Micro Grid-tie Inverter

19 June 2012

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I've bought myself two 250 Watt "micro" grid-tie inverters (SUN-250G) direct from the manufacturer Ningbo National Hi-Tech Park Sunshine Technology in China. They cost US$72 each plus US$85 for international courier, which converted to NZ$313.59 or $157 each. (They quoted US$60 to ship one.) It took them 4 weeks to get the shipment ready(!?), and 4 days in transit to arrive on my doorstep.

They're just a wee bit bigger than an A5 sheet of paper.

On Sunday I connected the first one up to two 80 Watt 12 volt panels connected series which provide about 38 volts with no load. The model I bought can accept an input of 22-60 volts DC.

Then I plugged it in to the mains and it's LEDs indicated it was feeding power back in to the grid.

It was late afternoon on an overcast day so I wasn't getting a lot of power - but at least it works. Given that we're in mid-winter here I won't be seeing significant power from it for several months.

I'll connect up my energy meter when the sun comes out to see what power is being generated.

Now I'm saving up to buy more solar panels to drive the second one.

Email me if you have any questions/comments.

Cheers, Paul


Model: SUN-250G
Normal AC Output Power: 225W
Maximum AC Output Power: 250W
AC Output Voltage Range at 230V Position: 190V ~ 260V
AC Output Frequency Range: 46Hz ~ 65Hz
Total Harmonic Distortion(THD): <5%
Power Factor: 0.99
DC Input Voltage Range (options): 10.8-30V or 14-28V or 22-60V
Peak Inverter Efficiency: 92%
Standby Power consumption: <0.5W
Output Current Waveform: Pure Sine-wave
MPPT Function: Yes
Over Current Protection: Yes
Over Temperature Protection: Yes
Reverse Polarity Protection: Yes
Island Protection: Yes
Stackable: Yes
Operating Temperature Range: -10 0C ~ 45 0C
Weight: 1.6Kg
Dimensions: 220mm*170mm*60mm

Some user experiences with the Sun-250G


Julian Ilett:

Power Jack Inverter repair videos:

9 Dec 2012

Sun 250G not working

One of my two units has stopped working. Given all the that this is a very low cost inverter I'm not that surprised. Having seen all the videos above I thought it was quite possible I'd have problems.

The red fault light is on and there is no power being output.

I've opened up the unit to see if there are any obvious burnt areas and to sniff for any burnt areas. Nothing obvious.

The main board is labeled: Ver 3.2 2010-09-03

Tomorrow night I should have enough time to pull the board out of the heat sink case and measure the main msfets and diode for any direct short (as per this video How to repair a Power Jack 3000W Inverter).

11 Dec 2012

I've opened up the unit and found one of the diodes was dead. So I've ordered a couple of replacements (RHRP8120 Hyperfast diode, 8A, 1.2KV TO-220AC) from Element 14.

21 Dec 2012

The diodes arrived yesterday and I've replaced the dead one. It's back up and running fine.

2 January 2013

Sun-250 hacks

The unit that I repaired last month seems to stop working in the hottest part of the day (it's mid-summer here). When I touch the outside of the box I can feel it is a little hotter than my other unit.

I'm guessing it is overheating and shutting down. It seems to self recover after it's cooled down a bit.

So I've made a couple of hacks to address that.

1. More holes in the fan mounting plate

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I drilled some extra holes to reduce the obstruction at the fan "mouth".

The end panel that the fan is mounted on is fairly strong steel so I might go back and cut out all the metal in front of the fan mouth.

2. Bolted on old PC CPU heatsinks

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I had a collection of old PC CPU heatsinks that I though would come in handy one day...

This looks pretty ugly but was fast, easy and cheap.

I'm aware the heatsinks are not in the optimum location (the hot IC's are affixed to the sides of the box) but this was the easiest way to mount them, with the least amount of fiddling inside the box. I'm hoping they're so big they do the job of cooling the chips enough for the inverter to function on hot days.

1 March 2013

Added two 500W units

I bought two SUN-500G units (500Watt, 22-60V).

29 July 2016

Quick review

The 300W unit died in 2014.

The two 500 W units have been going well - but I only drive them at a maximum of 250 Watts. For these cheap units I think it's best to assume the actual reliable capability is about half the stated rating.

Email me if you have any questions/comments.

Cheers, Paul

Page last modified on July 29, 2016, at 11:19 am
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