toolboy's Corner: Ryobi 18v Charger Testing

Ryobi has made various claims about it's line of 18v chargers. Ryobi has even given creative nicknames to some models.
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 established 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:
Consider the claim: "My battery recharges in 45 minutes". Really? I don't find this statement particularly meaningful. I'm thinking:

What model battery?

Ryobi 18v batteries have been manufactured in rated capacities ranging from 1200mAh to 9000mAh depending on model.

What model charger?

Not all chargers have the same charge rate.

Was the battery fully discharged before you began charging it? How do you know?

A battery which cannot drive a tool to operate is not necessarily fully discharged. The circuit board inside some Li-Ion battery packs is supposed to disengage the cells when the charge level gets too low. But for some packs the cutoff is mis-adjusted too high, and the pack may disengage while there still plenty of energy remaining. When this happens the battery NEVER fully discharges and the charge cycle is shorter than for other batteries of the same model for which the cutoff level is set correctly. (After testing literally thousands of Ryobi Li-Ion batteries I can tell you with confidence that yes, "this is a thing".)

Is "45 minutes" a total guess, or is this rounded to the nearest 15 minutes, or did someone actually use a stopwatch and clock 45 minutes and 00 seconds?

It's just human nature to "guesstimate" quantities, and time is often rounded to the nearest 15 minutes. This suggests a rounding error of up to half that time or 7:30, which can be significant for a process which takes an hour or less.

How old is the battery?

Many older batteries can operate a tool reasonably well even when operating with 70% or less of their original capacity.

How many times has the battery been cycled?

Each time a battery is cycled its capacity diminishes by a small amount. After a few hundred cycles this can be significant.

How recently was the battery last fully cycled?

Batteries do self-discharge when left idle, so if a battery is fully charged then shelved for months, its capacity at the end of that time will be less than when the shelf storage began. Furthermore, many claim that certain chemical layers form and build up on the anode or cathode of Li-Ion cells during storage. One initial cycle may be needed to burn off these layers before testing. (See the Battery University article BU-701 for further details.)

Was the battery hot before the charge cycle began?

Ryobi batteries contain a thermometer (actually it's a thermistor) which prevents an overheated pack from accepting a charge before it has cooled.

What was the temperature in the room where the battery and charger were located?

Temperature does affect how fast Li-Ion cells can accept a charge.



Basic Questions

Can we objectively describe how each of Ryobi's chargers actually operates?

Is it possible to accurately predict how long it will take to recharge a given battery on a given model of charger?

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 P116, P119, and P180. 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 model 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 will NOT be testing any of the NiCD-only chargers. Ryobi has discontinued the NiCD P100 battery so I don't see much value in testing these chargers. Furthermore, the only NiCD-only charger I still own is a P111 trickle charger.

I will not test the P113. I no longer own a P113 and I don't recommend the use of this model because it lacks the IntelliPort feature. What this means is that if a battery is left on a P113 charger after it has reached a full charge, the P113 can damage the battery by over-charging it.

I do own and regularly use a P114 but don't plan to test it as it's been out of production for awhile. I would guess that it charges about the same as it's successor, the P117. If someone contacts me and specifically requests testing of this model, I'll reconsider.

The model P137 Dual Platform Charger for RYOBI 18-Volt ONE+ and 40-Volt Batteries is brand new, I've just seen it for the first time this morning (27-Mar-2020). I don't own one and for the asking price of $99 on The Home Depot website it's unlikely that I'll ever purchase one. That makes it roughly the same cost as buying new 18v and 40v chargers separately, and I already have numerous 18v and 40v chargers mounted around my home.

