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Converting a scanner

 
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laser_red
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Joined: 02 Jan 2009
Posts: 3

PostPosted: Fri Jan 02, 2009 11:22 pm    Post subject: Converting a scanner Reply with quote

I have a portable scanner that is rechargable(7.2V/600mAh) and every time I get it out of the drawer, it has self-discharged. That's not much help if it's storming and the power is off. I would like to convert it to run on non-rechargable lithium batteries. As near as I can tell, there aren't any single cell 7.2V lithium batteries made that will fit in the space vacated by the old batteries. I really don't want to have to connect multiple cells together every time I have to replace them. Can I run it on a 9V battery without damaging it? The scanner is also capable of running on 12V DC from a car power point. Does that mean it can handle 12V but 7.2 is enough to power it? Would there be a way to regulate the 9V down to 7.2?

-Alan
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Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Mon Jan 05, 2009 9:49 pm    Post subject: Re: Converting a scanner Reply with quote

laser_red wrote:
I have a portable scanner that is rechargable(7.2V/600mAh) and every time I get it out of the drawer, it has self-discharged. That's not much help if it's storming and the power is off. I would like to convert it to run on non-rechargable lithium batteries. As near as I can tell, there aren't any single cell 7.2V lithium batteries made that will fit in the space vacated by the old batteries. I really don't want to have to connect multiple cells together every time I have to replace them. Can I run it on a 9V battery without damaging it? The scanner is also capable of running on 12V DC from a car power point. Does that mean it can handle 12V but 7.2 is enough to power it? Would there be a way to regulate the 9V down to 7.2?

-Alan


The device may have an internal regulator and the rechargeable battery pack could be connected to the same power input at the 12 volt input. When it is plugged into 12 volts does it charge the battery? If it does then they are not the same.

If you have an ohm meter you could check to see if there is a dead short between the 12 volt and battery connections. If they are the same then there would be no problem connecting it to a 9 volt battery, please note that the run time may be less if you can't find a 9 volt battery with a comparable mAh rating.

If size of the unit is not an issue another option would be to use a 12 Volt sealed lead acid battery something like the 1.3 Ah battery will hold a charge for a long time and give you a very long run time.
http://www.batterymart.com/c-04-12-volt-sealed-lead-acid-batteries.html

If you need to regulate a 9 volt battery down to 7.2 volts you can do it very cheap by using 3 diodes (we sell them).
http://alan-parekh.vstore.ca/product_info.php/cPath/12_16/products_id/68

By putting 3 diodes in series you will get the 7.2 volts you desire since each diode will drop 0.6 volts and 0.6*3 = 1.8 volt (total drop on the diodes of 1.8 volts, the rest will go to the circuit)

If you need a diagram of how to hook it up just let me know.
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laser_red
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Joined: 02 Jan 2009
Posts: 3

PostPosted: Tue Jan 06, 2009 7:05 pm    Post subject: Reply with quote

Now you reply. LOL I just 10 minutes ago went another direction and ordered a pair of 1/2AA size lithium batteries that together put out 7.2V. I would have prefered to step down a 9V that would be more easily obtained locally. Thanks anyway!
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Tue Jan 06, 2009 11:50 pm    Post subject: Reply with quote

laser_red wrote:
Now you reply. LOL I just 10 minutes ago went another direction and ordered a pair of 1/2AA size lithium batteries that together put out 7.2V. I would have prefered to step down a 9V that would be more easily obtained locally. Thanks anyway!


Bad timing... Let us know how it works out.
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laser_red
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Joined: 02 Jan 2009
Posts: 3

PostPosted: Fri Jan 09, 2009 4:37 pm    Post subject: Reply with quote

OK, that didn't work. Somewhere I'm getting a voltage drop. Each of the batteries alone show 3.65V but when I put them together and connect them to the scanner I only get 6.83V. That's not enough to power it. There's no continuity between the 12V and 7.2V connections so it looks like I'm going to have to go the 9V+diodes route. Do I just connect them in series from the (+) terminal of the battery? Do diodes have (+) and (-) ends?
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Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Sun Jan 11, 2009 1:34 pm    Post subject: Reply with quote

laser_red wrote:
Do I just connect them in series from the (+) terminal of the battery? Do diodes have (+) and (-) ends?


Yes you just need to place the diodes in series with the battery. For example from the positive terminal of the battery go to the anode of the #1 diode then from the #1 diode cathode go to the anode of #2 diode (do the same for the 3rd diode)...

Finally treat the cathode of the #3 diode as your positive connection to your device.

Note: The cathode of diodes have a white band on them.
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Alexander125
HG Master


Joined: 13 Jan 2009
Posts: 105
Location: Galati, Romania

PostPosted: Mon Feb 09, 2009 12:32 pm    Post subject: Reply with quote

Pb acid bateries are pretty heavy, but durable.
I took apart a cordless drill and found NiMh 1,2 volt 1,3 Ah bateries.
6 of them would do just fine.
I could give you some coz I don't need them but you pay the shipping.
They're free if you want them.
Only pay shipping.
I found some lead acid bateries 12V 1.3 Ah and they're 5 or 6 bucks each.
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