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Inverter cuts out when plugging in charger


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Hi!

I have a MotoQuip modified sine wave inverter I bought from outdoor warehouse years ago, it's rated at 800W (1200W peak).

Recently I've been trying to use it during load shedding and I find that it is impossible to connect some devices to it. My laptop charger (85W) causes the inverter to shut down immediately when I connect it. I suspect that the reason may have something to do with capacitors in the laptop's power adaptor drawing large initial current - triggering a shutdown?
I would like to think that the 800W inverter is more than large enough for the task, barring the fact it is a poor quality inverter. Does anyone perhaps have any experience or advice on how to overcome this?

Thanks
Clayton

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Surprised that it is the motorquip shutting down with 85W, my experience has more been along the line of the laptop charger just not working due to the modified sine wave.

Some things to be aware of though - VA & Watts are horribly interchanged on cheaper equipment, and there is a big difference. A lot of equipment with capacitors inside that are not high end equipment, will allow more than than 2A of 220VAC as "inrush" current, so easily tripping the Motorquip's 2 point something limit; Be aware that Motorquip invertors are usually labelled at the MAX Wattage, but are usually designed for much lower continuous use, so it could be an internal sensor trying to protect the unit; Lastly, the big quick draw might be pulling down the battery voltage that the Motorquip detects down too low for just a split second, so it thinks that the battery is flat and shuts down.

I think the size of the invertor may be the biggest issue. Even though you might not have a large continuous draw, there are some things that could exceed.

Some cheapie solutions (not the best use of power, but may help for basic load shedding):

1. Use a PC UPS of 1KVA, or bigger, as the main supply to your "goodies" and use the Invertor to power that - If loadsheding lasts longer than your battery, then you still have time to start a car and connect the wires to a vehicle (horrible use of power, but can keep you running), but also the UPS can take a slightly higher quick power hit. Warning - using and invertor to seperately power a UPS will decrease your batteries up-time due to increased power losses.

2. Try test with 2 batteries attached to the motorquip, it could just be the last reason mentioned above, 2 batteries might reduce the chance of the powerquip detecting the lower battery voltage.

3. Invest in a bigger invertor and batteries - I know this isn't always a solution based on finances, but an Ellies or Mecer 1.5-2KVA invertor with solar inputs that you get from Makro, Incredible Corruption, or elsewhere, are pretty good value for money and come in under 10k, with the advantage that you can add solar panels afterwards with the right invertor purchase. It is one of the cheapest ways to get into Solar, and it powers a LOT if connected correctly (imagine almost all your lights, fridge, freezer, TV & PC's running without disturbance during load shedding)

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20 hours ago, Clayton said:

Hi!
Recently I've been trying to use it during load shedding and I find that it is impossible to connect some devices to it. My laptop charger (85W) causes the inverter to shut down 

The first stage of a switched mode power supply is to rectify the mains voltage and produce a DC rail (350V approx)

This is smoothed by an electrolytic capacitor. So yes there is a surge in current when it is plugged in. To limit this current they add low resistance in series with supply to the DC but this is only for very short spikes on grid supplied power, not a small inverter.. 

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Try this: Get a 40W (approx) 220V incandescent lamp (you know those ones with a filament that was always breaking..)

On the mains supply to the laptop power supply connect the lamp in series with the mains. So any current flowing to the laptop PSU will also flow through the lamp.

Switch on and you should see the lamp light up briefly. This is the current spike when the power supply starts. Once it has settled down the lamp goes out because current drops. This should allow to plug your laptop PSU into the inverter without tripping it..

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Thanks everyone for your answers, I appreciate all the advice. I will certainly give the light in series idea a try since I am looking for a cheap, ad-hoc fix.

In the meantime however, it seems to be hit-and-miss. sometimes if I just leave the inverter on with the load connected, it eventually starts up after a few minutes and works just fine.

Cheers

Clayton

Edited by Clayton
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