12 Volt or 24 Volt?

[T1 Terry]

What wiring would you need to upgrade if you changed from 24v to 12v for the house power?
There are so many myths and untruths floating around regarding the advantages of MPPT over PWM solar control it's not hard to get mislead but from genuine hands on testing by myself and a number of other people who also have a good electrical/battery background the myth has been well and truly busted, MPPT can not deliver better than a well set up PWM system and often ends up behind in the output stakes over the full days charging. The theory is wonderful but the results show a few factors have been left out from the theoretical equations and others are simply blind to the real maximum current/voltage of a panel in full sun, it is no where near the figure published on the back of the panel.
Solar wiring, wire it right the first time and never have to think about it in the future, there are no short cuts when it comes to adequate sized cabling so spend the $$ and do it right once, it is far cheaper than the alternative.

T1 Terry

[Kappy]

What wiring would you need to upgrade if you changed from 24 volt to 12 volt for the house power?

T1 Terry

I either misunderstood when it was suggested that I needed to upgrade my wiring when going from 24 volt to 12 volt,I will certainly spend the $$$ on wiring from panels to controllers, batteries, inverter, thought I needed to upgrade house wiring that already is running 12 volt.

Think that's clear.

Now I believe to run 14 x 12 volt 100 watt panels in parallel, I need 2 controllers to handle the VOC that is around 294 volts and approx 84 amps.

I hear I need at least one if not two MPPT controllers so I'm confused again MPPT or PWM.

What do you use if you generate this much power.

I welcome non confusing opinions

Cheers
Kappy

[Wilbor]

I have already posted what I use but maybe you didn't read it

I have 1050 watts of solar in series.
Comes down off the roof a about 140v and about 8 amps
A Midnight Classic 200 MPPT controller turns it into 12v and 60+ amps

The big advantage of running the solar in series is you don't need battery cables to come down off the roof

[Busman]

I think if they were parallel that the total would be 12 volts ?
In series they add up, not in parallel.
We run 15 x 200 watt 24 volt panels in parallel and use pwm solar regs to control the input, works fine for us, 24 volts and 100+ amps.

[jon_d]

Rob,

When (time) does the controller start working and stop. I'm finalising a similar set up and am reckoning (yet to be proved) that the panels /controller set up will give better performance in shady conditions and start earlier in the day and finish later in the evening.


Your the first person that I've read about that has a similar idea.

Mine is 2 strings of 650W at about 130Volts. They are being wired in this week end.

JD

[Wilbor]

Rob,

When (time) does the controller start working and stop. I'm finalising a similar set up and am reckoning (yet to be proved) that the panels /controller set up will give better performance in shady conditions and start earlier in the day and finish later in the evening.


Your the first person that I've read about that has a similar idea.

Mine is 2 strings of 650W at about 130Volts. They are being wired in this week end.

JD

Jon, comes on before I wake up basically on not long after sunrise and at 0800 (in tassie) we have about 20 amps. Works through till about 1930hrs. Sunset is about 2030 now.. on a cloudy day we still get to 100%, rain is a different story though. As we speak we are in cloud and I am getting 15 amps in absorb

[jon_d]

yes and would would be the panel voltage?

Obviously they wouldn't be at full voltage???

[Wilbor]

Not overly sure of panel voltage at start and end of day. At the moment (1540hrs) tassie time, panels are 118v, 140watts, 10.6 amps 12v

[Wilbor]

Jon, I was trying to keep a record of what it is doing near sunset but we are having "thunderstorm" issues at the moment, 1855hrs, and while I have 109v I have no watts. At 1740 in sun it was 123v, 209 watts, 15.5 amps at 12v

[BruceS]

If the battery is fully charged you'll have max volts & no watts.
If the battery is half flat you'll have 12 (24) volts or so & lots of watts.
(especially if you have LiFePO4 batteries.)