Cordless yard tool battery with illuminated charge indicators on a garden workbench

What Amp-Hours (Ah) Mean on a Cordless Battery

ByKen

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If you are asking what does ah mean on battery, the short answer is that Ah stands for amp-hours, the capacity rating a maker prints on the pack. EGO’s battery guide says that choosing a battery with a higher Ah rating gives longer run times. Ah is not a measure of energy by itself, though. To compare packs you also need the voltage, because stored energy in watt-hours is voltage multiplied by Ah. This guide explains the rating, shows how it links to voltage, and lists what the sources do not say.

Quick answer

  • Ah (amp-hours) is the capacity rating printed on the pack. EGO’s 7.5Ah page prints “Amp Hours: 7.5 Ah”.
  • EGO says a higher Ah rating gives longer run times. The sources we opened do not give a run time formula that uses Ah alone.
  • Ah is not energy. Energy in watt-hours is voltage times Ah, so EGO’s 56V, 7.5Ah pack is stated at 420 Wh.
  • Compare Ah ratings only between packs with the same voltage basis. Two 5.0Ah packs can differ by almost three times in energy.

What Ah measures

Ah is the number a maker gives as the pack’s capacity rating. EGO’s 7.5Ah page lists “Amp Hours: 7.5 Ah” as a specification, and its formula calls the same figure “Capacity (Ah)”. DeWalt’s 5Ah page uses the wording “5.0AH capacity for Long Runtime”, and its 12Ah page says “12Ah capacity for maximum runtime.” In both cases the Ah number is the capacity figure on the label, and a larger number is the larger rating. DeWalt’s 12Ah FLEXVOLT page adds a footnote that gives 20, 60 and 120 volts as maximum initial voltages, so one Ah label can sit on packs with different voltage bases.

The rating does not tell you power by itself. EGO’s page makes the split between power and capacity when it says: “Power is measured in Watts and that is calculated by Voltage x Current.” Power depends on the current the tool draws, and the capacity rating only tells you how much the pack is rated to supply over time. The two numbers answer different questions, which is why a label with only Ah is incomplete for comparison.

Safety notes for charging and storing

An Ah rating does not change how you should charge or store a pack. Follow the maker’s instructions. The sources we opened agree on these points.

  • Charge within the stated range. EGO’s 7.5Ah page gives an “Optimum charging temperature: 32°F-104°F(0°C-40°C).”
  • Store and charge in a cool, dry place. DeWalt says: “Store and charge batteries in a cool, dry location.” EPA says: “It is best to store Li-ion batteries at room temperature.” OSHA’s workplace guidance lists “Storing batteries in cool, dry locations.”
  • Do not use a pack with visible damage. DeWalt says: “Do not use batteries with visible damage or cracks.” EPA says: “The swelling indicates damage to the battery and is a potential fire hazard.”
  • Return a wet or damaged pack. EGO says: “Batteries that have been exposed to water for longer than recommended should be returned to EGO dealers for inspection.”

Do not open a pack or attempt a repair. If a pack is swollen, cracked or wet, stop using it and contact the maker.

How to compare two Ah ratings

  1. Find the voltage of each pack. EGO’s 7.5Ah page prints 56V. DeWalt’s 5Ah page gives a maximum initial voltage of 20 volts and a nominal voltage of 18 volts in its footnote.
  2. Check that the voltage basis matches. If the voltages or the basis differ, do not compare the Ah numbers alone.
  3. Work out the energy. Multiply the voltage by the Ah rating. The result is the energy in watt-hours, and it is your calculation unless the maker prints it.
  4. Compare the energy figures, then read the tool’s run time claim. The run time a maker states is for a named tool and pack, not for the Ah number alone.

Ah ratings side by side

The table lines up two packs that share a 5.0Ah rating. The DeWalt energy figure is a calculation, because the page does not print one.

Pack Ah rating Voltage basis Energy (Wh) Source
EGO 5.0 Ah 5.0 Ah 56V, calculated from the chart; the chart does not print it 280 Wh, stated EGO battery chart
DeWalt 20V MAX 5.0 Ah 5.0 Ah 20V maximum initial; 18V nominal 100 Wh at 20V, calculated; not printed DeWalt 5Ah battery page
EGO 7.5 Ah 7.5 Ah 56V, printed 420 Wh, stated EGO 7.5Ah battery page

The calculation for the DeWalt pack is 20 x 5.0 = 100 Wh. The EGO figure is 56 x 5.0 = 280 Wh, which matches the chart. The two packs carry the same 5.0Ah rating, but the EGO pack holds 2.8 times the energy at the voltages used here. On DeWalt’s nominal 18 volts, the same pack works out to 18 x 5.0 = 90 Wh, so the basis changes the answer again.

The same method works within one maker’s line. Both EGO packs below run at 56 volts, so only the Ah number changes: 56 x 7.5 = 420 Wh against 56 x 5.0 = 280 Wh. The 7.5Ah pack holds 1.5 times the energy of the 5.0Ah pack. The voltage is the same on both sides of the comparison, so the ratio comes from the Ah numbers alone.

Why the voltage changes the Ah answer

The voltage of a pack depends on how its cells are wired. EGO’s page explains: “Arranging enough cells together in series delivers the required voltage (V). Adding an identical number of cells in parallel delivers more capacity and higher power (W).” Series wiring sets the voltage, and parallel wiring adds capacity. Two packs can therefore carry the same Ah rating at different voltages, and then the Ah numbers match while the stored energy does not. This is the reason a bigger Ah number is not enough to choose a pack across platforms. A label that prints only Ah leaves the voltage question open, and that is the first thing to check.

