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GWatPE

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Joined: 01/09/2006
Location: Australia
Posts: 2127

Posted: 03:59am 23 Nov 2010

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Readers may be aware from my postings on other threads, that I have a PowerJack 1200W GTI. This is dumping surplus power from my RE 24V nom battery to the grid.

Today was a bit warmer, approx 37C.

The unit has been sending approx 220W peak back to the grid, for several hours.

The fan has now come on, and the housing is hot to touch. There is no way that this unit is capable of supplying its nameplate 1200W rating. This unit would be probably pushed for even a 600W continuous rating. The efficiency is quite low, and I would not consider it really suitable for a direct solar grid connect setup. These are my opinions based on observed unit behaviour, on a 24V system, in not even extreme conditions.

The unit may work slightly more efficiently at a maximum 55VDC input.

I would be interested to hear of other readers experience with this brand GTI.

The units appear to work well at low power levels, but if pushed to their ratings, get excessively hot. I will not be testing with any more load than 300W max, and hopefully this will help keep the magic smoke in.

Gordon.

become more energy aware

VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 04:52am 23 Nov 2010

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Hi Gordon

I have a range of them, the 300 watt units have worked well all winter but now the heat is on they will drop out on overheat, the ones I have are 14 - 28 volt units used as I explained to you to get the early watts from the mills, I also have two hooked to the batteries at above 26 volts, they draw between 10 and 12 amps dependent on battery voltage and unit temp, and drop out on over voltage at 30 volts.
The 300 watt units went up to 15 amps at 28 volts 420 watts input and 380 watts output, however of all the ones I tested, they where all different some bit higher and some a lot lower.

I am thinking about cutting a hole in the case and fitting a bigger fan and bypassing the thermo switch so the fan runs all the time that its on, as some of the thermo switches don't work in the proper temperature range allowing it to get to hot and shut down on overheat.

The islanding and synchronizing worked well on all of them, taking 3 to 5 seconds to sync with the cap and up to 15 seconds without the cap.

The 600 watt units work alright on the batteries drawing 18 to 20 amps voltage dependent, they also drop out at 30 volts.

I have several 600 watt units rated at 28 volts to 55 volts, these come on when the battery voltage is 28 volts but draw only 5 amps and get as hot as the ones drawing more amps, fan comes on but dosent drop out. They seem to work better on the windmill, as when I had some serious wind they cut in and worked, but needed the cap across the input to stop them dropping sync all the time.

From what I have read and worked out from my experiments with these units is that they are a voltage dependent MPPT as the voltage goes up they draw more current until it hits a point where they draw very little or no more current but the watts out still increases.

I only have a little plug point watt meter but that is the impression I get from watching the output.

The ones hooked to the batteries, I found needed a 470K resistor to bleed voltage to them before switch on or they where inclined to blow the fuse on the inrush current and one blew a input capacitor I think for the same reason.

I found that mounting them upright to assist the little fan stops them from dropping out on overheat.

The 1200 watt unit 14 28 volt works on the mill but not enough wind at the moment to drive it to any useful input, just enough to get it to sync, I think it has potential but will have to wait for suitable wind, havnt tried it direct to the batteries yet but if you see a lot of smoke and some serious swearing from QLD you will know what happened .

All the best

Bob

Foolin Around

Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 02:46pm 23 Nov 2010

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VK4AYQ said
I found that mounting them upright to assist the little fan stops them from dropping out on overheat.

Bob

While my inverter is not the powerjack brand I also had issues with the fan running too often IMO. This inverter is bolted to a wall, its vertically oriented.
Simply mounting it upside down improved the cooling a lot. The fan is now at the bottom and it sucks air into the unit. Hot air exits at the top sides at grill like slots.
The fan now runs briefly when the connected fridge starts up and then stops again. Only when the shed temperature hovers over 30 degrees does the fan runs for longer periods. I never had any heat related shut downs with that unit.

I guess flipping the fan over on its mounting would also have helped without turning the whole unit upside down but having the air outlet slots on top was the best solution.

Klaus

VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 09:35pm 23 Nov 2010

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Hi Klaus

I have found the same for a load inverter as most of the time it isn't at capacity, but the GTI unit is always running at max capacity when connected to the batteries, when connected to the wind turbine only, the fan only comes on in high wind events when the load is constant.

When connected to the solar panels it is much the same as the batteries, but as the voltage goes higher the circuit seems to restrict the amps drawn to some degree.

The little GTI units only have a very small fan that is OK in cooler weather but as you say with your inverter over 30 degrees is a worry.

All the best

Bob

Foolin Around

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