Cordless drill...battery question

[mudflap]

Is it hard on Lithium batteries to run them all the way down...Had a close call today with one of my DeWalt batteries....Last thing i used it for was a fishing trip last fall...had it on an LED flashlight..ran it all the way down..its been sitting in the pantry wit some other stuff...The Wife evicted my tools from the pantry today...So i tried to charge it...no luck.. No way im paying $100 for a new DeWalt one...since i have switched my work stuff to Milwaukee...so i was looking at some knockoff ones on Amazon...and stopped by the Batteries Plus store to see how much it would cost to have that pack rebuilt.....The kid working there asked if i tried "jumping" it...He said alot of times when Lithium batteries have sat dead for a while you have to put some juice back in them..or the charger will deem them defective..and not charge...And since the pack was less than a year old..and not used much..i should try that before spending money on a rebuild.....I took it home and hooked it to my trickle charger for about 5min....and the kid was right....put it on the charger..and it fully charged..

 

[CrashmanS]

I bought a ryobi hammer drill with a "bad" 18 volt battery. Would not charge in my 6 port fast charger. Bought it for the drill anyways. Put it in the one port regular charger and next morning, charged!

Sent from my SM-N920P using Tapatalk

 

[Dimitri]

I've heard of jumping lead acid batteries.

Hard to jump a lithium ion pack when the BMS that controls the charge cycle is built into the pack. You'll have to tear it apart, and then apply ~4V to each of the cells individually for the BMS to be fooled. What your doing is fooling the charger itself. The BMS needs to be alive to allow the pack to charge.

My MacTools 12V/20V charger, turns on with lower over all pack voltages then my Dewalt 20V Fast charger. And the little Dewalt 12V/20V ultra-slow charger, turns on with the lowest volts per cell. Because fast charging unhealthy cells, kills them.

Running the battery pack dry didn't kill the battery. The BMS cuts off the power output once you hit 3.0V-3.5V depending on chemistry and design intent. So when it stopped powering the flash light, it was still carrying a 10-20% charge.

Lithium batteries, are some of the hardest batteries to kill due to normal use and discharge, due to the BMS. Unlike silly Lead Acids and Ni-Cd which like to die because you looked at them the wrong way.

Dimitri

 

[6PTsocket]

I've heard of jumping lead acid batteries.

Hard to jump a lithium ion pack when the BMS that controls the charge cycle is built into the pack. You'll have to tear it apart, and then apply ~4V to each of the cells individually for the BMS to be fooled. What your doing is fooling the charger itself. The BMS needs to be alive to allow the pack to charge.

My MacTools 12V/20V charger, turns on with lower over all pack voltages then my Dewalt 20V Fast charger. And the little Dewalt 12V/20V ultra-slow charger, turns on with the lowest volts per cell. Because fast charging unhealthy cells, kills them.

Running the battery pack dry didn't kill the battery. The BMS cuts off the power output once you hit 3.0V-3.5V depending on chemistry and design intent. So when it stopped powering the flash light, it was still carrying a 10-20% charge.

Lithium batteries, are some of the hardest batteries to kill due to normal use and discharge, due to the BMS. Unlike silly Lead Acids and Ni-Cd which like to die because you looked at them the wrong way.

Dimitri

I am familiar with the circuitry controlling max. charge and min. discharge but if the Li batt. is at min. and lays around for too long, can't it self discharge even lower? I think they tell you not to store them fully dischargrd for just that reason. Dunno. I have not found NiCds to be that delicate. They can sometimes be " jump started" too. They can grow dendrites, metal build ups that short out the cells. Applying high voltage from a high current source will sometimes blow the dendrites away like a fuse. The desccription of the process is all over the net. It has variable results as they can grow back and the battery is usually getting old at that point,anyway.

Sent from my SM-G900V using Tapatalk

 

[Dimitri]

Yes, the BMS can try and limit discharge, but never fully control it over long periods of time. So if you store them discharged, they will discharge internally just like any other battery chemistry and then eventually fail.

All batteries should be stored fully charged and checked on every few months.

I personally rotate through Dewalt's line, 4-5 12V, 2x 20V/2Ah, 4x 20V/4Ah and 2x 60V Flexvolt batteries.

I don't use them every day, and don't need to charge them every day either. But I rotate them between my tools and they each get used about once every 2-3 months, and get charged at that point. Some of the batteries are 5+ years old now with no signs of slowing down.

Dimitri

 

[DerekV]

Is it hard on Lithium batteries to run them all the way down...Had a close call today with one of my DeWalt batteries....Last thing i used it for was a fishing trip last fall...had it on an LED flashlight..ran it all the way down..its been sitting in the pantry wit some other stuff...The Wife evicted my tools from the pantry today...So i tried to charge it...no luck.. No way im paying $100 for a new DeWalt one...since i have switched my work stuff to Milwaukee...so i was looking at some knockoff ones on Amazon...and stopped by the Batteries Plus store to see how much it would cost to have that pack rebuilt.....The kid working there asked if i tried "jumping" it...He said alot of times when Lithium batteries have sat dead for a while you have to put some juice back in them..or the charger will deem them defective..and not charge...And since the pack was less than a year old..and not used much..i should try that before spending money on a rebuild.....I took it home and hooked it to my trickle charger for about 5min....and the kid was right....put it on the charger..and it fully charged..