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 simply claim to be "for Ryobi". Some boast built-in USB charger ports. I find this very deceitful and I wonder if these knock-offs actually contain all of the protection feaures which are standard on the genuine Ryobi P117. I'm certain that these knock-offs are not UL listed for safety. Genuine Ryobi chargers have passed UL testing and bear a UL certification number. 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 purchase decision. If you're considering the purchase of a new charger, be aware that The Home Depot is the exclusive dealer for new Ryobi tools in the USA. (Direct Tools Factory Outlet is authorized to sell new Ryobi accessories, new Ryobi tools marked as blemished/factory seconds, and reconditioned Ryobi tools.) All other sellers of new Ryobi tools in the USA (including myself) must therefore have purchased these tools from The Home Depot. If it's importatnt to you that you purchase a genuine Ryobi charger, look carefully at the sellers photo(s) and description. Does the seller's listing include a photo of the bottom of the unit? 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. Compare the seller's photo(s) of the unit with what can be seen on The Home Depot or ryobitools websites. If the photos are not identical, the seller is probably not selling a genuine Ryobi charger.


My Expectations

  1. I expect that Ryobi's "trickle/overnight" and EverCharge chargers are based on a 1-stage 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 (I'll guess 21v). The "Constant Current" charge rate is also known as the "Bulk" charge rate.
  2. I expect that all other chargers are based on a 2-Stage Constant Current/Constant Voltage (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 target voltage is reached, the charger will switch to CV mode and the charger current will decrease to zero as the battery pack voltage increases.
  3. I expect to find that the trickle chargers take the longest time to recharge a given battery.
  4. 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.
  5. 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 using Ryobi's lowest capacity battery, the P102, and I have a seldom used P102 whose date code begins with CS1630. This means that the battery was manufactured in the 30th week of 2016, so it's about 169 weeks old or 3 years and 12 weeks old. I don't expect this battery to operate at it's rated capacity of 1.3Ah/1300mAh.

Let the testing begin!

Afer the first discharge cycle the P102 tested at 1108mAh and on the next cycle it was 1144mAh, about a 3% difference. So I go again and get 1148mAh. That's a difference of about 0.35% between the last two cycles -- well within my 3% tolerance. So we'll count this last charge cycle as our first "official" cycle.

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 initial 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%.

Ryobi P117 "30 Minute" Charger

We'll count that last cycle as out "first" cycle of testing. I see on the label of the Ryobi P117 charger that it is rated 85W input.

1.3Ah P102 Battery on Ryobi P117 "30 Minute" Charger

Charger P117 (85W)
Battery P102 (rated 1.3Ah / 24Wh)
Total Charge Time 0:32:27 (1,947 sec)
Current In 1.1698A
Average charge rate2.171A
Measured Capacity 1.148Ah / 20.55Wh

In the above graph we see voltage in blue and current in brown.

When the charging begins, the current (brown line) jumps to 2.9A and remains steady until 19:38. At this time the current starts to decrease with a shape like the left half of a "U" until it reaches zero at 32:27.

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 (at 19:38). 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 minimum reading of +/-0.3 is required. This is probably why 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.

As stated before, the P102 was then discharged on the CBA and the total energy was evaluated as 1148mAh. That's a difference of 4mAh from the previous cycle, or well within my 3% tolerance.

As a sanity check, I repeated the charge on a P117:

1.3Ah P102 Battery on Ryobi P117 "30 Minute" Charger

Charger P117 (85W)
Battery P102 (rated 1.3Ah / 24Wh)
Total Charge Time 0:31:54 (1,914 sec)
Current In 1.1694A
Average charge rate2.207A
Measured Capacity 1.147Ah / 20.54Wh

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.

Ryobi P118 Charger

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.

1.3Ah P102 Battery on Ryobi P118 Charger

Charger P118 (50W)
Battery P102 (rated 1.3Ah / 24Wh)
Total Charge Time 0:45:29 (2,729 sec)
Current In 1.1621A
Average charge rate1.153A
Measured Capacity 1.152Ah / 20.59Wh

The curves on the P118 look much like to those generated on the P117, but with an extended X 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 point, holds 1.0A for 4 points, then jumps to 1.8A in two points. With 2pts/sec this means that it took 4 seconds to go from 0.0A to the full 1.8A. How curious. The total charge time is 45:29 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.

