Power laptops with AA

[ltiu]

This is interesting:

http://www.techtium.com/view.asp?page=155

 

[Fallingwater]

I call bullshit. No way in hell six AAs can power the average laptop for an hour and a half. Perhaps a super-low-power model with everything sleeping and spun down, or a particularly efficient netbook, but not a normal laptop that's actually doing anything.

 

[ltiu]

I call bullshit. No way in hell six AAs can power the average laptop for an hour and a half. Perhaps a super-low-power model with everything sleeping and spun down, but not a computer that's actually doing anything.

A regular laptop battery has 6x 14500 cells (AA sized Li-On), right? Each 14500 has about 4.5 watt capacity.

A L91 has about 4.5 watt capacity too ...

 

[LukeA]

A regular laptop battery has 6x 14500 cells (AA sized Li-On), right? Each 14500 has about 4.5 watt capacity.

A L91 has about 4.5 watt capacity too ...

Usually it's 18650, so about 8.6Wh/cell.

 

[LukeA]

An additional benefit of Embedded BackuPower for Notebook Computers is its bi-directional charging capabilities, whereby when the primary AA batteries are rechargeable, the BackuPower circuit recharges them from the notebook’s external power source.

And what does it do should the AAs not be rechargeable? Pop them and make them spew potassium hydroxide onto the computer's innards?

 

[matrixshaman]

Has anyone looked carefully at that description ? It says it's a hybrid of AA and Li-Ion. They were talking NiMH AA batteries in combination with Li-Ion. I'm not sure how much advantage this has versus just adding more Li-Ion cells but they are not running the laptop on just AA batteries. I do suppose that the NiMH could be recharged a lot quicker and those in turn could slow charge or maintain the charge of the Li-Ion.

 

[Fallingwater]

The way I understand it, it first drains the AAs, then switches to the LiIon.
But it's very late and I'm off to bed, so I might have screwed up :p I'll read it again tomorrow. :D

 

[ltiu]

And what does it do should the AAs not be rechargeable? Pop them and make them spew potassium hydroxide onto the computer's innards?

You did not read the specs, it did say very clearly that the TEC2020 chip can detect battery types and charge only rechargeable batteries.

 

[ltiu]

Has anyone looked carefully at that description ? It says it's a hybrid of AA and Li-Ion. They were talking NiMH AA batteries in combination with Li-Ion. I'm not sure how much advantage this has versus just adding more Li-Ion cells but they are not running the laptop on just AA batteries. I do suppose that the NiMH could be recharged a lot quicker and those in turn could slow charge or maintain the charge of the Li-Ion.

I think the point here is that NiMH AA are way cheaper than Laptop Li-On. So using NiMH AA is more cost effective than buying a spare laptop battery.

Also, if in a pinch, you could use alkaline AA. Don't know how much power you will get from alkaline but every minute of extra power will help, in a pinch.

 

[bob_ninja]

I think the point here is that NiMH AA are way cheaper than Laptop Li-On. So using NiMH AA is more cost effective than buying a spare laptop battery.

Also, if in a pinch, you could use alkaline AA. Don't know how much power you will get from alkaline but every minute of extra power will help, in a pinch.

Of course NiMH AAs are cheaper and for a good reason. First, it should be clear that LSD type more robust cells are necessary due to high load. Non-LSD might work but their lifespan would be abysmal.

Eneloop 2Ah x 1.2V = 2.4 Wh

Compared to:

Usually it's 18650, so about 8.6Wh/cell.

So of course NiMH cheaper but then it has less than 3x energy content. The comparison might be only slightly better for NiMH using a higher capacity type like 2700 PowerEx say.

Thus the same number of AA provides less than 1/3 of 18650 cells, or you'd need 3x more AA cells.

Alkaline would not be able to handle the high load well and would last even less.

So this could work only if it could take a large number of AAs - bulky, heavy, cumbersome.

 

[ltiu]

So of course NiMH cheaper but then it has less than 3x energy content.

Not to mention NiMH is way heavier than Li-On.

Your "3x more" estimate is inaccurate. Remember, size-wise 18650 are bigger than AA. So they have more volume to store chemicals for power.

 

[shadowjk]

I think this battery pack will have a big appeal to many users, not being locked-in to expensive proprietary packs but being able to use your regular stash of eneloops when you need the extra runtime :-)

 

[Fallingwater]

I think the point here is that NiMH AA are way cheaper than Laptop Li-On

Not necessarily.
A four-pack of LSD cells costs around €10 whatever the brand, and provides a total of 9.6 watt-hours (or thereabouts).
A two-pack of Trustfire 2500mAh 18650 cells from DX costs €6.6 (after US$-€ conversion) and provides about 18.5 watt-hours.
Considering TF cells have consistently proven surprisingly good, to the point that they actually have the stated capacity (gasp!), there's really very little point to using NiMH to power laptops.