As mentioned by others, modern lithium batteries from reputable manufacturers are pretty robust. However, to answer some of your questions/concerns:

Is what you did "hard" on the battery? Yes.

Will it have a shorter overall lifespan than one that didn't get a deep discharge? Yes.

After reviving the battery, will it still work and work pretty good? Yes and yes.

No real noticeable performance decrease, right? Yeah, probably not.

Will run times be shorter than before? Yes.


So the long and short of it is: it'll work just fine, it just won't have the run times of before the incident. It may charge a little slower than normal. It will also not last as long (lifespan wise). Irreversible damage has occurred, but again modern quality lithium cells are still "pretty good" even when beaten to death. Use it and try not to do it again!

 

[DerekV]

All batteries should be stored fully charged and checked on every few months.

Dimitri, you've made valid points and have offered some good-practice tips, but this is not one of them. Storing lithium fully charged for extended periods of time (> a week let's say) puts undue stress on the cells - stress that can be more harmful than discharge-charge cycling. As both you and I have mentioned modern lithium cells are pretty robust, so they'll still perform "well enough" that the user won't notice the wear and tear for some time.

The best storage voltage is 3.92v per cell, or around 75% full. Really anything above 50% SOC and less than 76% SOC is fine. I use Milwaukee, so basically anything with 3 out of 4 bars is fine for storage, and the magical 3.92v per cell (aka pack voltage of 19.6v) is reached exactly at the top of the 3rd bar. So when the charger blinks on the 4th light, pop the battery off a few seconds later. It'll come down and rest at 3 bars and should measure 19.6v for the pack. I've had some packs sit for nearly a year (60*F basement) and not lose a lick of voltage...like not even .01 volts. Seriously impressive! I hope to get many years out of them.

You don't need to be as "particular" as me because even beaten down lithium packs will still work great. Most people probably don't want to care that much about their power tools and that's perfectly understandable. The packs should last at least as long as the warranty period - probably much longer. But if getting the absolute longest life/most use out of your batteries is a priority, there are "best practices" to be followed, and keeping them fully charged all of the time is not one of them [emoji16]

 

[mudflap]

I've heard of jumping lead acid batteries.

Hard to jump a lithium ion pack when the BMS that controls the charge cycle is built into the pack. You'll have to tear it apart, and then apply ~4V to each of the cells individually for the BMS to be fooled. What your doing is fooling the charger itself. The BMS needs to be alive to allow the pack to charge.

My MacTools 12V/20V charger, turns on with lower over all pack voltages then my Dewalt 20V Fast charger. And the little Dewalt 12V/20V ultra-slow charger, turns on with the lowest volts per cell. Because fast charging unhealthy cells, kills them.

Running the battery pack dry didn't kill the battery. The BMS cuts off the power output once you hit 3.0V-3.5V depending on chemistry and design intent. So when it stopped powering the flash light, it was still carrying a 10-20% charge.

Lithium batteries, are some of the hardest batteries to kill due to normal use and discharge, due to the BMS. Unlike silly Lead Acids and Ni-Cd which like to die because you looked at them the wrong way.

Dimitri

Thanks....i just learned alot... The pack read 2.6v before i jumped it..

 

[mudflap]

As mentioned by others, modern lithium batteries from reputable manufacturers are pretty robust. However, to answer some of your questions/concerns:

Is what you did "hard" on the battery? Yes.

Will it have a shorter overall lifespan than one that didn't get a deep discharge? Yes.

After reviving the battery, will it still work and work pretty good? Yes and yes.

No real noticeable performance decrease, right? Yeah, probably not.

Will run times be shorter than before? Yes.
So the long and short of it is: it'll work just fine, it just won't have the run times of before the incident. It may charge a little slower than normal. It will also not last as long (lifespan wise). Irreversible damage has occurred, but again modern quality lithium cells are still "pretty good" even when beaten to death. Use it and try not to do it again!

Thanks for all the info..you and Dimitri....I think i know now how to take better care of my batts...they are expensive to replace...

 

[Dimitri]

The best storage voltage is 3.92v per cell, or around 75% full. Really anything above 50% SOC and less than 76% SOC is fine. I use Milwaukee, so basically anything with 3 out of 4 bars is fine for storage, and the magical 3.92v per cell (aka pack voltage of 19.6v) is reached exactly at the top of the 3rd bar.

And this depends on the specific cell chemistry, which even among the same manufacturer variations for high mAh or high discharge chemistry. Your figure is for cobalt based lithium ion cells (LiCoO2). Which is typically a low discharge rated lithium cell. And not really suitable for power tools.

Many cell manufacturers state anything from 50% charged to fully charged. Or simply state "charged" with no indication of how much.