Ryobi P116 Charger (an overnight/trickle charger)

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 than 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 quite 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.

Update March 2020: I've gone back and re-tested using my modified datalogger. This unit can record current down to 30mA with a resolution of 10mA.


The old and new curves look very similar and I'm honestly a bit shocked to find that the charge times are IDENTICAL at 4:21:11. The datalogger indicates 1174.4mA delivered. The CBA measures the total energy at 1104mA, but the discharge curve is missing an initial dip, so I don't really trust this result. But the data is clear, and I can conclude that the actual charge rate of the P116 is 270mA. During the charge cycle the P116 actually started at 290mA and took 10 minutes to drift down to 270mA. The charger delivered 270mA for 3 hours before drifting down to 260mA for the final hour. Of 15,616 data points collected, Excel counts 146 at 290mA, 469 at 280mA, 11,300 at 270mA, and 3,691 at 260mA. The average charge rate is therefore 267.967mA, but let's call it 270mA.

Ryobi P119 Charger (a pocket-sized overnight/trickle charger)

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 battery. 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.

Like the P116, I see aligned spikes in this graph. The current spikes go down to 0A, same as the P116. But unlike the P116, the voltage spikes go UPWARD and offscale with the P119! Here's the actual data for the first spike, including a few points before and after the spike:
TimeVoltageCurrent
1:01:01.2518.140.3
1:01:01.5018.140.3
1:01:01.7525.700.3
1:01:02.0027.020.0
1:01:02.2526.940.0
1:01:02.5026.940.0
1:01:02.7524.850.0
1:01:03.0018.140.3
1:01:03.2518.140.3
I see that the current dropped to 0A for 4 points and the voltage spiked above the "current value" of 18.14v for 5 points, peaking at 27.02v. Weird.

You may have noticed that 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 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.

Ryobi 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 graph sure looks the same as the P117, except that the Constant Current (CC) charge rate is 2.8A. The charge time is 32:56 and the datalogger 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.

Ryobi P117 "30 Minute" Charger, Test #3



No surprises. The total charge time is 33:53, the datalogger shows 1161mAh in, and the CBA measures the total energy as 1130mAh.

Ryobi P118 Charger, Test #2



Still no surprises. The total charge time is 47:21, the datalogger shows 1182mAh in, and the CBA measures the total energy as 1135mAh.

Ryobi P135 SuperCharger, Test #2



Still no surprises. The total charge time is 32:22, the datalogger shows 1176mAh in, and the CBA measures the total energy as 1138mAh.

Ryobi P131 In-Vehicle Charger

The label on the P131 lists the input as 12V DC at 6A and the output as 18V DC at 3A.

Please note that the P131 In-Vehicle Charger is designed to be used in your vehicle. The power connector is a standard Accessory Plug and is meant to be connected to a 12v DC source. This connector is also known as the "Cigarette Lighter" plug. In order to conduct this test, I used the 12V rail from a Corsair 430W ATX PC power supply, model CX430. The 12v rail is rated 28A, which is plenty for this test. I'm mentioning this because what I'm using for this test is therefore not necessarily a good representation of the environment this charger would encounter when actually used in a vehicle. My power supply provides a ripple-free 12.00v DC, whereas the voltage in one's vehicle is unlikely to remain so steady. If you're driving your vehicle while charging, the input voltage can rise over 14v and contain a significant ripple due to the alternator doing its job. If you use your charger while parked, then the input voltage will likely fall while charging and could dip to 11v or lower. I have no idea how much these input voltage fluctuations might affect charge time or how much the Ryobi battery is charged. I'm simply pointing out that these are unknowns which I'm making NO attempt to address at this time.

