Inverter requirement for Asus laptop power supply

[robdav]

Hi

 

I know there is a big difference of opinion on the use of inverters in motorhomes on here but here goes....

 

I'm looking to get a second leisure battery and fit an inverter wired directly to the batteries but not connected in any other way to the motorhome electrics. I only intend to use the socket on the inverter to charge my laptop.

 

However, I've been calculating power requirements for all other on-board devices today and need to add the laptop requirements via the inverter.

 

The link below gives the full spec of my laptop power supply. I reckon it needs about 3 hours to achieve a full charge from a flat laptop battery. Therefore what would be the calculation for Amp Hours required from the batteries for one charge a day? And what should I allow for inverter inefficiency and why?

 

https://store.asus.com/us/item/201412AM300000015/A19419-ASUS-120W-Notebook-Power-Adapter

 

Inputs

AC100 ~240V, 50~60Hz, 2A

 

Outputs

DC19 V / 6.32 A

 

Watts

120W

 

Thanks for any help as I've read multiple explanations on this but I need it to help size the new second leisure battery and possibly replace the existing one at the same time.

 

Rob

[sshortcircuit]

When charging laptop or electric bike battery, I use a 150w plug in inverter into a cigarette outlet, saves all the problems of additional wiring etc and off the existing leisure batteries or vehicle battery when on the move. Existing batteries are 2 X 90A/h

[spirou]

My laptop takes 4 to 5A via inverter, so assuming 3 hours to charge at full power (not realistic but...) it adds up to 15Ah. In your case 18Ah. As the laptop battery is only about 5Ah you can see why the max current will not stay that high very long and the efficiency is certainly higher than the assumed ~30% in this case. Anyway, not really worth getting a second battery for it.

[Keithl]

Rather than using an inverter to convert 12 V up to 230 V and then a power adapter to reduce the voltage back down to 19 V why not look for a 'car charger adaptor' for your laptop? I mean one which converts directly from 12 V to 19 V.

 

I use one all the time for my Dell laptops at home and work and they are far more efficient then the double conversion you are proposing.

 

Keith.

[robdav]

I have looked but can't find one. The Dell laptops seem to have lower power requirements than my laptop.

 

I have also tried a small inverter running off a 12v socket and it just keeps cutting out. One of these Bestek devices.

 

https://smile.amazon.co.uk/dp/B076P9PGX3/ref=pe_3187911_189395841_TE_dp_1

[Robinhood]

It certainly isn't easy to source the higher power ones, but they do purport to be available.

 

This, for instance, is listed for compatibility against various Asus laptops, and is advertised at the same rating as your mains charger.

 

https://www.ebay.co.uk/itm/Asus-N55SF-S1060V-Compatible-Laptop-Power-DC-Adapter-Car-Charger/362164913485

 

(I'd check the tip size for compatibility if you were considering it, though).

 

I use a DC to DC charger for my Lenovo, but it was easier to source (and somwhat cheaper).

[robdav]

robdav - 2019-01-29 7:01 PM

 

I have looked but can't find one. The Dell laptops seem to have lower power requirements than my laptop.

 

I have also tried a small inverter running off a 12v socket and it just keeps cutting out. One of these Bestek devices.

 

https://smile.amazon.co.uk/dp/B076P9PGX3/ref=pe_3187911_189395841_TE_dp_1

 

Thanks, I have emailed them to see if it's compatible or if they have another one that is.

[aandncaravan]

Robdav, 'our' Martin is developing a universal power supply for charging eBike batteries but it could easily power any other device, like a laptop.

 

They are very efficient because the cut the usual 'Dual supplies' to just one.

 

To use an Inverter on a eBike charger or laptop requires an Inverter to raise 12v to 230v. Then the Laptop's power supply drops the 230v to 19v, or whatever, hence the 'dual' supplies.

 

Because Martin's power supply runs from the 12v battery direct into the Laptop one of the inefficient supplies becomes redundent. The unit is itself more efficient than the usual Invertor.

 

 

It will depend on the existing power supplies efficiency and the efficiency of the Inverter, but typically Martin's device saves around 25% of the usual Ah from the batteries.

 

They can be wired to run from either the Starter battery or the habitation battery and the unit is adjustable so one unit can be used for several functions, like laptop and eBike charger..

.

 

 

 

[colin]

Alan, the idea of a universal charger is good, I have one for laptops, but there is a big problem, my charger has about ten different plug in tips, and I can charge my old HP and old Dell, but I don't have one for my latest Dell. As for e bikes, most are 24v or 36v, we have two 36v, but they have completely different plugs.

[Alanb]

Robdav,

 

I have used an "in car" type laptop PSU, as suggested by Keith, for many years. Due the inefficiency of using an inverter, I would regard that as a last resort.

