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.

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!!!!

Last edited by netomx (2007-11-17 1:21:54 am)

http://cgi.ebay.co.uk/11-1v-2100mah-20C … dZViewItem
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.

parag0n wrote:

http://cgi.ebay.co.uk/11-1v-2100mah-20C-Lipol-Lipoly-Battery-High-Quality_W0QQitemZ270114206128QQihZ017QQcategoryZ34056QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
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.com/batteries-and-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.

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

pamaluka wrote:

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.

eeeByGum wrote:

I was wondering if one of these would suffice.

http://search.stores.ebay.co.uk/all-bat … ameZRC0021

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 wrote:

I admit, I know nothing about this subject, but I noticed these 10,000mAh batteries on the market?
http://www.battery-force.co.uk/detail_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-tech.com/ncharge.asp

Last edited by Crast (2007-11-19 1:39:11 pm)

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 wrote:

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?

Try this

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? … 0184651660

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

Thanks for the detailed information Crast. I'll leave playing with electricity to you guys, but I appreciate that you took my pondering seriously.

Well

I popped along to Maplins and brought,
- 1 X PP3 Type Battery Snap  £0.49
- 1 X D Size Battery Holder - 6 Cell  £1.39
- 1 X DC Plug1.7mm/4.75mm - L47AY  £0.89
- 6 X Energizer Ultra+ Alkaline D Size Batteries  £7.48

For £10.49 I figured I had the makings of a 20,000~10,000mAh 9VDC disposable external battery pack.
Be it a fuse-less, non-current limited, slightly dangerous battery pack.

I soldered the plug to the battery clip and tripple checked that the plug was center positive when the clip was attached to the battery holder.
The no-load voltage of the battery pack was 9.63V. Near enough I thought.
The voltage should settle down to sub 9.5VDC when load is applied.

So I plugged it into my eee fully charged eee.

It didn't go well.
The on-screen charge state window flickered between 'Battery Mode' and 'AC Mode' charge states in the top left hand corner of the screen.
It flickered between states a few times a second.
Even worse, a "stressed electrical component" sound came from the eee.
I pulled the plug out quickly.

No damage seems to have been done.
The eee works, charges and dis-charges fine.

Can anybody shed some light on what might have happened ?
Why the flickering and "stressed electrical component" sound ?

I wondered if the eee tried to source a large amount of current from the non-current limited battery pack.
If so, I'm not sure why it would have. The voltage of the battery pack and the eee AC charger aren't vastly different.

Clues anybody ?

eeeByGum