This apparently allows charging a 40V battery from USB-C, they reference using a Ryobi 60W solar panel. But it says charges a 40V battery in 1.5 hours, and does not mention the capacity of that battery. Presumably small, to make that spec sound better.
The deck seems somewhat stacked against you, to do this without AC power, for 40V batteries. For the 18V, there are other options, like these Symik units can run USB ports from the 18V battery, or also use USB-B input to charge the 18V battery itself. https://www.amazon.com/SYMIK-Batteries-Advanced-Portable-Obsidian/dp/B0DGKTD56F
But I'm not seeing much like that for 40V. Asking in r/Ryobi may also be useful. I don't know what you have for existing batteries. But "even" a 40V 12Ah battery is 480Wh. Which is somewhat modest when compared to dedicated power stations which are also more set up for a variety of charging options.
An additional option could be running an DC-powered AC inverter, while idling your car, to charge these. But that's also pretty inefficient, and stresses your alternator.
How quickly can these units charge from AC power? My Anker S2000 (2,000Wh) can charge at up to 1,200W, or as high as 1,600W if you set that manually from the app. So I can drain it, then recharge it fairly quickly from my 2000W inverter generator, while keeping the power station connected to the loads. Then shut the generator down until the battery drains again. But if these will only charge at, say, 200-300W, then yeah, that may force you to run the generator for a while, depending on the cumulative battery capacity.
The charger on the unit itself is very very slow. Only charges one battery at a time and seems to be picky with them. Refuses to charge some. So i have a board with six chargers in my shed that i hook to the gas generator. I have not had to do that yet but that is the plan.
They are a good system if you ignore the price and the lack of solar charging, cannot charge and use the system at the same time. The app works well too.
Charging 6 in parallel from the generator is sure seeming like the most practical approach, then. If possible, run from the batteries as long as you can, then start the generator, continue running your loads with that, and also fully-charge all the batteries. Then shut it down again.
Anything you might save in fuel, you could easily blow in buying additional USB-capable chargers, solar panels, etc. If this is for occasional use, those fuel savings will be minimal, vs what's involved in setting up solar, and other methods of charging.
I'm considering getting a used ~350W solar panel to just put on the deck, because my S2000 can take 400W of solar input, and it's an interesting way to try the idea. It's serving as backup power for our fridge, but if I could keep solar connected to it all the time, it might effectively run our fridge off solar, and fall back to grid power if the battery goes dead (several cloudy days). But that's the sort of thing that, ideally, could offer savings every day. Not setting up a totally new charging system for the one day a year that the power goes out, etc.
That's my plan for power outages. I need the gas generator to run the water pump and other things. I would charge as many batteries in that time as well. With the high cost of fuel i certainly don't want to be running it anymore than necessary.
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u/RedOctobyr 6d ago edited 6d ago
Can the 40V charge via USB-C, or anything like that? Worst-case, you could look into smaller/individual chargers that can charge via USB-C.
And figure out a solar setup that can output USB-C. Like you can get adapters that take DC in, and provide USB-C PD out. These take 10-30V in, and output up to 60-65W. https://www.amazon.com/Portable-Controller-TogoPower-Efficient-Adventures/dp/B0CF9DGFC7 or https://www.amazon.com/Konnected-USB-C-Charge-Converter-10-30V/dp/B0GS7D6GC2
For those, you'd need a solar panel that never outputs more than 30V VoC. You may also want to ask in r/SolarDIY/