Ryobi has made various claims about it's line of 18v chargers. Ryobi has even given creative nicknames to some models.
"One Hour Charger"
"30 Minute Charger"
"Supercharger"
"Evercharge"
"Super Fast Charger" (Not avaliable in the USA)
I've also read many reviews written by consumers who state how long it takes to charge their battery, and the range of values reported is downright laughable. I have no doubt that consumers are honestly reporting their observations. But reporting the recharge time of a battery isn't particularly helpful unless the context of this observation has been extablished objectively. The time required to fully recharge a Ryobi One+ 18v battery depends upon a number of factors, the most obvious of which are: rated battery capacity, charger model, and battery depth of discharge. Factors which are less obvious but which can still greatly impact recharge time include:
ACTUAL battery capacity (affected mostly by age, number of cycles, depth of discharge, and time since last usage)
ambient temperature
temperature of battery pack when placed on the charger
So it is possible to accurately predict how long it will take to recharge a given battery on a given model of charger? And can we objectively describe how each of Ryobi's chargers actually operate?
If these questions interest you, read on as I try to answer them.
Initial Information
For several now I've stated on this website that the P118 charger recharges batteries at a rate of 1.4A and that the P117 and all of Ryobi's other "one hour" chargers operate 50% faster with a charge rate of 2.1A. So I'll test this for sure. Ryobi has also released several models of trickle/overnight chargers such as the P111, P116, and P119. I'll test these as well. Once we've established how the chargers actually operate we'll tackle the differences in Ryobi batteries and the lesser considered factors which affect recharge times.
Charger models not tested
Unfortunately I do not own a Ryobi "Super Fast Charger". You may not even be aware that such a model exists, given that it has not been released in the USA. If you do a web search you'll find that this charger has been released in Australia as the mode RC1815U, and Ryobi claims that the target charge time for a 5.0Ah battery on this charger is 60 minutes. This would certainly be faster than the P117, which is the fastest charger released by Ryobi in the USA.
I have also seen numerous non-OEM chargers available for sale online which claim to be compatible with Ryobi 18v batteries. Some of these chargers look very much like the genuine Ryobi model P117, and others look more like the genuine Ryobi models P113/P114. They are are molded in the same neon green plastic as the genuine Ryobi and some are actually labeled "Model P117". Read the description of these chargers carefully and you'll find that they don't claim to be manufactured by Ryobi, they claim to be "for Ryobi". I find this very deceitful and I wonder if these knock-offs actually contain all of the protection feaures which are stadard on the genuine Ryobi P117. I'm certain that these knock-offs are not UL listed for safety, like the genuine Ryobi chargers are. I have never purchased or tested one of these knock-off chargers so I'm unable to evaluate their claims of Ryobi compatibility and I don't know at what charge rate they operate. Given the lack of safety testing, I will not be purchasing or testing any of them. I'm simply pointing this out so that if you are considering one of these knock-offs you can hopefully make an informed purcahse decision. Does the seller's listing include a photo of the bottom of the unit, where there should be a Ryobi label which shows the model number, the factory number (like 140173004), the serial number, the power input and output, and the UL listing? If you're uncertain as to whether or not the unit you're considering is a genuine Ryobi, I'd suggest comparing the seller's photo of the unit with what can be seen on the Home Depot or ryobitools websites.
My Expectations
I expect that Ryobi's "trickle/overnight" chargers are based on a Constant Current (CC) design. If so, we'll see that they deliver a constant, low amperage current into a battery pack until a preset voltage limit is reached (21v is likely).
I expect that all of Ryobi's "EverCharge" chargers are based on a Constant Voltage (CV) design. If so, we'll see that the charger delivers a low current into the battery pack which decreases to zero as the battery is charged and voltage approaches a preset voltage (probably 21v).
I expect that all other chargers are based on a CC/CV design. If so we'll see the chargers start in CC mode and the charger will deliver a constant current into a battery until a preset voltage limit is reached (no guess at the value, though probably lower than 21v). Once the voltage target is reached, the charger will switch to CV mode and the charger current will decrease to zero as the battery pack voltage increases.
I expect to find that the trickle chargers take the most time to recharge a given battery. I expect that the P118 and P118B will take significantly less time than the trickle chargers but will operate at the same speed as one another. I expect that the P117 and all other chargers will each be about 50% faster than the P118/P118B.
