DC current pull from a 150 w inverter with 14 w load?

We don't even know whether the OP load is a laptop or whether they are boondocking. But, here is a solution:

1) Plug whatever electronics or small DC loads you want with whatever adapters and inverters you have.
2) Get more solar :)

When 14W load run an hour or two becomes an issue, somebody has serious problems with energy supply and storage.

I don't even know the efficiency of my cordless drill charger. Must be 40% or less, since it's a diode cutting a half of 120 VAC. Good news is - doesn't matter to me whether it's drawing 50 or 100 WH per charge. My panel generates upwards of 1,200 WH in all but exceptionally rainy days (then it could indeed harvest as little as 200 WH, but don't forget 3,600 WH battery bank).

Gdetrailer wrote:

I guess YOU better call my IT dept and tell them this.. They have for many years replaced the Dell Laptop chargers with GENERIC UNIVERSAL power bricks whenever someone loses one or they need an extra one..

Dell uses the same coaxial plug as the rest of the laptops, it is a DC only output on the charger and is typically 19V to 21.5V DC depending on the model.

I'm not going to call your IT department, but you could pass along some reading material if you'd like. The Dell power plugs are NOT the same as the rest. They use a 3rd wire to read a memory chip in the power supply. The laptop will accept the generic power plug, but without the proper power supply identification it will refuse to charge the battery. From one of the linked sites below:

"...had the explanation confirmed by the Dell engineer, here is what happens:
The power connector consists of 3 pins, 2 are power and earth, the 3rd is a signal line to identify the PSU as a compatible (Dell) unit. If the Laptop does not get the signal, it does not allow the PSU to charge the battery, it will, however, allow it to power the laptop."

An example BIOS message is:
"The AC power adapter type cannot be determined. You system will operate slower and the battery will not charge."

https://nctritech.wordpress.com/2010/01/26/dell-laptops-reject-third-party-batteries-and-ac-adapterschargers-hardware-vendor-lock-in/
http://superuser.com/questions/319684/dell-inspiron-1545-plugged-in-not-charging
http://techmonks.net/bypassing-the-dell-unrecognized-adapter-issue/
http://en.community.dell.com/support-forums/laptop/f/3518/t/19245866
http://www.tomshardware.com/forum/55106-2-dell-laptop-bypass-center-power-supply
http://www.laptop-junction.com/toast/content/inside-dell-ac-power-adapter-mystery-revealed
http://hackaday.com/2014/03/03/hacking-dell-laptop-charger-identification/
https://hclxing.wordpress.com/2014/02/09/hacking-the-dell-laptop-power-adapter-part-ii-2/
http://www.tomshardware.com/forum/9519-2-dell-laptop-power-jack-pinout
http://electronics.stackexchange.com/questions/16047/3-contact-laptop-power-supply
http://superuser.com/questions/104023/dell-inspiron-6400-indicates-the-wrong-power-adapter-is-plugged-in-and-will-not

MrWizard wrote:
Your 12v to 19v booster is still an inverter, just named something different
You have to cycle that DC to feed the transformer to raise the voltage
The difference being the output is regulated DC instead of regulated AC
You do skip one conversion stage so it is slightly more efficient
You only convert Up one time instead of up to 120 and then back down to 19

You ARE correct, a laptop 12V power supply TECHNICALLY consists of a switching power supply. BUT it differs slightly that it is designed to operate at 12V on the input..

Typically switching power supplies top out at about 92% conversion efficiency but most are in the 80%-90% range..

So, running TWO inverters you are adding an extra 10%-20% "overhead" in losses.. Doesn't sound like much BUT.. it is.

For example, a laptop uses 60W from the internal battery.. Plug in the power supply loss of say 10% you are now drawing 66W.

Now plug that into a inverter with say 10% loss that 66W is now 72.6W..

That is now a penalty of an additional 6.6W and all told 12.6W "overhead" which is burned up in heat..

But hey, you ARE welcome to do it your way..

road-runner wrote:

You can buy universal 12V laptop supplies which will have different laptop plug adapters and is switchable to the voltage your laptop needs..

....if your laptop doesn't require a specific charger. A Dell laptop, for example, communicates with the charger, and if it's not a Dell charger, it's not happy. It will run the laptop from the charger, but will not charge the battery.

:R

I guess YOU better call my IT dept and tell them this.. They have for many years replaced the Dell Laptop chargers with GENERIC UNIVERSAL power bricks whenever someone loses one or they need an extra one..

Dell uses the same coaxial plug as the rest of the laptops, it is a DC only output on the charger and is typically 19V to 21.5V DC depending on the model.

