Why do some batteries say 18V and others 20V?

They are the same class of battery, measured at two different moments. Five lithium cells in series read about 20V fresh off the charger with nothing drawing from them, and settle to about 18V once a tool is running. A brand that prints 20V is quoting the first figure and one that prints 18V is quoting the second. That is why an adapter between an "18V" platform and a "20V" platform works: there is no conversion to do.

How do I find the right adapter on this page?

Use the selector at the top: pick the platform on the other side of the pair and it takes you straight to the one adapter that joins them. Every combination in that list is one we actually make, so if it is there, it exists.

Can I go the other way round — run AEG 18V tools from another brand’s battery?

Yes. Use the swap button next to the selector above and the page turns the search around, from AEG 18V tools back to the batteries that can run them.

Can I charge a AEG 18V battery through the adapter?

No. The adapter carries current from the battery to the tool and does nothing else — there is no charging circuit inside it. Keep charging AEG 18V batteries on their usual AEG charger.

Will an adapter damage my AEG 18V battery or my tool?

Used with undamaged, compatible equipment it is not expected to. AEG 18V batteries are lithium-ion with their own protection circuit built into the battery, and it keeps doing its job through the adapter. Stop when the tool noticeably slows rather than running the battery flat, and stop using the adapter if it becomes unusually hot or the contacts look damaged.

Does it work with third-party AEG batteries?

Usually. What matters is the socket, not the badge: if the battery slides onto a AEG 18V tool and locks the way an original does, the adapter will take it. Aftermarket batteries do vary in moulding, so if yours looks unusual send us a photo and we will check before you order.