Testing strategy
I have a datalogger which can record voltage and current readings as fast as 4Hz. My intention is to use this datalogger to record the data while recharging the same battery on every model of Ryobi charger. It's reasonable to think that if one battery is repeatedly discharged in the same controlled way that each charger tested would need to deliver the same amount of energy in order to fully recharge the battery. But to be certain, I'll also record data during the discharge cycle of the battery. If the test which measures the energy delivered by the battery gives the same results each time, I'll conclude that the battery received the same amount of energy during the charge cycle on each charger.
In order to level the playing field as much as possible before I begin the "official" testing, I will use a P117 charger and my Computerized Battery Analyzer (CBA) to perform a series of charge/discharge cycles. I will continue cycling the battery until consecutive discharge tests indicate that the battery has delivered the same amount of energy (to within 3% -- a tolerance which I selected arbitrarily).
I have a lot of chargers to test, so it will take a long time to test them all. In order to minimize the total test time, I have decided to conduct this testing on Ryobi's lowest capacity battery, the P102, and I have a seldom used P102 whose date code os CS1630. This means that the battery was manufactured in the 30th week of 2016. It's now mid October 2019 (42nd week of 2019), so this battery is about 3 years and 12 weeks old. I don't expect this battery to operate at it's rated capacity of 1.3Ah/1300mAh.
Afer the first discharge cycle the P102 tests at 1108mAh and on the next cycle it's 1144mAh, about 3% difference. So I go again an get 1148mAh. That's a difference of about 0.35% between the last two cycles, or well within my tolerances.
Note that this means this P102 battery is operating at 1144mAh/1300mAh or 88% of its rated capacity. Not bad for a 3-year-old battery I guess. But let's not forget that if I had not performed this testing to determine actual capacity and instead took this battery head-to-head against another battery and just assumed that it was operating at it's rated capacity of 1300mAh, this battery's results would likely be biased by as much as 12%.
Next I logged the charge curve on a P117. I see on the label of the Ryobi P117 charger that it is rated 85W input.
In the above graph we see voltage in blue and current in brown.
The charging begins at 7:27:46 where the current (brown line) jumps to 2.9A and remains steady until 7:47:23. At this time the current starts to decrease with a shape like the left half of a "U" until it reaches zero at 08:00:12. The total charge time is 32:26.
The voltage (blue line) slowly rises to about 21v and then levels off. The 21v level is reached at the same moment that the current starts to decrease, or 07:47:23. A close examination of the raw data reveals that the current drops at 21.06v. The current drops at the 13th data point after 21.06v is reached -- at 2pts/sec this is exactly 6 seconds after reaching 21.06v. (I forgot to set the datalogger to 4pts/sec from the default 2pts/sec.)
I'll take a moment here to point out that the P117 delivered 2.9A at 21v into the P102 battery. That's (21v)(2.9A) = 60.9 Watts, which represents 72% of the charger's rated input of 85W.
I should mention that the datalogger has an advertised voltage range of +/-70v and resolution of 0.01v. The current range is +/-150A with a resolution of 0.1A, but a reading of at least +/-0.3 is neededare unreliable. This is probably when the current suddenly drops from 0.3A to 0A -- the current was actually decreasing for a little longer, but the datalogger could not detect it.
Next the P102 was discharged on the CBA and the total energy was evaluated as 1130mAh. That's a difference of 18mAh from the previous cycle, or well within my 3% tolerance.
As a sanity check, I repeated the charge on a P117:
Once again we see current steady at 2.9 and voltage increasing to 21v, at which point the voltage remains about 21v and the current drops like the left half of a "U" until it reaches zero. The total charge time is 31:43 and the CBA measures the total energy as 1147mAh -- a difference of 1mAh from the previous cycle. I'd say we're spot on.
Next Up: P118 (log 014) I see on the label of the Ryobi P118 charger that it is rated 50W input. That's 35W or 42% less than the P117, so I expect a lower charge rate than the P117.
The curves on the P118 look much like to those generated on the P117, but with an extended Y axis and the current curve shows a steady maximum of 1.8A instead of 2.9A. I did notice that the P118 does not immediately jump to it's maximum current (as the P117 did). The P118 goes from 0.0A to 1.0A in 3 poin, holds 1.0A for 4 points, then jumps to 1.8A in two points. With 2pts/sec this eans that it took 4 seconds to go from 0.0A to the full 1.8A. How curious. The total charge time is 45:28 and the CBA measures the total energy as 1152mAh.
