toolboy's Corner: Ryobi 40v Charger Testing

Note: Additional testing results can be found here: Ryobi 40v Charger Testing #2

Ryobi's 40v tool offerings are becoming quite expansive. I've purchased and regularly use a number of these 40v tools. I started with an attachment-capable power head and a leaf blower. All of the attachments I had already purchased for my gas-powered Troybilt TB575SS power head were 100% compatible with the 40v power head: a string trimmer, a brush cutter, a pole saw, an articulating hedge trimmer, and a cultivator. I soon purchased a 40v chainsaw, and I eventually picked up a lawn mower and a 300w pure sine wave AC inverter. These are all great tools! But I soon found that it can be difficult to stay busy, because once a battery has been depleted it takes several hours to recharge. This is especially true if other family members are mowing and/or string trimming the lawn while I'm working on something else. That's three batteries in use at once.

My arsenal of 40v batteries currently includes one 5Ah battery, two 4Ah batteries, and one 2.6Ah battery. If these are all drained and only one charger is available, it'll take a full day to recharge them all. It's really ridiculous that Ryobi has only recently released a rapid charger for these batteries. The cells inside these battery packs are designed to be recharged at the 1C rate. This means that, in theory, the cells should be able to go from completely discharged to fully charged in exactly one hour without exceeding the cell manufacturer's recommendations. Due to the way a modern CC/CV charger operates and how Li-Ion cells accept a charge, my expectation is that an additional 25-30% in time will be needed to keep the cells from overheating as they near a full charge. Let's call it 75 minutes or 01:15. If the charger takes much longer than this, then it's just wasting our time without adding any safety.

Are Ryobi's 40v batteries really 40v?

If you're familiar with Ryobi's ONE+ line of 18v tools, you might know that the 18v Li-Ion batteries contain five 18650 cells in series. Each 18650 cell has a nominal voltage rating of 3.6v, so five in series yields 5x3.6v= 18v. The claimed 40v can't be divided equally with 3.6v cells, so something is awry. It seems far more likely that Ryobi simply doubled the number of cells from their 18v batteries, or ten cells in series. That would mean the 40v batteries are really 10x3.6v = 36v. I've disassembled several 40v batteries and I can confirm that they contain ten cells in series (or two parallel strings of ten cells) so yes, they're really 36v batteries.

Do the Ryobi 40v battery models mean anything?

Yes, the battery model numbers indicate battery capacity. Each battery model begins with "OP40" to indicate the 40v battery line. The next two digits indicate the battery capacity in Ah x10 (e.g., 15 = 1.5Ah, 40 = 4.0Ah, etc.) The model may have an additional digit, which I presume indicate revision number. So the 1.5Ah battery is model OP4015, the 2.6Ah battery is OP4026 or OP40261, the 4.0Ah battery is OP40401, and the 7.5Ah battery is OP40751.

My 40v battery contains TWO strings of 10 cells. Shouldn't it be possible to recharge it safely in half the time, or 30 minutes?

No, it doesn't work that way. To stay within the manufacturer recommend charge rate of 1C the fastest that any individual cell can be charged is 1C or in one hour, regardless of how cells are wired within the battery pack. Ryobi has released 40v batteries contining ten, twenty, or thirty 18650 Li-Ion cells. These cells are wired as 10S, 10S2P, or 10S3P, which means that they are wired with ten cells in series and then 1, 2, or 3 sets of ten wired in parallel. Ryobi has released 40v batteries in the following capacities/configurations:
Capacity (Ah)Model(s)Cell ConfigurationCapacity per cell (Ah)
1.5 OP4015 10S (or 10S1P) 1.5Ah
2.0 OP40201 10S (or 10S1P) 2.0Ah
2.6 OP4026, OP40261 10S2P 1.3Ah
3.0 OP4030, OP40301 10S2P 1.5Ah
4.0 OP4040, OP40401 10S2P 2.0Ah
5.0 OP4050, OP40501 10S2P 2.5Ah
6.0 OP40601 10S2P 3.0Ah
7.5 OP4075? 10S3P 2.5Ah

Given that Ryobi has used twenty 3.0Ah cells in the 6.0Ah battery and thirty 2.5Ah cells in the 7.4Ah battery, I expect that at some point Ryobi will release a 9.0Ah battery containing thirty 3.0Ah cells which is about the same size as the 7.5Ah battery.

