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Old 21-01-2014, 11:22   #1
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Quality of MPPT? How good/bad are the cheap ones

What do you get for the money when looking at a Honk Kong night shift product like this?http:
30A 12V 24V Solar Controller Regulator Charge Battery Safe Protection CE CERTIFY | eBay

Currently I have a 500w panel similar to this:
10W 20W 30W 40W 50W 60W 80W 100W Mono Flexible Solar Panel US Stock Fast SHIP | eBay
and I am trying to decide what MPPT controller to get. The boat is in the West coast of Canada 49 degrees and above. So not very strong sun. The main load for the AGM house bank is the Danby 12v fridge compressor about 3-5 amps 50% duty cycle. So about 60AH/day.

1. What voltage to use when selecting MPPT 12v or 18v max of panel?

My argument for the cheap unit is this: being in a high latitude location the panel will not make full wattage and the ambient temp. is not extremely high thus why is there a need for high end unit. Or since the sun is not strong in my location I do need a high end unit to get the most power from what is available.

Any thoughts or experinces with these units?
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Old 21-01-2014, 14:39   #2
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Re: Quality of MPPT? How good/bad are the cheap ones

Most of the cheap MPPT controllers are poor.

The panels you list are all nominal 12v units. A simple non MPPT, PWM regulator is a better choice than a cheap MPPT controller with these sort of panels, but check your 500w panel has similar specifications (Vmp about 18v and a Voc about 21v). If the voltages are significantly higher you will need a MPPT controller.

If buying a MPPT controller I would get a better quality unit such as the Rogue, the new Midnite Kid , or Gensun for smaller panels. This adds significantly to the cost so this needs to taken into account when buying high voltage panels. Lower voltage panels that don't need an expensive MPPT controller are often more cost effective.
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Originally Posted by canadian cat View Post
1. What voltage to use when selecting MPPT 12v or 18v max of panel?
*
A MPPT controller will select and continuously adjust the input voltage automatically.
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Old 21-01-2014, 15:00   #3
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Re: Quality of MPPT? How good/bad are the cheap ones

You dont need a controller at all.
Just whack your solar pannels directly into the battery bank, with a fuse, of course.

With low levels of sunlight you wont be over charging the batteries, and whatever the people say, routing electricity through a box of goodies has to reduce it a bit, doesnt it? And you want as much as you can get.
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Old 21-01-2014, 15:21   #4
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Re: Quality of MPPT? How good/bad are the cheap ones

MPPT can extract a bit more power from the panels under most conditions than a direct connection. The voltage conversion technology acts like an electronic gearbox and extracts more power out of the panel than a direct connection. The self consumption of the electronics needs to be taken into account, but in most circumstances the extracted power is higher.
The gain is less than the manufacturers would like us to believe, but can be useful when there is no room for more panels.

Direct connection is only possible with a nominal 12v panel. If the battery is moderately charged and reaches one of the regulation points a lot of power is wasted turning the panel off, or trying to maintain the correct voltage with fixed loads. A regulator with PWM is a much better way to supply just the right amount of power to the batteries.

Direct connection is only really sensible with small panels (relative to the battery size). 500w is too large. Even with some care with larger panels the battery voltage is likely to rise to levels that will shorten battery life. In the early days of solar when regulators were very expensive and crude I had larger panels directly connected, but there is little justification not to use a regulator these days ( unless it is a very small panel)
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Old 21-01-2014, 15:31   #5
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Re: Quality of MPPT? How good/bad are the cheap ones

one of the main reasons I used a MPPT controller was for the programming options, the monitoring/recording it did, and that it could do an equalize charge

or course after I decided this I able to use a higher voltage panel that was a lot less expensive and became almost a break even for buying the controller
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Old 21-01-2014, 15:48   #6
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Re: Quality of MPPT? How good/bad are the cheap ones

There is no simple answer to this issue. It will depend on the voltage of the panel and the system being charged, the panels and a few other key items. I suggest to anyone intending to operate off-grid to read the Handy Bob Solar stuff. There is a multitude of between the lines good stuff here as well as direct logical help. HandyBob's Blog Ğ Making off grid RV electrical systems work This is the best one-stop source to help with solar, wind, battery, MPPT etc. Most people who read it agree.

The very short of MPPT is that it will help if your open circuit panel voltage is significantly higher than the battery system charge voltage. You will charge more evenly and correctly in high sun and you will gain some charging time as the sun is low or partly clouded. A good MPPT will operate as a multipoint charge controller. Panels on a boat need to be isolated with diodes and they work best in parallel instead of series. Use big wires.
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Old 21-01-2014, 17:33   #7
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Re: Quality of MPPT? How good/bad are the cheap ones

I waited so long to afford solar panels and good batteries that there was no way I was gonna short myself on a charge controller! My hippie friends ashore used Blue Sky. I found that MPPT dual stage controllers have so much more to offer such as dump loading excess power or charging another bank after first bank recieves total charge, better panel output. I suggest you research this on internet more then make decision. It seems all my projects require 90% research and design time and 10% installation. Best wishes,,,,/),,,,
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Old 21-01-2014, 17:54   #8
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Re: Quality of MPPT? How good/bad are the cheap ones

For what its worth, Solar Bob was not keen on Blue Sky. Per his recommendations, We bought The Morningstar-TS-MPPT-45. Part of the decision was based on the high open circuit voltage of our panels 54 - VDC & 660 watts. Our batteries are 24 volts.

