4x4 Action Group

It’s not the inverter that is not efficient, although there is some losses when you convert from DC to AC.

AC en general has less power than DC due to the shape of the sinewave (I need my crayons again!)

I’ll try and explain without the crayons AC oscillates between 220V and -220V 50 times a second, this transition is not like an on off switch, but in the form of a sine wave, if we look at the area under the sinewave, it is roughly 80% and hence the reason why we need a conversion factor of 80%




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Quack wrote: ↑

Thu Jun 13, 2019 10:59 am

It’s not the inverter that is not efficient, although there is some losses when you convert from DC to AC.

AC en general has less power than DC due to the shape of the sinewave (I need my crayons again!)

I’ll try and explain without the crayons AC oscillates between 220V and -220V 50 times a second, this transition is not like an on off switch, but in the form of a sine wave, if we look at the area under the sinewave, it is roughly 80% and hence the reason why we need a conversion factor of 80%




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Losses in the inverter are due to inefficiencies of the conversion process. Taking the 12V, switching it at high frequency into a step-up transformer is where most of the losses are incurred. The higher the frequency of this switching, the lower your losses will be but you have to keep in mind the load at which you would like to run. Transformers have to be big enough to handle the power but still cope with the frequency. That is where inverter efficiency is found. This is for a pure sinewave. Filtering the signal is required to make it a decent 50Hz sinewave but that happens on the control side (low voltage) of the inverter.

Modified sign does things a bit different and is cheaper.

so dc call on battery is about 20% more than appliance load ?

Ok, so now that the winter camping weekend is over...

The 1500w Pure Sine Wave inverter ran 2 x electric blankets with ease.
The single blanket only has 2 temperature settings, so it ran on high fo 10 - 15 mins before bedtime.
The double blanket has 3 settings, we ran this on 2 as that's plenty warm enough to make jumping into bed comfy.

SWAMBO & offspring were very happy, the inverter didn't even work hard enough to require the 2 cooling fans to turn on even with both blankets on at the same time.

Avon had a cheapie 350w modified sine wave inverter in his camp trailer setup, and as soon as he turned his electric blanket on the fans stepped up to full speed, but he too had a very toasty bed with the electric blanket set on 3/max.

We both have the same 110w solar panels and both ran 2 fridges, Avon only on 1 120ah gel battery, me on 2 x 102ah high cycle batteries, by the end of the day our batteries were back on 100%. So our setup seems to be running flawlessly for an offgrid winter camp.

i would like to see how the panels/battery setup would cope in high summer when the fridges have to work much harder due to high ambient temps.

i would like to see how the panels/battery setup would cope in high summer when the fridges have to work much harder due to high ambient temps.


To simulate summer conditions, just wrap your fridge in the electric blanket and turn everything on max.

AndreasR wrote: ↑

Tue Jun 18, 2019 9:53 am

i would like to see how the panels/battery setup would cope in high summer when the fridges have to work much harder due to high ambient temps.

I agree, I better book a camping trip to Kosi Bay or Kruger for Dec/Jan.

AndreasR wrote: ↑

Tue Jun 18, 2019 9:53 am

To simulate summer conditions, just wrap your fridge in the electric blanket and turn everything on max.

But surely that will restrict air movement around the fridges vents? Otherwise not a bad plan.