Sadly, the 40v batteries don't communicate with the charger to indicate what the maximum charge rate should be or how many strings of cells are present in 40v battery. So each 40v charger operates at the same charge rate irrespective of which battery has been selected. This works well for batteries containing ten cells (10S), but means that the charge times are 2x or 3x longer than they need to be for twenty cell (10S2P) and thirty cell (10S3P) batteries.

The Ryobi 40v batteries have SEVEN contacts, but only THREE are used for charging, and only FOUR are even wired. Hey Ryobi, why not use one or more of the three unused contacts to tell your chargers how fast they can charge the battery? For example, strap a contact to +Vcc to indicate TRUE or 1, to Ground or no contact for FALSE or 0. An old battery without these strappings would be 000. Then if we have a multi-level current charger, let bit 1 indicate increased rate, bit 2 = double rate, bit 3 = triple rate. For example: Perphaps the last two combinations should be illegal. At any rate, if we strap bit 2 or 3 to indicate a 10S2P or 10S3P cell configuration we safely cut the charge time in half or a third, respectively.

Some questions I'll try to answers on this page:

How long does it take to recharge a 40v battery on a 40v charger?

This is not a simple question with a simple answer.

Ryobi has released 40v batteries in capacities which range from 1.5Ah to 7.5Ah. Unless the Ryobi 40v chargers adjust their charge rate to fit the battery which is being charged it is reasonable to expect that it will take 5x as long to recharge a 7.5Ah battery as compared to a 1.5Ah battery on a given model of charger, since the 7.5Ah battery has 5x the capacity of the 1.5Ah battery. If it takes one hour to recharge a 1.5Ah battery, we should expect that it will take 5 hours to recharge a 7.5Ah battery on the same charger. So we can't really say how long it will take to recharge a battery without first knowing WHICH battery.

Ryobi has released at least SIX different models of 40v chargers. Do they all operate at the same charge rate? In order to recharge a 1.5Ah battery in exactly one hour, a charger must be delivering an average charge rate of at least 1.5A. (And the actual charge rate will be a little bit higher to account for energy losses due to heat and other factors.) If the charge rate of another charger model is 2.0A, then we should expect the 1.5Ah battery recharge time to be 1.5Ah/2A = 0.75hr, or 45 minutes. The second charger model is therefore 15 minutes faster than the first model for the 1.5Ah battery! Most consumers will not be sitting by with a stopwatch so this difference may go unnoticed. If we apply this same logic to the 7.5Ah battery, we see the charge time would be 7.5Ah/1.5A = 5 hours vs 7.5Ah/2A = 3.75 hours. That's an hour and fifteen minutes faster on the second charger, which may be long enough for many consumers to notice. So we can't really say how long it will take to recharge a battery without first knowing WHICH charger.

Here is the list of 40v chargers which Ryobi has released in in the USA: I happen to own at least one of each of these models except for the P137. I plan to test each of them except for the OP404 (which I can't imagine would operate any differently than the OP403).

I've selected a 4Ah battery for all of the testing. The 4Ah battery is in the middle of the range of available capacities, and it's the battery Ryobi is bundling with most of their $100-$200 tool kits. The actual battery I have for testing has a date code indicating it's age is 66 weeks or about 1 year and 3 months.

Ryobi 40v OP400 Charger

This model has been discontinued by Ryobi. Early reviewers of this charger reported that it was responsible for killing their battery. As I understand it, Ryobi offered replacement batteries and chargers to many consumers who complained. I've charged many 40v batteries on OP400 chargers (mostly the 2.6A batteries) and I've never had a problem. This label on this charger indicates that it's rated 88W input.