For a small inverter (300 watt) also Morininstar. It is a heavy well made brick.
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Old 21-01-2014, 19:22   #9
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Re: Quality of MPPT? How good/bad are the cheap ones

The controller you linked to is not an MPPT controller, it is a PWM controller, and for $33 even the Chinese can't give you a decent product.

I'm intrigued by the comment about PWM being better than cheaper MPPT controllers. My understanding is that a controller that is working properly, actually tracking the max power point, is going to be better than a PWM that is in effect rapidly switching off the output via pulses. However, I'm open minded and would like to hear the basis for that particular comment.

I have installed a few Blue Sky SB2000e controllers and they seemed to work OK. The bigger issue was partial shading of the panels rather than absolute efficiency of the controller.

Recently I've been installing a few of the 20A MPPT controllers from China. About $102 delivered. It's actually a lot nicer controller to setup than the SB2000e, since it has a 2 line menu that you scroll through and adjust bulk voltage, float voltage, disconnect voltage, etc. It's also a 12v/24v controller rather than just 12, and I prefer 24v panels both for efficiency and less loss for whatever size cable you're using (or less need for thicker cable, if you want to look at it that way.)

Although the components seem well mounted, it has a large toroid, mostly surface mounted components, nice thick conformal coating and uses the entire enclosure as a heat sink, I wouldn't say it is ideally suited for a marine environment. For land based use, it's nearly perfect.

With 2 x 200w panels, it peaks out at about 22amps by 9 or 10am and is producing 20-22 amps all day until nearly dusk, if the batteries can take it all. The ideal combo for it is about 300-320 watts of panels to produce 20 amps.

Conversely, my SB2000e is struggling to produce 9 amps at noon with 475 watts of panels, so either I have one or more bad panels or a severe shading problem, or both.
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Old 21-01-2014, 19:38   #10
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Re: Quality of MPPT? How good/bad are the cheap ones

Does anyone have a supplier for SunPower panels? I am looking for 4 e19 327w panels. Thanks
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Old 21-01-2014, 19:48   #11
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Re: Quality of MPPT? How good/bad are the cheap ones

Yes on SunPower
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Old 21-01-2014, 22:39   #12
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Re: Quality of MPPT? How good/bad are the cheap ones

Thanks for all the responses. Opps The spec sheet for my panel is on the under side of the panel which is glued down, but I just found a picture. I must have been having dreams of 500 watts. The specs are 150w, Vmp 18v and a Voc of 21v. After reading solar bob I have found a Morning star charge controller. Is this the one to go for Morningstar Prostar PS15 PS30 PWM Solar Charge Controller with Without Meter | eBay or with so little power will a china cheapie do the trick?

Question what amperage do I need to account for with the pwm?150w/12v=12.5A or 150w/18v=8.3A or 150w/21v=7.14A
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Old 21-01-2014, 23:15   #13
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Re: Quality of MPPT? How good/bad are the cheap ones

That is a good choice. The name brands are more reliable and PWM tend to be quite dependable even on the cheap end and are a better purchase than cheap MPPT.

My only slight criticism of the Morningstar is that maximum absorption voltage of 14.4v is a little low for some batteries. Models like the Plasmatronics brand are more adjustable and probably better made, but the cost may be prohibitive depending on your location.

The current at Vmp (18v and 8.3A) is likely to be the most that you see with a PWM regulator, but in exceptional circumstances it can be a little higher (you will never get more than about 9A) Most regulators will self protect and will not be damaged by larger currents, but having a regulator with a slightly greater capacity is a good idea especially in the hot conditions where the regulator is likely to be mounted.

Consider if you will expand the solar array in the future. It is often worth buying a larger controller to allow for some expansion.
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Old 22-01-2014, 03:23   #14
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Re: Quality of MPPT? How good/bad are the cheap ones

Before giving you advice, it is necessary (for me) to know the storage capacity of your battery bank.
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Old 22-01-2014, 03:45   #15
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Re: Quality of MPPT? How good/bad are the cheap ones

Quote:
Originally Posted by socaldmax View Post
I'm intrigued by the comment about PWM being better than cheaper MPPT controllers. My understanding is that a controller that is working properly, actually tracking the max power point, is going to be better than a PWM that is in effect rapidly switching off the output via pulses.
MPPT controllers use PWM as well. The PWM (rapid switching on and off) is used by both types of controllers to keep the battery voltage at the programmed set point.
When not regulating there is no effective PWM, so it is only when the panels are producing more power than the batteries can accept that PWM is used.

To work well MPPT controllers need to accurately track the maximum power point. This is particularly difficult on a yacht where rapid changes in the Vmp are seen as minor shadows from lines etc change rapidly as the boat swings and rolls.
If the controller chooses an incorrect power point the output can be poorer than a simpler non MPPT controller. MPPT controllers also have higher self consumption and the cheap models have a poor reputation for reliability.
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