Does it hurt the batteries to keep them on a charger all the time?

Does it hurt the batteries to use them for a little bit and then recharge them or should they run all of the way down before being charged?

I have the ryobi batteries and absolutely love them. I use them for a grass trimmer and blower as well as indoor power tools. If you’re on the fence about them I would take the plunge. Thanks in advance for the help.

My answers relate to Li-Ion rechargeable batteries, such as those used in Ryobi's ONE series.

quote:

Originally posted by cooger:
Does it hurt the batteries to keep them on a charger all the time?

It's not as bad for them as for Ni-Cads, but yes, in the long run, it's bad for Li-Ions too.

quote:

Does it hurt the batteries to use them for a little bit and then recharge them or should they run all of the way down before being charged?

All rechargeable batteries have a limited number of charge cycles. Ni-Cads operate best when completely discharged before recharging to full capacity. Li-Ions don't suffer the memory effect that Ni-Cads do. That being said, IMO, you should try to use a Li-Ion down to at least ~50% before recharging.

I don't know what you consider "a little bit," but I think of people who feel the need to recharge their cell phones or laptops when they get below 85%.

I use my DeWalt's down to the last bar and then recharge, not a one of my many 20V batteries have disappointed me in the last 4 years.

These Li-ion batteries have a not insignificant fire risk when left on chargers for long periods. It doesn't per se hurt the batteries but I wouldn't.

I just bought a Ryobi trimmer and edger. The manual for the battery and charger is detailed. Things such as removing the battery when charged. If storing for a month or more store at 50% charge etc. if you didn’t save the instructions go to the web sight and search for the manual.

Virtually all lithium batteries have overcharge protection circuits built in to prevent fires. Leaving on a charger will not hurt them.

However, lithium batteries are happiest when stored between 30-70% capacity.

Lithium batteries do not need to be cycled like NiMH. They do not suffer from "memory" effect.

quote:

Originally posted by iron chef:
My answers relate to Li-Ion rechargeable batteries, such as those used in Ryobi's ONE series.

quote:

Originally posted by cooger:
Does it hurt the batteries to keep them on a charger all the time?

It's not as bad for them as for Ni-Cads, but yes, in the long run, it's bad for Li-Ions too.

Incorrect.

Quality Li-Ion batteries on quality chargers will simply be kept topped-off. Since the chargers drop to a maintenance charge level when they sense the batteries are fully-charged, the batteries will not be damaged. And, since Li-Ion batteries do not suffer from the same "memory effect" as NiCad and NiMH batteries did, it will not affect their capacity.

(This is assuming neither batteries nor charger are defective.)

quote:

Originally posted by iron chef:

quote:

Originally posted by cooger:
Does it hurt the batteries to use them for a little bit and then recharge them or should they run all of the way down before being charged?

Li-Ions don't suffer the memory effect that Ni-Cads do. That being said, IMO, you should try to use a Li-Ion down to at least ~50% before recharging.

Incorrect.

The chief enemy of Li-Ion batteries is heat. Longer, deeper discharge/charge cycles generate more heat. Therefore: More-frequent, shallower charging is better. Best to get 'em on the charger when they get down no lower than 70-80% of full charge, when you can.

quote:

Originally posted by wreckdiver:
I use my DeWalt's down to the last bar and then recharge, ...

That is one of the worst things you can do for the lifetime of a Li-Ion battery. (For the reason cited above.)

quote:

Originally posted by hrcjon:
These Li-ion batteries have a not insignificant fire risk when left on chargers for long periods.

Incorrect. Yes: There is a not-insignificant risk in charging (and discharging) Li-Ion batteries, but the risk is greatest when they're generating the most heat. (Note: Another reason to charge more frequently.) Once fully-topped-off there is very, very little heat generated.

(This assumes neither batteries nor charger are defective.)