Well we do have a surprise this time! I had left the test rig alone with the P131 to charge the battery while I worked on other things, just like I'd done with all the other chargers. Every once in awhile I'd look back at the charger to see if the indicator had changed from blinking red (charging) to glowing green (charging complete), just like I'd done with all the other chargers. When the LED glowed green, I went back to the rig and noted that the datalogger indicated a charge in of 1034mA, which is disappointingly low. I was about to stop the datalogger when I noticed something unusual -- the reading on the datalogger increased to 1035mA! Huh? Looking more closely, I saw that the datalogger also indicated that 0.7A was still passing from the charger into the battery. Huh? Yes, the P131 charger indicated that the battery was fully charged, and yet the battery was still charging! I decided to let this continue for awhile. While it continued charging, I reasoned that in the name of safety I'd disconnect the battery if the Charge In reading reached 1200mAh. But the current dropped to 0.0A before the Charge In reached 1200mAh. It stopped at 1173mAh. This time I was anxious to extract and graph the data. My guess was that the green light illuminated at the end of the first stage of charging, when the voltage reached 21v.


I admit it, this was totally unexpected. The charge begins at the 2.4A level but quickly drops to 2.3A. The charge current slowly drops to 2.0A as the voltage rises to 21v, and when the voltage reaches 21.06v at 27:11 the current starts dropping. The current drops linearly over the next 90 seconds to 1.5A at 28:50, at which time the current drops to 0.0A. A minute later at 29:52, the voltage has dropped to 20.55v and the charge current suddenly reappears at 0.7A. When the voltage reaches 21.07v, the current drops to 0.0A. The total charge time for the P131 is 38:33, the datalogger shows 1173mAh in, and the CBA measures the total energy as 1134mAh.

I guess I'll conclude that the P131 charges at "about" 2.2A until the pack reaches 21v, at which point the LED indicates that the charge is done. But in reality the charger just goes dormant for 90 seconds, and then it wakes back up to charge the pack at 0.7A until it again reaches 21v. Who knows, if I'd been patient maybe the P131 would have rested another 90 seconds then re-awakened and started topping off the battery again. If the P131 charger does indeed continue with this sleep/top off cycle indefinitely, then I'd be concerned that this behavior might cause overcharging. I will have to test this again sometime.

Ryobi P125 SuperCharger

The model P125 was the original 6-port SuperCharger, later replaced by the P135. The P125 has no USB charge port. According to the label it's rated for an input of 85W, same as the P117.


More surprises! The P125 delivers a steady 2.9A until the pack reaches 21v. Then the charging stops for a second, and it picks back up at 2.0A until the pack again reaches 21v. Then the charger alternates charging at 2.0A and and resting every few seconds for about 3 minutes. Then the P125 charges at a steady 0.8A for about 3 minutes until the pack again reaches 21v. Then the P125 alternates charging at 0.8A and resting every few seconds. I wonder what would have happened if I'd left the charger alone for 30 minutes or more. The total charge time for the P125 is 33:53, the datalogger shows 1161mAh in, and the CBA measures the total energy as 1130mAh.

Ryobi P118B Charger

At this time (Dec 2019) the P118B charger is the charger which is included in the majority of Ryobi's tool kits. The P118B is much smaller than the P118, and unlike the P118 it has a "wall wart" instead of a standard 2-prong polarized plug. According to the label the P118B is rated for an input of 60W (which is 10W more than the P118).

I'm really disappointed with Ryobi's move to the P118B. Sometimes making something smaller makes it better, but I do not think this is one of those times. The LED lights on the P118 are located on the front, which is good. But once a battery is plugged in to be charged, the LEDs can no longer be seen due to battery overhang. One must bend down, back up, or more to the side to find an angle at which the LEDs can be seen. The charger has keyholes for wall mounting, but if mounted on the wall then the LEDs can really only be seen from a side angle. I'm also unimpressed with now having to deal with a wall wart. IMHO the best design would be to have all electronics within the main unit and a removable power cord. Hey Ryobi, it might cost a few more pennies to develop and implement a design which runs on 100-240V, but wouldn't you make up for that cost by manufacturing a single unit which could be shipped worldwide? Simply change the power cord and labeling as needed for each destination country/countries.