The real damage to cells happens when they are repeatedly charged up to 4.2V to squeeze an extra 10-20% battery life and left at that state. But some cordless tool manufacturers are smart enough not to. Like Dewalt who's chargers only go up to 4.1V per cell and they also seem to be using proper LiNiMnCoO2 chemistries designed for deep discharging applications.

Dimitri

 

[DerekV]

And this depends on the specific cell chemistry, which even among the same manufacturer variations for high mAh or high discharge chemistry. Your figure is for cobalt based lithium ion cells (LiCoO2). Which is typically a low discharge rated lithium cell. And not really suitable for power tools.



Many cell manufacturers state anything from 50% charged to fully charged. Or simply state "charged" with no indication of how much.



The real damage to cells happens when they are repeatedly charged up to 4.2V to squeeze an extra 10-20% battery life and left at that state. But some cordless tool manufacturers are smart enough not to. Like Dewalt who's chargers only go up to 4.1V per cell and they also seem to be using proper LiNiMnCoO2 chemistries designed for deep discharging applications.



Dimitri

Yes my Milwaukee's only charge to 4.1v per cell as well, which I agree is a good thing. The key part of what I said about the full storage voltage is how long the packs are kept (aka stored) at that voltage. So you're right in that charging them up full isn't harmful - because it's not - especially when using them right away, but keeping them at a full charge for more than a few days does stress them out. "How much" may be considered marginal with these new chemistries, but it does add up over time (aka 2 months > stress than 2 days) and definitely with higher temperatures (aka 85*F > stress than 55*F).



Generally speaking though, I charge mine up full right before using them when I know it's a big project. And it only takes 15 minutes or so (obviously depends on battery size) since they're already at 75%. Extra run time isn't the only benefit here: heavier loads at higher initial voltages (full vs. 75%) typically have less voltage sag, which yields both better tool performance and less battery stress (heat, discharge, etc.). Win-win all around.



I think there's something to be said about the "75%/3.92v per cell" charging/storage though. Literally zero self-discharge in a year's time isn't something to brush off as insignificant!



Anyways, this is beyond the scope of the OP's question, so I'm stopping here

 

[mudflap]

Yes my Milwaukee's only charge to 4.1v per cell as well, which I agree is a good thing. The key part of what I said about the full storage voltage is how long the packs are kept (aka stored) at that voltage. So you're right in that charging them up full isn't harmful - because it's not - especially when using them right away, but keeping them at a full charge for more than a few days does stress them out. "How much" may be considered marginal with these new chemistries, but it does add up over time (aka 2 months > stress than 2 days) and definitely with higher temperatures (aka 85*F > stress than 55*F).

Generally speaking though, I charge mine up full right before using them when I know it's a big project. And it only takes 15 minutes or so (obviously depends on battery size) since they're already at 75%. Extra run time isn't the only benefit here: heavier loads at higher initial voltages (full vs. 75%) typically have less voltage sag, which yields both better tool performance and less battery stress (heat, discharge, etc.). Win-win all around.

I think there's something to be said about the "75%/3.93v per cell" charging/storage though. Literally zero self-discharge in a year's time isn't something to brush off as insignificant!

Anyways, this is beyond the scope of the OP's question, so I'm stopping here

Thanks again guys.....True..most of this is way above my original question, but i have learned alot..find it really interesting..and really appreciate it....

 

[CTyankee]

I'll confess to not reading all the posts in the thread. Probably because since LI came out, I've never spent a lot of time worrying about the battery life of my cordless stuff.

I recently retired my Panasonic drill/driver set and it's 3 batteries. They date back to around 2008-9. The drill finally smoked itself and the batteries weren't holding up for my purposes. I'm talking heavy daily use and not unusual to be changed 2-3 times a day.

Of course they were babied.. They spent every day of their life in the back of my van, all winter and all summer. The batteries were drained down and not switched out until they stopped almost every time. I have seen certain battery brands not like to charge at colder temperatures, but nothing a little warmth didn't solve. All my co-worker pretty much follow the my same procedures, regardless of brand.

Guess everyones experience with cordless tools is going to be different. Some batteries and chargers might be duds or more susceptible to early failure. Personally I've never seen anything that would make me give storage, charging or usage a second thought. Especially for HO use. Maybe I've just been lucky. JMO..YMMV.

FWIW..currently using Milwaukee 18v brushless stuff.

 

[DerekV]

Thanks again guys.....True..most of this is way above my original question, but i have learned alot..find it really interesting..and really appreciate it....

[emoji106][emoji106][emoji106]

 

[jd_1138]

I'm glad you brought it back to life. But if you ever do need to buy a new DeWalt lithium, you can get them on ebay pretty cheap. I've seen brand new 3 to 4 amp ones go for $35-$45 or so. That's a lot cheaper than buying all new tools just because you don't want to buy a new battery.

Or another way to get a battery pretty cheap is to buy a tool that you need anyway. Get it in kit form, and it will come with a battery and a spare charger. It probably won't cost much more than the battery by itself.