Storing LI battery packs on the charger

[woodnerd]

According to the T15 manual "Storing the battery pack in an operating charger keeps the battery pack continually charged".  I took this to mean I can just leave my other battery pack on the charger until I'm ready to use it, then stick the other on until the insanely long battery life has expired.

However, on another forum, some fellow who says he's a "consultant with Festool" claims leaving the pack on the charger will damage it and that Festool service technicians agree with him.

So, what's the real story?

 

[fdengel]

I think the general story is that keeping the battery on the charger for a reasonable period of time is OK, but leaving it on indefinitely will eventually harm the battery.

Festool chargers/batteries are smarter than those of most other tool companies and they are more resistant to the types of problems that occur with other brands, but not completely immune.

Personally, once I see that a battery is charged, I take it off and unplug the charger (or put on the next battery to charge).

 

[Administrator_JSVN]

Rather than repeating myself, here's a link to a thread on the topic and the "official" verdict on leaving the batteries on the charger.

http://festoolownersgroup.com/ask-festool/batteries/msg77723/#msg77723

There is no problem with the Lithium Ion batteries and the TRC 3 charger to leave the battery on the charger, but there is no strong benefit after the battery has been fully charged either.

 

[Rick Christopherson]

Shane,
The discussion in question relates to long term storage of LiIon batteries. It is correct that the intelligent battery charger itself will not damage the battery while connected. However, the issue is with battery life in general.

Other battery technologies (such as NiCd, NiMH, etc.) have a lifespan that is dependent on the number of charge cycles. LiIon batteries are different in that they simply age with time. Even an unused battery has a limited lifespan. Factors that speed up the aging process of the battery are temperature and voltage. Keeping a battery at its maximum voltage (full charge) for extended periods increases the internal oxidation of the cell. It is not damage per se, but is simply speeding up the aging process of the cell.

Depending on how much usage the tool is getting, the unused battery can sit unused for weeks or even months before it is needed. In situations such as this, where tool use is low or sporadic, it is best to leave the unused battery at a partially discharged state (40-50%) and charge it just prior to its anticipated use. Maintaining the battery at 100% charge shortens the battery life. Obviously this would be a different situation for tools that experience heavy usage, where the battery is placed into service almost as quickly as it has been charged.

 

[Brice Burrell]

I don't see a real need to keep them on the charger since they'll hold their charge very well sitting on the shelf.

 

[BigHonu]

Shane,
The discussion in question relates to long term storage of LiIon batteries. It is correct that the intelligent battery charger itself will not damage the battery while connected. However, the issue is with battery life in general.

Other battery technologies (such as NiCd, NiMH, etc.) have a lifespan that is dependent on the number of charge cycles. LiIon batteries are different in that they simply age with time. Even an unused battery has a limited lifespan. Factors that speed up the aging process of the battery are temperature and voltage. Keeping a battery at its maximum voltage (full charge) for extended periods increases the internal oxidation of the cell. It is not damage per se, but is simply speeding up the aging process of the cell.

Depending on how much usage the tool is getting, the unused battery can sit unused for weeks or even months before it is needed. In situations such as this, where tool use is low or sporadic, it is best to leave the unused battery at a partially discharged state (40-50%) and charge it just prior to its anticipated use. Maintaining the battery at 100% charge shortens the battery life. Obviously this would be a different situation for tools that experience heavy usage, where the battery is placed into service almost as quickly as it has been charged.

Agreed 100%

I think the biggest users of Li-ion are the RC guys.  They go through a ton of batteries and are very picky about charging and maintenance.  I believe the majority will give almost the exact same advice.

IIRC, the no load voltage for a single healthy Li-ion (manganese) is around 4.2V fully charged.  You should stop using that battery once the voltage gets to 3.0V or so.  Long term storage voltage should be around 3.4-3.5V.

For those who use their battery equiped tools every day, the charge status is not a concern relatively speaking.  For those that only see intermittent usage, the charge status becomes more important to the longevity of the battery to perform at its highest level. 

I'm sure someone will correct me if I mistated/misremembered anything.

 

[Sean7a]

Awesome info in this thread.  My GM is a battery nut who works @ The Tool Nut.  Get it?

Anyways, I'm hoping he'll have a chance to chime in.

My limited knowledge of batteries, specifically li-ion technology and the chargers that are around today is that due to the "intelligent" chargers, batteries are fine being stored on a charger as the charger will halt it's charging once the cell is full.  You will not damage the cells.  Now Rick's input is some next level stuff....I'd heed his advice (storing it off the charger) unless you're using these puppies every hour of the day and constantly need batteries to be charged and ready at all times.

