Hi @Charles Kemp
Thank you for raising this with us.
Over time the machine will naturally lose its run time but the level of degradation over the years is very small - You can read more on battery degradation on one of our members post here (Understanding Battery Degradation | Dyson Community).
Battery degradation is not a fault of the machine. It happens to all batteries in everyday items, such as mobile phones and laptops.
I do suggest that you contact the Dyson customer service team to follow a few troubleshooting steps and they will provide you with the best possible solution.
Just a reminder that all parts purchased on the Dyson website or through the customer service team comes with a 12 month warranty and a 14 day return policy.
If you require any further assistance please do not hesitate to reply below.
Regards,