So, twice, above, I've noted "This assumes..." about the condition of batteries and chargers. Problem is: Murphy's Law. So, to be safe, it's best to charge 'em up, not leaving them unattended while charging (babysitting shorter charge cycles being yet another reason to charge more frequently), take 'em off the charger, and store them safely. If they've been sitting long since the last charge, top 'em off, then put 'em to use.

Additional precautions

Do not take Li-Ion batteries, or any rechargeable battery, directly off heavy use, while still warm from a heavy discharge cycle, and put it on the charger. Let it cool down, first.

Same thing when taking a battery that is still warm from the charge cycle, if it had been deeply-discharged.

Best to charge batteries in a cool location, rather than a blazing hot one.

Many matched battery/charger/tool combinations will refuse to use or charge a too-hot battery, but not all.

quote:

Originally posted by iron chef:
My answers relate to Li-Ion rechargeable batteries, such as those used in Ryobi's ONE series.

quote:

Originally posted by cooger:
Does it hurt the batteries to keep them on a charger all the time?

It's not as bad for them as for Ni-Cads, but yes, in the long run, it's bad for Li-Ions too.

quote:

Does it hurt the batteries to use them for a little bit and then recharge them or should they run all of the way down before being charged?

All rechargeable batteries have a limited number of charge cycles. Ni-Cads operate best when completely discharged before recharging to full capacity. Li-Ions don't suffer the memory effect that Ni-Cads do. That being said, IMO, you should try to use a Li-Ion down to at least ~50% before recharging.

I don't know what you consider "a little bit," but I think of people who feel the need to recharge their cell phones or laptops when they get below 85%.

Electric cars have driven a lot of studies on recharging effects on Lithium Ion batteries and they indicate that if these batteries are "topped up" frequently it actually extends the life of the battery. Turns out that there isn't any real number of charge cycles before the battery needs to be replaced because the determent for service life is the TOTAL hours on the charger and how much internal heat is generated when charging. Obviously if you are only topping up a battery with 85% of the charge remaining it will take much less time and create lower internal temperatures.

ensigmatic, that may all be true, but I can guarantee you that on every construction site across the globe, workers are slapping batteries on and off the chargers as fast as they can. I’ve used some of mine so hard I was rotating two tools through the refrigerator because they were so hot. Some of my batteries are still original ones from 2014 when I went cordless. This is, however, all Milwaukee Red Lithium, which is supposed to have a bunch of sophisticated charging logic built in.

The short answer, with quality batteries and tools, is I wouldn’t overthink it. If you’re prone to buy off brand, Chinese copies, then I would worry about it more.

Thanks for the replies. By a little bit I mean running them down to half life or less and then recharging. I was thinking that lithium batteries could get a "memory" if charged before being dead repeatedly but I guess that is not the case.

I am going to pick up one of the Ryobi emergency lights with the USB port for storms and whatnot. I got to thinking about the best way to keep my 3 batteries charged up without hurting them.

I'll say again- I am a huge fan of these things. I mowed yards on the side for 6 years and loved my Stihl 2 cycle trimmer. I quit mowing and that trimmer died so I decided to get the Ryobi trimmer. The electric whine hurt my pride the first time I used it because I wanted that sound of my old Stihl. It has proven to be quite a cutter though and perfectly adequate for my little half acre lot.

quote:

Originally posted by cooger:
Thanks for the replies. By a little bit I mean running them down to half life or less and then recharging. I was thinking that lithium batteries could get a "memory" if charged before being dead repeatedly but I guess that is not the case.

Setting aside the heat issues described by ensigmatic and others, you can think of a lithium-ion battery rated for 500 charge/discharge cycles as actually being rated for 50,000% charge/discharge.

So 500 cycles of using 100% of the battery life before charging will get you there... or 1000 cycles of 50% use, or 2000 cycles of 25% use, etc.

It's not really quite that simple, as others have mentioned, heat, rate of charge, and rate of discharge have a significant impact, too, but it's a good first approximation.