 

[GhostFist]

This topic of battery types and storage conditions is giving my head a spin. My drill is pretty much my hammer, meaning, it's my go to main tool for the vast majority of projects i'm working on. light weight is important but long life even more so. I'm really sick and tired of buying a new drill every 2 years and feeling it's not up to snuff after 1. What's the consensus here? Are Lithium ion's the way to go? I've had a few and they were great  until the batt's pooched out. Should i stick with big heavy Nicad's? I do not own a festool drill but am extremely keen on them and am debating the T-15 or holding out for the T-18. Currently using a giant piece of garbage Ridgid (DON'T BUY RIDGID CORDLESS TOOLS!!!!) and i want to sacrifice it to the garbage heap in the form of a well smashed up pile of rubble.

 

[nickao]

Bad luck.

I bought a Panasonic 15.6 V, its on its 7th or is it 8th year.

I have the same batteries and only just now can I tell a difference. They still work well, maybe not last as long. No Li-ion, it was long before that, just Ni-cad 3.5 ah. My brother has been through Milwaukee, DeWalt, two types of Rigid and one Festool, while my Pany just keeps kicking. Man they made some good batteries.

Try a Pany as your second and get a Festool if you must and I bet the Pany will be around for many, many years. As long or even longer than any Festool.

Old proven technology is still working fine for me.  

I recently(well about 18 months ago) got a couple of  little Makita's and they seem great too, time will tell.

 

[GhostFist]

Knew a bunch of guys that swore by Panisonic, they weren't even available here at the time. I'll dig deeper.

 

[Brice Burrell]

This topic of battery types and storage conditions is giving my head a spin. My drill is pretty much my hammer, meaning, it's my go to main tool for the vast majority of projects i'm working on. light weight is important but long life even more so. I'm really sick and tired of buying a new drill every 2 years and feeling it's not up to snuff after 1. What's the consensus here? Are Lithium ion's the way to go? I've had a few and they were great  until the batt's pooched out. Should i stick with big heavy Nicad's? I do not own a festool drill but am extremely keen on them and am debating the T-15 or holding out for the T-18. Currently using a giant piece of garbage Ridgid (DON'T BUY RIDGID CORDLESS TOOLS!!!!) and i want to sacrifice it to the garbage heap in the form of a well smashed up pile of rubble.

All batteries have a life span, lithium ions are no exception.  We'll see how long the new Festool batteries last in the couple of years, until then we aren't going to know.  The reasoning behind my decision to go for the new lithium ions was to take advantage of light weight and how long they hold a charge while idle. 

....I bought a Panasonic 15.6 V, its on its 7th or is it 8th year.

I have the same batteries and only just now can I tell a difference......

 

That's well beyond the norm.  I wouldn't expect it would have lasted everywhere near as long with daily use on most construction sites.  Your "shop" drill probably lives a pretty charmed life compared to most of the drill I've seen guys using out in the field.

 

[jonny round boy]

All batteries have a life span, lithium ions are no exception.  We'll see how long the new Festool batteries last in the couple of years, until then we aren't going to know. 

The 3 year Festool warranty on the drills includes the Li-Ion batteries, or so I was told by a Festool UK rep. Specifically he said the batteries were covered for 3 years or 800 charge cycles.

So if the batteries do die in a couple of years, Festool should replace them, irrespective of whether they've been left on the charger or not (unless it specifically says not to leave them on the charger in the instruction manual shipped with the tool).

 

[nickao]

Brice I worked with this drill in the field for the first 4 years. Yes since then its been shop used, but if you think a guy on site uses their tools more than me I think you are mistaken. I don't see what location has to do with it, time used is time used. And I know a couple guys that have these old Panys and they are still working..   They were just a Superior battery, its that simple.

This model right here I bought in 2003, November off Amazon. If the batteries are still made the same I suggest buying one and get back to me in 4 years. This appears to be the same drill, same model, same batteries, but who knows for sure. Hopefully the batteries were not sitting on a shelf since then, but looking at the ratings they seems consistent for the last 8 years. Just my favorite older cordless model by far..

http://www.amazon.com/Panasonic-EY6432GQKW-15-6-Volt-2-Inch-Cordless/dp/B00009KDGX/ref=sr_1_1?ie=UTF8&qid=1295635197&sr=8-1

 

[WarnerConstCo.]

I agree with dovetail (you change names more the Prince and Puff Daddy [big grin]) 

I think the Panny's are the only drills that give Festool's a run for their money.  If Festool didn't have all the different chucks....

 

[nickao]

Heck I only changed once and was originally dovetail65 to begin with.  

I am not comparing an 8 year old model to New Festool drills or any new drill. I am just saying these were great drills with great 3.5 ah batteries and still are. And that I have been very happy and not had the experience of changing drills every year or two . I don't think anyone that had one of these is in the group that had to change drill . That was my only point, Who knows maybe I got the cream of the crop. I can only go by my own experience.

