1. What do you need to charge?
Pick every type you own. This is the most important filter - chemistries can't be mixed in the wrong charger.
2. How many at once?
Cheap chargers often force you to charge in pairs - we only recommend independent-slot chargers.
3. What matters most to you?
Pick up to two.
How this shortlist is built
Chemistry is a hard filter, not a preference. A charger that cannot handle your cells is removed, no matter how good it is otherwise. After that, slot count is checked against the batch size you told us, and your two priorities add or subtract weight. The percentage is a relative match score against the best available option - it is not a review score, and an 80% match is not "better" than a 60% match on a different set of answers.
Every charger in the pool has independent slots. That is a deliberate exclusion: paired-slot chargers are cheaper, common, and the most reliable way to quietly kill a set of cells. For the reasoning behind each pick, see the best battery chargers guide, or how the charger brands compare.
The three things that decide a charger
Chemistry
NiMH (your AA and AAA rechargeables, 1.2V) and Li-ion (18650, 21700, 14500, 3.7V) charge on completely different profiles. NiMH is charged at constant current and terminated by detecting a tiny voltage drop or a temperature rise. Li-ion is charged constant-current then constant-voltage to a hard 4.2V ceiling. Applying the wrong one is not a performance issue, it is a safety issue. Use the compatibility checker if you are unsure what you have.
Slots
More slots is not automatically better - a 12-bay charger that charges slowly is a different tool from a 4-bay that charges fast. Match slots to the biggest batch you realistically charge at once, not the biggest you can imagine.
Termination
This is the invisible one, and it is what separates a good charger from a cheap one. A good charger notices the cell is full and stops. A bad one runs on a timer and cooks the cell. You cannot see termination quality on a spec sheet, which is exactly why we lean on testers who measure it.
Common questions
How do I know which battery charger I need?
Start with chemistry, because it is the only thing that truly disqualifies a charger: a NiMH-only charger cannot safely charge Li-ion cells, and vice versa. Then count how many cells you charge at once, and only then worry about features like an LCD or capacity analysis. This tool asks those three questions in that order.
What is an independent-slot charger and why does it matter?
A charger with independent slots monitors and terminates each cell separately, so you can charge one cell or four, of different brands and charge levels, at the same time. Cheap chargers wire slots in pairs and charge two cells in series, which means one cell is often overcharged while the other is undercharged. Every charger in this tool has independent slots.
Can one charger handle both NiMH and Li-ion?
Yes. Multi-chemistry chargers from XTAR, Nitecore, Vapcell and SkyRC detect or let you select the chemistry and apply the right charge profile. They are the right answer if you own both AA rechargeables and 18650 flashlight cells. The trade-off is that they are usually a little more expensive and some run warmer than a dedicated NiMH charger.
What does a charger that measures capacity actually do?
An analyzing charger runs a full charge, timed discharge and recharge cycle to measure how much energy a cell really holds, then reports it in mAh. It is the only reliable way to find the tired cell that is quietly ruining a set. The Powerex MH-C9000PRO and SkyRC NC2200 are the usual picks. A cycle takes many hours, so it is a diagnostic tool rather than an everyday charger.