Local government here doesn't make money recycling, they do it because they have to. So they are quite tolerant of independent recyclers, aka trash pickers and scrappers. I'm friends with a couple of them and because I have cash and the skill and time to fix some things, they share their findings with me. We all need and use battery powered hand tools and lawn equipment. I do a fair amount of lawn work at home and church and do not really like dealing with gasoline powered equipment anymore. There is too much ethanol in regular gasoline and it goes sour quickly here in the warm humid climate and fouls the carberators, esp. in 2-stroke machines.
At home I went all plug in 120v AC powered because the lawn is small enough. A 100 foot extension cord allows me to mow, sidewalk edge, weed whack and blow from the mains. At church we have 3 acres total land, so that is not practical.
I bought new 2 different leaf blowers (Walmart and eBay) and began looking for spare batteries for extra run time. The 2x20v HyperTough blower from Walmart I have works well but it wasn't made long enough for there to be free batteries to be had.
Ryobi, on the other hand, is sold at Home Depot, and "Black+Decker" is common because of it's low price. Neither brand has a "commercial" division. B&D advertises tool compability with it's 20Vmax line, but it isn't so. Some Craftman chargers will accept B&D batteries but real compatability isn't there. Recently I bought 2 aftermarket 20vMax batteries from eBay for a weed whacker. Both worked when they came in partially charged. Neither would initially charge even though the voltage was a bit low. They worked in a 20v B&D shop blower. Neither would recharge in a Crafstman charger that normally works for B&D. I used a variable voltage lithium battery charger and manually recharged both. Then neither worked in the weed whacker, shop blower or a small B&D hand drill. All had full voltage. The person who gave me shared the tools with me suggested the 20vMax label was intended to be taken literally. After discharging both some, they indeed did work in 2 of the 3 tools, but the drill still refused them.
Now, if they work in some tools sometimes and not other times, it's not the aftermarket battery that's the issue. I permanently fixed the issue with the weed eater by bypassing the circuit board in the handle. I bought a different aftermarket charger for $12 and that works. Bypassing the board means I don't have 2 speeds and a line bump button, but I prefer no drama when I want to use a tool. Off or on. Do or do not as Yoda used to say.
I bought a 40v Ryobi blower and wanted a spare battery only to find they cost more than the original blower plus battery. There are a lot of those batteries available in not working state because Ryobi seems to have the same quality control issues B&D does. I bought 2 "defective, for parts only" from eBay for $36. One new is almost $100. After taking them apart I could only find some light moisture damage but nothing obvious. A bit of searching on the internet turned up where the actual battery ground was. To force charge a battery you usually have to bypass the board to get either the true hot or true ground. One of the plus or minus external charge pins is isolated by diodes on the board. I soldered a short wire to the actual ground inside and ran it out when In reassembled the battery. Now I can easily force charge them without opening them up.
A real Ryobi charger refused both, but at least pretended to check them out before blinking error. After force charging both the Ryobi charger now freaks out as soon as you put either battery in. But both work fine in the blower. So I win this time. Almost $200 worth of spares for $36. The charger is a 42v eBike charger. It won't go over voltage and cost $20 on eBay.