111 replies to this topic

[Crast]

I ordered my black eeepc a few days ago, and have been doing research.

I'm considering building a simple battery pack. And when I mean simple, I mean cheap and ghetto. But it should do the trick for my purpose. Basically, I'm willing to let the total package be 4 lbs instead of 2 lbs if I can increase the total use time away from wall power to about 6 hours.

To achieve this, I am going to use something like this:
http://www.radioshac...pi-2062251.html an AA battery holder and
http://shop.mahaener...p?idProduct=415 2700mAH NiMH AA batteries.
(note I do not plan on buying the batteries direct from maha, and I may use a different holder depending on desired fit within an enclosure)

In order to get the battery time I'm looking for, I'll probably need two holders wired in parallel (for a total of 16 AA batteries.)

The total cost of all this (per 8 battery plus holder plus batteries some trinkets) will be about $25-$30. This does not include the cost of the charger, because I already have a charger for nimh AA's. You can get a basic charger for about $30. I will photograph and document my success (or failure).

The plan: to wire together the holder(s) to a standard connector (about $1 from your neighborhood radio shack if you don't have a bunch lying around already, which I do) and possibly put a small voltage meter circuit in parallel. I'll probably find a nice tin of some sort to stow the contraption in. I'd run the laptop off the pack I'm building until the pack is dead, and then use the built-in battery after that.


From what I can tell, the standard charger puts out 9V at 2.0 amps. When I get mine, I'll build a small shim circuit so I can wire an ammeter in, and find out what the nominal power draw is at idle, when charging, and when doing a compile, and then I'll possibly re-do my requirements if need be. However, I think I can achieve what I'm looking to do.

Has anyone tried or considered some external battery packs? I know there are some pre-made solutions that are more elegant (built in chargers, nice slim form factors, etc) but they are also in the order of about $120+ last I checked

[Haku]

The ~3.5 hour runtime of the standard battery has caused a lot of people to think before buying, but it's also caused people to ask about secondary and higher capacity packs.

I wish you luck with your project, I've given it a little thought about making a secondary pack to supplement the original or replace it completely with a double runtime one. The ideal solution would be something that has the same footprint as the Eee and clips/sticks to it's base, same idea as the battery packs for some portable DVD players.

BTW, 3800mAh AAs are now on the market.

The Eee PSU outputs 9.5v at 2.315A, to get a steady 9.5v from a battery source a DC-DC converter would be needed, Dimension Engineering sell some good adjustable stepdown ones that can be put in parallel to increase the ampage.
If you were to use 12x 3800mAH AAs in series to give you ~14.4v at 3800mAH, then DC-DC convert it down to 9.5v you'd have the equivilant of a 4900mAH 9.5v battery pack (that is if my rough calculations are any good with 90% efficiency of DC-DC conversion). Of course this is all theory, but would like to try it out for myself.

[Crast]

Quote

The Eee PSU outputs 9.5v at 2.315A, to get a steady 9.5v from a battery source a DC-DC converter would be needed, Dimension Engineering sell some good adjustable stepdown ones that can be put in parallel to increase the ampage.
If you were to use 12x 3800mAH AAs in series to give you ~14.4v at 3800mAH, then DC-DC convert it down to 9.5v you'd have the equivilant of a 4900mAH 9.5v battery pack (that is if my rough calculations are any good with 90% efficiency of DC-DC conversion). Of course this is all theory, but would like to try it out for myself.

3800 mAH, wow that's sexy. How much do they cost? I might actually consider 2500 mAH AA's, from a site I found with tests it showed that the 2500's were close to the powerex 2700's but much cheaper.
( http://www.users.on....ns/Reviews.html )


I'm hoping that I can get away running it without a dc-dc regulator, running a 8x nimh => 9.6v and hoping that the eee has internal regulating circuitry. I should probably check this else I might fry it; NiMH can vary from 1.4v to 1.0v per cell (though the nominal voltage is around 1.2v for the large majority of their life) and that multiplied by 8 cells is a pretty large voltage range.


To be safe though, I probably want something like this:
http://www.national....l%20Description

About $2 at radio shack for the regulator, plus some resistors and stuff.

