powertech 3735 mppt controller

I'd avoid the Chinese generic solar stuff Jaycar sells. It isn't cheap, nor is the quality reputable from what I've been able to determine on the web. I just installed a Victron 75/15 (75 is the max voltage input, while 15 is max amperage input), designed in the Netherlands and made in India. I paid $120 for the controller and another $140 for LCD controller/monitor from a authorised dealer on eBay. I considered other decent brands like Blue Sky, Outback and far more expensive (and future proof) US made options, but the Victron was too good value. One negative is that the smaller versions like mine lack the ability to monitor battery temperature at the battery, instead monitoring temp from the controller.

It it is only 15 amps, but Victron says adding additional controllers is no problem. It seems to get along well with my 40 amp AC smart charger.

I put an Australian made GSL solar regulator on Trek. Only worry was the electronics was open to the air (vents in case) so I had to dismantle it and spray insides with conformal coating before installing it. It really is an MPPT regulator, I tested it to make sure after buying a few fakes on Ebay. Going well for two years now.

Now they do have a water resistant one here www.gsl.com.au/mppt12p.html

It's fairly rare to find anything electronic not made in China now. Always worth a search on Alibaba to find the same item with different brand names. Even items advertised as being made in USA are often talking about the packaging.

There are just too many question marks with this Chinese designed controller.

http://www.wombattechnology.com.au/pages/articles/mp3735-ends-in-tears.php

Some guy claims here that it isn't even a MPPT controller but PWM.

forums.whirlpool.net.au/archive/2221368

Jaycar has it as discontinued, but apparently still have some units left for sale.

www.jaycar.com.au/12v-24v-30a-mppt-solar-charge-controller/p/MP3735

Why would a MPPT controller on a 12 volt battery throw an error when fed 38 volts of solar? Isn't that the whole point of having an MPPT?

One good thing about the internet is that empowers consumers to make decisions when buying, based on the experiences of other consumers. Why would that consumer buy a product where people post problems with it? There is a lot at stake with solar controllers- I've killed 2 battery banks in the past with an apparently faulty (but seemed ok) Plasmatronic PL20 controller.

Here's another

www.cruisersforum.com/forums/f14/powertech-mppt-controller-is-it-working-as-it-should-176505.html

BE AWARE OF POWERTECH!

Here is the situ:
Unfortunately, I bought a Powertech MP 3735 at Jaycar which did not work properly. When the charge fell below .5 Amps it went to 'night mode' and never ever recovered from it. Period.
Took it back, the guy hooked it up to batteries, not a solar panel, and after fiddling with it, he realised it is doing what l said, anddeclared the unit faulty. Gave me another one which does the same, cuts out when a cloud comes over and stays like that forewer.

I rang him and explained the situ. He said, they hooked up a panel to the faulty controller l took back, and it worked properly. Yeah, but it never went into sleep mode for luck of sun!

I have my old 40W panel at home and l hooked up the unit to that, thinking my new 120W panel on the boat must be faulty. It started charging nicely in full sun giving 22.6 V and 2.4 Amps while it was shining. When it became overcast the unit shut down and never restarted when the sun shown it's face again. (the same problem mentioned in the Cruiser forum article)
The panel on the boat gives 22.8 V and over 5 Amps at the panel joint and at the end of the PV cable as well.
So even Trek was not able to say anithing else but 'take it back' which l am planning to do and give Jaycar a miss in the future. Or fight them all the way if they are not willing to credit me.
No wonder, guys like Aquavolt survives in this eBay infested world. I am going to buy my next controller from him for a grossly inflated price and l am sure l can rely on the item because he backs up his range.

As far as the comments are concerned, l read all the quoted internet sites and it gave me the conviction that neither, Electus Distributors nor Jaycar gives a toss about what they are having on their shelfs as long as some fool buys them.

The guy at Jaycar cannot test an MPPT regulator as simply as he did.

A good MPPT regulator "tracks" the best load to put on the solar panel to get the most power out of it at any time, maybe updating at once a second. It does this by measuring the voltage and current coming out of the solar panel at the same time. Then it increases the current drawn from the solar panel until it sees the voltage start to drop and that is the maximum power point at that exact second. Next second it might be different. It might increase or decrease the load.

Then a second part of the good MPPT regulator charges and maintains charge on your battery/s like a normal charger.

To test one you need a bench top power supply with variable voltage (say 0 - 30V) and variable current (say 0 - 5A). This is common in electronics workshops. Then you need a flat battery and a voltmeter across it and and current meter in series with it. The battery has to be flat, if you try to test the regulator with a fully charged battery part two of the regulator might not put any charge into the battery at all because its already charged and you might erroneously think the regulator is faulty.

