Inverter size?

Hi John,
We have a 500w pure sine wave inverter hooked up to 2 x 120ah AGM's all fitted into a camper trailer. Haven't tried running a car type battery charger off it, only heater, laptop, DVD player,fan, radio etc. and AA type battery chargers. All worked very well, only run low on power once in 7 weeks on the road. Didn't run out of power, just low enough for the low power alarm on the inverter to sound a warning.

Cheers
Kev

The 150w inverter will run a laptop with ease. Curious, what are you going to run a battery charger for or with for that matter.

I used 400W inverter in the Simpson, Running laptop, external hard drive
and charging photo camera batteries at the same time without any problems...

300W should be just fine but 500W would be good for all other unexpected needs
like electric blanket, etc...

Stan

150W will cut it, 300W (600W surge) off ebay is $60 or so +postage. Your Transformers may run hotter, and you may shorten the life of them if you use the modified sine wave (cheaper type), but I had no probs. Charged laptop, ipod and mobile at the same time no probs.
FYI A 150W inverter will actually run a large TV and Playstation- no need for a huge inverter as they will eat your batteries constantly even when you're not consuming the residual power.

As laptop power requirements vary, check what the convertor (240V to DC adaptor) of the laptop says. It will have its power rating listed on the lable. Buy an invertor that exceeds this. If you are only going to use the invertor for the laptop then there is no need to go much higher than what the laptop requires.

Regards
David

I went down this road 3 years ago and eventually settled for a 150watt Pure Sinwave inverter from Jaycar for $250. On the first trip I did, a diode blew in the inverter with smoke pouring into the cabin. A new diode for $1.30 and some very good soldering by a mate saw the inverter working again. Now I mainly run the inverter to charge the laptop battery and use a Kerio DC Cig lighter socket to run the laptop. I also charge camera batteries from the inverter and run my camp light.

Only recently I have found out that one should get a laptop with a battery that can last four hours(not the usual 2)(something to do with the laptop running processes) so that it does not put too great a drain on the inverter and make it work too hard. Others have told me that they have had an issue with hardwiring the inverter. But I have had no further issues since the first mishap and my inverter is hardwired to the aux balttery.

Invertors are complicated things, and in their nature enefficiant. I have a 450w Puresinewave that we use for charging the camera batteries and running the external DVD drive for the laptop (and the lounge room at home when the power goes out!) ;-) But for running the laptop I use a 12v Laptop power supply, much more efficiant. They cost about $70 from Jaycar and are well wroth while, they run generally 15-22v DC (selectable) at about 4amps. Now the best thing to do when running your laptop off the car to conserve power is to ensure that you REMOVE the laptop's battery when running it from the car, that way you are not wasting power charging the battery that you are not using.
With the NEC P4 I used to use in the car it would draw nearly 4amps with the battery in and barley 2amps with it out! So when the kids were watching a DVD off it, I HALVED the power consumption by simply removing the battery.

Now the more expesnive the Invertor the less power it'll use (generally speaking). The more expensive units have auto sensing which means they only activate all the circuts once there is a load detected (ie you plug somthing into it). Others run all the time and can draw anywhere up to 2 amps just by being switched on with nothing plugged into them! Puresinewave is the way to go, modified sinewave will work, however if your going to be running fluro lights or switch mode power supplies (cameras, computers etc etc) then it is not all that good for them, but worse it will make them draw more power than neccessary, you might end up drawing an extra 50% on top of what the item needs just because it should be running off a pure sinewave unit.

Twigiee

Re sine wave and modified square wave inverter efficiencies: with respect, the opposite of your statement is more true. Most good sine wave inverters now exceed 92.5% efficiency over most of their range.

A further general comment - in many instances the energy draw of a plug-in power supply may remain substantially the same whether the connected device is switched on or not. This is particularly true of lap top computers. Always switch these things off at the supply outlet.
Collyn Rivers

Twigiee

You may have been misled by earlier advt for modified square wave devices - many were. Some absurd claims and phony comparisons were made by comparing only those parts of the operating range that most suited whatever claim was being made.

By and large inverters are like gen sets in that they are most efficient from about 20-80% of their range.
Collyn

50 megawatt minimum for a laptop...