The P118 delivered 1.8A at 21v into the P102 battery. That's (21v)(1.8A) = 39.9 Watts, which represents 80% of the charger's rated input of 50W.
Next Up: P116. The P116 charger was discontinued years ago, so I may be one of the few folks who still has one. I believe it was advertised as a "four hour" charger. According to the label it's rated for an input of 12W.
This chart looks different that the others.
The voltage slowly rises to 21v, and when this voltage is reached the charge cycle ends.
The current remains steady at 0.3A for the entire charge cycle. This is unfortunate, because the lower limit of the datalogger is 0.3A and the resolution is 0.1A. So while the results show a steady 0.3, it could be that the current varies beneath that 0.3A line uite a bit but we can't see it because all values are beneath the lower limit for our test equipment. The total charge time is 04:21:11 and the CBA measures the total energy as 1128mAh. That's a couple of % less than the other chargers, but perfectly acceptable.
The other thing I notice in this graph is the three aligned down spikes. When I look at the raw data I see that these occurred at 1:01, 2:06, and 3:12, or about once an hour. At each spike the current drops to zero for 5 points or 2.5 seconds. The voltage drops sharply by about 0.25v but raises back to about where it started before the datalogger record a current. Therefore I suspect that the dropout is actually more like 0.5-1sec and that the datalogger records the rising current under 0.3A as zero until it reaches some critical level for detection.
The P116 delivered 0.3A at a maximum of 21v. That's (21v)(0.3A) = 6.3 Watts, or 53% of the charger's rated input of 12W. However I question the 0.3A figure and at some point I will go back and measure this with a tool better suited to the task. Stay tuned.
Next Up: P119. The P119 charger is Ryobi's current offering for trickle charging. It is sold separately and included in the lowest-cost "Special Buy" kits one might see for special events such as Black Friday. According to the label it's rated for an input of 7W.
When I connected the depleted P102 battery to the P119 charger, the P119 charger did not detect the battery. My guess at the problem was that the voltage on the battery was so low that the P119 trickle charger didn't think it was an 18v battery at all. So I popped the battery on the P117 charger for about 20 seconds to give it a boost, then I moved it back to the P119 charger and this time it detected and started charging the batter. This can be seen on the chart as an initial spike to 2.9A along the left edge of the graph.
This chart looks most similar to the P116 chart: the voltage slowly rises to 21v at which point the charge cycle concludes, and the current remains fixed at 0.3W (hah!). The total charge time is 4:59:42 and the CBA measures the the total energy as 1043mAh. That's quite a bit less than the other chargers. Our original assessment was 1144mAh, so this is 101mAh or 8.8% less.
The P119 delivered 0.3A at a maximum of 21v, so we see the same 6.3 Watts as the P116, or 90% of the charger's rated input. Once again, I find the 0.3A figure highly suspect.
Next up: P135 SuperCharger. The P135 is a 6-port unit and is nicknamed the "SuperCharger". According to the label it's rated for an input of 85W. That's the same as the P117.
The prior test on the P119 test ran overnight, and I've taken the time to reconfigure things a bit. I doubled the datalogger data rate to 4Hz, and I've inserted a genuine "Watt's Up" meter inline with the datalogger. The Watt's Up meter measures current 0-100A with a resolution of 0.01A and an accuray of +/-2% + 0.06A, and it measures voltages 0-60v with a resolution of 0.01v and an accuracy of +/- 1% +0.035v. It also measures cumulative power (W), Charge (Ah), and Energy (Wh) while powered on. I'll try to eyeball and compare readings between the Watt's Up and the datalogger during use.
The graph sure looks the same as the P117. The charge time is 32:56 and the Watt's Up meter shows 1162mAh pumped into the battery. But the CBA measures just 973mAh, which is 171mAh or 15% less than our original reading! I think I'd better repeat the P117 and P118 tests with these new settings.
Wh Rating
Some of Ryobi's battery packs have an energy ratng on the label, expressed in "Wh" or Watt-hours.
In its simplest terms, Watt-hours is an expression of Voltage x Current.
This is a more precise measure of the amount of energy in a battery packs than milliamp-hours (mAh),
as it takes into account both voltage level and current draw during the discharge of the battery.