 

You quote a 120W output capability for your existing Asus PSU. It is possible that your laptop does not require the full output of the PSU. May I suggest that you check the actual power requirements, as shown on the label underneath your laptop, the power required may well be less than the rating of your PSU.

 

Laptop chargers with a nominal 12V input and rated up to 90W, are readily available from Ebay and other sources. However you would have check that a connector tip suitable for your Asus is included. If such a tip is not available, it is possible to buy adapters that plug into a more common 2.1 x 5.5 connector, which are commonly used for 12V supplies to security cameras.

 

Alan

[robdav]

Alanb - 2019-01-29 10:23 PM

 

Robdav,

 

I have used an "in car" type laptop PSU, as suggested by Keith, for many years. Due the inefficiency of using an inverter, I would regard that as a last resort.

 

You quote a 120W output capability for your existing Asus PSU. It is possible that your laptop does not require the full output of the PSU. May I suggest that you check the actual power requirements, as shown on the label underneath your laptop, the power required may well be less than the rating of your PSU.

 

Laptop chargers with a nominal 12V input and rated up to 90W, are readily available from Ebay and other sources. However you would have check that a connector tip suitable for your Asus is included. If such a tip is not available, it is possible to buy adapters that plug into a more common 2.1 x 5.5 connector, which are commonly used for 12V supplies to security cameras.

 

Alan

 

Hi Alan

 

It's a power hungry laptop and the label on the bottom states 120W.

 

Thanks though, Rob

[robdav]

Hi Alan (aandncaravan)

 

Any idea when this might be available?

 

Thanks, Rob

[Will86]

I cannot understand why you need such a high basic input having used many laptops over the years, all from a standard van socket.

 

Is your laptop a very old one and why do you think you need such a high input ?

 

If that's your decision and charging otherwise fails then charge while driving.

 

I'm of the opinion that you're using the laptop as an excuse because you feel another leisure battery will give you more 'self-esteem' in the Motorhome world.

[robdav]

Will86 - 2019-01-30 11:31 AM

 

I cannot understand why you need such a high basic input having used many laptops over the years, all from a standard van socket.

 

Is your laptop a very old one and why do you think you need such a high input ?

 

If that's your decision and charging otherwise fails then charge while driving.

 

I'm of the opinion that you're using the laptop as an excuse because you feel another leisure battery will give you more 'self-esteem' in the Motorhome world.

 

Because I have a very powerful laptop < 2 years old with 4 cores and 16GB RAM required for my work.

[aandncaravan]

colin - 2019-01-29 9:50 PM

 

Alan, the idea of a universal charger is good, I have one for laptops, but there is a big problem, my charger has about ten different plug in tips, and I can charge my old HP and old Dell, but I don't have one for my latest Dell. As for e bikes, most are 24v or 36v, we have two 36v, but they have completely different plugs.

 

The unit comes with the required charger plugs for the application, it is bespoke but 'universal' in that most types of adaptor can be used.

 

Expected to be available mid February..

 

.

 

 

[Will86]

Robday,

 

Great, thanks Rob, it's way out of my range so cannot comment any further and I've always avoided converters.

[plwsm2000]

robdav - 2019-01-30 8:50 AM

 

Alanb - 2019-01-29 10:23 PM

 

Robdav,

 

I have used an "in car" type laptop PSU, as suggested by Keith, for many years. Due the inefficiency of using an inverter, I would regard that as a last resort.

 

You quote a 120W output capability for your existing Asus PSU. It is possible that your laptop does not require the full output of the PSU. May I suggest that you check the actual power requirements, as shown on the label underneath your laptop, the power required may well be less than the rating of your PSU.

 

Laptop chargers with a nominal 12V input and rated up to 90W, are readily available from Ebay and other sources. However you would have check that a connector tip suitable for your Asus is included. If such a tip is not available, it is possible to buy adapters that plug into a more common 2.1 x 5.5 connector, which are commonly used for 12V supplies to security cameras.

 

Alan

 

Hi Alan

 

It's a power hungry laptop and the label on the bottom states 120W.

 

Thanks though, Rob

Do you have a plug in "Power monitor" so you can read the actual power drawn by the laptop in normal use?

 

The 120W stated is usually the MAXIMUM power required and could be significantly greater than the power in "normal" use. Bear in mind that most of the power will be converted into heat inside the laptop. At 120W, the laptop will be quite hot!

 

Maximum power would be at highess screen brighness, processors at max speed, battery on charge, USB ports loaded etc. If you could tolerate not using the laptop while the batteries are charging /lower screen brighness etc, you may get away with a smaller adaptor.

