Confusing specs on 500W inverter

**welo** · 10-02-2009, 05:06 AM

I bought a power inverter yesterday to be able to run some tests in my car for my planned CarPC. I will switch to a DC-DC regulator/supply later. Just let me mention that I don't have easy access to otherwise normal/common CarPC equipment. So I was pretty happy to find this inverter.

The problem is that the advertised specs on the packaging and the device itself (500W/1000W peak) do not match the label I found on the systems board inside the device (150-300W).

The fuse inside says 40A, the cable from 12V input to the transformator is labeled 'AWM 1A FT1 105°'.

I am a bit puzzled now what to expect from this device. I don't need 500W at all, most of the time I will only connect my laptop (which has a 70W power supply), but I might have another laptop added from time to time and think about getting one of those cooling boxes.

It might well be that the device is just a 150W inverter with 300W peak - it's not uncommon that products sold here just not match the product description - but wouldn't a 40A fuse be too big then?

Can somebody help me out here?

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Here more details on the inverter:

It is a no-name product ('designed in USA, Made in China'

), has a solid metal case, two 220V outlets, a power switch, 2 indicators (fault and power), and the case is labeled '500W' and further states '500 watt DC to AC power inverter' and 'DC 12V to AC220V'.
The manual states the specs for different models ranging from 100P to 500P.

Code:

model: 100P/150P/300P/500P
continuous AC output power: 80W/120W/240W/400W
30-minute AC output power: 100W/150W/300W/500W
Maximum AC output power: 200W/300W/600W/1000W

input voltage range: 10.0-15V
Fuse: 10A/15A/20A/40A/70A  (that's right, it states 5 sizes here)
Low battery alarm(nominal): 9.7-10.3V
High battery shutdown point(nominal): 14.5-15.5V

Battery drain with no AC load (at 12V input): <0.3A
Peak efficiency: >90%

**malcom2073** · 10-02-2009, 07:20 AM

Perhaps it was a labeling mistake, and you actually got as 150/300? That seems unfortunate, but not entirely unlikely. Regardless it should be plenty enough for your application but I'd be a bit worried about the quality. See how it does in the cold. Most cheaper inverters crap out when they get really cold.

**welo** · 10-02-2009, 09:49 AM

Thanks for your comment, malcom.

Actually I'm more worried about heat, since I'm living in a hot climate. The spec says 32°-104°F (0-40° Celsius). Well, I will mount it somewhere near the front seats, so ambient temperature should not be that high and humans would probably pass out before the inverter shuts down

What about the fuse? If it's a 150W device wouldn't the 40A fuse be much too big?

Assuming that calculating the amps takes the continous power into account and not the peak ('slow blow' fuse?), and 10V as the lower voltage limit, it would be
150W / 10V = 15 A

So I am still confused. If they just mislabeled the packaging and this is a 150W inverter why would they put a 40A fuse.

Is there a way to rate the power of an inverter? Could I just try to draw say like 200W and see what happens? Would the inverter take damage or would it just not power the device (talking about a short period of time here not about several minutes).

Of course I could just bring it back, but I was so happy to find it, even if it's just a 150W inverter

(I know that's so sad, but it would take me 2 weeks or more to buy another one online).

welo

**PaulF** · 10-02-2009, 10:02 AM

Heres my guess... the inverter manufacturer probably gets the boards from a different manufacturer and it is probably capable of different outputs at different temperatures. The hotter it gets, the lower the temperature. It probably is also related to how the manufacturer cools the inverter (active vs passive cooling).

I would say you're good for 400 watts under normal conditions.

**welo** · 10-03-2009, 10:50 AM

Sounds reasonable. That's why they state 500W for only 30minutes, beause it will build up too much heat at 500W. And 150W - 300W as stated on the board would be without active cooling.

Which makes me also think about removing the active cooling since I will never pull more than 300W, most times a lot less (1 laptop at 70W).

Had the inverter installed today. I need the computer tomorrow for a longer trip so didn't have the time to mess around myself. Since it's only a temporary install and they didn't have a big enough relay it's a non-switched cable now. I take my laptop out of the car every time anyway, so there is no risk of draining my battery.

They wanted to sell me a 70A Bosch inline fuse, which doesn't seem too smart from what I can understand - the fuse protects the cable, isn't it. Well, so it depends on the cable size whether a 70A fuse would make sense. Whatever, I chose a 40A instead to match the fuse in the inverter. Was cheaper too.

Thanks for your help!

welo