Comment by bluGill

Fortunately you can get adapters to take 18/20 volt batteries to any other (18 and 20 volt rechargeable are the same cells, but they measure the voltage differently). Likewise most 12v systems have adapters.

There are two issues: some manufactures put more smarts in the battery than others. So never run the battery completely dead which some combinations allow. Never charge the battery with other than the OEM charger.

Don't buy the off-brand batteries (which sometimes are counterfeit that look like the real thing) since they sometimes are not safe.