Which charger should I buy?
Answer three questions about the cells you own and get a ranked shortlist with the reasoning shown.
What battery replaces this one?
Cross-reference any battery code - LR44, CR2032, AG13, PP3 - to its true equivalents, its upgrades, and the lookalikes that will damage your device.
Will this charger charge these cells?
Check a charger against a cell type before you plug it in, and see the chemistry rules that decide the answer.
Which rechargeable is best value?
Sort AA and AAA rechargeables by capacity, cycle life and cost per unit of energy.
mAh to Wh converter
Convert capacity to energy, and check a power bank against the 100Wh airline limit.
How long will it run?
Estimate device runtime from cell capacity and current draw.
How long to charge?
Estimate NiMH charge time and see whether your charge rate is gentle, healthy or hot.
Series and parallel pack builder
Work out pack voltage, capacity and energy for any S/P configuration.
How to pick the right tool
If you are buying, start with the charger finder - it filters on the one thing that actually disqualifies a charger, which is the chemistry of the cells you own. If you are replacing a battery and the code on it means nothing to you, the equivalents lookup tells you what genuinely swaps in and, more usefully, what looks like it fits but does not.
If you already know what you own and just need a number, go straight to the maths: mAh to Wh, runtime, charge time, or the pack builder.
What The Bench is, and what it is not
We are a curation project, not a test lab. Everything here is aggregated from manufacturer datasheets, independent testers who publish their methodology, and community consensus that has held up over years. Where a claim is contested - the IKEA LADDA and Eneloop Pro question is the classic one - we say so rather than pretending it is settled.
Prices and capacities are approximate and move around. Treat them as ballparks for comparison, not quotes.
Common questions
Are these battery tools free?
Yes. Every tool on The Bench is free, needs no account, and runs entirely in your browser - nothing you type is sent to a server.
Where does the data come from?
We do not run our own lab. The Bench aggregates manufacturer datasheets, published independent test data (such as lygte-info.dk) and long-standing community consensus, and shows the reasoning behind each result so you can check it yourself.
How accurate are the calculators?
They are planning estimates, not guarantees. Real runtime and charge time depend on temperature, discharge rate, cell age and how your charger terminates. We show the formula on every calculator so you can see exactly what is being assumed.