Originally Posted by
3speed
I have to say I don't quite understand a desire to use rechargeable AA/AAA batteries and charger. If you're going to do that, you'd be better off, power and space wise, using a GPS that charges via micro usb and a power bank. The power bank requires no charger(self contained) and packs more battery power for the same amount of space taken up by AA/AAA batteries. They'll also charge faster, I believe. One large power bank would charge fairly quickly with a modern 2A or higher charging base and last you days(or longer?) of GPS use. It's also easier to make a rechargeable device reliably waterproof if it has a micro usb flap vs. battery slot, and rechargeable GPS units are generally a bit smaller and more compact. As another plus, you can charge multiple other devices from the power bank. Just get one decent sized one and basically never have to worry about any of your devices going dead. Or if you don't have many devices, get a smaller one and never really have to worry about the one or two devices going dead.
If you are only using the GPS for cycling and have a convenient place to plug into an outlet every couple days to recharge everything, what you propose would work fine.
I can't speak for others, but I want to be able to use the same GPS for backpacking, kayaking, canoeing, and cycling. I prefer AA batteries for when I don't have a way to plug into an outlet for a couple of weeks.
And using NiMH rechargeables is greener than disposable batteries. I have not bought any AA or AAA non-rechargeable batteries in over a decade with one exception, my taillight batteries were dead and I was riding home in the dark so I bought a small pack of AAA at a Walgreens to use to get home about eight years ago.
But I can charge my GPS AA batteries from the dynohub with a USB charger and pass through cache battery, I have no reason to have a dedicated cycling GPS in addition to a general recreation GPS for other activities. I should clarify here that Garmin will say you can only charge their proprietary battery pack in a Garmin 64, can't recharge NiMH batteries in it, but there is a work around that I use to do it, thus I can use the same AA batteries in my GPS as in my headlamp (for my head in the campsite) that uses one AA battery.