4Ah OP40401 Battery on Ryobi OP400 Charger

Charger OP400 (88W)
Battery OP40401 (rated 4Ah / 144Wh)
Total Charge Time 2:23:23 (8,603 sec)
Current In 3.8755A
"Bulk" charge rate 1.73A
Average charge rate1.638A
Measured Capacity 3.751Ah / 137.02Wh

The graph shows that the OP400 is a typical CC/CV charger.

Ryobi 40v OP401 Charger

This model replaced the older OP400. It has a slightly smaller footprint than the older OP400, and it's not nearly as tall. The OP401 is rated 72W input so I expect a lower charge rate and longer charge time than the OP400.

4Ah OP40401 Battery on Ryobi OP401 Charger

Charger OP401 (72W)
Battery OP40401 (rated 4Ah / 144Wh)
Total Charge Time 3:13:37 (11,617 sec)
Current In 3.9156A
"Bulk" charge rate 1.28A
Average charge rate1.221A
Measured Capacity 3.569Ah / 129.44Wh

Once again we see the curve of a typical CC/CV charger. As expected, this is a lower charge rate and a longer charge time than the OP400.

Ryobi 40v OP403 Charger

The OP403 charger is very small compared to the OP400 and OP401. It consists of two parts, one part which attaches to the 40v battery and a "wall wart" on the other end which plugs into your household AC outlet. The part which attaches to the battery is similar to an oversized bar of soap. The OP403 has an indentation in one corner with a USB port providing 5v at up to 2.1A. This can be used for charging cell phones or with other USB-powered devices. The USB port can be powered by the "wall wart" AC adapter or by the battery alone, making it useful as a power source during power outages or while camping, etc. The "wall wart" is rated 80W input, which puts this charger halfway between the OP400 and the OP401.

4Ah OP40401 Battery on Ryobi OP403 Charger

Charger OP403 (80W)
Battery OP40401 (rated 4Ah / 144Wh)
Total Charge Time 2:35:29 (9,329 sec)
Current In 3.7757A
"Bulk" charge rate 1.47A
Average charge rate1.467A
Measured Capacity 3.644Ah / 132.73Wh

I'm a little surprised to find that the OP403 is strictly a CC charger, not a CC/CV charger like the OP400 and OP401. The "bulk" and average charge rate are pretty much the same thing for a CC charger.

Ryobi 40v OP406A Rapid Charger

This charger is the beast. Ryobi claims "Up to 300% Faster Charging than Standard RYOBI 40-Volt Charger". Ryobi also claims that the charge time for a 2Ah battery is 30 mins, 4Ah/40 mins, 5Ah/50 mins, 6Ah/60 mins, and 7.5Ah/75 mins. The OP406A is rated a whopping 295W input.

4Ah OP40401 Battery on Ryobi OP406A Charger

Charger OP406A (295W)
Battery OP40401 (rated 4Ah / 144Wh)
Total Charge Time 0:48:40 (2,920 sec)
Current In 3.8508A
"Bulk" charge rate 6.15A
Average charge rate4.797A
Measured Capacity 3.060Ah / 109.42Wh
Wow! The OP406A is indeed a RAPID charger! It's a CC/CV charger with a bulk charge rate of 6.15A! The OP406A has an integrated fan which kicked in immediately when the charge cycle began. My 4.0Ah battery got warm to the touch while charging. I'll mention this in case anyone isn't sure: HEAT = BAD when it comes to battery longevity. When I heard the fan cut off I looked over and saw thay the green light was still flashing, as if to indicate that the charge cycle was ongoing. But my datalogger showed that no current was going in or out of the battery. I decided to leave everything alone for awhile. Maybe the charger had detected that the battery was warm and wanted to let it cool off before declaring the charge cycle complete. If so, then do I include this cool down period in the total charge time I record for this charger? After watching the blinking green light for more than 45 minutes without a change in charge current (it remained zero) I stopped watching. 24 hours later the green light was still blinking, and after 36 hours I noticed the light was no longer blinking, it was just out. I find it curious that at 34:20 when the pack voltage reached 42v, the charge current dropped from 6.15A to 4.62A, where it remained until 35:35. The remainder of the curve was typical for a CV charger. Tht total charge time was about 48 minutes, which is very fast but about 20% longer than the advertised claim of 40 minutes for a 4Ah battery.

