Hello Ssoo,
Thanks for sharing your experience. Runtime that short is definitely frustrating, especially with a combo kit like this. For the 48V (24V x2) 17" mower in model CK24L4222, the mower relies on both 24V batteries working together, so performance can drop quickly if one battery is undercharged, out of balance, or not fully seated. A few things to check: make sure both 4.0Ah batteries are fully charged, cooled, and inserted securely before use, as the system will only perform as well as the weaker battery. If the grass is thick, wet, or overgrown, that can significantly increase power draw, try raising the deck height for the first pass and lowering it gradually to reduce load. Also, avoid running at maximum load continuously and check that the blade is sharp and the underside of the deck is clean, since buildup can reduce efficiency and shorten runtime. It can also help to rotate the batteries between tools and note if one drains faster than the other, which may indicate a battery imbalance. If you are consistently getting under 15 minutes in normal, dry mowing conditions after these steps, there may be an issue with one of the batteries, and reaching out to support would be the best next step for further evaluation. They can be reached either using the online chat function, on Greenworks Tools page, or by calling 1-888-909-6757.