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Old 09-20-12, 08:30 PM   #1
creeky
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Default Should MPPT be the standard?

I propose that, given today's tech and pricing, MPPT controllers, and a darn good one from one of the best manufacturers, should be mandatory spec.

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Old 09-21-12, 06:31 PM   #2
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I would rather have the specs from each component and add those to the specs of the MPPT to get my output, instead it sounds like you want the rated output of a panel to be what it would be if it was connected to 'X' device, right? so if I get a cheap MPPT then my output is less if I get next years model then my output is higher then spec and the only way to know is by looking at what the specs of the 'X' MPPT is?
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Old 09-21-12, 08:06 PM   #3
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I took his post as meaning that people should be installing MPPT period. Anything else is substandard.
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Old 09-21-12, 10:35 PM   #4
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MPPT, PWM or whatever, it all depends on the application.
Since I knew that a basic PWM charge controller would keep my backup bank charged up,
I decided to skip MPPT on my little system..

At the time, I think the MPPT version of my TS-45 was about $300 more..
For $300, I could have ordered another panel..

The nice thing about the TS-45, I can turn off the PWM and just let do slow
on-off charging and not have any RFI hash.. (Not good for ham radio reception).

When the pack is really charging during sunny condx, the PWM % on the display changes to BULK.
Which means full power to the bank..
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Old 09-23-12, 02:37 PM   #5
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strider, you are correct. I posit that mppt solar controllers should be the only way to go. Ryland, an analogy would be batteries. Nobody would build a solar system with car batteries for storage. You get the best deep cycle batteries you can afford.

With mppt in the solar controller you get two things 1) mppt captures the most power from the available power in the panels 2) mppt controllers convert Voltage to Amps.

So, in my case I have 48 volt "ongrid" panels and a 12 volt battery bank. With a pwm controller my 4 250 watt panels at 48 volts become 4 62.5 watt panels at 12 volts.
The effect you see at the batteries is:
- a pwm controller shows 15 amps at 12 volts
- while a mppt controller (converting the 48 volts to amperage) shows 60 amps at 12 volts

So a mppt controller offers higher real output to your battery/home system; as well as more flexibility within the system itself.

I make this point because I had to assemble my own system from here there and everywhere as there was no option to buy reasonably priced "complete" systems. My system, which I put together myself for under $5k was selling for 14k from solar suppliers at that time. and they were assembling it from pieces that they had caged together.

As part of this self assembly I took advice from many sources on the internet. Largely to their credit (suitable wiring etc). However a number of sources recommended that pwm controllers were adequate for battery systems that rarely fell below 80% fully charged. What wasn't clear, was the inability of pwm controllers to handle variables like 48 volt panels and 12 or 24 volt battery systems. (note that some of these advisers have since added pwm/mppt provisos to their advice pages). And the thing is, deals happen all the time. I got my high voltage panels, at the time, at about a 20-30% discount over what was available, and I could drive to the guys farm and pick them up.

A lot of people thinking or in the process of building offgrid systems read these posts. That's why I want to propose that mppt controllers become basic spec. No one should be putting in a pwm controller.

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