While it "may" be possible they could make the power supply "communicate" by imposing a AC signal over top the DC voltage of the power supply it would COST MORE MONEY TO DO SO.. Dell and most of the other manufacturers are not going to waste money on non value added features..

What you may have seen as a characteristic of not charging most likely was from the INCORRECT VOLTAGE SELECTED OR TOO LOW OF WATTAGE RATING OF THE POWER SUPPLY..

Too low of a voltage or not enough wattage will result in the battery not charging while the laptop is turned on (IE not enough power to supply the PC AND battery charge functions at the same time).

Besides, Dell DOES offer their own 12V to laptop power supplies for most if not all of their laptop models so really THERE IS NO EXCUSE to use an inverter even for a Dell..

Even if you bought a generic universal supply, 99% of the vendors WILL be willing to refund your money if it doesn't work within 30 days NO QUESTIONS ASKED(provided you buy it from non ebay sources)..

Conservation is cheaper than buying bunches of 12V batteries, and you can really save on Ahrs by skipping just one of the "conversion" steps..

Heck even folks that are into building "car PCs" get it.. They will build a mini PC based on a Mini ITX form factor system board (6"x6") and run it off a ATX power supply that is designed to operate from 11V DC to 16V DC.. No 12V to 120 inverter to a 120V ATX power supply..

I even did that myself for our camper PC, using a Intel dual core Atom system board, all told with HD, DVD drive that PC draws a mere 27W at full bore (20W idle), add in a 12V LCD monitor and my PC was only using 36W! Which is about half of what a laptop uses sitting idle..

red31 wrote:
15.6 watts in x .9 eff = 14 watts out = 120v x .116A

15.6 watts = 12v x 1.3A

@80% eff, 17.5 watts in, 12A x 1.46A

Very good! This will help with planning where a meter won't help.

You can buy universal 12V laptop supplies which will have different laptop plug adapters and is switchable to the voltage your laptop needs..

....if your laptop doesn't require a specific charger. A Dell laptop, for example, communicates with the charger, and if it's not a Dell charger, it's not happy. It will run the laptop from the charger, but will not charge the battery.

Your 12v to 19v booster is still an inverter, just named something different
You have to cycle that DC to feed the transformer to raise the voltage
The difference being the output is regulated DC instead of regulated AC
You do skip one conversion stage so it is slightly more efficient
You only convert Up one time instead of up to 120 and then back down to 19

Almot wrote:
Laptop might only need 1.5A but its wall wart charger is very inefficient. Between the wart losses and inverter losses I wouldn't be surprised to see 2.5-3.0A drawn from inverter. And it gets worse if you want to charge it - the battery losses come into play. In the end, if you are spoiled and want everything wireless, it may cost you 4-5 AH daily to charge the laptop battery, more when it's getting old.

My LP fridge, few LED lights and pump draw 20-25 AH, detectors draw next to nothing. 5 AH would be a significant correction to this budget. Not that I personally am worried about this, with 500W solar harvesting about that much even when it rains all day.

Hmm..

Laptop power bricks ARE switching supplies.. In reality by themselves are not "inefficient" and should be about 90% efficient..

Where the problem with efficiency comes in is when you run a laptop power supply from a inverter.. Then you are talking much less efficiency..

Personally, if the inverter is for just a laptop, I would suggest skipping the inverter and buy a laptop 12V DC to laptop 19V-21V power supply.. Then you skip the extra step of the inverter and go directly to the voltage the laptop needs.

You can buy universal 12V laptop supplies which will have different laptop plug adapters and is switchable to the voltage your laptop needs..

Even my cellphone chargers I use a plug in 12V to 5V USB charger, I keep several in my vehicles and even in my TT.. at $5 each they are dirt cheap and use next to nothing in battery capacity..

When my laptop battery are failing they no longer accept large charge currents. They only accept very little for a short period of time before charging stops.

A new laptop battery sucks much more amperage for longer before tapering to zero. Bigger gas tank requires longer to fill.

I am on my 4th replacement laptop battery with the correct tools to monitor laptop electrical consumption.

I use a DC to DC converter. I rarely bother with an inverter for anything, and certainly not for powering this laptop.



Right now it is pulling 70 watts with a 80% charged battery. With fully charged battery this is between 35 and 43 watts. If laptop battery were below 505 it would be pulling 85 to 95 watts

When the laptop battery is failing with a 20 minute maximum runtime or less, the laptop never pulls more than 49 watts

15.6 watts in x .9 eff = 14 watts out = 120v x .116A

15.6 watts = 12v x 1.3A

@80% eff, 17.5 watts in, 12A x 1.46A