NiMH vs alkaline batteries
NiMH is rechargeable at 1.2 V nominal, alkaline single-use at 1.5 V. NiMH wins on cost per use and high drain; alkaline on shelf life and availability.
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NiMH is the ordinary rechargeable AA or AAA. It reads 1.2 volts against alkaline's 1.5, which sounds like a problem and almost never is: an alkaline cell drops below 1.2 volts early in its life anyway, so devices are built to cope. NiMH is the better cell for anything hungry — game controllers, flashes, toys — and pays for itself after a handful of charges. Alkaline still wins for a smoke alarm or a clock, where the battery must simply sit there for years.
- Verdict:
- NiMH for anything you replace often, alkaline for anything you forget about
Side by side
| Specification | NiMH | Alkaline |
|---|---|---|
| Nominal voltage | 1.2 V | 1.5 V |
| Rechargeable | Yes, 500–1000+ cycles | No |
| Capacity (AA) | 1900–2500 mAh | 1800–2900 mAh |
| High drain | Excellent | Poor |
| Self-discharge | Low-self-discharge types hold most of a year | Years |
| Cost per use | Very low over time | Low up front, adds up |
| Leak risk | Low | Real when left flat |
The 1.2 V question
A device specified for 1.5 V works on NiMH because alkaline does not hold 1.5 V for long — it starts there and slides. NiMH sits near 1.2 V for most of its discharge instead. The exceptions are the few devices that read voltage to estimate charge, which can show a NiMH cell as half-empty from the start.
Low self-discharge changed the maths
Older NiMH cells lost much of their charge sitting in a drawer, which is what gave rechargeables a bad name. Low-self-discharge cells, sold pre-charged, hold the large majority of their capacity after a year. If you last tried rechargeables before those existed, the comparison you remember no longer applies.
Where alkaline still wins
Smoke alarms, emergency torches and anything sealed for years. Not because NiMH cannot do it, but because a cell that must be trusted after five years untouched is the one job single-use chemistry is genuinely better at.
The devices worth converting first
Game controllers, camera flashes, children's toys with motors, and anything running a wireless mouse or keyboard. These are the high-turnover, high-drain devices where NiMH both saves the most money and performs better than the alkaline it replaces.
What a good charger changes
A charger that handles each cell independently, rather than in pairs, will charge to the right point and stop. Cheap paired chargers overcharge whichever cell fills first, which is the main reason a set of rechargeables underperforms and dies early.
Storing them
NiMH keeps best at partial charge in a cool place, and low-self-discharge cells will still hold most of that after a year. Alkaline stores best fully charged, which it always is, but should be taken out of any device left unused — that is when it leaks.
Check before you swap. Batteries with similar dimensions are not always interchangeable. Always verify voltage, chemistry and the requirements printed in your device manual before fitting a replacement.
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NiMH vs alkaline batteries: common questions
What is the difference between NiMH and Alkaline?
NiMH is the ordinary rechargeable AA or AAA. It reads 1.2 volts against alkaline's 1.5, which sounds like a problem and almost never is: an alkaline cell drops below 1.2 volts early in its life anyway, so devices are built to cope. NiMH is the better cell for anything hungry — game controllers, flashes, toys — and pays for itself after a handful of charges. Alkaline still wins for a smoke alarm or a clock, where the battery must simply sit there for years.
Which should I choose, NiMH or Alkaline?
NiMH for anything you replace often, alkaline for anything you forget about. NiMH is rechargeable at 1.2 V nominal, alkaline single-use at 1.5 V. NiMH wins on cost per use and high drain; alkaline on shelf life and availability.
Nominal voltage — how do they compare?
NiMH: 1.2 V. Alkaline: 1.5 V.