 

 

[robdav]

plwsm2000 - 2019-01-30 12:42 PM

 

robdav - 2019-01-30 8:50 AM

 

Alanb - 2019-01-29 10:23 PM

 

Robdav,

 

I have used an "in car" type laptop PSU, as suggested by Keith, for many years. Due the inefficiency of using an inverter, I would regard that as a last resort.

 

You quote a 120W output capability for your existing Asus PSU. It is possible that your laptop does not require the full output of the PSU. May I suggest that you check the actual power requirements, as shown on the label underneath your laptop, the power required may well be less than the rating of your PSU.

 

Laptop chargers with a nominal 12V input and rated up to 90W, are readily available from Ebay and other sources. However you would have check that a connector tip suitable for your Asus is included. If such a tip is not available, it is possible to buy adapters that plug into a more common 2.1 x 5.5 connector, which are commonly used for 12V supplies to security cameras.

 

Alan

 

Hi Alan

 

It's a power hungry laptop and the label on the bottom states 120W.

 

Thanks though, Rob

Do you have a plug in "Power monitor" so you can read the actual power drawn by the laptop in normal use?

 

The 120W stated is usually the MAXIMUM power required and could be significantly greater than the power in "normal" use. Bear in mind that most of the power will be converted into heat inside the laptop. At 120W, the laptop will be quite hot!

 

Maximum power would be at highess screen brighness, processors at max speed, battery on charge, USB ports loaded etc. If you could tolerate not using the laptop while the batteries are charging /lower screen brighness etc, you may get away with a smaller adaptor.

 

 

I have a "Smart socket'" that has an energy monitor built in but I tried it with the laptop yesterday and it said it was pulling more than 120W, more like 224W so I'm not sure how reliable it is.

 

Can you recommend one?

[Alanb]

Robdav,

 

To sumarise all the advice given to date, you have three options.

 

1. To use a suitable 12V adapter such as that linked to by Robinhood. This will be the most efficient route in terms of demand on your habitation battery, but given the high power rating of your laptop I would recommend an increase in total battery capacity if you intend to use your laptop for several hours while not on EHU. You should also consider the extra lwork that your charging systems (mains, solar, alternator) have to do in recharging the batteries

 

2. The universal charger being developed by Allan's (aandncaravans) associate. This system while comendable is unproven, and not yet available. However if perfected would be more flexible than the option above..

 

3. The invertor option that you were considering. It as not as simple as it may seem. The 300W invertor that you linked to, has a standard cigarette lighter plug. The socket and wiring will not generally be rated at more than 15A, and could overheat at that current. Further 15A only equates to 180W at 12V. I suspect that the 300W, may be a peak output rating. Another possible problem is that your existing PSU will almost certainly be a switch mode device. These are efficient, but draw large peak currents from the supply. The inverter may not like this. Perhaps someone with experience in this area could comment further. A plus point for an inverter would be that like Allan's suggestion, it could be used for other applications. Again habitation battery capacity and charging systems should be considered.

 

In conclusion, unless you have or are considering an ebike, I would recommend the 12V dedicated charger option, or consider more frequent use of EHU.

 

Edit

 

In relation to the point raised by "pwlsm" above, I have just checked my 90W rated laptop after running on battery for a considerable period the consumption is 50W. If your laptop is consuming the indicated 224W, I would not like to use it as a laptop without an insulator betweem me and it!

 

Alan

[robdav]

Alanb - 2019-01-30 2:06 PM

 

Robdav,

 

To sumarise all the advice given to date, you have three options.

 

1. To use a suitable 12V adapter such as that linked to by Robinhood. This will be the most efficient route in terms of demand on your habitation battery, but given the high power rating of your laptop I would recommend an increase in total battery capacity if you intend to use your laptop for several hours while not on EHU. You should also consider the extra lwork that your charging systems (mains, solar, alternator) have to do in recharging the batteries

 

2. The universal charger being developed by Allan's (aandncaravans) associate. This system while comendable is unproven, and not yet available. However if perfected would be more flexible than the option above..

 

3. The invertor option that you were considering. It as not as simple as it may seem. The 300W invertor that you linked to, has a standard cigarette lighter plug. The socket and wiring will not generally be rated at more than 15A, and could overheat at that current. Further 15A only equates to 180W at 12V. I suspect that the 300W, may be a peak output rating. Another possible problem is that your existing PSU will almost certainly be a switch mode device. These are efficient, but draw large peak currents from the supply. The inverter may not like this. Perhaps someone with experience in this area could comment further. A plus point for an inverter would be that like Allan's suggestion, it could be used for other applications. Again habitation battery capacity and charging systems should be considered.

 

In conclusion, unless you have or are considering an ebike, I would recommend the 12V dedicated charger option, or consider more frequent use of EHU.

 

Alan

 

Thanks Alan.

 

Well summarised.

 

1) It turns out the company that Robinhood's link took me to do have an adapter that can support my laptop so I have ordered one.