 

[David NY]

However, on another forum, some fellow who says he's a "consultant with Festool" claims leaving the pack on the charger will damage it and that Festool service technicians agree with him.

So, what's the real story?

Hello guys. new to the forums. Sean gives me too much credit but I do love this stuff so I'l offer some humble advice.

I would NOT store in the charger. Doing so will maintain a peak charge of 4.2 volts per cell which is not recommended. For a number of reasons that will bore most everybody here, it is not optimal for batteries to maintain a voltage at their peak. Charge the battery and then let it sit. It will soon have a voltage drop to its nominal (3.7 volts) and then slowly drain from there.

David

 

[David NY]

 

I think the biggest users of Li-ion are the RC guys.  They go through a ton of batteries and are very picky about charging and maintenance.  I believe the majority will give almost the exact same advice.

IIRC, the no load voltage for a single healthy Li-ion (manganese) is around 4.2V fully charged.  You should stop using that battery once the voltage gets to 3.0V or so.  Long term storage voltage should be around 3.4-3.5V.

For those who use their battery equipped tools every day, the charge status is not a concern relatively speaking.  For those that only see intermittent usage, the charge status becomes more important to the longevity of the battery to perform at its highest level.  

I'm sure someone will correct me if I mistreated/misremembered anything.

Quite true. Being a RC guy myself, i really have to keep on top of my stuff, or planes crash/burn.Although many feel that 80% of peak charge is enough capacity for long term storage, it is generally agreed that optimal health is at 3.85 volts per cell. Again this is optimal storage. Most of us use our power tools frequently enough that storage is not an issue. Most of these batteries have a LVC (low voltage cutoff) at 20% (again all of this assuming Lipo batteries) but if a battery pack is being run hard down to its LVC event hat is not good for the battery (if its very warm to the touch, its being overdrawn and should never been run that "hot" until it is "dead" ie LVC and needing to be re-charged).

If a battery/tool setup is not going to be used fro several weeks, it should be discharged down to storage capacity as mentioned, but for most of us this is not practical (putting a voltmeter on our batteries is a little obsessive right?) but for those of us that truly want to get the best out of our batteries' lifetime potential, what;s the bottom line?

Don't leave on a charger. Period. If it is going to sit around not being used charge it up, then run it a few minutes and let it sit in a cool dry place.

Again, this is the rambling of a deranged madman...

p.s. here's a nice link to peruse:
http://www.rcgroups.com/forums/showpost.php?p=16421261&postcount=1

 

[jonny round boy]

David,

Aren't Li-Po batteries completely different to Li-Ion?

 

[woodguy7]

Dovetails, i have 2 of the pannys, a 15v & a 12v.  Both around 15 years old.  Pretty useless now but only this last year have they started letting me down.  But hey, at their age & the work they have done then they owe me nothing  [big grin]

Woodguy.

 

[David NY]

David,

Aren't Li-Po batteries completely different to Li-Ion?

Johnny,

I was waiting for someone to ask that question (and its a great question). let me explain what little I know. Lithium in its raw state is combustible at atmosphere- not very good in our case. BUT, it can be made to release energy. Which is good in our case. SO, we create a compound to mix the lithium with to create a stable, rechargeable matter that can release and re-store energy for continual use.

The  most common forms (at present) of compositions that are being mixed with Lithium to create a rechargeable energy state are phosphorous, iron, cobalt  and sodium (though there are others). Lithium-ion is  generic term to refer to a lithium based battery (in this case) with a cathode (or part B mixture) of another substance that can be changed at a molecular level (rechargeable).

I may be wrong, but I believe when I was at Festool training last fall in Indiana, I was told it was a Lithium Cobalt Oxide, but I could be mistaken.

Either way, they all will exhibit, more or less, the same tendencies and behave the same, to the extent of our concerns with cordless drills. Some of the finer points, without digressing too much, is whether a manufacturer uses, Lithium Phosphate verse Lithium Cobalt refer to capacity of runtime verse number of times battery can be recharged, both with their pros/cons depending upon the n-users' needs. This is what causes so much confusion and disappointment with consumers today. They don't know what kind of Li-ion battery they are purchasing with their tool, and may not be best suited for their specific needs.

Apples to apples the following general principle can be applied:

Lithium Phospate gives less runtime and more life cycles ( lower Mah capacity)
Lithium Cobalt gives more runtime and less life cycles (higher Mah capacity)

Again, apples to apples

Hope this helps a bit.

David

p.s. there is older technology that is also referred to as Lithium-ion that was the pre-cursor to the lithium-ion (Li-Po) batteries of today. Many times the characteristics of those batteries are swapped with this newer generation of lithium batteries which adds to the confusion. But again, in general the rechargeable lithium based batteries out in the tool market today will all exhibit the same preferences in regard to peak, nominal, and LVC voltages.