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Nuvi Battery Pack Writeup

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I know many of us geocache with a Garmin Nuvi. One of their serious limitations of the nuvis is battery life given that their internal battery usually only lasts 4 hours or so. I know of only one supplier that sells a AA battery pack for the nuvi to extend battery life. They are $20 and can be bought here - http://www.gomadic.com/garmin-nuvi-200-eme...y-extender.html


I've created my own battery pack for about $7. I haven't yet tested how long it will extend the nuvi's battery life, but I've read one report that this kind of setup with allow the nuvi to run for 12-13 hours on a single set of 4 AA batteries. The important thing is that it allows you to use AAs so you can effectively have unlimited battery life by changing out batteries. If you're interested in saving a little money and having some fun making your own, here's how to do it:




Items Needed:

1. Battery Box (see below where to buy one)

2. Power Cable (see below where to buy one)

3. USB Extension Cable (see below where to buy one)

4. Soldering Iron

5. Solder

6. Electric Tape

7. Multimeter

8. 4 RECHARGABLE AA batteries (non-rechargeable batteries should NOT be used and could destroy your nuvi)


Disclaimer: I will not be responsible for any damage to your property if you choose to try this out. Proceed at your own risk. This has worked perfectly for my nuvi 255w and I believe it will work with any Garmin GPS that has an internal battery that is charged with a mini usb cable, but I will not guarantee anything. Furthermore, I do not guarantee that any products I mention and you buy will actually work. Finally, I have no relationship with any seller mentioned; I have no financial interest in having people make these battery packs.


The Cable: We want a cable that will charge the nuvi WHILE it is being used to navigate. There are two kinds of cables for the nuvi: data cables, and power cables. The power cable accomplishes this task (charging while navigating), and the data cable can also, but only in a round about way (it involves putting the nuvi into test mode, restarting it, and waiting a couple minutes for it to lock to satellites). In other words, a data cable CAN work, but it's a hassle and a power cable is really the way to go. The difference between the data cable and power cable are explained below in the “The Unimportant Details” section, but you don't need to read that if you aren't interested. Basically the power cable has a resistor in it and the data cable does not. So I would recommend that you buy a power cable for your battery pack, that's what I'm currently using and it works great. The cheapest place that I’ve found power cables is from the seller firegadgets on ebay for $4.50 shipped. To find the power cables he/she sells:

1.click on this link which shows all of the products he/she sells - http://shop.ebay.com/firegadgets/m.html?_n...p;_trksid=p3686

2. Search for “nuvi cable” (without the quotes).

3. You will see multiple usb cables called something like "FOR GARMIN GPS PC USB CABLE NUVI 200w 250w 255W 260W" or "FOR GARMIN GPS PC USB CABLE NUVI 785T 200 205 250 255." Some of these cables are data cables and some are power cables. The data cables will have in their description (you must click on it to see the description), in bold, that they are data cables. The power cables will not say that they are data cables. I would HIGHLY recommend emailing firegadgets after purchasing a power cable to remind him/her that you do NOT want the data cable, but that you want the power cable.

I ordered my power cable from firegadgets and the transaction went smoothly, hopefully it goes well for you as well.


The Battery Holder: You will need a battery holder that holds 4 AAs. You might have one lying around; otherwise, I used RadioShack’s Model 270-409 - http://www.radioshack.com/product/index.js...oductId=2062253

You should be able to find it for about $2 at your local RadioShack. This holder is nice because it has a switch and is enclosed so that the batteries don’t pop out.


The Batteries: You should ONLY USE RECHARGABLE AA batteries. To charge your nuvi you need about 5 volts. Rechargeable batteries put out around 1.2 volts, therefore 4 of them put out around 4.8 to 5.2 volts. Non-rechargeable batteries put out around 1.5 volts, therefore 4 of them put out around 6 volts. This may be too high for the nuvi to handle and therefore I recommend that you ONLY use rechargeable batteries.


