12v VS 24v panels

[SternWake]

A MPPT charge controller is nothing but a DC to DC voltage transformer with some built in logic control, but I will not derail this thread further as requested.  I've Got nothing more to add on this transformer topic anyway.  

Back to 12vs24v solar

 

[akrvbob]

So we need a new thread for Transformers?

Do you see anything in the title or Original Post about transformers for laptops?

Transformers for anything but solar charge  controllers need there own thread.
Bob

 

[Reverse Engineer]

Do you see anything in the title or Original Post about transformers for laptops?

Transformers for anything but solar charge  controllers need there own thread.
Bob

OK.  I don't have anything further to add on the transformer topic at this time, but if somebody starts a thread on the topic I will contribute to it.

 

[jimindenver]

Jimin Denver.18 amps out of a panel rated for 8 amps?Boy howdy these mppt controllers can even defy the laws of physics.Please don't pile the bs quite so high.

Bob

Do you really think I would have anything to gain by misleading anyone?

But you got me, my numbers are off. The actual Isc of my 250w Navajo Poly panes is 8.37a, it's the Imp that is 8.02a. Being that I an at high altitude the realistic amps are a bit above 10a. I can't tell you exactly because it blows my cheap HF multimeters.  ( Isc= short circuit, Imp= working amps)

The actual peak I have seen tracking is 18.5a at around 12v while running the little A/C

Now that has little to do with what is the output of my system. The three panels wired in series have the very same Isc/Imp as just one panel. Set those babies up and track the sun, they are good for around 50 +/-. I see 40-48 amp while flat. The Isc/ Imp is still low so I must really be piling it on now huh. The truth is in MPPT the Isc matter little. it's the voltage that counts and the voltage of my array in series is over 100v. the voltage of just one panel is 37.74v and in either case it's the MPPT controller that does what seems impossible.

A MPPT controller converts the higher DC voltage of the panel to AC and then back to DC again. It does this with what's called a buck converter. By converting it back and forth from DC to AC and then DC again it allows the MPPT program to convert the voltage and amps to what ever it decides is the best way to raise the voltage of the bank. The voltage and current is sent to get this, a PWM charger that sends it to the bank.

so the gain from a 12v panel is limited unless you run them in series, 24v panels have the excess voltage to do it on their own.

Now if you are still thinking I am pulling your leg, the nice thing about the Morningstar TS-MPPT-60 is it makes extremely detailed logs if I chose to do so. If one of the many that I have from series vs Parallel test, mismatched panel test or just running the AC for 5 or 6 hours won't do it for you, I'll make one just for ya as soon as I get caught up a bit. The 250s are in the rig but I have a 230w and 220w here at the house still.

One last thing. 18.5a is not the true potential of the 250w panels. My testing this summer was always flat as they will be mounted. My 230w saw a increase from the altitude 15a to 16.24 amp. My 220w saw a 3/4 amp increase from being in freezing cold weather. Get the 250s cold and tracking at 10.000 ft and I bet they could get close to maxing out the controllers.

 

[Canine]

As the old saying goes"If you can't dazzle em with brilliance.....Well you know the rest.

 

[jimindenver]

you win Bob

 

[wagoneer]

Call me a simpleton but when I installed my solar many moons ago I got the biggest and cheapest leftover panel 2 x 6 volt AGM and a MPPT. Done.
I have no idea what the panel puts out and don't really care. It works (until it stops working). No shunts no fuses no fancy wiring just a power source and a place to store it. I used the largest gauge wire I could.

 

[Reverse Engineer]

Call me a simpleton but when I installed my solar many moons ago I got the biggest and cheapest leftover panel 2 x 6 volt AGM and a MPPT. Done.
I have no idea what the panel puts out and don't really care. It works (until it stops working). No shunts no fuses no fancy wiring just a power source and a place to store it. I used the largest gauge wire I could.

KISS Principle is usually best.

 

[Optimistic Paranoid]

Call me a simpleton but when I installed my solar many moons ago I got the biggest and cheapest leftover panel 2 x 6 volt AGM and a MPPT. Done.
I have no idea what the panel puts out and don't really care. It works (until it stops working). No shunts  no fuses no fancy wiring just a power source and a place to store it. I used the largest gauge wire I could.

While I generally agree that the KISS principle is a good one, I also agree with the electrical engineers #1 rule of thumb:

Any unfused circuit is just a fire waiting to happen!

Regards
John

 

[akrvbob]

While MPPT is not magic, it is very, very smart.

When it steps DOWN the voltage of a 36 volt panel three times to 12 volt, it also steps UP the amperage and triples the amperage. It does appear to be magic, but it's simply Ohms law meeting some great electrical engineering.

When a PWM controller steps down voltage, it isn't able to increase the amperage, so all the amperage is simply flushed down the toilet.

Yes it's a crime but smart things cost more money and some people don't want to spend the money.
Bob

 

[Reverse Engineer]

Yes it's a crime but smart things cost more money and some people don't want to spend the money.
Bob

Some people don't have the money to spend.