Once again I'm surprised by what I see. The P118B is clearly a CC/CV charger, but it has a few characteristics unique to this model. The fist thing I notice about this graph is that the "lines" are very wide, indicating a great deal of fluctuation around the readings. What I saw after zooming in was odd enough that I decided to include a second graph to highlight the behavior. Look at the second chart and you'll see that the P118B charger's otherwise steady output of 2.0A is interrupted every 3 seconds with a dip to about 1.6A. The current may drop even lower, but if so then at 4pts/sec my datalogger isn't fast enough to capture it. Each of these drops lasts for 1 or 2 points, so that's between 1/4 and 1/2 seconds. Let's split the difference and call it 0.375 seconds.

The next oddity I can see is that the charger current begins the CV drop BEFORE the battery voltage reaches 21v! The P118B is the only one of Ryobi's CC/CV chargers which does this; all of the others continue in CC mode until 21v is reached. Looking at the raw data I see that the CV mode engages when the voltage reaches 20.80v, which is close to the 20.06v we've seen on other chargers. Maybe the factory-adjusted setpoint for this particular charger is off, or maybe it's by design. There's no telling which is the case, and I guess I should test a P118B charger with a significantly different date of manufacture to find out.

Aside from those two anomalies, the curve is similar to the other CC/CV chargers and as noted before the steady CC chargre rate is 2.0A. The total charge time for the P118B is 48:14, the datalogger shows mAh in, and the CBA measures the total energy as mAh.

Yes, you read that correctly. The P118B has a HIGHER "bulk" charge rate than the P118 (2.0A vs 1.8A) and yet the P118B recharges a P102 battery with a SLOWER time. How can this be? It's got to be one of two possibilities (or both). The first possibility is that P118B's effective bulk charge rate is lower than the measured rate due to dips we see in the second graph. The charger delivers 2.0A for 3 seconds, then decreases that rate to 1.6A (or lower?) for 0.375 seconds. That's an average charge rate of 1.956A, which is faster than the P118's 1.8A rate. But if we suppose that the drop is actually down to 0.0 for that 0.375 seconds the averate rate becomes 1.778, which is lower than the P118. The second possibility is that P118B takes longer than the P118 because it switches to the CV mode sooner than the P118 (and other CC/CV chargers). When the charge mode switches to CV, the charge current decreases and it continues to decrease as the battery reaches a full charge. This behavior is probably gentler on the cells of the battery, but it could contribute to the elongated charge time.

Ryobi P119 Charger (pocket-sized overnight/trickle charger) #2

It's been a couple of months since I ran the first round of charger testing, and I've found some time to re-test the P119. During testing the first time I discovered the specs of my datalogger were inadequate for this particular charger. The datalogger requires a minimum 0.3A of current flow and results have a precision of 0.1A (300mA and 100mA). This is about what the charger delivers, so it's not possible to be certain of the actual charge rate. To address these issues, I've modified my datalogger by replacing the shunt resistors with values 10x larger and I've wired in a multimeter to spot-check current readings. The shunt resistor replacement means that current values will be reported by the datalogger as 10x larger than actual. So for example a reading of 3.1A will actually mean 0.31A. This should effectively lower the threshold current to 0.03A and the precision to 0.01A (30mA and 10mA).

