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Asus eee - connect straight to 12v?

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#1 Tim C

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Posted 10 April 2009 - 10:51 AM

Hopefully the last of my series of netbook questions. I came across some threads elsewhere that said the Asus eee netbooks run on 12v. I can't find that anywhere in the online spec so was looking for confirmation. If it is 12v, does that mean I can hook it directly to a 12v deepcycle battery (the same one running my mount)? I would think I'd need to modify a power cord or buy an adapter to do that.

thanks,

Tim

#2 daev

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Posted 10 April 2009 - 10:59 AM

9.5V from everywhere I've seen. Looks like it's going to take some circuitry to run off a standard battery.

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#3 mclewis1

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Posted 10 April 2009 - 11:39 AM

ASUS Eee PC EPC1000HE AC Adapter Output: 12V, 36W
ASUS Eee PC 901 XP AC Adapter Output: 12V, 3A

Info off of Newegg.com ... so yes it would appear that you can run at least some of them directly off of a 12v external battery.

Dave, where you getting that 9.5v info from?

#4 daev

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Posted 10 April 2009 - 01:17 PM

LOL apparently from an unreliable source! :lol: I hit up a few random message boards for eee owners. I'm much more inclined to believe neweggs reported specs.

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#5 JAT Observatory

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Posted 10 April 2009 - 01:59 PM

First - the EeePC 700 series uses 9.5vdc not 12vdc, the 900s and 1000s are 12vdc powered.

I have a EeePC 1000HD. and had issues powering from a 12vdc external source. The AC to DC adapter lists the output as 12 DC @ 3A.

Over this past weekend I was readying my 10" LX200GPS for an upcoming outreach event. The EeePC and the scope were both connected to a 12 vdc 25 amp power supply. During the course of the checkout I found a problem with the scope that took a few hours to repair. I left the netbook on and connected to 12vdc supply. When I came back to the netbook the it had turned off and battery was completely discharged.

Looking at the system I found the following:
-There were 12 volts at the plug that goes into the netbook.
-The polarity was correct.
-The netbook showed charging when the after market 12 vdc powered plug was originally inserted.

Even after the battery was removed the EeePC would not power up when using the aftermart 12vdc power source.

The factory EePC AC adapter was reconnected and the netbook booted and the battery begin charging.

After about 10 minutes there was enough charge in the battery to power the netbook without the factory AC adapter connected, so I removed it.

I then brought up the battery monitor screen and it showed the battery had about a 30% charge left and the battery was discharging. I connected the factory adapter and the battery monitor window showed the battery was charging. After a few minutes the battery level increased to a 31% charge.

I disconnected the factory adapter and connected the cable and plug from the 25amp supply. The battery windows showed charging, but after a few minutes the battery level dropped from 31% to 30%. The battery level continued to drop as long as the plug was connected, but the status showed the battery was charing and connected to an AC supply. Clearly the external supply was not charging the battery.

At that point I disconnected the after market supply, changed the tip and connected it to the scope. The scope worked fine and I was able to slew it etc.

I have not tracked down the reason for why the external supply was not powering the EeePC correctly, but until I do that I can't use it from a external 12 vdc source. I will be trying a slightly different setup and I'll let ya'll know what happens.


#6 daev

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Posted 10 April 2009 - 04:30 PM

That makes me wonder if they're not using a chip in their PS, much like Sony does in their battery packs to lock in the market for replacement PS adapters.

dave

#7 JAT Observatory

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Posted 10 April 2009 - 05:51 PM

I found a Asus built EeePC car charger and it has a brick inline, not just a cigarette plug and a power connector.

I decided to be a lab rat and ordered it.

#8 mclewis1

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Posted 10 April 2009 - 06:34 PM

Won't that be interesting ... 12v in and 12v out.

