Hello, it’s recommended to use a 22650 battery with a continuous discharge current of 15A, which can maximum the performances of ODL20C.
A battery with 10A discharge current is also usable.
Battery brands with well-reputation should be the first choice.
For safety concern, we strongly recommended using the protected cell to avoid potential reverse polarity connection.
If a reverse connection with unprotective 26650 cells, it will result in a damage ODL20C.
Hope that can help, thanks.