So a typical 18 volt, 1.3Ah P103 battery could be described as having 18v x 1.3A = 23.4Wh.
The first battery I saw with a Wh rating was the P103, and it was rated 24Wh, so that seems about right.
Here's a list of Wh ratings I've seen:
24Wh - P103 (1.3A cells, from release until some time in early 2012)
24Wh - P102 (1.3A cells, Oct 2012)
27Wh - P100 (1.5A cells)
28Wh - P103 (1.5A cells, starting sometime in early 2012)
28Wh - P107 (1.5A cells, starting Aug 2012)
31Wh - P100 (1.7A cells, I have not actually seen a P100 with this rating, just guessing)
45Wh - P105 (1.2A cells x2, Oct 2012)
45Wh - P104 (1.2A cells x2)
46Wh - P104 (1.2A cells x2)
48Wh - P104 (1.3A cells x2, starting in Dec 2009)
72Wh - P108 (2.0A cells x2?, starting Aug 2012)
Holds charge 4X longer and reduces the need to recharge during long periods of non-use
This refers to the Lithium Ion chemistry's low self-discharge rate as compared to that of Nickel Cadmium.
Say what??
Have you ever charged a NiCad pack, then put the charged pack on the shelf for a few weeks or months before you needed it?
If so I bet you noticed that the pack was not fully charged when you went to use it.
That's because Nickel Cadmium cells lose charge over time just sitting idle.
So do Lithium Ion cells, but the rate of loss is 4X slower.
So after sitting for a month or two unused a NiCad pack may seem nearly discharged
while a Lithium Ion pack may still seem nearly fully charged.
Which batteries are compatible with my tools?
As far as I can tell, any 18v Ryobi battery will work with any 18v Ryobi tool.
See the photos below to see each of the four battery types plugged into an old drill.
Do the serial numbers mean anything?
Yes! All Ryobi batteries (and tools) are stamped with a date code, and newer batteries have a serial number.
The date code indicates when the battery was manufactured.
The first two digits are the year and the second two are the week of manufacture.
Some batteries may have one or two letters before the four numbers, not sure what they mean but my guess is the site of the factory.
Examples:
0903 = "09" for 2009 and "03" for week 3
G0734 = 2007, week 34
CS0850 = 2008, week 50
CS12374N420709 = 2012, week 37 = Sep 2012
In 2012 Ryobi started printing a 2D barcode on each label which is encoded with the manufacturer part #, serial number, and model #.
I want to buy NEW batteries, but everything in the store is at least 3 months old! What's up with that?
It's perfectly normal to visit The Home Depot, check date codes, and find that everything on the shelves was manufactured several momths ago. Why?
Let's not forget that Ryobi tools are manufactured in China.
They're sent to the USA via boat, whose transit time can be a couple of months.
While I have no knowledge of the actual process, I might expect additional delays.
For example, the Ryobi factory probably manufactures a tool or kit in a "run" which lasts for several weeks.
The items manufactured in the first week(s) may sit around until enough product has been produced to make a full shipment.
Additional delays are likely at the shipping ports in China and in the USA, and of course some time is required for distribution.
Tools manufactured for a special event sale (Memorial Day, Father's Day, Black Friday)
may be held a little longer so they appear on shelves on the day that these sales begin.
Without making a heroic effort, I doubt that new Ryobi tools can reach the shelves of The Home Depot in less than 2 months from the date of manufacture.
Based on my personal observations I'd say that 3 months (or more) is typical for the factory-to-shelf process.
Hey! I just bought some new batteries and the date code says they're 9 months old! Is that a problem?
Not necessarily. These batteries are designed to sit on the shelf for months before sale.
I have no hard data to support this, but I suspect that "new" batteries up to a year old or more are still 100% fine.
Even still, when I go to The Home Depot I always check the serial numbers printed on the tool package before I buy
(especially if the package contains batteries) and I'll always select the newest ones.
Ryobi ships all batteries with a low charge, and all batteries self-discharge over time.
When the voltage on Lithium Ion cells gets too low the cell begins to deteriorate.
This phenomena doesn't really occur to NiCad batteries.
NiCad packs are very resistant to problems when sitting on the shelf with a low charge for a long time.
NiCad packs that are 18 months old or older may test lower than expected on the first cycle,
but after 3-4 cycles they should recover back to like-new performance.
Lithium Ion packs DO NOT like to sit idle on the shelf with a low charge for a long time!
