Altoids Power Pack - Is it feasible?

[zen_cabbie]

I think that this and this are great ideas for movie watching or wardriving.  After finding a Penguin mints tin (only fitting) and following the basic concepts on the sites, I came up with a power pack that used 4 AA batteries, an LED and a switch (the latter two to add 1 volt of resistance). I can't really measure the amps, so I don't know if I'm close to meeting what the 5600 needs.

After getting a baseline test of Zaurus battery (Wi-Fi card on, brightness 100%), I charged it up and tried it again. with the battery pack in and on, the Zaurus had no more battery life than what it did before.

What did I do wrong, what am I missing? Has anyone gotten this to work, and if so, please help me figure this out.

Thanks in advance.

j

[V-Man]

OK, the Z wants 5V at up to 2A to power it through the power port.  There is another thread here on connecting through the internal battery connections, but I won't cover that.

With 4 AA NiMH batteries, at full charge you get 5.34V (approximately).  You do not need the diode to lower the voltage.  If you use one, you will lower the voltage to the point that the Z will not use it.  On the measurements I made (all with a fully charged internal battery), the Z never used more that 1A (actually more like 750mA), and that was with WiFi and full backlight.  If you really want the LED to indicate power on, wire it in parrallel so it won't drop your output voltage.  I really like the container you found for your power pack.  You can also use a voltage regulator chip (LM7805) and a 7V or greater battery to supply 5V regulated.  The 7805 is only rated to 1A, but you can use two in parallel to get more amperage.  There is another chip rated to 2A at 5V, but I don't remember the part number.  I have used both with good results.  At home, my desk is wired for 12V due to a ham radio addiction.  I have 75A to play with (and a 124Ahr battery backup system), so I easily made chargers for my iPaq and Z.

For additional information search for "battery" under my name "v-man" and you should find two recent threads about external and internal power packs.  Shadow Dragon (not correct spelling) has a very ambitious project using inexpensive lithium batteries hooked up to the internal battery connections.  My experience is only about the external packs.  

Let me know if I can supply any additional information for you.  It may take a day or two to respond though.

V-Man

[omega]

zen_cabbie: Watch what your doing....  1 volt of resistance - those are two seperate things.   It sounds like you wired the led in series with the battery pack?   If so then the led can't possibly pass enough current to make the zaurus charge properly...   Get yourself a normal diode 1n5401 or 1n4001 instead to provide the voltage drop.

Be very careful connecting the battery pack directly to the Z, as there is a good chance that you will exceed the 5.5vdc voltage limit that is usually associated with modern devices. If not, then you're also going to make the zaurus put out more heat as it deals with the extra voltage.

[zen_cabbie]

V-man,
Thanks for your response, your input is awesome.

This is my first DIY/modification project, so the 7805 has me a bit confused. How would I wire it up? I see three connection points and it has me confused.

If I am understanding correctly, I will need to wire two batteries (9volt) in parrallel with the voltage regulators?, then to a switch (to stop leakage) then to the power connector?

If I am not understanding this correctly, please let me know.

j

[V-Man]

The 7805 has three leads.  One is to the input +, one to the input -, and one to the output +.  I will dig up some schematics for the entire circuit this weekend if I can find them.  If you are using it from a noisy supply, such as a vehicle's electrical system, you should use a couple of capacitors in the circuit.  If you are using a regulated supply or a battery, you can forgoe the capacitors, but I still use them just to be safe.  The regulator chip that is rated for 2A, has five leads.  I will try to get the additional information you need.  

Remember the safest way is using the regulator chips to eliminate the possibility of over-voltage damage, rather than using just a battery.  A battery's output voltage will vary according to the charge.  4 AA NiMH batteries in parallel (what I use) will vary in voltage from 5.34V fully charged to 4.1V when depleted.  Alkaline batteries have a higher initial voltage, I think that NiCd batteries have approximately the same voltages as NiMH batteries.  I have never measured lead/acid batteries voltage drops in a 6V setup (all of my ham radio stuff uses 12V and my measurements were from a bank of 4 28AmpHour batteries).  If I make enough money from off-duty jobs over the Christmas holidays, I will make a pack using the 5V regulators and either a 7.2V or 9V battery pack.  I have not tested the results when the supply voltage drops to the point that the 7805 chip drops out of regulation.  I will check that before using it on my beloved Z.  I don't know if it just stops supplying power or if it passes whatever voltage it is receiving.  If you intend to build anything to power expensive items (such as a Z), invest in an inexpensive multi-meter.  It will be worth the money (probably less than $20).

V-Man

[kahm]

I built a battery pack using 2 sets of 4 AA NiMH batteries for my 5500. Using 1700mah batteries I got about 16 hours out of it. Using 2300mah batteries lasted well over 20 before I got sick of waiting for them to die and just left the thing running overnight. Now that I have an 860, I can't wait to find out how much run time I can get.

Makes the thought of war-walking very interesting.

[dz]

Wow, you guys should sell these things.  I suck at hardware things like this, so I'd buy one if it was reasonably priced.

[qx773]

External battery packs for the Zaurus SL-5500, C750, C760, and C860 are occasionally sold on eBay.

[Merardon]

If someone makes me an external battery pack for the C860 out of a Penguin Mints tin, using as many 2300mah NiMH batteries as you can cram in there safely, I'll buy it off you for a reasonably high price. Many thanks in advance. (Best make it the Peppermint tin, best looking.  ) You'll also get my gratitude, such as it is.

[xatax]

All your posts are really great and I have learned a lot, and I want to make a powepack myself, but after doing some search I haven't found one single schematics    Please can somebody post one or take a pic to the way the batts are connected to the LED and the resistor? Thanks a lot in advance.

[Mahoro]

Go Check the SL-5500 Zaurus  hardware discussion, they have the battery box discussion going.

[waalkman]

All your posts are really great and I have learned a lot, and I want to make a powepack myself, but after doing some search I haven't found one single schematics    Please can somebody post one or take a pic to the way the batts are connected to the LED and the resistor? Thanks a lot in advance.

Here you go:

http://www.fairchildsemi.com/ds/LM/LM7805.pdf