I did locate and cycle the same P102 battery before I began. It measured 1143mAh on the CBA which aligns with previous testing. Once again I discovered that the P119 would not charge the P102 battery when it came fully discharged off the CBA. I put it on a P118 charger for about ten seconds, then tried the P119 charger again. It still wouldn't charge the P102 so I put it on the P118 charger and watched until the voltage reached 17v (maybe 30 seconds). Then I popped the battery onto the P119 and it proceeded with the charge. While charging I compared the charge rate as reported on my multimeter with the rate displayed on the datalogger. I found that the readings on the datalogger were slightly higher. I observed 2.6A datalogger vs 247mA multimeter in the first few minutes, then 2.5A vs 239mA at 20:00, 2.4A/235mA at 30:00, 2.4A/233mA at 1:30, 2.4A/232mA at 2:40, 2.4/230mA at 3:45. Remember, the datalogger's results are inflated 10x and rounded to 0.1A, so that first reading of 2.6A really means 0.26A or 260mA with rounding to the .01A or 10mA. It occurred to me while this was going on that I had no calibrated test equipment, so I had no way to be certain which equipment was more accurate. At about the 3:45 mark I swapped out the multimeter with another multimeter (same make and model) then swapped them back. I read 230mA on unit #1, 228mA on unit #2, then once again 230mA on unit #1. That's within 1% of each other so I guess I'll trust these more than the datalogger for now. I noticed in the last 15 minutes of charging that the datalogger started to flicker between 2.4A and 2.3A as the multimeter flickered between 229mA/228mA. The P119 maintained its current output for hours, so I'm going to hereby declare its charge rate to be 232mA.

The total charge time was 5:03:55, which includes twice on a P118 charger (48 seconds total) in the first 90 seconds. The charge rate was steady at 0.24A, although an independent multimeter showed the rate to be more like 232mA. The datalogger showed 12394mA in and the CBA measured the total energy as 1124mA.

Ryobi P180 EverCharger

The label on the Ryobi P180 EverCharger indicates that it's rated 7W, same as the P119 charger. I did not originally test this charger but I've gone back and tested it for completeness.


Looks a lot like the curve from the P119 charger to me! This curve has spikes around 90 and 180 minutes, with the voltage going up and the current going down, just like the P119. The total charge time is 4:33:33 and the datalogger indicates 1103.4mA delivered. The CBA measured 1105 but again the curve is missing the initial dip, so I don't really trust this result. The P180's charge rate is 240mA. During the charge cycle the P180 bounced between 240mA and 250mA. Of 16,178 data points collected, I count 10,670 at 240mA and 5,500 at 250mA. The average charge rate is technically 243.293mA, but let's call it 240mA.

Conclusions

We have enough data to respond to all of my expectations.

To recap: All chargers tested (except the P119) were shown to be capable of recharging the test battery to within 3% of it's prior charge level. All testing was performed in a room where the ambient temperature was maintained in a temprature range of 68F-72F. The same 3-year-old P102 battery was used for all testing, this battery was never recharged when warm to the touch, and this battery was initially shown to have a capacity of about 1,144mAh (88% of its rated capacity). The table below shows the actual recharge time for each model of charger tested. Following each test, the battery was subjeted to a capacity test to verify that the battery had actually received a full charge. For some of these tests the amount of current delivered while charging (Current In) and the results of the capacity test (Current Out) are provided.

Elsewhere on the website I've mentioned that the P117 charges at a rate of 2.1A and the P118 charges at 1.4A. Clearly this is not true. The P117 charges at a "bulk" rate of 2.9A, then switches to a rate which tapers to 0 as the pack reaches a full charge. The P118 behaves the same way but with a "bulk" rate of 1.8A. But can one calculate the "average" charge rate? Sure! All we need to do is divide the total amount of charge by the charge time. I'll choose the Current Out colum as the total amount of charge, as this represents the usable amount of energy in the battery. I've added this column as "Average Charge Current" to the table below.
Charger Model Charge Time "Bulk" Charge (A) Current In / Datalogger (mAh) Current Out / CBA (mah) Average Charge Current (A)
P11700:32:272.91,169.81,1482.171
P11700:31:542.91,169.41,1472.207
P11800:45:291.8 1,1521.5
P11604:21:110.3 1,1280.26
P11604:21:110.2701,174.41,1040.268
P11904:59:420.3 1,0430.2
P13500:32:562.81,1629371.7
P11700:33:532.91,1611,1302.0
P11800:47:211.81,1821,1351.4
P13500:32:222.81,1761,1382.1
P13100:38:332.41,1731,1341.8
P12500:33:532.91,1611,1302.0
P118B00:48:142.0   
P11905:03:550.241,239.41,1240.223
P18004:33:330.2401,103.41,1050.243


