External battery power for laptop

I asked a similar question in the Mobile section, but got no answers. As here is Power Supplies, this question is about one type.

I have an Asus N56J laptop, and when I travel I would like to power it from an external battery.

The external DC supply is 19.1v, but I'm not completely sure that voltage (or the precision) is essential. Can someone tell me if it is?

I didn't measure it under load, to see if there's any lag. If there is any, then I will know it's not regulated, which I'm not sure these supplies are.

The second part of the supply is inside the laptop, quite for sure, like battery charging and so on. Additional regulation, no doubt. The battery itself is 10.8v, so it's quite likely the external voltage is regulated down inside the computer.

Having no service manual, we can only guess. Getting one might be a good beginning.

For now I'm considering the Makoak 50000mAh, very much recommended in Amazon. But I wonder if lower voltages, like 12v from an Anker, wouldn't work as well. Or. most important, will they do any harm to the battery?

Please chime in anyone who did any of this. Thanks

Looking at the specs on the laptop, the power draw is too much for the Maxoak unit (only supports 20VDC @ 5A max current = 100W) while the laptop is rated at 19VDC @ 6.3A = 120W. It is likely that the battery bank would just power itself off on the overcurrent condition ... or worse -- overheat and damage the external battery if it wasn't engineering properly. You would probably have to go with something that has an AC power outlet, like the Anker PowerHouse, which supports 120W on the AC power outlet. Your power adapter for that laptop per Asus' website says 19VDC @ 6.3A -- so the laptop needs 120W.

I'm not sure where you got those specs, but the supply says 3.4A for 19VDC. There are no other specs on the manual: voltage, current or anything.

What I would like to know is the minimum voltage the laptop will work with. External AC supplies are many times higher in voltage to work cooler and to prevent for eventual.AC drops.

Perhaps it's a matter of cutting the external supply cable and measure the actual current.

The internal battery is 10.8v, with a 5.2A capacity. It works for about two hours.

I think that is the spec to work from.

I will say you are safe with +/- 5%, pushing it with +/- 10%. There is a distribution system before the battery that expects 19.1 volts, and that is what you should be working from, not the battery specs. 20 volts is just outside of +5% so it should be fine to do 20 volts.

I meant going down with the external battery voltage, not up as you suggest. How low I can go (if you can) on the battery: 12v, 15v?

It would be great to get a service manual for this Asus, but I'm not sure if it's possible. That would be the only way to answer these questions, I think.

My reasoning is based on my Blackmagic video camera.

The external AC supply is 19vdc, and there's a 7.4v battery that can go inside.

But you can power it for hours with an external 12v NimH battery.

So I wonder if there are no similarities in the power supply principles.

Laptops are more sophisticated. They will detect if a power adapter cannot supply enough power, and then limit power usage (lowered clocks, etc).

Of course I would expect more sophistication from a laptop. But it's interesting how little information is available over this on the web.

Maybe the first step to learn something would be to measure current in the AC supply in a common day.

This is the second matter (the other being internal cooling) that I have not seen having a proper mention as an important test on laptop reviews.

Maybe I'm looking at the wrong reviews.

carlmart said:

I'm not sure where you got those specs, but the supply says 3.4A for 19VDC. There are no other specs on the manual: voltage, current or anything.

What I would like to know is the minimum voltage the laptop will work with. External AC supplies are many times higher in voltage to work cooler and to prevent for eventual.AC drops.

Perhaps it's a matter of cutting the external supply cable and measure the actual current.

Click to expand...

I was going off the specs found on the Asus website for the laptop. Maybe you have a different version than shown on their website.

carlmart said:

Of course I would expect more sophistication from a laptop. But it's interesting how little information is available over this on the web.

Maybe the first step to learn something would be to measure current in the AC supply in a common day.

This is the second matter (the other being internal cooling) that I have not seen having a proper mention as an important test on laptop reviews.

Maybe I'm looking at the wrong reviews.

Click to expand...

I have plugged in 65 watt power supplies into a laptop that requires 95 watts, same voltage. The laptop will tell me it cannot charge the battery and will only operate in low power mode.

w1retap said:

I was going off the specs found on the Asus website for the laptop. Maybe you have a different version than shown on their website.

Click to expand...

The 6.3 amps is for the i7 version of the laptop. The i5 has a smaller power supply.

Coming back to this thread that I started. This time having done some tests.

I found a battery on eBay which is sold as car jump starter. It also has four USB outputs and one DC output that you can switch to 15v, 16v and 19v.

To power the laptop it has to be in 19v, and lasts for one hour.

Now, the battery is very light, can't say how much, but it weighs less than my 12v 4.5Ah NimH battery.

The amp spec (68.8Ah!!!) is probably for the USB 5v outputs, not for 19v.

So I wonder what other 19v batteries are around that are heavier and will probably last longer. Any suggestions?

It's a pity I can't buy from here the Maxoak 50Ah or the Crave CRVPP101 50Ah batteries sold by Amazon, because I'm now pretty sure they would do the job for more hours. Only eBay to count on.

My search there didn't get me too far.