The Setup: We now need to attach the battery pack to the cable which will then plug into the nuvi. I'm not sure if the resistor in the power cable is in the usb end of the power cable or the mini usb end of the power cable, therefore, instead of risking it and cutting off the usb end and soldering the rest of the cable to the battery pack, I used a usb extension cord so that I could keep my power cable intact. A usb extension cord has a usb male end on one side of the cable and a usb female end on the other. If you don't have one of these lying around, you can buy them on ebay for around $2 shipped (or any any radioshack or places like that). First, cut about a foot above the usb female end of the usb male to usb female cable. Next, set the male end aside, you won't need it until later. Next, solder the red wire from the battery box to the red wire of the usb cable, and the black wire from the battery box to the black wire of the usb cable. See here – DSC03904.jpg

(You won't need the other two wires in the usb cable so I just clipped them). Then I wrapped the ends carefully with electric tape. Make sure to wrap them with both of the wires parallel so that you don't strain the cables. You can see how to wrap them here –




and here –




I next wrapped them a little more to make them extra secure and safe –




Finally, I taped the cable down onto the box so that the weight of the box wouldn't pull any of the wires loose –




Make sure you tape the cable on the side of the box that has the on-off switch as this is the side that isn't removable.


Test it: If you haven't checked yet to make sure everything is working, this is a good time to do it. Get the male end of the cable that you cut off and strip the red and black wires on the end of it. Then plug the male end into the female end and turn your battery box on. Use a multimeter on the wires you just stripped to check the voltage and make sure that red is positive and black is negative. REMEMBER THAT YOU SHOULD ONLY USE RECHARGEABLE BATTERIES FOR YOUR NUVI. You'll notice that rechargeable batteries will read between 4.8-5.2 volts, perfect to power your nuvi, while normal batteries will read around 6 volts, which is too high (like all usb devices, around 5 volts is perfect for the nuvi). The nuvi might work ok with normal batteries, but I don't think it's worth risking it. My multimeter said around 5.1 volts with my 4 rechargeable batteries - perfect. (Note that it's nice to check everything with the male end of the usb cord plugged into the female end because it's much easier than trying to reach the pins inside the female usb connector.) Now you are set to try it with your nuvi. You should be good to go! Let me know if you have any questions.


The Unimportant Details: You do not need to know any of the following information, but if you’re interested go ahead and read it. If you look at the mini usb end of the cable, you'll see

that it, like all mini usb connectors, has 5 "pins." If you are looking at the cable with the narrower side up, they are 1 2 3 4 5 from left to right. 1 is positive and 5 is negative. 2 and 3 are what the computer and the other electronic device (the nuvi in our case) communicate through. Garmin created the nuvi to only charge while nagivating if the 4 pin is connected to the 5 pin through a resistor with 17.3K ohms.

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UPDATE: I finally got around to testing the battery pack for myself and got 16 hours 24 minutes out of it with rechargeable 2100 mah NiMH batteries (very basic and inexpensive rechargeables)!


Setup: I tested it with the battery pack plugged in and my nuvi fully charged.

(Later I'll test it by just letting the internal battery run down to 1 bar and then plug in the battery pack for awhile until the internal battery is up to full, upon which I'll disconnect the battery pack and repeat once the internal battery is low again. This is more realistic for how I'd like to geocache with the nuvi because I'd rather not have the battery pack plugged in constantly and getting in my way. I'll do this new test soon and post it here.)


Testing Conditions: I tested it by putting the nuvi near my window so it could get satellite locks and put in a destination so it would create a route. Then I put it in locked mode (pushing the power button to the right) so that it would stay on but dim the screen. This is usually how I geocache because I want it to record my tracks and also to maintain satellite locks (then I unlock it when I'm near a geocache and use it to hone in on the cache).


I'm very pleased with the results and I'm excited to do the next test mentioned above.

Edited by hoyshnin
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