I'm not sure what happened the first time the P135 was used. As I look at the numbers now I see that the datalogger indicated 1162mAh was delivered to the pack, which is pretty much the same as other charge cycles It's the CBA which measured the pack as not having a full charge, but when I look at the discharge curve I see that the curve is not shaped like all the others. For all CBA tests except this one and the one which immediately preceded it (which was the second lowest energy measurement at 1043mAh), the discharge curve starts above 20v and ramps down for about 15 seconds/1 volt at which point voltage starts dropping much more slowly at about 0.12v in the next 15 seconds. Then the voltage abruptly starts to ramp up at a rate of about 1v over the next 15 seconds. At this point the voltage drops slowly and steadily until the voltage reaches about 16v, at which point the voltage starts to drop at an increasing rate. The two discharge cycles in question are missing the "ramp up" seen in the first minute of all the other discharge curves. This could easily explain these two results are lower than the other. I'm unable to tell from the data whether the problem is with the battery or with the CBA, but it's clear that the problem is NOT with the charger. So I think it's safe to accept the first P135 charge time of 32:56 and Current In of 1,162mAh, but I reject the "Current Out" readings of 1,043mAh and 937mAh as anomalies (hence the strikethrough in the table above). I've rejected a couple of other CBA measurements which did not show the initial dip. Three of the four suspect CBA measurements followed a charge cycle on a trickle charger, so I'm beginning to think that somehow the trickle chargers don't completely "reset" a battery during a charge.


I find it reassuring that the CBA measures the usable energy in the battery so consistently. After rejecting the anomalous points, the remaining readings are in tight a range of 1,128mAh to 1,152mAh. That's an average measurement of 1,138 +/- 14mAh. That 14mAh range is +/- 1.23% of the average, well within the 3% tolerance I'd hoped for. I think this suggests that all of Ryobi's chargers deliver the same amount of charge and that in this case testing bias due to other factors was minimal.

In order of slowest to fastest chargers, we have now observed that for my particular P102 battery at room temperature:
  1. [VERIFIED]   I expect that Ryobi's "trickle/overnight" and EverCharge chargers are based on a Constant Current (CC) design.
  2. [VERIFIED]   I expect that all other chargers are based on a CC/CV design.
  3. [VERIFIED]   I expect to find that the trickle chargers take the most time to recharge a given battery.
  4. [VERIFIED]   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. The "bulk" charge rate of the P118 is 10% lower than the P118B (2.0A vs. 1.8A), but the charge time is actually faster (marginally). Testing on the P102 shows the P118 to be a few % faster than the P118B, but subsequent testing reveals that this difference is negligible. For example: a 6Ah P193 charged in 03:35:31 on a P118B but on the P118 it charged TEN SECONDS faster, a difference of about 0.08%.
  5. [FAIL]   I expect that the P117 and all other chargers will each be about 50% faster than the P118/P118B.
I figue 4 out of 5 ain't bad. I had expected that the P117 was faster than the P118 by about 50%, and while it is faster the rate is more like 40%. Furthermore, the P131 was a real surprise. The P131 does charge faster than the P118, but it's slower than the P117 and others. It's "in a class by itself"!

Let's not forget how I've stated for years that the P117 charges at a rate of 2.1A and the P118 charges at 1.4A. As per the data above, this isn't exactly true. These chargers actually charge at a higher fixed rate, then change to a slower rate which tapers to zero. However the data above shows that the AVERAGE charge rate for the P117 is 2.1A and for the P118 it's 1.5A.

