Panel voltage vs battery voltage.

[Sunking]

I thought AMPS were what I need to charge the batteries and voltage was the driver to get the AMPS there" it is not clear because change voltage only reduces resistance lost in the wire.

Then you do not understand fundamentals. Yes amps is what you are after on the output side of the controller. On the input you want amps as low as possible. Here is one thing you do not understand. Power is a product of voltage and current. Example all these statements are true.

100 watts = 1 volt x 100 amps
100 watts = 10 volts x 10 amps
100 watts = 100 volts x 1 amp

A MPPT controller is a power converter much like a transformer of 95% and higher efficiency. So if I go in at 100 watts, I come out with 95 to 97 watts. MPPT Output Current = Watts / Battery voltage. So using an extreme example If I input 100 volts @ 1 amp(100 watts) on the out put I have 100 watts / 12 volts = 8.3 amps.

So with MPPT you want to run as high of a voltage as possible. Not only is it more efficient, but saves some serious cash.

So lets say with his 5 panels in series he is required to have a fuse on each panel circuit going to a combiner, A fuse on the output combine, and rather large #8 to 6 AWG wire to handle 42 amps. That adds up to some serious cash.

But if he had say a Midnite Solar Classic 200 he can wire all five panels in series operating at a voltage 150 volts @ 8.35 amps, you eliminate all hardware, combiner and fuses, and use a very inexpensive #14 AWG wire. That is a lot less expensive, more efficient with lower line losses and fewer eggs in the basket to go wrong. On the output of the controller you get 1275 watts / 24 volts = 53 amps.

[sdold]

So lets say with his 5 panels in series he is required to have a fuse on each panel circuit going to a combiner, A fuse on the output combine, and rather large #8 to 6 AWG wire to handle 42 amps. That adds up to some serious cash.

did you mean parallel?

[Sunking]

did you mean parallel?

Yeah my bad.

[GlockG20_10MM]

Which is why it's bad that your voltage isn't high enough.


Your MPPT charge controller converts the extra voltage into amperage. It's not perfectly efficient either way but there's probably a chart of it's efficiency at 24v and 48v somewhere you can look at.

The area highlighted answered my question and clears a ton of things up for me. THIS is the answer I was needing, now the rest is starting to sink in. THANK YOU!

[Bucho]

He would still incur the cost of another controller and misc hardware and wiring. When for about the same cost or less just could buy the 6th panel to make things right...

Can he just throw a 6th panel on his current charge controller and configure things so the system would work, I didn't think it was an option?

You would still be left with a panel voltage that is too low where he is at now right?

Hopefully not, I agree with you that he needs a 6th panel.

The voltage would never get to a high enough state to match the output of the other string with a higher source voltage. About the only time it would ever be useful and functional is when the system drops down to Float voltage of 27.2 volts. Kind of like a 5 foot tall basketball player in a field of 7 foot players. The poor guy will never be part of the game and never see the ball 5 feet above his head of reach.

Interesting, I'd been wondering how that would work.

[Sunking]

Can he just throw a 6th panel on his current charge controller and configure things so the system would work, I didn't think it was an option?

I do not see any reason why not. He could configure 2 x 3 or 3 x 2.

[GlockG20_10MM]

In the interim...

So now that I understand how to improve the system performance as well as how the controllers work, I have a BlueSky MPPT charge controller sitting in storage. What if I took the 3 Renesola panels and put them in series on the Outback MPPT controller and then put the 2 Talesun panels on the BlueSky controller in series as well. I am looking for a single Talesun 250W panel now and of course the $$$ to get it. Would this work for an interim solution?

[Bucho]

I do not see any reason why not. He could configure 2 x 3 or 3 x 2.

Cool, I thought the Amperage would get too high for the charge controller, glad to hear I was wrong.

[Sunking]

So now that I understand how to improve the system performance as well as how the controllers work, I have a BlueSky MPPT charge controller sitting in storage. What if I took the 3 Renesola panels and put them in series on the Outback MPPT controller and then put the 2 Talesun panels on the BlueSky controller in series as well. I am looking for a single Talesun 250W panel now and of course the $$$ to get it. Would this work for an interim solution?

Yes better than you have now.

[GlockG20]

Yes better than you have now.

Thank you for your time! I am sure I will have other questions in the future! Learning... sometimes it's painful, sometimes it's expensive and sometimes... both!

[Sunking]

Thank you for your time! I am sure I will have other questions in the future! Learning... sometimes it's painful, sometimes it's expensive and sometimes... both!

You are welcome. Glad we finally got through to you. Yes solar is expensive, very expensive and extremely limited. FWIW don't feel left alone. 95% of everyone that comes here made the same mistake of buying something then comes here to find out why it does not work. It is expensive doing it right the first time, but a lot less expensive than doing it right the second time around or have to give up and take your losses. Education is not cheap.