I'd love to understand how a laptop/notebook knows what type of power adapter is attached to it. I have a Dell Vostro 1500 laptop with both the original power adapter (90w) and a Dell auto-air adapter (65w). Whenever the auto-air adapter is plugged in (and it doesn't matter if this adapter is powered from 110v AC or 12V DC) the laptop displays a message about how the 65w adapter may not charge the laptop as fast as the 90w unit.

#9 Pedestal

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Posted 10 April 2009 - 06:54 PM

Output from the charger for my eee 900 model measures 12.3V, center positive... Be interesting to see what Marcus comes up with.
Hubert

#10 JAT Observatory

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Posted 10 April 2009 - 08:23 PM

Won't that be interesting ... 12v in and 12v out.


The spec for the car charger lists the input range from 10 to 16.5 vols.

#11 bigbeck

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Posted 11 April 2009 - 08:51 PM

Marcus, Maybe you've got the wrong size plug on your DC to DC adapter? Or a faulty plug? I once had the cigarette plug back itself out of the socket. I ended up cutting off a little bit of the spring to decrease the tension.

If you'd like,I could hook up my 900A to my deep cycle battery to see if I get the same results as you. I just have to see if I can find a plug to fit the computer.
I use a 15" compaq laptop in the field with the factory DC to DC adapter. It also has an inline brick, but it puts out 19.5V.

I'm thinking maybe that brick you're talking about could be sending a high frequency signal on top of the DC to control an internal switch in the laptop. That would be sneaky, huh?

#12 JAT Observatory

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Posted 12 April 2009 - 07:32 AM

The was power to the tip so I know the plug, cable and adapter is good.

While the adapter plug is not the exact size it think it was close enough. I tried two different ones and they both cause the laptop to show a charging state when inserted (even though it wasn't).

The factory DC charger should be here in about a week, so I'll just wait.

#13 JAT Observatory

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Posted 16 April 2009 - 09:24 PM

The ASUS 12 volt DC charger showed up today. I typing on the EeePC that is being powered by a 12 volt, 17 Ah battery. It is charges perfectly and will also run with the EeePC's battery removed.

The adapter looks just like the standard AC unit with a cigarette plug on the end instead of the 2 pronged AC plug. The power LED is green instead of blue like the one on my AC adapter.

The spec on the unit says:
Input 10 to 18 volts DC 5A
Output 12 3A
model ADP-36FH A

It works so I'm happy.

#14 JAT Observatory

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Posted 16 April 2009 - 09:26 PM

The ASUS 12 volt DC charger showed up today. I typing on the EeePC that is being powered by a 12 volt, 17 Ah battery. It is charges perfectly and will also run with the EeePC's battery removed.

The adapter looks just like the standard AC unit with a cigarette plug on the end instead of the 2 pronged AC plug. The power LED is green instead of blue like the one on my AC adapter.

The spec on the unit says:
Input 10 to 18 volts DC 5A
Output 12 volt DC 3A
model ADP-36FH A

It works so I'm happy.

#15 AlienFirstClass

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Posted 21 April 2009 - 11:38 AM

Any laptop expects a supply of filtered DC power.

You may want to consider that hooking a laptop directly to a battery with other items attached exposes the laptop to voltage spikes. Depending on how well the laptop is filtered, it may or may not damage the laptop, cause software problems, loss of data.

Keeping a power supply in line provides that filtering.

Even a "direct" 12v to 12 v connector from the manufacturer will have filtering elements inside the larger 12v connector.

I realize that it is desirable to connect everything directly but it is not a good idea.

#16 mclewis1

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Posted 21 April 2009 - 04:56 PM

Sorry but the large batteries being discussed here put out a very stable 12.5-13.8 volts ... no spikes and such, and adding other devices will only produce a slight sag not a spike in the supplied voltage. You would be very hard pressed to find a dedicated AC-DC power supply that provides as good (stable and clean) a 12v supply as a large 17amp/hour battery.

