charger features an automatic tuneup mode which equals or balances the individual cells in the battery pack to allow it to function at peak capacity. Battery packs should be tuned up weekly or whenever the battery no longer delivers the same amount of work. To use the automatic tune-up mode, place the battery pack in the charger and leave it for at least 8 hours._


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## ZZZZZ (Oct 1, 2014)

Ed ke6bnl said:


> my understanding is the new lithium ion battery have no memory like the NiCads do. The big no no to lithium ion is to drain them way down, too far and they may not take a charge.


How can you tell when you have drawn down Li-ion batteries too far?

I have 6 of the 18V Ryobis: 3 older NiCads, 3 relatively new Li-ions.The Nicads start to slow down when the charge is low, but the Li-ions seem to work at full speed right to the end. They work fine and then just stop completely, no slowing down.
.
.


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## Ed ke6bnl (Aug 8, 2017)

ZZZZZ said:


> How can you tell when you have drawn down Li-ion batteries too far?
> 
> I have 6 of the 18V Ryobis: 3 older NiCads, 3 relatively new Li-ions.The Nicads start to slow down when the charge is low, but the Li-ions seem to work at full speed right to the end. They work fine and then just stop completely, no slowing down.
> .
> .


Li-ons give out all at once and perform well to the very end and the first sign of slowing it is time to put on charger. what I have read was that person that wants to just get the next dozen screws in can damage the battery. I just learned also that the makita 18v brand if the battery has a star on the bottom and when it is used with a tool with that same star on its bottom there is a chip in it that will shut down the tool when too much stress is on the tool/battery and prevent damage.This was from Makita co. video


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## mathmonger (Dec 27, 2012)

I've tried to figure out rechargeable batteries once or twice. I always get bogged down in the different technologies and jargon. It's more complicated than it seems. My old Dewalt 18v Ni-Cad charger instructions had similar verbiage to what Drachenfire quoted. I think "you get what you pay for" and "read your manual " still seem to be good rules to go by. 

I still wouldn't buy a rechargeable tool from Harbor Freight. I do, however, have a charger and some AAA's from Harbor Freight and they seem to work fine. But I'm careful to take them off the charger when they are done charging. :biggrin2:


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## SeniorSitizen (Sep 10, 2012)

Ed ke6bnl said:


> whats the thought on leaving your lithium ion or ni/cad batteries on the charger for long periods like several days to several weeks. Can the battery be ruined by doing this. Right now I have my chargers on timers that go off at night and start in the mourning.


No experience with Lithium but this is what I've observed with NiCd.

The NiCd batteries charge being monitored with a Killowatt Meter. 

A old 12 V discharged Hitachi battery that will barely turn the chuck on a drill motor reads 51 watts and quickly drops to 48 watts and reads 02 watts when fully charged.

A DeWalt 18 V does approximately the same except with a battery that's fully charged the Killowatt immediately reads 02 watts when plugged in to the charger.

I see this as batteries being over charged would be nearly impossible if on the charger for a few weeks.


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## Oso954 (Jun 23, 2012)

Part (perhaps all) of the 2 watts is just powering the charger. Only a portion (if any) of it is going into the battery. 

Any part that is entering the pattern is basically a float or maintenance charge level, offsetting the self discharge that all batteries have.

Nicads can loose 10-15% of their charge in the first 24 hours, followed by another 10-15% per month.

Li-ion loses about 5% in the first 24 hours, followed by 1-2% per month. Battery safety circuits (which the Hitachi has) will increase that by about 3% per month. One of the protections of the safety circuit is to prevent overcharging. It also protects against overload and over discharge.

The over discharge protection is part of the reason the battery shuts down so quickly after the first sign of slowing.


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## chandler48 (Jun 5, 2017)

> has a star on the bottom and when it is used with a tool with that same star on its bottom there is a chip in it that will shut down the tool when too much stress is on the tool/battery and prevent damage


I, unknowingly bought two replacement Makita 18v, but no mention was made of the star on the bottom. My understanding was my older tools would not work with them. After full charging they seem to work great, but will shut down in a split second rather than winding down like the old batteries. I have two drivers, a drill, two chargers and 6 batteries, that go all day long, so I can't attest to their sitting around much.


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## DexterII (Jul 14, 2010)

I happen to use my cordless tools a lot, and consequently have numerous batteries, both NiCad and LiOn, which I don't give a lot of thought to, except that I did start painting the date on new ones about 8-10 years ago, more as a matter of curiosity than anything, and have gotten very good life out of the majority of them, at least compared to buddies who I hear talking about theirs when the topic comes up. My approach has always been to leave them right in the tool, use them until they won't do the job, grab another battery, charge the used one for whatever it takes, and put them back on the shelf or in a tool bag. Now there are obviously exceptions, like if I have to climb up a ladder, go on a roof, or crawl into a crawlspace, sure, I make sure the battery I have is freshly charged, but otherwise keep running it until it needs to be replaced. But we're all different, with different jobs, hobbies, interests, and lifestyles. In my opinion, if you're not going to have extra batteries on hand, only use power tools occasionally, or have to consider battery maintenance, despite how convenient they may sound, I still think corded tools are the best choice. But then I'm a guy who still uses a hand miter box for small jobs, rather than lugging a power miter box up a flight of stairs or makes several trips up and down and in and out to trim a single window or door opening.


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