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Garmin III - What setting for NiMH batteries?

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Hey there. I use a few brands of NiMH batteries (they're great!) for my Garmin GPS-III. However, the battery gague can only be based on three battery types:






What setting is the most accurate to gague remaining power when using NiMH batteries? I'm guessing Nickel-Candium, but I just was curious.






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You've probably made the correct choice. Most battery charge indicators measure the battery's voltage. NiCd and NiMH recharegeables both produce about 1.2V fully charged, while conventional "alkaline" batteries generate 1.5V.


I'm a bit surprised at the "lithium" choice; I wonder what Garmin had in mind? Until recently, lithium primary (non-rechargeable) batteries produced about 3V; there are minor differences depending on the specific chemistry used. Both lithium / manganese dioxide (Li/MnO2) and lithium / poly carbon monofluoride (Li/(CF)x) batteries are sold for consumer use, also some lithium / thionyl chloride (Li/SOCl2) are occasionally seen. All of these are roughly twice the voltage of "conventional" batteries like carbon/zinc and alkaline, so they were sold to be used with a dummy battery that took the place of a second battery in series. I don't know if the GPS III could take these batteries; check the manual.


There are 1.5V consumer lithium batteries now on the market, sold under the Energizer brand. The "alkaline" setting would be appropriate for these.


Hope this helps.

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Last year, I asked Garmin about NiMH batteries in my GPS-III. Here's their reply.


Thank you for contacting GARMIN. Yes, you can use NiMH batteries in your unit. However, even selecting NiCAD will not give an accurate reading of the power consumption of the batteries. You will have to change the batteries based on when you think they are getting low.


Thank you and best regards,


Garry Marshall

Customer Service Representative

GARMIN International


913-397-0836 (fax)


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NiCad setting gives very useful power reading for me using NiMh batteries. The meter is full when they are fully charged, gradually goes down to empty, and abt half an hour after I get low power warnings, the device goes blank and turns off, and the batteries are really flat.

Fully charged they have abt. 5.1 V on the GPS voltage reading

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