The "direct" 12v to 12v connection is actually a small switching power supply but there is something more going on than just supplying a nice smooth 12 volts. Many laptops including the Asus eee's have the ability to sense what type of power supply is being used, exactly how I don't know. So the question of directly attaching a 12v power source to an Asus eee Netbook is more complicated than just protection and quality of the voltage source.

#17 bigbeck

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Posted 22 April 2009 - 07:31 PM

You would be very hard pressed to find a dedicated AC-DC power supply that provides as good (stable and clean) a 12v supply as a large 17amp/hour battery.


Very true. Batteries are about as clean as you can get. AC-DC adapters is where the dirty power comes from. Unless you have good filtering built in.

#18 rboe

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Posted 23 April 2009 - 12:43 PM

Can the laptop take the over voltage a fresh battery will supply? A fully charged 12V rated battery is putting out closer to 14 volts. I suspect this won't be a problem but I've gotten burned in the past assuming too much.

#19 JAT Observatory

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Posted 23 April 2009 - 12:49 PM

The DC input device (brick) is rated from 10 to 18 volts DC, but the output is regulated at 12 volts +/- .2

I wouldn't trust the laptop surviving a large voltage swing.

#20 daev

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Posted 23 April 2009 - 08:40 PM

You would be very hard pressed to find a dedicated AC-DC power supply that provides as good (stable and clean) a 12v supply as a large 17amp/hour battery.


Very true. Batteries are about as clean as you can get. AC-DC adapters is where the dirty power comes from. Unless you have good filtering built in.


This is why telecommunications run on batteries. AC power is there solely to keep the batteries charged, and filtering is very robust. Over-engineered, in fact.

For what astro-peeps do with a laptop in the field, a lappy that runs on 12V natively is a must.

dave

#21 daev

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Posted 23 April 2009 - 08:44 PM

The DC input device (brick) is rated from 10 to 18 volts DC, but the output is regulated at 12 volts +/- .2

I wouldn't trust the laptop surviving a large voltage swing.


So what I wanna know.... will the unit charge off of raw 12v or does it require a "licensed" charger?

dave

#22 mclewis1

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Posted 23 April 2009 - 10:27 PM

Dave,

So far from what has been posted the raw battery (~13v) doesn't work, the eee seems to need the charger regardless if its 110v-12v or 12v-12v. Don't understand why this is but that seems to be what is required.

#23 daev

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Posted 24 April 2009 - 12:04 AM

Pity that, they just lost a sale. There is but one reason for that: intentionally complicating their hardware for monetary gain. Oh well.

dave

#24 JAT Observatory

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Posted 24 April 2009 - 05:54 AM

"intentionally complicating their hardware for monetary gain" - I personally don't believe that is really that case. I believe they are just trying to protect the laptop.

As I said the input voltage to their DC-to-DC adapter ranges from 10 to 18 volts which is a rather wide range. I doubt if the laptop was directly connected to that kind of power fluctuation it would not survive.

It may not require a "licensed" charger and 3rd party charger may work, but I wasn't willing to try. All I know is I could not get mine to work straight from a 12 vdc power source, and since I had to purchase an adapter I figured I would purchase thiers.

#25 ccs_hello

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Posted 24 April 2009 - 05:05 PM

Few key items in modern laptop / netbook power supply system:
1. Any measurement has to be exactly on the power jack input of the netbook. Most importantly, sufficient voltage has to be maintained to make the internal battery charger work. I.e., thick power cable is good, power (temporarily) dip is bad, high consumption (both PC and battery charging systems are on) can easily cause the power to drop below threshold.

2. Some laptops/netbooks have voltage detection circuit to avoid over-voltage and under-voltage problems. Usually, approximately correct supply voltage, sufficient current rating, and thick power cable will get the detection circuit happy.

3. External (Lead-acid) battery output voltage varies depend on load and its charging status. A proper power rating DC-DC inverter makes voltage regulation easier (8-15V input range to a fixed 12V output).

Clear Skies!

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