> For the complete documentation index, see [llms.txt](https://docs.spectralink.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.spectralink.net/amie-advanced/metrics-reference/battery-capacity.md).

# Battery capacity

How much charge a battery can hold when full, compared with what it held when new. It is the figure behind every **Health** value in the product, and it is the measure that tells you whether a battery should be replaced.

## What the battery measures

Every Spectralink Versity battery contains a small circuit called a fuel gauge. It watches the battery's voltage, the current flowing in and out, and its temperature, and uses the known behavior of the battery's chemistry to work out two things: how full the battery is right now, and how much it can hold when full. AMIE reports the second of these as capacity.

A Spectralink Versity battery holds 3020 mAh when new, and that is the figure every health percentage is measured against. Capacity falls as the battery is used, so the same battery at 80% health holds roughly 2400 mAh. Charging it fully still shows 100% charge on the handset, because charge is measured against what the battery can hold today, not against what it held when new. A worn battery therefore reaches 100% sooner and runs down sooner. This is how every rechargeable battery behaves, in a phone, a laptop or a car. What AMIE adds is the ability to see how far the decline has gone on each battery in your fleet, before someone is left without power mid-shift.

The fuel gauge is good and its readings settle down over the battery's life, but they are still estimates. Two things in particular move them:

* **Temperature.** A hot or cold battery reports a different capacity from the same battery at room temperature.
* **Long spells in a charger.** A battery that sits fully charged for a long time without being used gives the gauge nothing to measure, and its reading can drift until the battery is next discharged.

AMIE averages the readings it receives to smooth out this variation, so the figure you see moves less than the raw readings do. Even so, expect a battery's capacity to shift by a few percentage points from one report to the next, and treat it as a guide rather than a precise measurement.

## How the product shows it

**Health** is the capacity as a percentage of the capacity when new, placed in one of three bands: **Good** at 80% or more, **Warning** from 65% up to 80%, **Replace** under 65%. A battery that has never reported a capacity reading is **Unknown**. The band is decided on the exact figure while the percentage is shown rounded, so a battery at 79.6% is banded **Warning** and its percentage reads **80%**. See [Battery Health Distribution](/amie-advanced/metrics-reference/battery-health-distribution.md) for how the bands are counted.

On [Battery details](/amie-advanced/using-the-platform/battery-details.md), **Health (Full Charge Capacity)** adds the capacity in milliamp hours (mAh). That figure comes from what the battery reports holding when full. Where the report is missing, or does not agree with the health percentage, AMIE works the figure out from the health percentage instead. The screen does not say which of the two you are looking at, so read the percentage rather than the mAh figure when deciding about one battery.

## Capacity is not charge

Capacity is how much the battery *can* hold; charge is how much it holds *now*. **Charge Level**, **Charge** and the **Battery** label on [Device details](/amie-advanced/using-the-platform/device-details.md) are charge. A worn battery at 100% charge is still worn: it reads **Replace** under **Health** and **100%** under **Charge** at the same time, and it will run down faster than a healthy battery charged to the same level.

## Edge cases

* **A reading that goes up.** Capacity is an estimate and can rise a little after a full discharge and recharge. A rise of a few points is normal; it does not mean the battery recovered.
* **A battery at exactly a boundary.** 80% is **Good**; 65% is **Warning**; 64.9% is **Replace**.
* **Unknown.** The battery has never reported a capacity reading. It is counted under **Total Managed** on the [Batteries overview](/amie-advanced/using-the-platform/batteries-overview.md) but in no health band.
* **Third-party batteries.** Batteries not made by Spectralink may report inaccurate readings or none at all, and may share a serial number with another battery. AMIE does not support them.

## Where you'll see it

* [Battery details](/amie-advanced/using-the-platform/battery-details.md) — **Health (Full Charge Capacity)**
* [Batteries inventory](/amie-advanced/using-the-platform/batteries-inventory.md) — the **Health** column
* [Batteries overview](/amie-advanced/using-the-platform/batteries-overview.md) — **Health Distribution** and **Replace Now**
* [Dashboard](/amie-advanced/using-the-platform/dashboard.md) — **Battery Health Distribution**

## Related metrics

* [Battery Health Distribution](/amie-advanced/metrics-reference/battery-health-distribution.md): how the bands are counted across a fleet
* [Cycle count](/amie-advanced/metrics-reference/cycle-count.md): how much work the battery has done, which is what wears capacity down


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