After 9 months or more on the shelf in the store or warehouse the deterioration of Lithium Ion cells can begin.
That's why I would not purchase a Lithium Ion battery that's more than 9 months old.
Update 13-Apr-2010: Beware of new old stock P104 batteries!
I've found that "new" P104 batteries taken from old kits (more than a year old) are often dead or operate at a greatly
reduced capacity. I recommend avoiding the purchase of kits containing P104 batteries that are more than a year old.
Batteries with a date code between and including 0821 to 0832 have had an especially high DOA rate.
If you do purchase new old stock P104s, test them immediately using the "flashlight test" or other means to ensure
that they are operating properly. Exchange or return the batteries if they're not OK!
Update 12-Jul-2010:
Last week I received some CS1018 batteries (1st week of May, 2010?),
These are the most recent date codes I've seen.
The behavior of the built-in tester has now changed a bit.
Ryobi has now built a 2-3 second delay into the formerly momentary check-while-you-hold-the-button device.
So press the button for just a moment and it stays lit for 2-3 seconds for you to read it.
Not a big deal, but it's clear that Ryobi are continually changing their products.
The batteries in my new kit take a charge. Should I assume that they're all OK?
Absolutely not! The kit may have been new, and the batteries may take a charge, but that DOES NOT MEAN
that your batteries are working as they should. I have purchased literally hundreds of Ryobi kits containing batteries,
and I can tell you from experience that "New" does NOT necessarily mean that the batteries are in good working order,
even if they take a charge! ALWAYS test your batteries soon after you open your kit! The sooner you
test them, the greater the chance that you will be allowed to return/exchange your kit should you find a problem.
The easiest way to test your batteries is to fully charge them, then fully discharge them at a controlled, slow rate.
A battery's capacity can be estimated from the length of time that it takes to discharge.
The "Flashlight Test" is easy and accurate:
A battery's capacity in mAh is 10x a flashlight's run time in minutes.
(See the Battery Rebuilds, etc. page for a more detailed description of how
to do this.)
I've found that the P104 is the battery most likely to have problems. This is especially true if the
kit is more than 9 months old. It's unusual to find a bad P103 at all, and downright rare to find a bad P103 or P104
in a kit that's less than 6 months old (though it does happen). I would immediately return a Lithium Ion pack
that tests below 80% capacity of its first charge. (At HD it's far easier to exchange a whole kit than it is to
get a single battery from a kit exchanged, which is why I test batteries FIRST, remove the tools only after the
batteries have tested good.)
If you buy a kit containing P104 batteries that's more than a year old, you should expect problems. Period. When
you open the kit I suspect that the batteries may or may not take a charge. If they do, I'd expect their
capacity to test below 50%. I know that Ryobi discounts discontinued tool kits when they're about a year old,
and I suspect that Ryobi (and other makers who do the same) count on consumers not realizing that the batteries are no
longer good. Let's face it, if the battery takes a charge and comes from a "new" kit, then the average consumer will
think that it must be good, right? Wrong.
I further suspect that some of the negative reviews given by first-time buyers of cordless tools who mention
poor battery life and performance are actually consumers who purchased a kit containing bad batteries, and because
they have no "new" reference packs to compare against they don't realize that this is what has happened.
As above, kits over a year old containing P103 batteries are also likely to have batteries which can no longer operate
at full capacity. Case in point: I recently purchased two P542 chainsaw kits, each containing a P103 battery that
was 70 weeks old. The batteries would not test over 900mAh even after several cycles. Otherwise they were fine.
These old stock batteries wll never operate above 70% of their rated capacity. An uninformed consumer who purchases
such a kit may simply think that this is the best a P103 can do.
The story with NiCad batteries is not the same as with Lithium Ions. New old stock NiCad packs seem to show a
diminished power at first, but recover well after a few cycles. For example, I received two new old stock P100s
recently that were 86 weeks old(!!). After the first charge they tested just under 1000mAh, but the discharge curves
did not contain the telltale stairstep of bad cells. So I cycled them and retested, getting about 1200mAh the second time.
I decide to go once more and got about 1360mAh. A few more cycles and they'll be fine.
Is there a "Quick Check" I can do in-store to see if the batteries in an old, discounted kit are still OK?
Maybe, and this would work only for Lithium Ion batteries (P103 and P104).
Open the kit and press the battery tester on the P104. If it lights up to any color at all, the pack is probably OK.
