Laptop measured consumption 12V versus 240V

[Guest]

I resuscitated "Frankenstein" my Acer (ish) laptop for the umpteenth time yesterday.
I have been thinking lately as to whether my 12V:19V boost converter (Maplin type ) was more economical than using a very small (but excellent)  recently acquired inverter ( fag lighter type.) 
After testing the results are in.
Computer on and idle under test:
Inverter average 1A draw.
Boost converter average 0.7A draw.

 

Bigger difference than I expected TBH. The 12V booster has it for laptop use.
 

[Paul C]

You've measured the quiescent current - or more accurately, the difference in quiescent currents between two devices.

[Guest]

1 hour ago, Paul C said:

You've measured the quiescent current - or more accurately, the difference in quiescent currents between two devices.

Nope.

Perhaps I have worded it badly. The computer was booted into Win8 and sat doing nowt, as in not playing a DVD etc.

Just measured quiescent of both devices off load and the Maplin boost shows zero amps, whilst the small inverter indicates 0.28A (some of this will be the fan.)

 

Just measured Playing DVD:
Inverter consumes 3.47A
Maplin 12V boost consumes 2.84A

Quite a difference and as I watch DVD's/youtube and stuff a lot on the lappy it is quite a power saving, especially in winter when little solar about (doesn't matter much in summer.)

 

Edited April 11, 2019 by Guest

[Paul C]

2 hours ago, catweasel said:

I resuscitated "Frankenstein" my Acer (ish) laptop for the umpteenth time yesterday.
I have been thinking lately as to whether my 12V:19V boost converter (Maplin type ) was more economical than using a very small (but excellent)  recently acquired inverter ( fag lighter type.) 
After testing the results are in.
Computer on and idle under test:
Inverter average 1A draw.
Boost converter average 0.7A draw.

 

Bigger difference than I expected TBH. The 12V booster has it for laptop use.
 

Quoted the above, the original post, just in case. I am going to assume when you say "fag lighter type" its a typically around ~150W, costing around £30?

 

5 minutes ago, catweasel said:

Nope.

Perhaps I have worded it badly.

 

Ok no worries now its been cleared up. 

 

---------------------------------------------

 

Anyone running an inverter and trying to manage their power consumption should know, or at least know that there is, the quiescent current of the inverter (however big or small) on a boat with limited battery capacity or other 12V power sources. Often it is the case that the cheaper the inverter, the higher the quiescent current. Also its often the case that a larger (higher power) inverter will have a higher quiescent current than a small one - so if you don't need that "1500W inverter" but only need 150W, buy the smaller one. A case of knowing what your power requirements are, in detail.

 

Of course the other side of the coin being, many better inverters (some costing £1000+) DO have power management features and better specs which might make them much more suitable for a particular use, eg a typical boat use (I know they will vary though). 

 

It would be interesting to know if there is a middle ground of inverters which don't have a 'silly money' price tag, yet have decent specs including a low quiescent current and maybe some power-saving features when idle. 

 

-----------------------------------

 

On another point, of course a laptop has a battery of its own. It would be interesting to see the overall power usage for running a laptop while plugged in and powered through either of the aforementioned devices, vs running on its own battery (with an inverter possibly turned off completely) then being charged (maybe while the laptop is off itself). And it should also be possible with a decent laptop to (for example) use it through the evening on its battery, then charge it up during the next day whilst cruising and the engine is on, thus not needing to worry about the domestic bank being depleted at all (of course, the laptop battery would cycle and its life shortened instead).

[Guest]

22 minutes ago, Paul C said:

Quoted the above, the original post, just in case. I am going to assume when you say "fag lighter type" its a typically around ~150W, costing around £30?

 

Ok no worries now its been cleared up. 

 

---------------------------------------------

 

Anyone running an inverter and trying to manage their power consumption should know, or at least know that there is, the quiescent current of the inverter (however big or small) on a boat with limited battery capacity or other 12V power sources. Often it is the case that the cheaper the inverter, the higher the quiescent current. Also its often the case that a larger (higher power) inverter will have a higher quiescent current than a small one - so if you don't need that "1500W inverter" but only need 150W, buy the smaller one. A case of knowing what your power requirements are, in detail.

 

Of course the other side of the coin being, many better inverters (some costing £1000+) DO have power management features and better specs which might make them much more suitable for a particular use, eg a typical boat use (I know they will vary though). 

 

It would be interesting to know if there is a middle ground of inverters which don't have a 'silly money' price tag, yet have decent specs including a low quiescent current and maybe some power-saving features when idle. 