Edited by Crast, 17 November 2007 - 05:17 AM.

[netomx]

Wow, this seems to be a good mod for the battery!

I was thinking about this, go to walmart and buy this:

1. Express charger (Energizer) with 4 2500mah batteries (like $25)
2. 4 more energizer batteries (i think $10)
3. buy that caddy (or something fancy) in radioshack (probably $2)
4. buy a jack and cord ($1 ??)

Ill try this tomorrow!!!! =D

Edited by netomx, 17 November 2007 - 06:21 AM.

[Haku]

The pack of 4 3800mAH AA's are about £10 / $20 inc. postage from eBay: http://search.ebay.c...999999QQsalicZ3

Whatever I do I think I'll be using DC-DC regulators so it gives me peace of mind that I won't over or under voltage the Eee, it should also allow me to hook up the Eee to a car battery and my electric bike battery (26v 12AH).

Edited by Haku, 17 November 2007 - 03:07 PM.

[parag0n]

http://cgi.ebay.co.u...VQQcmdZViewItem
may be more useful, 11.1v, 2100mAh, small and light. chuck a couple of them in parallel into a small container, add a switching regulator to change it to the 9.5v DC you need (TI make some good modules), and use it as a passthrough to charge the eee.

[Crast]

Quote

1. Express charger (Energizer) with 4 2500mah batteries (like $25)

Beware the super-fast NiMH chargers (1 hour or less), they have a tendency to reduce the life of the battery and/or the number of charge cycles possible. The batteries have internal catalysts which turn excess energy into heat to avoid damaging the battery, but with the chargers faster than 4 hours, you'll probably put in more than the heat it can put out. Your mileage might vary, this is just what I've read.

4 hour chargers are a good compromise between reasonable charging speed and safety for the battery. There are some 1-hour chargers which have special protection circuitry that will stop charging when you reach a certain point, then resume when it cools a bit, some also have fans, so it might not be so bad. The 15-minute chargers are probably a really bad idea.

[marktee]

Quote

http://cgi.ebay.co.u...VQQcmdZViewItem
may be more useful, 11.1v, 2100mAh, small and light. chuck a couple of them in parallel into a small container, add a switching regulator to change it to the 9.5v DC you need (TI make some good modules), and use it as a passthrough to charge the eee.

I too have considered using an 11.1v Lithium Polymer battery and step-down regulator, but *BEWARE*, these batteries require a special charger or they will explode. You cannot use the same charger for that you would use for NiMH. I have worked with LiPo batteries extensively in electric radio controlled model aircraft. For more information about how serious this is, refer to http://www.rcgroups....d-chargers-129/ and go through the first two sticky posts. Although similar batteries are often used in portable devices these days, they always have special circuitry built-in to protect the battery and the user. Packs like these do not have the circuits built-in. Even a punctured battery could catch fire, and they can puncture more easily than a NiMH.

[eeeByGum]

I was wondering if one of these would suffice.

http://search.stores...PageNameZRC0021

The spec claims that it has a capacity of 39.00 Watt/Hours and that it has a typical operating time of 2-3 hours.

39.00 Watt/Hours translates to 4333 mA for an hour at ~ 9VDC.
I guess at that capacity, it would run the EEE for about 2.5 hours on its own.
That's proved that the specs aren't a little 'over optimistic'.

Has anybody tried one of these with the EEE ?

[pamaluka]

is it not possible to open the eee battery pack and replace the 4 cells with new onces witch have a bigger capacity?

[Haku]

As far as I know, the Eee battery pack contains the highest capacity cells available, to increase the capacity you'd need to modify the shell of the pack to hold 1 or more pairs of (the same capacity) cells to increase battery runtime.

The standard battery pack contains 4 cells, apparently Asus will be bringing out a 6 cell pack for 50% longer runtime.

[Crast]

Quote

is it not possible to open the eee battery pack and replace the 4 cells with new onces witch have a bigger capacity?

No.