Carry a P150 Fuel Gauge with you into The Home Depot and use it to test P103 packs.
Why would this be an adequate "Quick Check"? I have a theory that I haven't quite proved yet, but well here goes.
We know that the irreparable damage occurs to Lithium Ion cells only after the cell voltage has self-discharged
below a certain threshold.
And we know that the pack's self-protection circuit kicks in and disconnects the cells before the cells have discharged
below this lower threshold voltage. So my theory is that if a pack can light up a battery tester, then the cells
must not have discharged below the lower threshold yet, and must therefore still be "good".
The pack could still be faulty (e.g., one cell has died while the others are OK enough to light the tester, or bad
circuit board). But if the tester won't light up at all, the pack almost assuredly has problems and you should either
pass up on the deal altogether or be prepared to return later with the faulty battery for an exchange.
How should I store my batteries when they're not in use?
This is the subject of much debate. I offer my opinions below based on my understanding and experience. YMMV
All Batteries
Keep them plugged into an IntelliPort Charger all the time, such as the P114, P115, P116, P117, or P126 SuperCharger.
The IntelliPort Chargers are designed to keep batteries at a full charge without ever overcharging.
If you don't have an IntelliPort charger, or (like me) have more batteries than chargers, then read on.
DO NOT leave your battery connected to a charger while the charger is unplugged --
when unplugged the charger will actually discharge and potentially damage a battery pack.
It's also VERY important to keep your charger inside the house and NOT in the garage. This is because the charger will refuse to charge the battery if the ambient temperature is too high or too low. When the temperature is too high or too low, the charger's IntelliPort feature won't work and the charger can actually drain a battery that's plugged into it (possibly killing it) rather than maintain it. If you must keep your charger in the garage, then be certain to unplug your batteries once it's fully charged and set them aside. Ryobi manuals indicate that ambient temperatures must be between 50 and 100 degrees Farenheit for proper operation, and most garages will go outside of this range at some time during the year. (Note: I keep a P125 SuperCharger in my garage, and I use it year 'round. But I don't leave batteries plugged into it for long after they've reached a full charge.)
NiCads (P100):
NiCad batteries will degrade in performance if left idle for a long time with a charge on them.
That's because dendrites form across the plates when in the presence of a charge. These dendrites are like little
jumper wires that short out a cell. This phenomenon is often observed as "memory effect". One can usually
"burn off" an accumulation of dendrites by putting a huge charge across the plates of a cell. Some folks advocate
momentarily connecting a pack to a large voltage source to burn off dendrites. This does work, but also decreases
the overall capacity of each cell each time it's done because it also leaves holes in the plate surface area (where
each dendrite had been located) and cell capacity is a function of the total surface area of the cell. To avoid
a buildup of dendrites, once can completely drain a NiCad cell and then short it out and store it in a cool, dry
place to prevent a charge buildup. This works. Unfortunately this applies to the storage of single cells and
does not translate well into the storage of a multi-cell pack such as the P100. In a multi-cell pack it's very
difficult to ensure that every cell in the pack has been completely discharged, and simply discharging a pack is
sure to result in the "reversing" of several cells as the pack's overall charge reaches zero. Cell reversing is
generally more harmful than dendrites, so avoid this if possible. What does this mean for NiCad battery storage?
Unfortunately not much, but I thought I mention it all so folks could get an understanding of what's going on in a
NiCad pack like the P100.
The best advice I can give on NiCad pack storage would be to fully charge them before putting them away for storage.
Then store them in a cool (55F to 75F) and dry place. I would further recommend that you discharge then recharge them
ONCE PER MONTH. Mark your calendar if you need to. An idle pack will develop dendrites over time, so the best way to avoid
this is to USE THEM periodically. I recommend using a flashlight, just plug the battery in and leave it on until
the battery is depleted, then charge the battery and put it back into storage. It's a pain, but NiCads really
don't like to be left alone for extended periods of time.
Lithium Ions (P102, P103, P104, P105, P108):
Lithium Ion packs degrade in performance when the charge on a cells goes out of the service range. This range is
about 2.8 volts to 4.2 volts. Ryobi packs have five cells (P103) or five pairs of cells (P104) in series, for a
safe voltage range of 14v to 21v. Sitting idle, packs can only discharge (slowly) so the best way to store these
packs is to give them a full charge before storage. If left with a full charge, it should take more than a year
before a Lithium pack will self-discharge enough to drop below 2.8v on a cell! I'd still recommend topping off the
charge on an idle pack periodically (once every 6-12 months?) but there's no need to discharge them first like with
the NiCads.
