Power loss is proportional to the square of current.
Off-grid shed question...
- Thread starter JTC
- Start date
Power loss is proportional to the square of current.
You're not considering power. Low-voltage loads must draw more current for the same power, and this high current exacerbates the effect of cable resitance.
A 60 Watt load draws 5 amps at 12 V. That 5 amps through cable resistance of 0.2 ohms = 1 Volt. 12 V - 1 volt = 11 volts. A loss of 8%
Raise the supply voltage. Now a 60 W load draws 0.25 A at 240 V. That 0.25 A through 0.2 ohms creates a drop of 0.05 Volts, which is negligible.
Ohm's Law still applies at any voltage, but you have to consider the full picture.
(and I wish AC was the same as DC, because then I'd never have had to learn phasor analysis...)
Errrrrrrrrrrrr - most of that covered above. Posts 10, 15 and 16.
You really have very, very little clue what you are talking about. Just as well it is just 12V.
Maybe read above, where I covered that? Just a suggestion.
Albeit irrelevant here as tthe suggestion is/was that 12VAC and 12VDC obey Ohm's Law differently.
You're making rather hard work of this, a typical inverter in the context above not only converts the DC to AC but also 12 V to 240V.
To the OP - you need to keep your 230Vac totally separate from your 12V solar panel and lighting bit. Earthing your 12V is at best pointless and at worst potentially dangerous if you start mixing them up via a wiring problem.
So keep your 230Vac as is. Treat your 12V dc as you do if you put your car in the garage. Do you earth it? No. It has its own standalone 12V electrical supply- and battery, so you run that as you see fit and the fixed wiring in the garage has nothing to do with it.
So keep your 230Vac as is. Treat your 12V dc as you do if you put your car in the garage. Do you earth it? No. It has its own standalone 12V electrical supply- and battery, so you run that as you see fit and the fixed wiring in the garage has nothing to do with it.
Sue Pertwee-Tyr
Accuphase all the way down
No, he isn't. AS he, and you both said, that 12V would lose around 1 Volt over a 5m length of cable. That's >8%. It's significant, in the scheme of a 12V system.
You're doing that thing you do, again, of assuming nobody but you has a scooby about anything.
Come come Sue, everybody here knows that Vinny is the only person on here with a science or engineering qualification, and that only he knows the answer to anything with any remotely scientific context.
I will say again - actually READ what is posted, do not make it up as you go along.
The statement was made that AC is better than DC becaiuse DC voltage drops. That is total horse droppings, no more, no less.
READ EVERYTHING, not selected twadddle.
Sue Pertwee-Tyr
Accuphase all the way down
That wasn't the statement that was made. The statement about AC was that the OP might be better off using an AC inverter off their 12V battery. No mention of voltage. You just assumed 12VAC rather than DC, so you're not immune to inferring rather than reading what is written, yourself.
My exact words were "12V DC doesn't travel far", and that's true as soon as you draw any kind of current.
You're the only person who made the decision to assume that when I said to consider AC via an inverter I was referring to creating 12V AC, rather than using the kind of 230 V AC inverter you can buy for any 12 V battery at Halfords.
Had I meant 12 V AC I would have said so, because it's such an unusual thing to produce from a 12V battery.
You had two possible interpretations of my use of the term "AC": 230 V, as previously mentioned by the OP and thus part of the discussion context... or 12 V, something boneheaded, unusual and not mentioned before.
You decided on the unlikelier option and chose to have a snark at me on the basis of that wrong interpretation, rather than reply with a civil "12V AC would be just as bad for voltage drops, you know", after which I would have clarified, and we'd be still having a civil discussion. Why you went for that unlikely reading, I have no idea, but doubling down on the insults when it became clear that it was a misunderstanding on your part was pathetic. How hard is it to say "my mistake" and proceed?
The upshot is that you've wasted my time and yours, and the only output of it is that now I think you're an asshole, despite lots of previous evidence to the contrary.
JTC
PFM Villager...
Yep, typical PFM flame war 
But, to wrap this up, I'll just leave it as a separate install, since it'll be driving tiny loads for efficient LED bulbs on a timer (external) or switched (internal). 200w panel, 110Ah LB (albeit a bit tired, but will replace with a better battery when it finally dies) and the CTEK DCC/MPPT charger (won't need the DCC part, it's designed for vehicular use but will work fine for my porpoises....
But, to wrap this up, I'll just leave it as a separate install, since it'll be driving tiny loads for efficient LED bulbs on a timer (external) or switched (internal). 200w panel, 110Ah LB (albeit a bit tired, but will replace with a better battery when it finally dies) and the CTEK DC
C/MPPT charger (won't need the DCC part, it's designed for vehicular use but will work fine for my porpoises....
Beobloke
pfm Member
The voltage has a great deal to do with it.
It's why, at work, we can get away with sending 600V down a 500m cable to obtain 500V at the other end, but when we're using a 3km cable, we start with 3000V.