Then you vary the power supply to all kinds of voltage and current settings that the MPPT regulator claims it can handle and you should always see the battery charging. You can work it out by power. If you set the power supply to 23.5V and a current limit of 4.6A then the power supply can put out a maximum of 23.5x4.6 watts. (Like an example of the maximum power point of a fully loaded solar panel). Thats a maximum of 108.1 watts. Next, assuming the battery is flat at 12.0V we can work out what the amps will be going into it if we have 108.1W of power available. So 108.1/12 is 9A. "Derate" it 10% for losses in the unit is 8.1A. That means if its a real MPPT regulator and its book says it can charge at say "up to 10A" you should see 8.1A going into the battery.

Then theres another parameter called "buck/boost". All MPPT regulators (if they a real ones) can "buck" a high voltage from a solar panel down to the 12-14V level to charge the battery. Not many do "boost". ie. boost up say 10V from the solar panel to the 12-14V level to charge the battery. You need to check your MPPT regulator to see if it does what it is supposed to do.

You can test an MMPT regulator, but not how the Jaycar guy did, its not that simple!!

i agree. lots of the stuff at Jaycar nowadays is cheap and nasty. not enough care is going in to their selection of products. i guess they are struggling hard to compete and survive in the consumer realm...

Well, the Jaycar saga ends here.
I took it back and they refunded the money, which was a right thing to do. Appreciated Jaycar!

Now, l am on the hunt for a good mppt controller which is going to work doing the things it supposed to do.

I do not want anything which has to be dismantled and sprayed or any other mumbo. (sorry Tony)
I want a good product with warranty back up, made by the devil or in china l don't give a toss.

Any ideas of a reliable brand, you are using, fellows? (30 Amp load, LCD display for 300W panels)
Ah, and no eBay either.

Morningstar MPPT "Tristar 45amp" I have the 60 amp model and works a treat. These are a top of the line and top price regulator, but you get what you pay for.
www.morningstarcorp.com/products/

In this world you get what you pay for your absolutely right Jode 5 .
I'm a little bit nervous to leave that controller on the boat once I fill it with house batteries

I found this paragraph on an educational solar page - it may explain Sirgallivant's PowerTech regulator behaviour:

"...There are a few non-computerised (that is, linear) MPPT's charge controls around. These are much easier and cheaper to build and design than the digital ones. They do improve efficiency somewhat, but overall the efficiency can vary a lot - and we have seen a few lose their "tracking point" and actually get worse. That can happen occasionally if a cloud passes over the panel - the linear circuit searches for the next best point, but then gets too far out on the deep end to find it again when the sun comes out. Thankfully, not many of these around any more...."

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Charriot said..
Hi Trek, like your test, I didn't have chance to test MPPT yet. I wonder when you record the data of the test and
replace MPPT with schottky diode and re-run the test, what would be a difference.
Secondly, when solar voltage drops below chargeable level MPPT / the good ones only / can boost, but I wonder
is there any worthwhile current left - justify expensive MPPT. thanks

A real MMT regulator could give 3 or 5 times more charge current than a Shottky diode. Even though Schottky diodes are better than silicon they dont let the solar panel develop its full power for a given amount of sunlight, but it depends on the exact solar panel. If you look at graph below middle curve its maximum power point is at 28V where you would get 7A which is 196W. If you used a diode you would get 13V and 3.5A which is only 54W. (Green circles).

The current left at 10V is small but worthwhile (red circle) if you are in a heavily cloudy place. On this graph the middle line solar panel develops up to 2.8A at 10V. Thats 28W. If your battery is flat (12.0V for example) then charge current should be around 28 x 0.9 / 12. ie. 2.1A if your MPPT regulator can do "boost". So even with 10V from the solar panel on a cloudy day you can charge a 12V battery with 2A charge current. That would come in handy on Lake Zurich for example where it was fogged for two months straight once when I was there!!

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sirgallivant said..
Karsten, you might be right, but it is not my problem any more.
My problem is, who is going to try to rip me off next time?

Quite right - there is a five mile long queue of petty and not so petty vendors waiting to do the rip at the earliest.

Here's a possible approach:
- If you want economical, then buy a very simple device; less parts, less design, less to fail. Not a disaster if it breaks. Get sub-optimal battery charging.
- If you want smart, intelligent, algorithm driven charging, buy only expensive brand name from established physical store. And keep away from online sellers of said device.

I know this approach is painful to adhere to in practice.

That is interesting, because at the same time yesterday l did the same. I googled the living daylight out of the subject and managed to go further with the search. Managed to find the gsl mppt 30-2 model from gsl and searched amongst the retailers - on suggestion of the gsl guy - to find a much better price. After eBay did not prove a success l found rexel distributors in Alexandria. The guy discounted the price much further and instead of $470.- + $193.- for the mppt unit and remote display respectively, l got the offer to buy the lot for $473.- incl.gst.
Ok, it is not cheap at face value, l admit, but after paying for the jaycar stuff $250 and wasting 3 days on fitting and removing and exchange and more fitting and frustration it is not that expensive either.

So here we go presently, the manufacturer is approachable, helpful, the firm is next door, in Seven Hills not in whoknowswhere, hiding behind a web addresse.
This means a tangible two year warranty! Not a chase of a web addresse.
Thanksfor the idea Trek!