Lithium-Ion packs are sealed for a reason, and that is because they're very complicated (have a board with protection circuitry inside as well as the cells), and the individual cells inside are probably not packaged for handling outside of the enclosure. They are probably prone to leaking if you open the plastic pack.

Even if you found the cells in the right size/shape to fit inside the battery pack, it's likely the protection circuitry (which needs to talk back to the laptop as well as monitor the cells) is hard-wired (probably non-updateable firmware) to the capacity of the cells. This means it will not "recognize" the larger cells, and will either operate at the same capacity as the smaller cells, or worse, simply not work.

The hacks described above use NiMH AA cells instead of Li-Ion, which are much simpler cells. Each individual AA-sized NiMH cell is about $3-$4, so it's not too expensive to replace if one of them dies or gets reversed. it also means that once you build the pack, if you don't use a sealed enclosure, you can just carry a bunch of spare AA's and get as much battery life as you're willing to carry in AA's. A setup with a regulator could use alkaline AA's in a pinch also, which is a major benefit.

Quote

I was wondering if one of these would suffice.

http://search.stores...PageNameZRC0021

That would be great! A pre-made solution weighing 1.5 lbs and with ~4300 mAh for only ~$40? If it is really as advertised, and not 'optimistic' in its capacity, it would be decidedly sexier than building your own for close to the same price and then having to charge 8-12 batteries individually all the time. So long as the eee is content with running off only 9v instead of 9.5v on the input, I might consider this instead of building my own.

I had looked at some of the laptop battery packs before, and those are over $140 and often 2-3 lbs in weight, though they do provide a lot of juice. Also, they typically put out 18V, not 9v, so you'd need another regulator if you bought one of those. This DVD pack seems ideal, really.

[Teacup]

I admit, I know nothing about this subject, but I noticed these 10,000mAh batteries on the market?
http://www.battery-f...AMDNIM002B.html

[Crast]

Quote

I admit, I know nothing about this subject, but I noticed these 10,000mAh batteries on the market?
http://www.battery-f...AMDNIM002B.html

Those would work, but it'd be pricey. You need a minimum of 8 NiMH cells, so 4x £21.45 = £85.80 = ~$175. The weight would be 1310 grams ( 2.88 lbs) for the set. You would get a 10 Ah battery though, which would provide a lot of runtime.

Another option which will give you >10 Ah (you'd need a step-down regulator since it outputs 16-24V) in 3 lbs is this: http://www.valence-t...com/ncharge.asp

Edited by Crast, 19 November 2007 - 06:39 PM.

[digitalfreeze]

I emailed mugen power battery to see if they plan on offering a high-cap battery for the eee.
They make good quality high-cap batteries for other devices (pds/umpc/etc.) so I figured I'd hit em up.
I will post their reply when I receive it.

[stevefazek]

how many volts does the EEE PC use? They do make 10 amp hour batteries for like 10 bucks each 1.2 volts. they are in the D size cell.

[Eeefreak]

I found a battery pack for portable DVD players that should work. It puts out 9 volts and is around $30 at Walmart.

Edited by Eeefreak, 12 April 2008 - 10:45 AM.

[digitalfreeze]

Quote

I found a battery pack for portable DVD players that should work. It puts out 9 volts and is round $30 at Walmart.

hey freak....any links?

[Crast]

Quote

I found a battery pack for portable DVD players that should work. It puts out 9 volts and is round $30 at Walmart.

Just bought one of those myself off ebay:
http://cgi.ebay.com/...em=270187969021
product page: http://www.energizer...&prodcode=30102
My eee should be in today, and hopefully the battery pack will be in within a week, then I'll post my results.


If you have some cash, this is also an option, at 8000mAH: http://www.batteryge...batterygeek.htm

They have a 14,000 mAH available for $200 also.

Quote

how many volts does the EEE PC use? They do make 10 amp hour batteries for like 10 bucks each 1.2 volts. they are in the D size cell.

It uses 9.5 volts. So you'd need 8 D cells minimum.

Edited by Crast, 20 November 2007 - 03:23 PM.

[Jon Bradbury]

Try this

http://cgi.ebay.co.u...em=270184651660

20,000mAh should give around 13 hours...