> We don't need more heavy metals in our air/water.

Batteries in landfills are pretty inert. None of the heavy metal reactants in a NiMH or lithium cell[1] are ever in a liquid or dissolved state (the charge carriers are hydroxide and lithium ions respectively). One of the reasons they're so pervasive is precisely that these chemistries are safe and relatively non-toxic.

Really, if you're worried about discrete cell batteries and the environment, the solution is to minimize your use of them, not to worry about recyclable vs. not.

[1] Lead acid batteries are an exception, because the sulfuric acid does indeed dissolve some lead. But these really aren't the subject of the article, and in fact they're already being quite effectively recycled in practice.

Yes, I'd imagine so in properly capped and lined landfills. But those are on their way out as our landfills are filling up up[1] faster than new ones built. More and more towns are moving to incineration.

[1] https://www.globalcitizen.org/en/content/us-landfills-are-fi...

I've had good luck with the Nitecore intelligent chargers. Most of those allow for independent charging including different chemistry between slots.

The Panasonic BQ-CC55 charger will charge from 1 to 4 cells, AA or AAA, in any combination. I've got 2 and they've worked great.

For about $10 more, also see La Crosse Technology's BC700. It can do some neat things like measure the capacity that was charged or run a "refresh" cycle that repeatedly drains and charges a battery (up to 20 times) until the measured capacity stops increasing.

Like the BQ-CC55, it has four independent channels that can charge either AA or AAA in any mix. You can even run different modes on each channel, like charging 1 and 2 while refreshing 3 and 4.

Ha! You beat me on making that recommendation. I have used a BC700 for about two years now, and am very satisfied with it.

I particularly appreciate how each of the four battery slots is separate. Not only does that mean each battery can be doing something different (charging, refreshing, etc.), it also means you can remove and insert different batteries at different times. This is great when some batteries are more (or less) discharged than others.

Also, worth noting that the BC700 supports NiCd and NiMH, in addition to AA and AAA.

I've had the BC700 (or possibly one of the identical builds under a different brand name) for years, but switched to the BQ-CC55.

The latter is "put in and forget". The former means fiddling with really bad buttons (because you can! Not really because you have to. But if I can manually set and micro-optimize the charging current, by God I will).

I worry much less about charging nowadays.

I can't say I've used the custom charging current options, but the refresh mode has rescued some batteries that (very unscientifically) did not seem to be holding much charge.

IIRC the default behavior is to charge at 200 mA and discharge at 100 mA.

These are great but toward the end of the charge cycle they make a lot of high-pitched sounds.

There are a lot of chargers with separate charging circuits for every slot.

I've had good luck with an Opus brand charger. The one I have allows selecting charging rates (200-1400 mA), and it has an LCD that tells you voltage, rate, status, etc. It also supports some discharge/refresh/test cycle stuff, although I don't know if the practicality of that is real. (If a battery isn't performing right, I feel like it's usually a lost cause.)

> Any recommendations for chargers that don't require paired batteries?

I've had a Powerex MC-C9000 [1] that I have used for at least a decade with no problems, mostly with Eneloops. It does not require pairing.

[1] https://www.amazon.com/Powerex-MH-C9000-WizardOne-Charger-An...

I've recharged alkaline batteries and reused them quite a bit before they turned to muck.