# Lithium Ion Battery



## Graybeard (Jun 8, 2015)

I recently picked up a Dewalt 20 volt lithium ion drill at Home Depot for under a $100. Thought I got a good deal until trouble started. Sadly I also bought a reciprocating saw that would use the same battery.

The trouble started when one battery pack wouldn't hold a charge. I called Black and Decker who owns Dewalt and Stanley tools and they sent me a replacement battery pack at no charge. Well now I have three battery packs that won't hold a charge. I was told to send them to the factory repair shop in West Milwaukee and they'd check them out and if they needed replacement they'd do so.

The problem I realized was my drill's batteries were only 1.3 amp. The larger battery is a 4 amp. So being a total knob on electrical issues I have some questions.

When drilling hard stuff the drill stops and will not run at all. It may or may not run after a wait of a minute or two. Is that called poor under load and would a 4 amp battery be better under load.

The same thing happens to my reciprocating saw. 

Really not acceptable to be on a ladder with a newly charge battery only to have it fail. I have a hell of a time getting up the dad gum ladder by itself.

Thanks for the education.

Graybeard


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## woodtickgreg (Jun 8, 2015)

All of your batteries are 20 volt and the same power. The different amps or amp hours as they are called is how much charge they hold and how long they will run. Like the difference between a quart jar and a gallon. Lithium batteries don't get weak when they are losing their charge like nicads, they just run until they are discharged and then just stop, done, time for a recharge.

Reactions: Like 1


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## Graybeard (Jun 8, 2015)

Thanks for the information. Very clearly explained - thanks.
Graybeard


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## Graybeard (Jun 9, 2015)

Follow up. I sent the charger in for a check up and possible replacement. Hopefully that's the problem. Once I get a full charge everything works well. Sometimes it works and sometimes it doesn't. The charger indicates a full charge and the meter on the battery says 1/3 charged.
Graybeard


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## SENC (Jun 9, 2015)

They also, in my experience, don't like to be on the charger for long periods once fully charged. The little study I've done suggests the problem is more with certain chargers that don't cycle properly... but my L-ions that have lasted have been kept off the charger except for brief charging cycles.


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## Schroedc (Jun 9, 2015)

SOunds to me like a charger issue, I've got a bunch of Milwaukee Lithium Ion battries and never had an issue unless they gut dropped hard off the ladder.


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## Nature Man (Jun 9, 2015)

I have a Dewalt impact gun with lithium ion 20V battery. I can't seem to run it out of its charge! It runs forever, seemingly. Chuck


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## Graybeard (Jun 9, 2015)

Thanks for the feedback. I sent the charger off today. We'll see what they say.
I do have a question about leaving it on the charger. Isn't being able to leave them on the charger a benefit of the lithium ion over the Nicad battery?
Graybeard


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## woodtickgreg (Jun 10, 2015)

The advantage with li batts is they don't discharge like nicads when sitting on the shelf.


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## SENC (Jun 10, 2015)

Here are a couple of excerpts from batteryuniversity.com. I can't swear to the site's overall accuracy as batteries aren't my area of expertise, but I've found it pretty helpful when I've had questions. I think the short answer to your question is yes, if you had the perfect charger - which may not exist but in theory. There have been a number of fires reportedly caused by L-ions left on chargers that do not cut off at peak voltage, which apparently has lead many consumer products mfrs to create chargers that shut down early. One other knock on L-ions is that they should not be "deep discharged" but rather partially discharged and topped off regularly. Maybe @Brink will come along and set us all straight.
_
Li-ion does not need to be fully charged, as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge, because a high voltage stresses the battery. Choosing a lower voltage threshold, or eliminating the saturation charge altogether, prolongs battery life but this reduces the runtime. To satisfy maximum runtime, most chargers for consumer products go for maximum capacity; extended service life is perceived less important_.

and

_Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge (maintenance charge) would cause plating of metallic lithium, and this could compromise safety. To minimize stress, keep the lithium-ion battery at the 4.20V/cell peak voltage as short a time as possible.

Once the charge is terminated, the battery voltage begins to drop, and this eases the voltage stress. Over time, the open-circuit voltage will settle to between 3.70 and 3.90V/cell. Note that a Li-ion battery that received a fully saturated charge will keep the higher voltage longer than one that did not receive a saturation charge.

If a lithium-ion battery must be left in the charger for operational readiness, some chargers apply a brief topping charge to compensate for the small self-discharge the battery and its protective circuit consume. The charger may kick in when the open-circuit voltage drops to 4.05V/cell and turn off again at 4.20V/cell. Chargers made for operational readiness, or standby mode, often let the battery voltage drop to 4.00V/cell and recharge to only 4.05V/cell instead of the full 4.20V/cell. This reduces voltage-related stress and prolongs battery life_

Reactions: Informative 1


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## Graybeard (Jun 10, 2015)

Very helpful. When I had a battery on that charger and nothing seemed to be happening I worried about a possible fire in the back of my mind. I sure hope they either repair (unlikely) or replace it with one that works and I won't leave any battery on the charger over night anymore.
Graybeard


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## Brink (Jun 10, 2015)

Li-ions do burn hot.


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## Graybeard (Jun 11, 2015)

Sent the charger in to be checked on Tuesday of this week and got a new charger today. The new one mounts flat where the old one was a wall mount and the new one appears much sturdier. I doubt they even tested the old one.
Good service, but I wish it would have worked from the get go.
Graybeard

Reactions: Like 1


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