Hack to charge RYOBI 40V Batteries - Directly connect MPPT solar charge controllers

I've made several movies of how to charge RYOBI batteries by putting them in charge mode using a 1.2K Ohm resistor between the + and T1 connectors. Jim Shupe has figured out that you can put a RYOBI 40V battery into charge mode using a 300K Ohm resistor between the + and T1 connectors. This is great news because we can now directly connect a MPPT solar charge controller to the 40V batteries.

The 3D print files are located at:

Things I used:

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[NexGen-D]

You sir, are a legend, also 330k works as well, and also, the after market Ryobi 40v do not require the resister at all and will charge directly, I was looking to use these for camping, and the fact they don't have a 12v Auto charger for these is just ridiculous, and using an inverter to charge them.

[jasonbroom]

That's some really cool stuff. You would think that with the burgeoning interest in green energy generation and storage, and Ryobi manufacturing a huge number of batteries suitable for such storage, that they would engineer and sell a solar solution for charging their 18 and 40 volt batteries.

[aspdad]

Chris, you and Jim are amazing! However, I feel so out of the loop for not knowing half of what you just said. I watch, I learn. Best I can hope for. Grateful to have such smart people in our lives!!! 🤯 😆

[trevorperez]

THANK YOU SO MUCH. seriously you just saved me sooo much time

[sin]

thanks keep up the great work, getting into the hobby bought my first ryobi supercharger and will turn it to a power station.

[IM_A_BEAR_LOL]

The OP403A "hat" charger is current limited by the AC adapter. I modified the cable for the OP403A to connect it to an MPPT charger and have seen over 4amps charging current. Charged up my 40v batteries this way all last summer without any problem.

[droopy-nyrv]

Great video as always, Thank you. Can you use this method to charge multiple batteries at the same time? The cheaper MPPT seems to a accept up to 300w. If you can charge multiple batteries would you need to use blocking diodes on the positive lead from the battery out to allow pass through charging? Or would one MPPT only charge one battery at a time? Thank you again.

[fluffyeggs]

Thanks for the info on the resistor. I'm able to successfully charge my batteries from a panel and the boost controller. Just need to rig up a load to see if it'll discharge with the charge mode resistor in place.

[paultalalay]

How many Watt 300K resistor did you use?

[poransingh]

this is great, any chance you can rig it to work with pass through charging with the ryobi power station?

[jonathanyokley]

I finally put this project together! I was able to install the 300k resistor directly to battery and It looks like i'm charging and discharging at the same time.

Question Chris.... You said it's best to charge under 4 amps, but 2 will make batteries last longer.... HOW do you limit the amps with the setup we're using here. Currently i'm showing about 5.8amps charging with 16v from the panel.

[corychamberlain]

Any idea on charging this workx 24v directly

[BrandEver]

Is there any way possible to charge a 40v battery with 12v? I have a 12v charger for my 18v batteries and it would be great if I could also charge 40v in my car

[rossbrawley]

CAN YOU HELP ME Im trying to figure out how to use 40vdc to run a trimmer, but there are 2 pins more than positive and negative. it is a hart brand 40v . i cant find any info anywhere.

[aussieknowhow]

Hi, do you know how to get the 36v ryobi battery into charge mode? I've tried a 300k and 1.2k resistor across the two pins you show. All 4 leds light up, but as soon as I provide 40.5v the leds go out and no current goes into the battery. Any thoughts?

[carlisleherron]

For a 40V Ryobi battery that gets the "Red/Green" flashing indicator (means "defective" I believe) on the hat charger, how long do I need to have my battery connected to the power supply using the resistor as show in this video before I then move it to the hat charger and try to charge it up?

[versatec]

What is the voltage on the third contact on the 18v ryobi battery (the one with the 1.2kohm resistor) ? Thanks

[reymanagapito]

Hi chris, why the 300k resistor didn't work with my 36v 4Ah battery? Plus of battery to T1.. But my battery is good, when i pressed the battery indicator it says 2 bars, what went wrong? im using the supplied 36v 1.7amp power supply, much appreciated, thanks

[namAehT]

While I don't need to solar charge my 40V batteries I *do* need to rescue a few of them from under voltage. Turns out if you leave them sit "empty" for a few weeks they'll go below what the charger deems a safe charging voltage and refuses to take a charge.

[jonathanyokley]

Any idea why the new Ryobi 12ah 40V battery won’t work with this configuration.

All of my 40 V batteries will charge and discharge at the same time with this set up.

For some reason the new 12ah battery just plugs in starts working for a moment, and then shuts itself off.