 

-----------------------------------

 

On another point, of course a laptop has a battery of its own. It would be interesting to see the overall power usage for running a laptop while plugged in and powered through either of the aforementioned devices, vs running on its own battery (with an inverter possibly turned off completely) then being charged (maybe while the laptop is off itself). And it should also be possible with a decent laptop to (for example) use it through the evening on its battery, then charge it up during the next day whilst cruising and the engine is on, thus not needing to worry about the domestic bank being depleted at all (of course, the laptop battery would cycle and its life shortened instead).

Yes I think it is 200W but can't remember cost now. Doubtful if I would pay more than thirty quid for it though.
Yes the big inverter that runs our fridge and washer (ancient 3kW psw Sterling) has quite a large quiescent current, but is in standby when the fridge cuts out, so not too bad. Would be dreadful for long term laptop power or TV though!
I bought the small inverter to power another laptop for which it is very difficult to obtain a 12v supply at sensible money (HP with stupid 3 wire system on DC side.) Also to power a region 1 DVD player, and camera charger. Actually very useful, use it in the car too.
The self contained battery is a good point. It was fully charged when measurements taken, but the meter I have will measure the wattage over time. Will give it a go when I can.
Edited to add, yes when cruising it is no real difference. The battery would easily last the evening, as it will when there is good solar.
Like everybody, we have different needs, and  in winter we are in a marina with no shore power. A few watts here and there soon add up.
I was just trying to see how much difference there was in consumption between the two devices. Our telly is 12/240 so it will be interesting to test that.

Edited April 11, 2019 by Guest

[Sea Dog]

3 hours ago, catweasel said:

After testing the results are in.
Computer on and idle under test:
Inverter average 1A draw.
Boost converter average 0.7A draw.

 

Bigger difference than I expected TBH. The 12V booster has it for laptop use.

Have you taken measures to ensure that none of the current above is going towards charging the laptop's battery or that any draw due to charging is identical in both cases?

[WotEver]

9 minutes ago, Sea Dog said:

Have you taken measures to ensure that none of the current above is going towards charging the laptop's battery or that any draw due to charging is identical in both cases?

 

34 minutes ago, catweasel said:

The self contained battery is a good point. It was fully charged when measurements taken...

[Guest]

11 minutes ago, Sea Dog said:

Have you taken measures to ensure that none of the current above is going towards charging the laptop's battery or that any draw due to charging is identical in both cases?

Yes it was 100% charged in both cases, sat idle with windows open and screen on. Just done it again and readings tally. Got the W/hr meter up and running now so will try this later when watching a dvd.

Edited April 11, 2019 by Guest

[Sea Dog]

6 minutes ago, WotEver said:

 

Oh I'm fed up of you always reading things properly!  

 

Crikey though, even when you'd pointed that out and I knew where to look it took some finding!  Anyway, it's all bullocks - the laptop has a battery, so charge it when cruising or whilst the inverter is on for other things and quiescent current is immaterial. 

 

 

[Paul C]

29 minutes ago, Sea Dog said:

quiescent current is immaterial. 

 

 

Far too simplistic to simply say that. And this is a small inverter, its very likely its the only device powered at the time (I never had much luck trying to power two laptops at once through a small inverter). As has already been explained, a larger inverter for the fridge only runs part of the time (because the fridge power requirement cycles) so it would have not been suitable/available to power other devices steadily.

[Guest]

45 minutes ago, Sea Dog said:

Oh I'm fed up of you always reading things properly!  

 

Crikey though, even when you'd pointed that out and I knew where to look it took some finding!  Anyway, it's all bullocks - the laptop has a battery, so charge it when cruising or whilst the inverter is on for other things and quiescent current is immaterial. 

 

 

Not bullocks in our case in winter  Matters not a jot in better weather though.
My laptop is my entertainment centre and used a lot (and it shows  )

[carlt]

 

24 minutes ago, catweasel said:

My laptop is my entertainment centre and used a lot (and it shows  )

 

Are the white stick and golden labrador the giveaways? 

[Guest]

2 minutes ago, carlt said:

 

 

Are the white stick and golden labrador the giveaways? 

They always said it would make me go blind............

3 minutes ago, carlt said:

 

 

3 minutes ago, carlt said:

 

 

[bizzard]

I think laptops still work with their batteries removed if plugged into mains or the 12v thingy, which might give a more accurate test.

[Guest]

5 minutes ago, bizzard said:

I think laptops still work with their batteries removed if plugged into mains or the 12v thingy, which might give a more accurate test.

Might be worth a try sometime. My long dead Fujitsu laptop would definitely work without the battery.

[Sea Dog]

16 hours ago, Paul C said:

Far too simplistic to simply say that. And this is a small inverter, its very likely its the only device powered at the time (I never had much luck trying to power two laptops at once through a small inverter). As has already been explained, a larger inverter for the fridge only runs part of the time (because the fridge power requirement cycles) so it would have not been suitable/available to power other devices steadily.