That is, of course, obvious even if you don't do any calculations at all; laptops of all kinds did use NiMH cells back when LiIon still wasn't widespread enough, but they switched chemistry en masse after it became so. Aside from the OLPC, which is not exactly a standard laptop, I don't think you can even buy a NiMH-running laptop today.

 

[ltiu]

Not necessarily.
A four-pack of LSD cells costs around €10 whatever the brand, and provides a total of 9.6 watt-hours (or thereabouts).
A two-pack of Trustfire 2500mAh 18650 cells from DX costs €6.6 (after US$-€ conversion)

You missed my point.

My point is you need to pay $100+ for a 6 cell laptop battery pack from Dell/HP/Lenovo/Acer/Gateway when you can spend $25 on Eneloops ...

 

[carrot]

This is pretty exciting, until you think back and realize how much battery power computers suck up.

My Sega Genesis Nomad took 6 AA's and tore through them in no time at all.

I would rather see more efficient, less bloaty software so we can use smaller and more efficient machines.

 

[Fallingwater]

My point is you need to pay $100+ for a 6 cell laptop battery pack from Dell/HP/Lenovo/Acer/Gateway when you can spend $25 on Eneloops ...

You spend a quarter of the money for a quarter (or less) of the performance. Eight NiMH still don't come close to the energy contents of a proper LiIon pack.
Also, laptop batteries can cost a lot less than $100 if you don't buy brand-name ones. At the time of writing I could get a pack for my Toshiba M30X for about €33, and batteries for more widespread notebooks would probably be cheaper still.

I would rather see more efficient, less bloaty software so we can use smaller and more efficient machines.

Software for general purpose computers is bloated by definition. We do have what you want, in the form of embedded operating systems, but they tend to have much less compatibility. At the current state of technology, it seems you just can't have both.

 

[HarryN]

I think my HP laptop with a 14 in screen and dual core AMD pulls about 30 watts when working hard, maybe 1/2 that on average. There are some newer LED backlit setups that can get down in the 20 watt peak / 10 watt loafing range. Even that is a lot for AAs, not impossible, but my expectations are low for time period from any brand of 6 x AA cell.

Small dia cells tend to enhance current delivery and larger dia cells tend to enhance capacity. For my normal laptop use, I would go for capacity any day.

NiCads and NiMHs have their place, but it is a tough sell to convince a traveler to lug the extra mass of Ni based cells vs Li based cells.

I guess for an emergency or special situation, a battery pack full of 20 x energizer Li AA cells would could be useful. There are some conditions where AAs are plentiful and everything else is not available.

 

[shadowjk]

Not necessarily.
A four-pack of LSD cells costs around €10 whatever the brand, and provides a total of 9.6 watt-hours (or thereabouts).
A two-pack of Trustfire 2500mAh 18650 cells from DX costs €6.6 (after US$-€ conversion) and provides about 18.5 watt-hours.

Obviously the ideal would be if someone made a laptop battery pack that was actually a battery holder with protection and balancing circuitry, taking 18500 cells :-) You could further improve it by splitting it into two parts, so that you could swap batteries without having to shut down.

 

[Fallingwater]

Obviously the ideal would be if someone made a laptop battery pack that was actually a battery holder with protection and balancing circuitry, taking 18500 cells :-) You could further improve it by splitting it into two parts, so that you could swap batteries without having to shut down.

Y'know... that's actually a pretty neat idea. It shouldn't be too hard to manufacture something like that.
Crack open a standard pack, remove the bottom and replace it with a removable cover, then unsolder all the cells and put tab and spring connectors in place of the wires. It'd be a tight fit, but it's probably doable.
Since cells are almost always in a 2p#s configuration, you could do what you said and remove one of the parallel strings without shutting down. You'd probably confuse the hell out of the remaining power gauge, but the laptop shouldn't stop working.

If my laptop survives until its battery finally dies (currently more than 4 years old and still going strong) I'll try this.

 

[ltiu]

http://www.blackanddecker.com/ProductGuide/Product-Details.aspx?ProductID=17894

Has 8x2 NiMH (16 total, 2 banks of 8 in-parallel). I can confirm it can power my old inefficient laptop (max rated at 70 watts, average of probably 35 watts) for 1 hour (I need to get a Kill-A-Watt to really measure it).

So 6 NiMH AA can power a modern more efficient laptop for a while.