I did receive a surprise when I tested the battery capacity on the computerized battery tester. The battery tested at 3.06Ah / 109.42 Wh, or at about 76.5% of it's rated capacity. That's really awful, given that had tested between 89%-94% with all of the other chargers. Below is the graph which shows this. Can you guess which curve followed the OP406A charge cycle? Yup, the orange one.

The OP406A's "bulk" charge rate of 6.15A actually exceeds the cell manufacturer's recommended maximum charge rate for most Ryobi 40v batteries. Here's why: As can be seen above, the charge rate of the OP406A charger exceeds the 1C rate for all Ryobi 40v batteries except for the 7.5A OP40751.

I recommend using the OP406A sparingly or not at all on batteries under 7.5Ah in capacity.

Can we predict how long it takes to rechage a Ryobi 40v battery?

Maybe, but we must know WHICH battery and WHICH charger, and we must make some additional assumptions. I'm not going to go into great detail wrt the assumptions, more details can be seen on my web pages which discuss Ryobi 18v charger testing. I'll just state that my assumptions for the table below are that (1) each battery has been tested to be operating with the ACTUAL capacity as stated in the table, (2) each battery has been fully discharged before beginning the charge cycle, and (3) both battery and charger are at room temperature before strting and during the charge cycle. The table below lists actual recharge times that I've measured using a datalogger configured to capture 4 pts/sec. I'll add to this table as I gather more data.

Will the recharge times be the same with your battery/charger combo? Probably not. But if your battery's ACTUAL capacity is the same as the one I performed testing with, then the recharge times should be about the same. If your battery's ACTUAL capacity is greater than my test battery then recharge times will be longer. If your battery's ACTUAL capacity is less than my test battery then recharge times will be shorter.

Battery Model(s)Rated Capacity (Ah)ACTUAL Capacity (Ah)
/ % of Actual
Recharge Time on Charger Model
OP404014.03.675 / 92% 2:23:23
(8,603 sec)
11,617 sec
9,329 sec
2,920 sec
OP40262.62.305 / 89% 1:27:32
(5,252 sec)
7,065 sec



Can a Ryobi 40v charger be modified (safely) to work faster?

When I look at the OP403/OP404 40v charger I see two main components: a charger and a power supply. And the testing performed above shows that the OP403 is a CC only design. That got me thinking. Which component is responsible for limiting the charge current, the charger or the power supply? If it's the power supply, then can the charge rate be increased by replacing the power supply with a more powerful one? The OEM power supply is rated 80W in and 42V DC at 1.5A out. A quick check on eBay reveals many sellers of inexpensive power supplies rated for an output of 42V DC at 2.0A. If it works, that would be 33% faster than the OEM power supply.

Before buying anything I decided to do a proof of concept test. I looked though my supplies and parts bins and decided that I could test this concept by combining the power from two OEM power supplies. We can't just tie the outputs together as small manufacturing differences between the two would likely cause the one with the slightly higher voltage output to backfeed into the other unit and possibly fry something. So instead I connected one directly to the OP403 charger, and the other I connected through a resistor. Actually I used two 10 Ohm 10W power resistors in parallel. I figured that that power supply with no resistor would supply a full 1.5A and the other one would kick in a little extra, perhaps as much as 0.5A. I did expect that the "extra" juice provided by the second power supply would decrease as the battery voltage increased.