I did say quiescent current won't matter if you're cruising (hence the alternator is providing power) or if the inverter is already powering something else.  Clearly it matters otherwise, but that's the beauty of a device with rechargeable batteries - you can charge it whilst the above is the case and use it off its own battery when not. I agree that this won't be the case if the laptop is on for longer periods than its battery can manage.

[mrsmelly]

1 minute ago, Sea Dog said:

I did say quiescent current won't matter if you're cruising (hence the alternator is providing power) or if the inverter is already powering something else.  Clearly it matters otherwise, but that's the beauty of a device with rechargeable batteries - you can charge it whilst the above is the case and use it off its own battery when not. I agree that this won't be the case if the laptop is on for longer periods than its battery can manage.

My chromebook will last ten hours in constant use between charges. Clever stuff innitt theses days.

[Guest]

1 hour ago, mrsmelly said:

My chromebook will last ten hours in constant use between charges. Clever stuff innitt theses days.

Yes batteries have come a long way. My first laptop was struggling in a very short time.

[Johny London]

Interesting test - thanks for sharing the results. Another consideration is what these devices use if you don't disconnect them from the 12v when not in use. I bought a little (300w) inverter recently for running tv/box/etc rather than having the main one on and that is a big saving on power too. It's "standby" current of 300ma seems about typical for the "small" modified sine inverter (the one I bought has several in the range, from 150w - 600w and they are all specified at 300 ma) but I'm not sure if that means it's quiescent or what it consumes when it is switched off at its on/off switch but still connected to the 12v. Not sure what the running losses are either. 

The 12v regulators/power stabilisers (is it called a buck converter?) interest me too - running anything directly off 12v seems to need one of these and I wonder how much do they use in standby and self consumption.

 

If only there was some way of using the technology found in laptop batteries, in the domestic bank

 

[Guest]

3 minutes ago, Johny London said:

Interesting test - thanks for sharing the results. Another consideration is what these devices use if you don't disconnect them from the 12v when not in use. I bought a little (300w) inverter recently for running tv/box/etc rather than having the main one on and that is a big saving on power too. It's "standby" current of 300ma seems about typical for the "small" modified sine inverter (the one I bought has several in the range, from 150w - 600w and they are all specified at 300 ma) but I'm not sure if that means it's quiescent or what it consumes when it is switched off at its on/off switch but still connected to the 12v. Not sure what the running losses are either. 

The 12v regulators/power stabilisers (is it called a buck converter?) interest me too - running anything directly off 12v seems to need one of these and I wonder how much do they use in standby and self consumption.

 

If only there was some way of using the technology found in laptop batteries, in the domestic bank

 

According to the meter that I am using, the 12V buck appears to use nothing when idle with no load. It must of course have some inefficiency when under load. 
The small inverter appears to have reasonable efficiency at low loads such as powering a laptop, but the more you push it the more inefficient it becomes (if that makes sense!)
I only did it as an experiment as I often wondered if there would be much difference between a buck and a small inverter for such purposes. Next test will be watching a DVD whilst measuring wH. Watch this space for the next thrilling installment
 

[Johny London]

That's very interesting about the buck converters. Sounds like it would be economical to have one for each piece of equipment. I wondered if all that quiescent/standby current would add up to more than a little inverter but doesn't sound like it. Presumably same for a converter operating down to say 5 or 6v for items that require that?

[Guest]

46 minutes ago, Johny London said:

That's very interesting about the buck converters. Sounds like it would be economical to have one for each piece of equipment. I wondered if all that quiescent/standby current would add up to more than a little inverter but doesn't sound like it. Presumably same for a converter operating down to say 5 or 6v for items that require that?

Don't know TBH. I have a couple for my guitar stuff so will give it a whirl.

[Sea Dog]

4 hours ago, mrsmelly said:

My chromebook will last ten hours in constant use between charges. Clever stuff innitt theses days.

Fazakerley illustrating my point. 

[Guest]

8 hours ago, Johny London said:

That's very interesting about the buck converters. Sounds like it would be economical to have one for each piece of equipment. I wondered if all that quiescent/standby current would add up to more than a little inverter but doesn't sound like it. Presumably same for a converter operating down to say 5 or 6v for items that require that?

The 9V output Bucks that I use for the practice amp etc show negligible power use with no load connected (too small to measure at 2 decimal places.) This is similar to the boost converter for the laptop.
Definitely more economical to use the amp from 12V via buck rather than the small inverter.
These are cheapo bucks off Ebay maybe 2 or 3 quid ones.

Edited April 12, 2019 by Guest