Project: Extended Battery Pack (to extend battery x4)

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I have an on-going project of creating a battery extender for my xda and I want to share it.

This is composed of 8 rechargable NiCAD or NiMh battery connected in series to produce a 9.6 v. The 9.6 v will be regulated by a 5v regulator (LM7805) then it will be connected in the XDA power dongle.

With this project, the battery life can be x4 or more depending on the batteries used.

I'm currently (no pun intended) trialling a Mugen 4500mAh battery which looks likely to give me >16 hours continual use ob my XdaII. Probably much more expensive than your solution but perhaps more convenient being 'built-in'.

Good idea though, I could have done with your solution two years ago!

Update on my project

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I already assemble it and have try it already and here is the update.

The good news is the battery is charging.
The fall back is that the regulator that I have used is emitting too much heat.

I also have done some bench test and here are the data for those who are interested.

1. XDA IIs is drainning about .700 Amperes when charging supplied by 5v
2. XDA IIs will not charge with 4.8 V or below
-I got this data using a adjustable power supply with an Ampere meter

Project Fall down

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For the fall down, I think it is because of two reason:
1. It is because the total Voltage supplied by the batteries is 9.6V and the out put regulation is 5V, therefore the 4.6V is being converted to heat.
- I should have use 6 battery insted of 8 to 7.2v instead of 9.6.

2. Since 5v is the out put of the regulator and it is charging the battery with a 4.8v (for i.e.) this will mean that the .2v drop will be in the line between the charger and battry which also mean the current is the max output of the regulator (Applying OHMs Law I=V/R, and R being 0 will result to infinity in theory and maximum in reality)

____________
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V1=5V V2=4.8V
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-I think I should have put a resistor to control the current or I should have designed a regulated current supply instead of a regulated voltage supply


For the #2 reason i'm not still sure about this because, this can only be true if the XDAIIs or it's battery does not have a built in charging circuit.
I have read some articles on mugen battery that it has a overload protection circuit my guess is that XDA also have it my I dont have any information yet. Incase XDAIIS or the battery alreadhave a charging circuit I only need to resolve my #1 Fall down.

I think I need to do more research, but if anybody could provide me information it will be highly appreciated. XDAIIs service manual maybe a greate help.

resolved

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My project is now working, the over heating was resolved by putting a heat sink on the IC regulator and reducing the numbers of AA battery to 6 pcs (6 x 1.2 =7.2).



I'm still not sure where the over charging protection circuit is installed (XDA unit, battery or in the power supply/Craddle) incase it is not with the xda or the battery then I need to be carefull not to overcharge my battery with my project but if it is in it then my project is now perfect.


Any body knows where the over charging protection circuit is please help.

Re: resolved

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there is a russian link for the same project - http://forum.pocketz.ru/index.php?sh...xtender&st=100
Adapter:
http://wince.box.ru/russian/caradapter.htm

typically you can take any car adapter, give 12v to its input and take 5v from output for charging your PocketPC battery. Most car adapters would give 5V output if input is between 8...12V

hi kabayan,

i think the over current protection is in the device.

i converted an external battery charger (using 4x AA battery) intended for blue angel to my himalaya. there's nothing inside it except for a 10K resistor in series with the output.

i also noticed that even with the correct regulated voltage applied, my hima won't charge without a current limiting resistor, so its definitely an over current protection in the device!

congrats in your project!

Schematic Diagram

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Anybody has a schematic diagram of XDA? Please share

If you have the money might as well buy additional battery so no need for you to go thru all thoses stuffs. My project had work for me actually it is easy just basic ohms law. The challenge I have encountered in the project was the heating up of the regulator but it was resolved. by the way the reason I made a battery extender is because that time extra battery is not easy to find and I dont have a budget for it so I just salvage some electronic parts from my previous projects. But now I already bought an extra battery- a lot convience than before