Can we now predict the charge time for a given model of battery on a given model of charger? Maybe so for the CC chargers, but we need more data for the CC/CV chargers. Stay tuned. For the CC chargers (P116 and P119), we can calculate a good estimate of a fully depleted battery's recharge time by dividing the battery's ACTUAL capacity by the charger's average charge current But most folks won't know the ACTUAL capacity of a given battery, they will simply know the battery's rated capacity, which could be MUCH greater than the ACTUAL capacity. Without knowing the ACTUAL capacity of a battery one can only perform the calculation then state that the full recharge time will be "up to" this length of time. For example, for the P102 on a P119 the calculation is 1300/223 = 5.83 so we'd estimate the recharge time as "up to 5:50". Our P102's ACTUAL capacity was measured at about 1144mA, so following this logic we'd estimate the full recharge time as 1144/223 = 5.13 or 5:07:48. We measured the actual recharge times as 4:59:42 and 5:03:55, both under but within 3% of our estimate.

Final Thoughts

Ryobi chargers do not adjust their charge rate to suit each battery. As batteries get larger in capacity the charge time required increases and a given battery will always take proportionally longer to charge on a slower charger than on a faster one. But at the same time battery stress due to charging decreases because the effective charge rate decreases and the relative difference in charge rate between these chargers also decreases.

Let's say you have a P119 charger and a P102 battery. The P102 is the smallest capacity Lithium Ion battery Ryobi has released, with a 1.3Ah rating. With only 88% of rated capacity our example P102 needs about 5 hours to fully recharge on a P119 charger. If we'd tested with a 3Ah P191, the time needed would likely be 11.5 hours. Move to Ryobi's largest battery, the 9Ah P194, and the time needed would be about 35 hours! Seriously, a day and a half to recharge one battery? That's crazy, yet true.

Some will argue that this slow charge rate is better for the cells. Right? Well let's see. The cells in these batteries have a maximum recommended charge rate of 1C (e.g., as fast as one hour). IMHO if we stay beneath this rate we'll maximize cell longevity, and I suspect that any charge rate beneath 1C will have negligible effect on cell longevity as compared to the harsh manner in which the cells are discharged. The P119 is Ryobi's slowest charger, and at 235mA it charges the cells in a 1.3Ah P102 at 235/1300 = 0.18C, the cells in a 3Ah P191 at 235/3000/2 = 0.039C, and the cells in a 9Ah P194 at 235/3000/3 = 0.026C. The P117 is Ryobi's fastest charger, and at 2900mA it charges the cells in a 1.3Ah P102 at 2900/1300 = 2.23C, the cells in a 3Ah P191 at 2900/3000 = 0.97C, and the cells in a 9Ah P194 at 2900/3000/3 = .32C. Yes, the P117 charges the P102 at a rate which exceeds the cell manufacturer's recommendation, which can therefore affect cell longevity. This is also true for a P102 on the P118, P118B, P135, P125, P114, P113, P131, and P130 chargers. For the P102, using a P119 (or P116) charger instead of a P117 could make a difference in battery longevity. This is true for a few other Ryobi battery and charger combinations. But for batteries rated 3Ah and larger, the per cell charge rate will be below 1C no matter which charger is used.

If one's battery is 3Ah or larger then using a slower charger will have no effect on cell longevity as compared to a faster charger.
The slower charger will simply require a longer time to recharge the battery.



I wish Ryobi would go ahead and release their Super Fast Charger in the USA. As far as I'm concerned, the time to recharge Ryobi batteries has become the real Achilles Heel of this line. The cells in these battery packs are rated by their manufacturers to be recharged in one hour, so consumers should be able to purchase a charger which can recharge even the largest battery in one hour. Why not release a charger which adjusts its charge rate to match the battery which is being charged? Surely the "HP Technology" terminals could be used to let the charger know to use the highest charge rate, and to charge batteries without this technology at a slower rate.

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Last revised 26-Mar-2019
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