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DC/AC Power inverter experiences
Monday, 13 October 2008
One of our most universal devices in our camper truck is probably the power inverter, generating 220 Volt AC mains from our DC 24 Volt home batteries. It allows us to use most of our electrical appliances on a daily basis. Specially for the ones which require a clean energy source like a computer, printer and so on. 220 Volt Mains outlets in Pakistan, India and Nepal are far from stable and can easily damage sensitive electrical equipment with nasty and frequent power glitches. We chose for the Alessi 750 VA sinewave DC/AC Power inverter and it exceeded our expectations.

Power inverter search

Power Inverter requirements

From a requirement perspective we needed a power inverter which is robust, energy efficient and reasonably priced and suitable for every day use. The operating environment is though; extreme heat, high humidity, excessive dust and jolts from the many bad roads. It should at least be able to supply power for a drill and a normal computer without a problem. We calculated we needed a power inverter with an average 600 Watt capacity and capable of taking a load of 1200 Watt for a short time.

Marine power inverter

We estimated that an average low-priced inverter wouldn’t last very long specially with daily use in a though abusive environment. A quick scan of the upper part of the power inverter market came up with only a few inverter manufacturers for the marine industry. A top brand is Phoenix from Victron Energy – a brand producing long lasting equipment for professional use. Their equipment is expensive and also hard to get for a low price in the 2nd hand market.

Power inverter market secrets

Alessie Power Inverter
750VA - 24 Volts Power Inverter
After few calls to marine shops another brand popped up. The Alessi power inverter series from TBS electronics. The Alessie series is now sold as the Powersine series. And surprisingly their power inverter brand has an amazing similarity with the Victron -  Phoenix compact product range. Comparing power inverter specs gave the impression it’s the same product sold under different brand names. A few calls more confirmed there is a link between the 2 companies for power inverter products, specially in the compact range. Of course the price for the Alessi power inverter range is a bit more favorable too. It was a quick decision after comparing the Alessi specs with a few cheaper mid-range power inverters. The choice became the Alessie Sinewave 750 VA @ 24 Volt.

Victron Phoenix Power Inverter
Victron Phoenix Power Inverter
This true sinewave power inverter is now operating in our camper truck for about 3 years without any problem. It’s used on a daily basis to run a computer, USB disks, printer and occasionally a 800 Watt Hilti drill and a 750 Watt Black & Decker grinder. 

Best features – Alessi Power Inverter

One of it’s best features is load sensing combined with energy saving standby mode. Connecting the Hilti drill shows that it’s stepping up AC voltage when the power inverter is confronted with a high load. The drill revs up in steps to prevent it from tripping the overload function. The result is that the drill can still be used although it’s operating in the high end of the specs of the power inverter. From experience, a cheap inverter immediately trips and goes into overload mode – the drill doesn’t work.

The standby mode kicks in when the power inverter senses a low load. The AC output goes into pulse and power consumption is reduced to a minimum of 1 watt. Connected low power 220 Volt lights flash on a 2 second interval. For us it’s good feedback the power inverter is disconnected and energy is saved. The threshold of the standby mode is adjustable on the inverter.

Another feedback  mechanism is the switch-on beep. The inverter beeps when it’s powered. A purple light shows the power-on status, a red light shows when it’s gone into overload shutdown after a few beeps.

Power Inverter Installation

Our power inverter is installed with a few extra’s. First of all an external switch to disconnect the power inverter from the battery. It’s a big switch suitable for high currents when the power inverter running on maximum capacity. The position of the switch is easily seen from a distance.

Secondly the power inverter is permanently connected to a special clean 220 volt power rail for computer and other sensitive equipment. Mains gets unreliable from Iran and eastwards with India as the top country with the most unstable 220 Volts grid we’ve ever experienced.

3rd  the power inverter output is separated by a 220 Volt relay. When outside 220 volt mains is connected, the power inverter output is disconnected from electrical devices which can take dirty glitchy mains, like lights and chargers for mobile phones. More important, sensitive electrical equipment stays connected to a clean 220 Volt AC sinewave from the inverter. The relay is a heavy duty magnetic operated switch with it’s coil connected to the outside mains. It shuts down at about 70 volts AC – reverting mains back to the power inverter. The mechanical slowness of this heavy relay filters out glitches in the low voltage range.

The internal fan of the power inverter switches on when room temperature exceeds about 40 degrees or when it’s heavily used. A filter sponge is attached to the fan to prevent dust being sucked in.
Power Inverter Quality

As backup we carry a 24 Volt - 1500 VA Sundox Power Inverter producing a trapezium 220 Volt wave.  It can’t compete with the Alessi power inverter. It shuts down on the Hilti drill as well as the 750 watt Black & Decker grinder. A small fan is running from start producing a lot of noise. Quality shows itself immediately but of course it’s more affordable. For short intervals or sporadic use the sundox power inverter might do well.

Power Inverter specifications.

In the end it’s all about the specifications and how these are measured under what test conditions. For most appliances there’s a startup current which is usually a lot higher than the specified nominal wattage. And in the Power Inverter market it’s all about the output. More is better – but as it shows the Alessi outperforms the Sundox power inverter with ease when used in real life situations. In fact 1500 VA is not the same as 1500 Watt – it depends on the load connected. As a rule of thumb 1500 VA equals to 975 Watts AC – about 65 % of the VA rating.

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