Your opinion on my lighting (MR16 12V vs GU10 220V)

[Forhorse]

Why are you talking about an 20 factor?

P = U x I
if you go from 230V to 12V, for the same power the current is 20 times bigger
For 10W it does not play so much, for 100W it's already different.

The photovoltaic production is continuous, as the batteries: switch to 230V then back to 12V, it's an excursion with a lot of losses and expensive hardware to power 100 or 200W.

Yes but that's not in the initial post.
And then at the level of the losses that is calculated.

Take the extreme 200W lighting 12V case, enjoy calculating the necessary cable section between the batteries and the point of use to keep a valid voltage arrived at the lamp (normatively one tolerates 2 to 3% of fall of voltage)
Compare the price this cable (and the difficulties to ask it in view of its size) to that of a beast 12V / 230V 200W converter
Finally, evaluate the losses between the efficiency of the converter and the losses due to the joule effect in the cable.

In the end I am not convinced that it is always to the advantage of an installation in 12V.
I confess I did not do the math and I could be wrong, but my intution tells me that I am not far from the truth.
Have fun doing these calculations and show us that I'm wrong.

[bernardd]

I just counted 20 bulbs of 20W (equivalent 100W filament) on 4 starts: 5 bulbs / start on average, or 100W electrical, not all lit at the same time.

So not really worry with a normal pair on 10m long ...

100W for 230V is 0,43A or IxI = 0,18
100W for 12V is 8,3A or IxI = 69
100W for 24V is 4,2A or IxI = 17,36

Actually you were referring to this factor 20 on the current, but it is 383 for the square of the current, and it is 100 for 24V.

It is clear that the loss by Joule effect is much more important.

Starting on R = 0,017 x L / S with L = 10m and for an extion of 2,5mm2 S = Pix1,25x1,25 = 4,9mm2, let R = 0,83Ohm, the losses become:
100W for 230V is 0,43A or IxI = 0,18 and P = 0,15W
100W for 12V is 8,3A or IxI = 69 and P = 57W
100W for 24V is 4,2A or IxI = 17,36 and P = 14,47W

You're right, putting 12V in distribution, even for lighting only, it's not at all interesting.

The worst thing is that I refused to put the output of a wind turbine at low continuous voltage for this reason, because the losses in 1000W seemed really too big. I wanted a high voltage at the natural variable frequency, so I could also measure the speed from a distance :-)

But I did not do the math for the house: thank you!

[elephant]

That's why we put more and more small transformers in the ceiling: 1 for 50 W or 1 for 3 X20 or 3 X 35

Only large cable or rail systems or chandeliers involve large 300 watts processors. One of the biggest source of boredom in BT is heating up at the junctions: sometimes it's a mess. On a line of 10 spots, if certain precautions have not been taken, we clearly see the difference in luminous intensity between the first and the last of the line. Let's not forget that 300 VA / 12 V = 25 Amperes: it takes at least 6mm² to minimize losses.

[Flocomotive]

I read carefully all your answers, thank you!

First, concerning the bathroom, I only want to change existing spots, knowing that the electrical diagnosis of housing has not revealed anything bad. I imagine they are where they can be. Do you still recommend staying in 12V there?

Then, for info, I do not plan to produce my electricity even in the long term.

On the other hand, luxmeter in support, one is at -50% flux after one year with ultra compact. Larger ones keep their flow longer.

What do you mean by ultra-compact?

I did some shopping. I bought a 15W multidel bulb (3 dels) in E27 230V AC for a bedside lamp. The amount of light is very satisfactory and the light is warm enough (3000 ° K). The store offered the same model in MR16 12V, with specified AC / DC. So I bought one to test, and it looks pretty good. It's a little less light than halogen bulbs 35W (which is normal), I'll see in the long run. In any case, it does not seem to be a problem for the transformer.

But I still wonder if I have to switch to GU10 220V. The bulbs cost the same price ... After your remarks, I tell myself that it is easier to do without transformer.

FYI, I bought his bulbs between 6 and 7 €, at a hard-discounter (at which I often buy without being disappointed by the quality). It is a very good price if they are good, but I keep the receipt!

Thank you

Flocomotive