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How can I power walkie talkies (3 AAs each) using my vehicle cigarette lighter? Answered

Motorola Talkabout T5200, 4.5V, uses 3 AA batteries.  I would like to build a power unit that would plug into the vehicle dc outlet / cigarette lighter and continuously power a single unit.  We use these on trips when we are follow one another or when we have multiple vehicles in a convoy but storing them with batteries in the vehicle for random use is problematic at best.

http://reviews.cnet.com/two-way-radios/motorola-talkabout-t5200/1707-3502_7-6753112.html

This seems very doable but I sure don't know how and haven't been able to find directions online.  Thanks for the help!!

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user
kelseymh (author)2010-08-25

See this Instructable. Instead of a regular AC wall-wart, get (or use) a cigarette-lighter plug instead (e.g., RadioShack model #270-028 or 270-049).

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user
Re-design (author)2010-08-24

Get a plug in power adapter and a plug to fit your walkie-talkies. Now get a variable voltage regulator it is a 79##. Don't remember the exact number just right now. You set the voltage out put by varying the resistance. Follow the data paper.

Radio shack used to have (Maybe still does) several different power adapters that had different voltages.  Check there for an easy fix.

Probably motorola has a accessory cord that will power these perfectly.

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user

+1

Use a 7805 voltage regulator. Make sure that the one you get is rated for 500 mA minimum. More is better, less may impede the working of the radio. The 78## denotes positive (78) and the numbers in the ## area are the voltage. So this one is a 5 V positive regulator.

5 V is close enough as most fresh alkaline batteries put out almost 1.65 V when new. That would amount to 4.95 V with new batteries.

Follow the schematic #8 on the DataSheet (first linked PDF) on page 21. Don't forget to leave room for good airflow and most definitely a heatsink, as the regulator will be dropping 8.6 V (running automotive voltage is nominally 13.6 V) and dissipating around 4 watts. It will get hot.

The 79## series is the negative voltage sister. These won't work for your application.

Good luck,
Qa

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user

I shoulda looked up the number instead of trying to remember it!

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user

Age'll do that! ;)  ...now what was I posting... oh yeah!

I looked it up prior to posting just to make sure I had it correct. Still a great call.

Qa

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user
ANDY! (author)2010-08-25

If there is a transformer for charging the walkie talkies and it is rated 12 volts, you can get a cigarette lighter plug and wire it to the plug that goes into the radio.

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