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# Charging

## Safety

Use only [Freefly SL8 Fast Chargers](https://store.freeflysystems.com/collections/astro/products/sl8-fast-charger).

Make sure someone is nearby while batteries are charging. Do not charge batteries unattended. Place the batteries in a fireproof container for charging and storage.

DO NOT charge the battery above 4.2 volts per cell. DO NOT exceed 1.5C charge rate.

## Charging Time

SL8-Air batteries charge from empty in about 90 minutes.

Firmware v1.9 gives a conservative charging time estimate. Actual charging times can be faster than the time shown on the display.

![](https://firebasestorage.googleapis.com/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LaNHxABbg20hfA0zTDQ%2Fuploads%2FdAf3A8KrKwgq23mXvxPQ%2Ffile.png?alt=media)

## Temperature

The charging temperature range is 0 to 50 C°.

* If a charger is connected while the battery is too hot or cold to charge, the battery will not charge and an error message will be displayed. If the charger remains connected to the battery, charging will begin automatically when the battery cools/warms sufficiently.
* In cold environments: If charging begins while the pack is above 0 C°, the heat of charging can be sufficient to keep the pack warm enough to charge even if the ambient temperature is lower.
* In hot environments: Charging will stop when cells get to 50 C° and restart charging automatically at 45 C°.


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