Cordless tool battery charging

[Harry in Ky]

I'm wondering if anyone has an opinion on leaving batteries on a charger for extended periods after full charge. Is it necessarily detrimental to overall battery life, or does it really matter at all.

The reason I'm asking is I recently acquired a cordless grinder with a 12v charger that I plan to keep in the truck. I expect it will see only occasional use. If I leave the charger on with the battery in it until needed, will that be a problem at some point? It's an 18v type 1 battery if that means anything.

 

[timcasbolt]

(quoted from post at 15:56:00 12/21/21) I'm wondering if anyone has an opinion on leaving batteries on a charger for extended periods after full charge. Is it necessarily detrimental to overall battery life, or does it really matter at all.

The reason I'm asking is I recently acquired a cordless grinder with a 12v charger that I plan to keep in the truck. I expect it will see only occasional use. If I leave the charger on with the battery in it until needed, will that be a problem at some point? It's an 18v type 1 battery if that means anything.

In theory, once the battery is fully charged, the charger shuts off and nothing bad can happen. In practice, once in a blue moon something goes awry in the charger and the battery overcharges and reduces battery life, or the battery and/or charger overheats.

 

[in-too-deep]

I don't know what kind of battery you have, or brand, or intelligence of the charger, but I leave Milwaukee Li-Ion batteries on the charger all the time. No trouble.

 

[RM-MN]

With my Ryobi 18V batteries, I have a few hours to get them off the charger or the charger will discharge them. If they discharge, I have to take them off the charger for a few hours, then recharge them. It doesn't seem to hurt the batteries.

 

[Steve@Advance]

I leave them on the charger at work full time. It's a multi port Ryobi charger, they get shuffled around pretty regularly.

Once the green light is on steady, the charger levels off, doesn't seem to hurt them.

I leave them on the charger at home, probably more than I should. Doesn't seem to be a problem.

It is a good idea though, to unplug it when away from it for extended periods, and keep batteries properly stored, away from flammables. Anything is possible!

 

[Harry in Ky]

It's a DeWalt tool, battery is marked 18v XRP. Not much experience with cordless tools, and the first with a 12v charger.

I have a 120v grinder I carry with me as well, but sometimes I find myself where no 110 outlets are available, so I thought this might help fill the gap. It may not get much use, but it certainly won't if the battery is always dead or nearly dead.

I'm toying with the idea of powering the charger with an accessory circuit so it's on when the truck is running, but off when parked. I guess I'll need to ride it out for a while and see how it works out just plugged into a live power outlet. Not sure what might be the down side to either method just yet.

 

[Keith True]

My neighbor had a shed burn down two years ago,The insurance investigator asked it there were any cordless tool chargers in
there.He said yes,and the investigator asked if it was a Makita.It was,and the investigator said he would find it,and as he looked
he described exactly the condition it would be in,and the chain of events that led to it starting the fire.He described a hole that
would be burned through the bottom of the charger,and how it ignited what was under it.His exact words were,Makita makes a fine
tool,but a crap charger.I had a little battery maintainer melt down one time.It was one of those that was supposed to float,or just
charge when needed.It was on the head of a Kohler engine in a Wheel Horse tractor,I picked up the hood and saw a blackened pile of
warped metal.

 

[Mule Meat]

Not knowing fully the type of charger you have.

Some Dewalt 18 volt XRP chargers have a cycle mode built in that will balance the batteries if left on the charger. So it is good to leave the battery on the charger for an extended period once in awhile. Not sure if your 12volt powered charger will have that option built in.

Thing to remember is that the charger will drain juice from your truck battery if the engine is not running as long as it is plugged in. Maybe be a good idea to plug it in the morning when you are ready to head out and unplug it when you get home. Use to have three or four chargers plugged in at one time all day long. But would never leave them overnight.

 

[Geo-TH,In]

All lithium charges will automatically shut off after the battery is fully charged.
You can convert your old 18v tools to 20v lithium. Just buy or make the adapter. Buy 20 Li and 20v charger and be done with the old school crap.
All these tools can be powered with 20v dewalt. To my knowledge no 20v battery is old

school Cadium or Nickle metal.

 

[Harry in Ky]

One more reason to power the charger on a switched circuit. relying on MY memory to plug and unplug every day is asking a LOT.

Also wondering what's the prevailing wisdom on the batteries themselves? I've read/heard that cordless tool batteries should be run down to near dead and then charged fully. Is that "old school" technology that no longer applies to today's batteries or was it a myth to begin with? I have no idea how well that would work out with my (expected) limited use. Would it be better to use the tool occasionally even when not needed just to keep the "juices flowing" rather than sitting idle? I know that improves lifespan with wet cell batteries.

Too many questions, too little knowledge.

 

[Geo-TH,In]

I've read/heard that cordless tool batteries should be run down
to near dead and then charged fully. Is that old school
technology that no longer applies to today's batteries or was it
a myth to begin with?

That is old school batteries and it no longer applies to Lithium
because Li will auto shut off before you can fully discharge it.
No memory, No self discharge. Use it and forget it.
I like to keep mine from freezing and excessive temps.

 

[Bret4207]

I did something absolutely insane when one of my boys gifted me a Dewalt 20V 1/2" impact- I READ THE MANUAL!!!!!!!!!!!! No, really, I did. Found out they recommend not trying to charge a battery below 45F as it can hurt the battery and IIRC to remove battery after it's charged. I'll have to re read it, but the 45F thing I found concerning since they sit in a mostly unheated garage. I intend to come up with an insulated container for them all- maybe a dead refrigerator with a low watt light bulb inside for warmth. Should be pretty fire proof too.

 

[guido]

Bret4207,

What a novel idea! Read the owners manual.

Many questions posed here are usually
answered on the owners manual.

Short tool life is usually result of using
the manual in the out house like the old
Sears catalog,

Guido.

 

[carpenter]

you may have a defective charger

 

[DR. EVIL]

Years and years ago, like 30+ yrs, I had a cordless 3/8 Skill ratchet, that I kept the charger plugged in constantly, it SELDOM got used, and finally stopped holding a charge, and it got scrapped. I've got 6 Craftsman 19.2V batteries, 3 NICAD, 3 Lith-ion, my one charger charges both, it's the charger I use, I have a Nicad charger and a Lith-ion charger but you can charge the nicad batteries with the Lithium ion charger but can not charge lithium ion batteries with the nicad charger, I'm about 90% sure I'm correct on that.
But NOTHING stays plugged in constantly, except things like the compressor & welders, and the breakers get shut off before I go back in the house.