4Ah OP40401 Battery on Ryobi OP403 Charger with extra power supply

Charger OP403 (80W + extra 80W power supply via 5 Ohm power resistor)
Battery OP40401 (rated 4Ah / 144Wh)
Total Charge Time 1:34:53 (5,693 sec)
Current In 3.7217A
"Bulk" charge rate 3.02A-1.62A
Average charge rate2.375A
Measured Capacity 3.354Ah / 120.98Wh
Firstly let me mention that the battery's actual capacity tested low. This is the first charge cycle following a charge on the monster OP406A, so I'm not certain if the problem is with this POC test or if the battery is still recovering from the wallop that the monster OP406A charger gave it. I may cycle it a few times on an OP401 (the slowest 40v charger) to see if it recovers, then try this POC again.

The 4Ah battery DID charge faster with the extra oomph, so I think it's the power supply which limits the current to the OP403 charger. The charge rate starts high and diminishes during the charge cycle, as expected. The charge rate starts at 3.02A and slowly drops during the entire charge cycle, ending at 1.62A. This is a positive result for the POC test, and I think it's worth purchasing a 42v 2A power supply to see how this works. I might even get a 2.5A unit if I can find one. I see that 3A and 4A power supplies are available, but I'm hesitant to get one of these because (1) they are substantially more expensive than the 2A models, and (2) the charger is actually sold with a 1.5A power supply, so the more power we use the more likely we are to exceed what the charger can handle and violate some internal component(s).

From the table above which lists all battery models in the OP406A section, we determine if a 2A, 2.5A, or 3A power supply would exceed the cell manufacturer's maximum charge rate for any of the Ryobi 40v batteries. I calculate that a 2A power supply would exceed the max rate for just the 1.5A OP4015 battery. A 2.5A unit would exceed the max rate for both the 1.5A OP4015 and the 2.0A OP40201 batteries. A 3A or 4A unit would exceed the max rate for the previous two plus the 2.6A OP4026 and OP4026A. I don't happen to own any OP4015 or OP40201 batteries and I don't plan to get any, so a 42v 2.5A power supply sounds perfect to me.

So would this be faster than an OP403 alone? Yes! Remember the OP403 took 2:35:29 to recharge the 4Ah battery, whereas in this POC test the recharge took only 1:34:53. This shaved a full hour from the charge time. That's (5693 sec)/(9329 sec) or 61% of the original time. The POC test averaged a 2.375A charge rate, so with a 2.5A power supply the charge time should be even faster.

Bear in mind that there is some risk with this approach. The charger was sold with and was probably designed to be used with a 42v 1.5A power supply. A larger power supply could potentially overheat the unit, causing permanent damage. The unit could even catch fire. You have been warned!

Summary and Conclusions

Ryobi's fastest 40v charger is the OP406A, and it is MUCH faster than all other models. Don't use the OP406A as your standard charger for batteries under 7.5Ah in capacity.

The next fastest Ryobi 40v charger is the OP400, then comes the OP403 and OP404, and in last place comes the OP401. The difference in charge rate / charge times for these four models is not large. Basically the slowest OP401 charges at 1.25A, the OP403/OP400 is 20% faster at 1.5A, and the OP400 is 40% faster than the OP401 at 1.75A. The 4Ah battery I used for testing clocked a time of 2:23 on the fastest OP400, 2:35 on the OP403, and 3:13 on the slowest OP401. You can save some time by choosing the OP403 over the OP401, but the charge time is so long that no matter which of these you choose if you have just one battery you'll likely need to interrupt what your're doing and wait for the charger to do it's job.

The OP403/OP404 chargers could easily become the second fastest chargers by simply replacing the 42v 1.5A OEM power supply. I suspect that a 42v 2A unit would be a reasonable replacement to the OEM unit and would make these chargers 33% faster. I'm certain that the increased charge current would be safe for all Ryobi 40v batteries, but I cannot be certain that this would not overload the charger's circuits so please be careful!

I think my strategy will be to only use the OP406A rapid charger while I'm actually working. One depleted battery on the OP406A will likely be fully recharged before I need it again. The slower chargers will be used when I'm not in a hurry to get back to work.

Note: Additional testing results can be found here: Ryobi 40v Charger Testing #2

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Last revised 29-Apr-2020
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