I have a Ford activ Fiesta and so far haven't noticed any difference in performance or  anything different from my old car. How do I tell when it's charging and when it is actually running on battery instead of fuel?

That don’t run just on battery, it’s not that kind of hybrid.

It's only a mild hybrid, not a full hybrid like a Toyota Yaris for example, so never runs on the battery alone. The battery stores energy through regenerative braking etc, and uses it to help the petrol motor along in certain situations, particularly at low speed when it boosts torque.

There are some informative diagrammatic videos showing how the system operates on the Ford website.

https://www.ford.co.uk/shop/research/hybrid-electric/mild-hybrid#overlay/content/overlays/hybrid-electric/focus-mhev

 

You should be able to see which way the energy is flowing from your instrument display as per the online handbook eg:

Hybrid Gauge

1. Using the information display controls on the steering wheel, select MyView.

1. Select Hybrid Gauge.

Note:   If you select any other screen than the hybrid gauge then the current status indicator of the hybrid system appears in the information display.

Illuminates in the information display when the mild hybrid system is charging the battery.

Illuminates in the information display when the battery is assisting the powertrain in driving the vehicle.

Illuminates in the information display when the battery is providing a large amount of energy to the powertrain to support a higher rate of acceleration.

Illuminates in the information display when the mild hybrid system cannot provide energy to the powertrain.

Thanks so much for the info Roger.