 

Link to power4laptops

 

2) As you say, not ready yet.

 

3) The 300W inverter I have tried but it kept cutting out in the only 12v socket I have (preference being USB sockets). I tried both with and without the engine running and it couldn't cope. I suspect, as you say, the wiring to the socket is not up to supporting it.

 

I am going down the route of a second leisure battery anyway as we need it regardless.

 

Thanks for all the advice/help.

 

Rob

 

[aandncaravan]

I agree with Alanb's excellent summary, and would like to add that if you go down the Inverter route it is likely that even at a 'peak' 6 amps charge, a good Starter battery will support that current drain for about 2 hours without impacting Starting.

As pointed out above, the Laptop will probably consume half that current in real use, especially if you start with a 'full' Laptop battery. I would guess about half that 6 amps is to charge the battery while the other 3 amps are to run the Laptop? If you start with a full laptop battery, the Inverter has just got to supply enough to keep the machine running.

 

So I would suggest that you wire the Inverter from the Starter battery, with isolation switch, that way the laptop will charge when driving without impacting your habitation battery, or the need for additional batteries. In an 'emergency' you can always run the engine to charge up both the Starter battery and Laptop battery if you need more than about 5 hours Starter battery + Laptop battery capacity?.

 

 

There is likely to be less impact on the charger/controller by wiring it this way. If you want to use the Habitation battery, then it should be wired from a suitable output on the Charger/controller unit, which remember modern units often monitor power used and calculates what is left in the battery.

If you take power direct from the habitation battery, it won't be party to the power taken so may not 'record' it via it's shunt. If that is the case the 'percentage available'/'AH left' display will be nonsense.

 

Summary.

So if you go the Inverter route, my suggestion be use the Starter battery as the source and when using the Laptop, run it's battery low first and then power on the Inverter so the Inverter charges the Laptop battery and runs it.

 

Try and use power to the laptop from the Alternator when driving as your prime charging source. That is the approach we are suggesting with the eBike chargers.

 

 

Edit : I was obviously writing this while the other replies were coming in.

Still suggest you use the 12v to 19v adapter from the Starter battery for the reasons stated or use a suitable feed from the Charger/controller so it is aware of the draw.

[bolero boy]

Alan, re: charging ebike batteries, would your comment re charging whilst on the move also be applicable if the inverter were linked to leisure batteries which in turn were charged by the alternator while driving?

 

I'm also interested in the development you mention as we use ebikes when we can, even off grid, and anything to make the process more efficient would be welcome.

 

rgds,

Chris.

 

[aandncaravan]

bolero boy - 2019-01-31 9:27 AM

 

Alan, re: charging ebike batteries, would your comment re charging whilst on the move also be applicable if the inverter were linked to leisure batteries which in turn were charged by the alternator while driving?

 

I'm also interested in the development you mention as we use ebikes when we can, even off grid, and anything to make the process more efficient would be welcome.

 

rgds,

Chris.

 

Chris,If you connect a big inverter to the habitation batteries and then start the engine, the Inverter/habitation battery will try and draw lots of amps from the Alternator circuit.

On most modern vans this potential 100amps plus will go through the Charger/controller as the best have the 'split charge' relay inside the Power controller unit.

The current from the Alternator goes through the charger/controller then to the habitation batteries via spindly cables.

 

You can imagine the result?

 

 

In the case of a low power inverter the current will be less, but still needs to be monitored.

The extra load is likely to impose a greater voltage drop so the habitation batteries won't charge as fast while the Invertor is active..

 

 

[bolero boy]

thanks Alan....it's a 500w inverter.

I'm happy to do them when on site via solar and inverter....usually one bike at a time.....

I was just curious following your earlier comment...

thanks again.

[robdav]

Me back again....

 

So I purchased one of these 12v DC adapters for my laptop.

 

https://www.power4laptops.co.uk/p/asus/g501jw/compatible+laptop+power+dc+adapter+car+charger+2092750#.XFGrb1z7SUk

 

I only have a single 12v socket in the van for which I have to use an Adapt-It 5 socket because it's not a normal size 12v socket.

 

I have just tried the DC power supply in the van when not on EHU and the laptop switches from charging to not charging to charging .... and the laptop display goes bright, dim, bright etc and the fan on the heating in the van was cutting in and out as well. I tried turning the heating off completely but the laptop continued to be charging/not charging.

 

I plugged in the EHU and the DC adapter when plugged in to the Adapt-It 5 socket charges the laptop fine and behaves as expected.

 

So my question now is, does this rule out the socket with the Adapt-It 5 socket combination and indicate the leisure battery is weak or could it be the cabling from the battery to the 12v socket not being up to the job?

 

Thanks

 

Rob