Energy and power explained, Energy and Power Explained – Updated 2019

Some batteries are promoted as producing massive power. They may well do but in most stand-alone systems it’s energy, not power, that matters. Here’s why and how you can save a lot of money by doing this.

Energy enables work to be done: here electrically. The energy needed to start a 4WD is tiny: about that drawn by a five watt LED for an hour. Were it otherwise it would have been impossible to start an engine by manually turning a handle. That it was shown below. 

Energy and power explained, Energy and Power Explained – Updated 2019

Pic: reproduced here by courtesy of the Henry Ford Museum (copyright Henry Ford Museum). 

In the author’s younger days he had a 51 kg girl-friend who could readily hand-start his vintage four-cylinder four-litre Bentley. She could (and did) replace that energy with a single gin and tonic.

Power is a measure of how quickly energy is used.

Weightlifter Svetlana Podobedova (pictured at the top of the page) readily lifts a 160 kg barbell two metres high. In doing so she exerts a great deal of power. A young child, however, can over time, readily lift 160 1 kg cans two metres high. That child needs little power but (over time) uses exactly the same amount of energy.

LiFePO4 batteries are the Svetlanas of the solar world. Lead acids and AGMs are the equivalents of young children. Costly batteries can release a great deal more power but, unless you truly need it, buying them is like hiring a weightlifter to stack those cans. If lead acid (and even more so AGM) battery bank exceeds about 350 amps at 12 volts (4200 watts) it can release powers like Svetlana anyway.

Knowing this difference can save you thousands of dollars!

Our books: Solar That Really Works cover cabins and RVs. Solar Success covers homes and properties. The associated Caravan & Motorhome Electrics covers every aspect of RVs in depth.