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.
AA / AAA rechargeables (NiMH)
C / D / 9V (NiMH)
18650 / 21700 etc. (Li-ion)
2. How many at once?
Cheap chargers often force you to charge in pairs - we only recommend independent-slot chargers.
Just 1-2
Up to 4
A lot (8+)
3. What matters most to you?
Pick up to two.
Cheap & simple
See voltage / status on a screen
Measure true capacity (find dead cells)
Charge fast
Maximum battery lifespan
| Battery | Size | Chemistry | Capacity | Cycles | ~$/cell | $ / 100 units* | Best for |
|---|
* Value = price per 100 capacity units (mAh for NiMH, mWh for Li-ion). Lower is cheaper energy - but remember cycle life: a cell that lasts 4× longer is cheaper over its life even if pricier upfront. Capacities/prices are approximate 2026 figures.
🔋 Energy - mAh ↔ Wh
Convert capacity to energy. Wh = mAh × Volts ÷ 1000.
mAh
V
Energy
2.40 Wh⏱️ Runtime estimator
How long a cell powers a device. Uses ~85% usable efficiency.
mAh
mA
Estimated runtime
11.3 hours🔌 Charge time estimator
Rough NiMH charge time. Includes ~1.4× charging inefficiency.
mAh
mA
Approx. charge time
2.8 hours 🧱 Pack builder (series / parallel)
Configure cells into a pack. Series adds voltage; parallel adds capacity.
VmAh
SP
Voltage
11.1 VCapacity
6000 mAhEnergy
66.6 WhUses 6 cells total.
Estimates These are planning approximations. Real runtime, charge time, and pack behaviour depend on temperature, discharge rate, cell age, and charger behaviour. Building lithium packs requires a proper BMS and safety knowledge - don't wing it.