extension cable?

The longest extension cable I can find is 50m. Dependent on make and spec, expect to pay about £50-100. You could 'roll your own' to get the length but buying a 100m reel of suitably rated cable, plus a plug and trailing socket, would be over £60, plus you'd need something to wind it onto, as 7 or 8 kg of cable is a pain to lug around.

Assuming your hedge isn't too huge, just far away, a cheap cordless trimmer would be a lot less faff. Maybe a few birthday pressie hints?

There's nothing like a nicely trimmed bush.
June 2020

I'm a pensioner too. The 'how to work it out' bit I posted is just sums. The techie bit us all taken care of.

Did that help?
June 2020

Thanks all, but my knowledge of Electrics are I know it hurts and can kill if I touch the red/brown conductor.
Battery ones are out I can't afford them on State pension. I am now exercising to return to manual units. Shears, broom, collection bag and third had scoop's I have the barrow and sheers, got to get new broom
Thanks again and stay safe.

bobuk
June 2020

Yeah, it'll be fine.
Try to find a 60m extension reel rather than joining two shorter ones together. Also remember that you get a petrol trimmer for less than £100 which will be a lot less bother than worrying about breaking Ohm's Law ;-)

Rupert
June 2020

Why not answer your own question by going back to basic physics that you should have covered in 4th or 5th form.

Assume your trimmer is rated at 500 Watts. At 240 Volts, that's 500/240 = about 2.08 Amps.

What voltage drop will be caused by the cable?

Let's assume you've chosen a weedy mains extension cable and that it has a conductor of - say - 0.75 sq mm

A quick Internet search suggests a resistance for 0.75 sq mm copper cable of 26 Ohms per 1000 m ( FYI, a 0.5 sq mm cable has a resistance of 40 Ohms per 1000m)

Your cable proposed is 58m, which is two conductors of 58m, or a total length of 116m. Call it 100 m.
.
Resistance is therefore 116 * 26/1000 = 3.01 Ohms

Voltage drop is current X resistance, so 2.08 A X 3.01 Ohms gives a voltage drop of 6.26 Volts. Scarcely worth getting out of bed for.

Power dissipation in the cable is Volts X Amps (or Current squared X resistance). So 2.08 A X 6.26 Volts = 13.02 Watts.

Think how warm a 15 Watt light bulb can get and you'll understand why makers of extension leads warn you not to leave them tightly coiled. Unwrapping the cable gives the heat a chance to dissipate.

If your trimmer is rated at 750 watts, just increase the volt drop and power dissipation by 50% (Or do the sums for fun)

Did that help?
May 2020

Unlikely. However, before splashing out on decent heavy duty extension cable, an earth leagage protected plug, would a cordless trimmer and a couple of batteries be a lot more convenient?

Dr hiiyfc
May 2020