DeWalt’s footnote shows why the voltage basis matters within one maker’s label: “Maximum initial battery voltage (measured without a workload) is 20 volts. Nominal voltage is 18.” When a page gives both figures, use the one the maker ties to its Wh or run time claim, and say which one you used.

Mistakes to avoid

  • Reading Ah as energy. A 5.0Ah rating does not fix the energy in a pack. The EGO 5.0Ah pack is stated at 280 Wh, and the DeWalt 5.0Ah pack works out to 100 Wh at 20 volts.
  • Assuming a bigger Ah means a longer run time in every tool. EGO’s statement is about choosing a higher Ah rating for longer run times, and it is a manufacturer claim for its own tools.
  • Using the nominal voltage without saying so. DeWalt’s footnote gives 20 volts as maximum and 18 volts as nominal. The same 5.0Ah pack at 18 volts works out to 90 Wh, not 100 Wh.

What Ah does and does not tell you

EGO’s battery guide says that for even longer run times, you can choose a battery with a higher Ah rating than the one recommended. That is the clearest link between Ah and run time in the sources we opened. The same guide says that its chart “tells you which battery is best for your tool,” so the chart works as a guide to pack size for each tool, not as a run time table.

Run time still depends on the tool and the work. The sources we opened do not give a power draw for any mower, trimmer or blower, and the DeWalt 5Ah page does not state a run time in minutes. A higher Ah rating is a reason to look at a larger pack, but it is not a number you can turn into minutes by yourself.

EGO’s chart runs from a 2.5Ah rating to a 12.0Ah rating, and its Wh figures rise in step with the Ah numbers. The chart does not say how much longer a tool runs at each step, so read each step as more capacity, not as a set number of minutes.

For voltage first, read lawn mower battery voltage and amps. For how voltage ratings appear across lawn and garden tools, read lawn and garden battery voltage. For the voltage labels on mower packs specifically, see what voltage a lawn mower battery is.

How we chose

We opened the pages we cite and chose them for three jobs. EGO’s battery chart and 7.5Ah page give the Ah ratings and the energy figures that appear next to them. DeWalt’s 5Ah and 12Ah pages give the Ah ratings and voltage footnotes for two DeWalt packs. EPA, OSHA and DeWalt’s safety article supply the storage and damage points. We did not use retail listings, review sites or blogs. The pages were opened on 2026-10-22. The sources were read as written and are not ranked against each other.

What we could not verify

The pages we opened do not state whether EGO’s 56V figure is a nominal or a maximum voltage, so the energy figures for EGO packs carry that open question. The 100 Wh figure for the DeWalt 5.0Ah pack is a calculation and does not appear on DeWalt’s page. We could not find a run time in minutes for the DeWalt pack, so no run time for that pack appears in this guide. The sources we opened do not include a plain definition of amp-hours from a standards body, so this guide relies on how the makers use the term.

What the sources do not say

  • The sources we opened do not define amp-hours as a unit of electric charge. This guide uses Ah only as the capacity rating printed on each pack.
  • The sources do not state how Ah affects charging time on a given charger.
  • The sources do not give a run time formula that uses Ah alone, so no run time is calculated from Ah in this guide.

FAQ

What does Ah mean on a battery?

Ah means amp-hours. It is the capacity rating a maker prints on the pack. EGO’s 7.5Ah pack carries the printed figure “Amp Hours: 7.5 Ah,” and EGO’s formula calls the same figure “Capacity (Ah).”

Ah tells you the capacity rating. It does not tell you the stored energy on its own, because that also depends on the voltage.

Is a higher Ah always a longer run time?

Not by itself. EGO says that choosing a higher Ah rating gives longer run times, which is a manufacturer statement about choosing a pack. Run time still depends on the tool, the work and the power the tool draws. The sources we opened do not give a formula that turns Ah into minutes.

Does Ah tell me how much power a battery has?

No. Power is measured in watts, and EGO’s page says power is voltage times current. Ah is a capacity rating, so it does not give power on its own. If you need stored energy, multiply the voltage by the Ah rating.

Can I compare Ah ratings across brands?

Only when the voltage basis matches or when each maker prints the energy figure. The EGO 5.0Ah pack is stated at 280 Wh, while a 5.0Ah DeWalt 20V MAX pack works out to 100 Wh at 20 volts. The same Ah number can mean very different energy, so compare the Wh figures with their voltage basis.

How do I turn Ah into Wh?

Take the voltage and multiply it by the Ah rating. For a 56V, 5.0Ah pack, 56 x 5.0 = 280 Wh, which matches the figure in EGO’s chart. For a 20V, 5.0Ah pack, 20 x 5.0 = 100 Wh, which is a calculation on DeWalt’s voltage figure.

Does a higher Ah pack need a different charging routine?

The sources we opened do not say whether a larger Ah pack charges more slowly on the same charger. EGO gives an optimum charging temperature of 32°F to 104°F (0°C to 40°C), and DeWalt advises a cool, dry place to store and charge its packs.

Bottom line

Use Ah to compare two packs only when their voltage basis matches. When the voltages differ, multiply each voltage by its Ah rating and compare the watt-hour results, and treat any figure you calculate yourself as your own number.

Sources

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