Powering Your GPS Receiver

Before you can start using your GPS receiver, you obviously need to give it some power. For portable GPS receivers, that usually means AA or AAA batteries. Manufacturers all give estimated battery lifetimes for their GPS receivers, but the actual number of hours a GPS receiver will run depends on how it’s being used. For example, with the backlight on, battery life goes down because more power is consumed. In addition, what type of batteries you’re using can also make a difference.

Battery Tech 101

You can really get geeky with batteries and powering your GPS unit. If you get a charge out of electricity, here are some links to nitty-gritty information sources that cover voltage, mil-liamperes, and GPS drainage rates:

Battery drain for selected GPS receivers:

www.gpsinformation.net/main/ bat-5.txt.This site offers the lowdown on just how much juice different GPS receiver models consume.

The Great Battery Shootout!: www. imaging-resource.com/ACCS/BATTS/ BATTS.HTM. This site is more orientated to digital cameras (not GPS receiver-specific),but you’ll find some good data on how different types of batteries perform.

Newsgroups:sci.geo.satellite-nav. Do a Google Groups search in this USENET newsgroup for batteries and be prepared to spend a couple of hours reading through educational (and sometimes controversial) posts.

When you check these sources, you’ll run into mAh, which means milliampere-hours. Most rechargeable batteries like NiMH have the mAh rating printed on their label. This rating is the battery capacity. Typically, the higher the mAh number, the longer the battery will last.

Battery basics

Although batteries may have the same size and shape, they definitely don’t perform the same. In Table 5-2 are the pluses and minuses of some of the different types of batteries that you can use with your GPS receiver.

Table 5-2 Battery Comparison

Expect to pay about $4 for a four-pack of alkalines (the more you buy in a single pack, the cheaper they are) and about $15 for NiMH. Chargers can run you anywhere from $20-$50. (Some chargers come bundled with a set or two of batteries.) When it comes to batteries and chargers, online prices are almost always cheaper than full retail, so be sure to shop around.

Battery saver mode

Some GPS receivers have a battery saver mode that can greatly extend the life of your batteries. (Check your user manual to see whether your model has this feature and how to turn it on.) Normally, a GPS receiver processes satellite data every second and determines your speed and location. Based on this information, the GPS receiver predicts where you should be the next time it gets satellite data. If the prediction is close to your actual position and battery saver mode is turned on, the GPS receiver will start receiving satellite signals every five seconds or so instead of every second. In addition, some of the internal electronics are turned off during this wait period. Because a reduced amount of power is needed, the battery life is extended.

The GPS receiver continues to access satellite data every five seconds until the predicted location isn’t accurate anymore, at which time it switches back to receiving data every second, starting the process over again. (Some GPS receivers provide you with a number of choices of how often satellite data is received. The more seconds, the more battery efficient the receiver is.)

If you’re environmentally conscious or want to save some money over the long term, use NiMH rechargeable batteries in your GPS receiver. Although a charger and pack of batteries obviously cost more than disposable alkalines, rechargeable batteries are a wise investment because they can be recharged hundreds of times before they end up in a landfill.

Power to the people

After you select the type of batteries you’re going to use, you should be aware of some other issues when it comes to powering GPS receivers:

Battery life gauges: In the GPS receiver’s setup information page, you can specify what type of battery you’re using, such as alkaline or NiMH. The battery type setting helps the GPS receiver make an accurate guess how long the battery will last. Remember that different battery types have different discharge rates. All GPS receivers also have an onscreen battery gauge that shows you how fully charged the batteries are. If you set the wrong type, the worst that will happen is that the gauge won’t be accurate. See how to extend battery life with some GPS receiver models in the sidebar, "Battery saver mode."

Always check the battery level of your GPS receiver before you head out on a trip and also remember to carry spare batteries. One way to tell which batteries are new or charged is to put a rubber band around the good ones. By feeling around in your pack or pocket, you can instantly tell which ones are fresh. Note: Rechargeable batteries discharge faster than alkaline batteries when they’re not in use, so if you haven’t used your GPS unit in a couple of months, don’t be surprised if those rechargeable batteries are dead or don’t have much life left in them.

Cigarette lighter adapters: If you’re primarily using your GPS receiver in a car or truck, you can save on battery costs by powering the GPS receiver with a cigarette lighter adapter. These handy devices run a GPS receiver from your car’s electrical system. You can buy a generic version or one made for your model (sold by that GPS receiver manufacturer). Depending on the model, adapters cost between $20-$40, with the generic versions a bit cheaper than the manufacturer models.

Cigarette lighter power adapters have straight or coiled cables. Although coiled cables are tidier, if your cigarette lighter isn’t close to the dashboard, a coiled cable can pull your GPS receiver off the dashboard if it’s not securely mounted. Adapters with straight cables don’t have this problem; you can tidy up any slack in the cable with a plastic zip tie.