Update 02-Jun-2013:
I've changed my opinion somewhat on how to use and store Lithium Ion batteries, based on the results of studies carried out
by Battery University.
Of the various results, one can see that the number of cycles a battery can deliver can be increased significantly
by not fully charging or discharging the cells, and by not storing the cells at extreme temperatures.
I'm talking 2, 3, 4 or more times as many cycles per battery! Battery University reports that for maximum longevity,
batteries in long-term storage should be kept at a 40% charge. This is difficult to achieve with the available tools,
since a Ryobi charger will bring a pack to 100% charge. The older chargers will trickle charge packs when they reach a full
charge, keeping them at 100% charge continuously and which will decrease the pack's recoverable capacity (by 20%/year?).
But an Intelliport charger stops charging when a pack reaches a full charge, allowing the pack to self-discharge a bit.
After a period of time the charger "wakes up", checks the battery, and tops it off.
This behavior is actually quite beneficial to the longevity of the battery. But it still keeps packs near a full charge,
which is not ideal.
If you're really serious about the longevity of your Lithium Ion batteries, then you should actively monitor your use of them.
Try to avoid fully charging and discharging them. If you have a battery with a meter (or a P150 pocket meter), try to stop using
your battery when you're down the the last bar. And don't allow the battery to reach a full charge -- pull it off the charger
when the fourth bar gets illuminated. Finally, avoid exposing your battery to extreme temperatures. Keep your batteries stored
in your house, not in your vechice or in the garage (which can get very hot or very cold).
Of course, for many of us the advice in the preceding paragraph will be very difficult to follow. To simplify: swap the battery
you're using more often to avoid fully discharging any of them, get an IntelliPort charger or quickly remove your batteries
from older chargers once the charge is complete, and always try to keep your battereis in the house (even if you kep the rest of
your tools in the truck or garage).
Which battery pack do you recommend?
First of all, I recommend having two or more packs and a one hour charger if you're doing anything that drains a
pack before you're done with the job.
Then you can swap packs, put the drained pack on the charger, and get back to work.
If you already have a P100 NiCad pack and a one hour charger, then getting a second P100 pack would be your
least expensive option and a reasonable one.
I've now made the switch to Lithium Ion and I'm not looking back!
I use mostly P108 packs, sometimes P103. If you have the need for more or new batteries and have the money to buy them,
I recommend going with the Lithium Ions over the NiCads.
I feel that per charge they do last longer than the NiCads and they can sit on the shelf between jobs
without needing to recharge before use.
And for single-handed tools the weight difference can be noticeable.
I find that I usually reach for a compact battery when I want to use a flashlight or a drill.
I use a full-height battery with the reciprocating saw, canister vac, and yard tools.
I've made the switch to Lithium Ion. Any reason to keep using NiCads?
Well, there's no reason to throw out good batteries, period.
But actually, yes, there might be some very good reasons to continue using NiCads.
If you work in a very cold environment, NiCads might be a better choice than Lithium Ions because you can recharge them when cold.
Lithium Ions will not take a charge if too cold.
If you need to push your tools to the limit with maximum torque, then NiCads may be the best choice for you.
That's right, if you need every bit of torque from your drill as it slowly crawls that spade bit through wet lumber,
NiCads are for you. Why? It's because the Lithium Ions contain an internal protection circuit that cuts them off when pushed to the limit like this.
NiCads do NOT have such a circuit, so you can push them as hard as you need to.
I don't measure 18 volts across my P108 battery. What's up with that?
Ryobi's newest batteries, the P107 and P108, are being marketed as "Lithium Plus".
I'm not sure what this hype means, but they've apparently changed the internal circuit board design.
As a result, the voltage at the terminals remains low until a load is detected.
When used with most tools, you'll never notice the difference.
But if you use a P740/P741 radio you may find that the radio doesn't come on when you press the power button.
The quick fix is to press the battery's power level meter first, which briefly "wakes up" the battery.
With all other Ryobi batteries, a voltmeter across the terminals will measure the voltage of the pack.
This can give an indication of the battery's charge level, much like the P150 Fuel Gauge will do.
