Battery Extenders Based On Rechargeable Nimhs

[Reaper]

yep! i'm thinking of something like that in "waterproof", maybe a constuction with some of these heat shrink tubes

do you have experience with zaurus and low voltage, say, below 4.8 or 4.7 volts?
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About the lower voltages...

Yes, some time ago I've found a scheme for DC/DC converter that needs (in theory) as few as ONE or TWO large, fresh, fully charged 1.2 V battery or batteries. One of community guys assembled it, it worked, so look and give it a try if you want.

[a href=\"http://pdfserv.maxim-ic.com/en/ds/MAX641-MAX643.pdf]http://pdfserv.maxim-ic.com/en/ds/MAX641-MAX643.pdf[/url]

[cmonex]

results for second test run with zaurus:

c3100 battery was down to 10%, i put 4 freshly recharged NiMHs in the battery pack (see above) and connected it to zaurus, input voltage of the regulator with "zaurus-load" dropped from 5.7something to a little bit more than 5.4 volts, output was fine with 4.97 volts

but then voltage rapidly dropped, within 25 minutes output voltage was below 4.60 volts so that zaurus didn't recognize this anymore as being "plugged to ac"

any suggestions are appreciated (i'd like to stay with NiMHs though)
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guess ni-mh sucks..
if the zaurus battery was only at 10% when you started charging it it may have wanted as much as 2000 mA. your ni-mh's were 2500's, so this means it would be almost 1C of current. and you know ni-mh's voltage will drop a lot then. (it can recover later though) especially if they weren't good quality ones..
if you could attach the ni-mh's to the battery connectors they would last longer probably.
or buy a li-ion battery 1700 mAh for 15$ at laptopsforless.com

[Da_Blitz]

[Begin things you dont need to know or care about]

Reaper is on to something, if you know electronics and dont mind wiring an inductor or two then you can do that with a buck-boost switch mode power supply, bassically it takes in DC, converts it to AC, uses this to double the voltage (or more depending on the parts) then spits it back out as DC

the only problem is they normally have a minum load thot they need in order to work properly and can be tricky to get working/design

also note that these are POWER converters so doubling the voltage means increassed current draw

ie
power = voltage * current and as its a power converter you get both sides equal
voltage * current = voltage * current
< battery side > = < zaurus side >
1.2V * i = 5v * 2A
simplyfing we get
(5v * 2) / 1.2v = i
i = echo $((10 / 1.2)) #
i = 8.3A

bassically this would be a bad idea off 1 cell 2 might be alright but it wont charge the zaurus up much, and using a switch mode power supply at low voltages is not as good in terms of effeciancy as your standard 7805 linear regulator or zener diode (ultra low drop out voltage stops regulating at rated voltage so normally 5.1v's) based regulator

keep in mind analog electronics are not my strong point, im much happier desighning an SDRAM interface circuit than i am designing somthing as simple as an amplifier

We now return to our regular broadcast

[Reaper]

Here is the photo of that device, DC/DC converter

[img]http://www.hpc.ru/board/files/cimg7301_.jpg\" border=\"0\" class=\"linked-image\" /]

It does start with 3 batteries (3.6V), also should with 2, but from AA, it draws too much current. It should work with 2 C or D batteries, though.