are inverters that power hungry?

Inverters use lots of power, better off with a 12 volt power supply for your laptop. John

Davoe
Inverters are very power hungry, they can also be very inefficient, to get that 300w output some inverters will require 400 or 450w at 12v going in.
Much more efficient to use a 12v supply for the lappy, tricky dickies and Jaycar sell universal type units if the genuine one for you lappy is too dear. Kerio brand have a good rep.
Flattening the truck batteries is not good for their longevity.

Gday Davoe,
My 300watt Jaycar inverter uses 0.3 amp when turned on, sitting idle and nothing plugged in.

Did you turn it off or unplug it? If you did, then maybe your battery has seen better days - not one of those Calcium ones is it?

Cheers
Phil

Sounds like the battery could be dying.

Also depends on the size of your laptop. Some can be drawing as much as 10amps from your battery at 12V for the larger screen laptops which over several hours can just about flatten a battery if it is dodgy. This means that at even say at 8 amps of current draw over say 3 hours, you have used 24amp hours of battery capacity and most batteries will be 60 to 80 AH so you really have gone as far as you should with a good starter battery.

I am lucky to get more than 3 or 4 years out of a battery in my Troopy (1st or second battery, both the same length of time)

Generally inverters are very efficient ie not much power is lost converting from 12VDC to 230VAC, they are usually about 95% efficient.

Some 12VDC adapters for laptops can cause problems with the laptop. I have 2 for my laptop and one of them causes the laptop to strange things - the filtering on the adapter is not much good as causes interference to appear in the laptop power supply which causes it grief.

Davoe,
Agree with comments that it is much better to use 12v supply ect and remember to turn off inverter.

My laptop - a newish ASUS is rated at 65w max. Assume it runs at this max when viewing dvds. If the inverter is a decent one then it should be 80% efficient or better. Take worst case - The inverter will need about 81w to supply 65w, this means ~6.8A at 12v. For 3 hours this is ~20AH.

Accepting the assumptions made, if you battery is flat after supplying 20AH it is either very small or stuffed. Are you sure they were fully charged at the beginning?

I have an inverter in my rig. If I have time today I will measure the current drawn whilst running my laptop.

cheers

I have a 300W pure sine inverter and a toshiba Tecra S3 laptop.

Measuring by a clamp meter I get the following readings

Inverter switched on (no load) 0.6 amps
Laptop power supply plugged in (charging laptop) 3.4 amps
Laptop switched on 6.3 amps
Playing video 6.5 amps

I guess there will be some slight variation as while the video was playing it would have also been charging the laptop battery.

Hope this helps as a guide.
I suspect your battery as I have played videos before without flattening any battery.

Alan

Davo, The compliance plate on my inverter states to allow 9 amps d.c for every 100 watts a.c demand. Do your calculations to assess you current draw. This should give you an idea as to the condition of your batteries.
Good luck

about 85% effficient is the norm for a good one....
(however the makers of a certain fridge will tell you otherwise)

Davoe,
The problem would be with the 12v Cranking battery and not the actual Inverter performance.
Yes, a low priced inverter may be less efficient than a much higher specified inverter, but even they (the cheapy inverter) should not run down a charged 12v battery to the point of the same "tick tick tick" scenario you have posted above.

Cranking batteries are specifically designed to supply a huge charge momentarily to start an engine and are not designed to run accessories for long periods of time, as is the specific design of Deep Cycle batteries.

Mainey . . .

Yes inverters are very power hungry. You should buy a 12v universal adapter to suit your laptop, they are on Ebay for $30 of thereabouts. The problem with an inverter is that it requires more 12v power to in turn generate 240v power. So inverters are really IMO better suited to short stints like 3 minutes to run a Microwave etc etc. A laptop does not require much power so you are raping the battery to generate 240v when it isn't needed. On my boat we used to run the engines to charge the batteries whilst running the inverter to generate 240v 800 watts for the Microwave for 3 minutes etc, nowdays I have much bigger batteries and wouldn't need to run the engines to do this.

Hi Daveo,

We (8ZED) recommend that for all Inverter use you should always re-charge your battery once every hour, or at the minimum, get a voltage display gauge that you can monitor.
It's not that Power Inverters are power hungry, it's more so the appliances you are using in comparison with your batteries. Most Inverters run above 80% efficiency, 8ZED Power Inverters run at or more than 90% efficiency. This is to be expected due to the energy losses that are experienced in the 12VDC to 240VAC process.

One thing i have to clarify is that a 12VDC laptop power supply uses near the SAME power as a Power Inverter that you can use for multiple applications. YES, that means that they too only run at around 90% efficiency. This is something that is unfortunately not mentioned on most dedicated laptop power supplies. In fact, most of them don't list any specifications at all.
So, just remember that if you are using a dedicated 12VDC laptop power supply, it would drain your batteries at near the same rate.
Usually, these 12VDC laptop power supplies have very poor filtering and in some cases can melt/destroy the connection to your motherboard of your computer (happened to me once before i changed to a 300W 8ZED Inverter). Considering 12VDC laptop Power Supplies are not much cheaper than a 300W Power Inverter (most cases, the same price), i know which one i would prefer.

As mentioned by Phil G, it is also recommended to unplug the Inverter when not in use. Even though most 100-600W Inverters only use 0.2-0.3Amp when left on standby, it equates to leaving a Dome light on.
If you have an Inverter hard installed, you can easily connect an inline switch on the power line.

Another thing i've read is that a lot of people are using laptops/appliances directly from a cigarette lighter plug. Even though in most small cases this is perfect, it is recommended to not use an appliance above 150W from this connection

This isn't to do with the Inverter or 12VDC power supply, it's more to do with the durability, size and strength of your accessory plug wires and fuses. Most vehicles use less than 12GA wiring for this plug, which in the end you will get less power to the Inverter, but the same amount is being pulled from your battery.
I know most laptops now days require 200-250W (especially when using the DVD drive). So that's another thing that should be considered.

The last thing i could suggest is that you invest in a power pack that you can use to easily jump start your vehicle in the morning. There are varying sizes/strengths, but they range in prices from $30 to $500.

Sorry about the long post, but i hope it helps. Any more questions and i would be more than happy to answer them.

Cheers,
Andrew

Well i had both batteries load checked and both came up OK
so i guess yea a lappy running off an inverter playing DVDs for a few hours is enough to suck a 700cca cranking batery dry