Battery Extenders

[speculatrix]

Okay, here is the diagram for my battery.
This is my first diagram, so I hope it makes sense.
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erm, that diagram looks scary, as if the resistor is in the wrong place to limit charging of the battery.
as a rough guess, the attached is what I think it should look like. usb charges battery pack through resistor, and can power Z at same time. battery pack powers Z bypassing resistor using diode

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charging resistor chosen so if batteries are really flat, i.e. half voltage (2.5V) then charging current is 125mA. Could probably happily use a 15 ohm res to speed charging, but have to be careful to not overload USB port if also powering Z, nor to cook the batteries.

[pelrun]

Ntw's circuit is pretty scary.

The only component in the circuit that's doing anything is the diode (the resistor only protects the LED), which drops the charging voltage to approximately 4.4V.

LiIon cells explode when charged beyond 4.3V.

And that's assuming it's plugged into a properly regulated USB port giving 5V. A cheap AC-to-USB charging adapter might be putting out more than that.

I'd build a simple charger from a LiIon charger IC (say Maxim's nifty looking MAX1555, I really must order some samples) which would be almost as simple as Ntw's circuit, safer, and you get a "battery full" indicator into the bargain!

[Da_Blitz]

i am assuming nicads here, if so then the charging circuit makes sense, not the best or the most efficent but its ugly and it works.

things to watch out for: the 0.6v drop across the diodes (in this case the drop should be closer to 0.6 rather than 0.7) not the best way to do it but its very robust. now for 0.6V*0.5A we get 0.3W so you could use a small signal diode instead, saves alot of room

i would actually look into a 2 cell charger with a buck boost converter. hackaday had one. you put 2 cells in series giving you about 3v and use the boost to pump it up to 5v at high efficcy. you would be looking at about 80% efficency at such small voltages where as your design relies on resistive parts giving it a good iffence on discharge (only loss is via the diode) but really bad on the charge (lot of power wastage in the diode)

other thing to watch out for is reling on the nicads to give 1.25V, this is a VERY BAD IDEA, at full charge they can give more than that for about 5 mins, meaning a dead Z if you are unlucky. also as the battries discharge  once you hit 80% capacity the voltage falls rapidly, meaning you could lose up to 20% of the total battery capacity

if you have a pic programmer then you can get really good high effincy battery charger/discharger plans off of the net. if you dont then there are others that reliy on discreete ICs that have better effincy but less features. the advantage is they all fit in an altoids tin

[jpmatrix]

hi here
i've just found and bought the Etitech Nano mobile charger :
http://etitech.com.my/products.php?sm=prd1
it is only 2100mA, but it is slim, chargeable via usb and at least it seems to charge the zaurus!
i'll let you know more later

[Capn_Fish]

I'm looking at building a battery extender for my Z, and I think I have most of the materials, but am lacking in the knowledge department.

I've got 2 900mAh, 3.7v iPAQ batteries to use, but need to know how to wire them up. Could somebody sketch up a diagram? I'm looking to have a power input jack (probably from a Z's adapter), a power output jack, and the batteries.

EDIT: The batteries are Lithium-Ion

[speculatrix]

I've got 2 900mAh, 3.7v iPAQ batteries to use, but need to know how to wire them up. Could somebody sketch up a diagram? I'm looking to have a power input jack (probably from a Z's adapter), a power output jack, and the batteries.

EDIT: The batteries are Lithium-Ion
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if they're lithium ion, and you don't have the original charging circuit, I would strongly recommend you don't try it... it's too easy to overcharge and damage them or make them go bang!

[a href=\"http://www.google.co.uk/search?q=lithium+ion+explosion]http://www.google.co.uk/search?q=lithium+ion+explosion[/url]

[Capn_Fish]

I've got 2 900mAh, 3.7v iPAQ batteries to use, but need to know how to wire them up. Could somebody sketch up a diagram? I'm looking to have a power input jack (probably from a Z's adapter), a power output jack, and the batteries.

EDIT: The batteries are Lithium-Ion
[div align=\"right\"][{POST_SNAPBACK}][/a][/div]

if they're lithium ion, and you don't have the original charging circuit, I would strongly recommend you don't try it... it's too easy to overcharge and damage them or make them go bang!

[a href=\"http://www.google.co.uk/search?q=lithium+ion+explosion]http://www.google.co.uk/search?q=lithium+ion+explosion[/url]
[div align=\"right\"][a href=\"index.php?act=findpost&pid=162558\"][{POST_SNAPBACK}][/a][/div]

What do you mean by original charging circuit? I have the adapter/cradle to charge them, but that's probably not what you mean.

EDIT: OK, what if I charge the batteries externally? Can somebody draw up a pattern then? (2 batteries, power output, and resistor)

[speculatrix]

you have to have an intelligent charging circuit for LiIon, as there are two phases to charge it up. if you do have an external charger for it.

[pelrun]

It's really a bad idea to do this yourself, unless you've got some electronics experience. You definitely can't do it without a few IC's designed for the task.

You could actually get away with charging a single cell or a parallel array of cells with just a big current limiting resistor, but it's still a really bad idea. You definitely can't do it to a series array, which is what you're considering to get the 5v the Z needs. If you were to use a parallel array, it would need a step-up converter to get from ~3v to 5v, and that's at least another IC and an annoying-to-procure inductor, with layout and filtering rules that make my brain hurt.

Sadly, the resistor is how the 9800mah packs are wired - mine broke and I needed to open it up to effect repairs. I'll probably replace the charging circuit with a dedicated IC in mine at some point (but retain the stepup converter, because of the aforementioned brain hurt.)

[laan]

Purchased this one today:

http://www.portablepowersupplies.co.uk/usb...batterypack.htm

feedback to come

[speculatrix]

http://www.portablepowersupplies.co.uk/usb...batterypack.htm

I'd really like a battery extender with a built-in usb hub, a memory card reader. oh, and a 1.8" hard drive. Oh yes,, and a GPS and a 3G modem or bluetooth adaptor

(edited to add GPS)

[laan]

Purchased this one today:

http://www.portablepowersupplies.co.uk/usb...batterypack.htm

feedback to come

Well the battery is light but strong, tried with blackberry, V3x and later Zaurus worked perfectly on both and nothing burned down, all charged and battery still has food next step is trying with my USB powered HUB... same connector... who knows

[tanjian2]

I've had a Zap Universal Power supply (blew up with a flash and bang) and a 9800mAh PSP battery - never seemed to hold its charge for too long - currently unable to recharge........
I am still searching for a viable battery source for the Z - preferably just as speculatrix describes +GPS :-)
Seriously though let us know how this thing works out....

[jpmatrix]

Purchased this one today:

http://www.portablepowersupplies.co.uk/usb...batterypack.htm

feedback to come

i've bought quite the same product ! the Nano mobile charger from Etitech :
http://www.etitech.com.my/products.php

it works quite good, with my PSP, my nokia6630 and my Zaurus; although it works best when charging while the device is switched off... mine is only 2100 mAh whereas the portablepowersupplies' one is 3400 mAh so it should be stronger. this is definitely the kind of charging device i was looking for

[Capn_Fish]

Something like this:

http://www.sparkfun.com/commerce/product_i...roducts_id=8610

would be neat (6000 mAh! 3.7v, that's what the Z is, no (for internal battery)?).

I realize it's used, but for $10... I just thought that somebody may find it useful.