Battery Equivalents and Replacements

What's Ah in Battery - Battery Ah Meaning

From time to time, people ask us what does Ah mean on a battery - well, Ah or Amp-Hours is a unit of capacity that describes how much current a battery can provide under certain conditions.

While some batteries feature capacity in hundreds and thousands of Amp-Hours, smaller batteries feature capacities that are measured in milli-Amp-Hours (mAh) or even micro-Amp-Hours (μAh).

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Battery Capacity Definition

Generally, the battery capacity is a unit of measure that describes how many Amps (A) or milli-Amps (mA) the battery can provide for 20 hours before its voltage drops below a certain level - that "certain level" is commonly labeled as a cut-off voltage or drop-off voltage.

This definition of the battery capacity is usually given for lead-acid batteries, although some manufacturers provide capacities for other discharge rates, for example, for 1h, 2h, 3h, 5h, 10h, etc.

The capacity of wet/flooded, AGM, and Gel-Cell 12V lead-acid batteries is determined by how many Amps can a new, fully charged 12V battery deliver for 20 hours without its voltage falling below 10.5V at 77-80°F (25-27°C).

Note: Draining the rechargeable battery below cut-off voltage could cause permanent damage to the battery - cut-off voltage primarily depends on the battery chemistry, but also on the battery construction and design, since it is not the same to fully discharge starting or deep-cycle lead-acid battery.

Since rechargeable lithium batteries don't suffer from the capacity decrease like lead-acid batteries when they are discharged with 0.5-1.0C or stronger currents, many manufacturers of lithium batteries provide 1h capacity of their batteries, which is "almost" the same as 20h capacity of the lithium batteries.

The capacity of the battery depends on the exact chemistry and the battery construction.

For example, two batteries may be based on the same chemistry, but one is optimized for low-drain applications (high capacity, low discharge current), while another is optimized for high-drain applications (lower capacity, higher discharge current).

The following table lists some of the most popular chemistries commonly found at cylindrical batteries - the data are given for the cylindrical AA batteries.

Chemistry Common Name Rechargeable Typical Capacity (mAh) Voltage (V)
Zinc Carbon R6, 15D No 600 - 1600 1.5
Alkaline LR6, 15A No (Mostly No) 1800 - 2700 1.5
Li-FeS2 FR6, 15LF No 2700 - 3300 1.5 (1.8 max)
Li-ion 14500 Yes 600 - 2000+ 3.6 - 3.7
Li-SOCl2 (14505) No 2400-2700 3.5-3.6
Li-MnO2 CR AA No ~2000 3.0
Lithium - Yes 1000-2000+ 1.5
NiCd KR6, 1.2K2 Yes 600 - 1000 1.2
NiMH HR6, 1.2H2 Yes 700 - 2800 1.2
NiOOH - No 2200 - 2700 1.5 (1.7 max)
NiZn ZR6 Yes 1500 - 1800 1.6 - 1.65

As one can see, although the batteries in the table share the same physical dimensions, their electrical characteristics differ significantly.

Such differences exist in all battery sizes, from small button/coin-cell batteries to large automotive/light industrial batteries.

If You are looking for the battery capacity of a certain battery, feel free to use the Search: write down the battery size, click Search, and the system will find it for You, assuming that the battery exists on the Battery Equivalents site.

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