Extending battery life of 3.7 volt GPS

I need to extend the life of a retail GPS device. The current battery appears to be bad, but it appears to be user-replaceable and in fact disconnects cleanly from the unit. A few questions:

1. There are three wires coming from the battery. One I assume is ground, another I assume is 3.7V, what is #3?

2. Is there a way to get a good amount of amp hours in a 3.7 volt battery that is for sale? The ones for this unit are quite expensive for the tiny amp hours they provide. I was thinking of linking it to an external brick-type battery by crimping wires to the plug and leading them outside the GPS unit.

BP-LP720/11-A1B

 

The bad internal battery appears to be affecting GPS reliability so it is more than just a capacity issue. Otherwise yes I'd connect the Magellan 9212 to the car.

I was thinking of getting 3 x Panasonic Eneloops and connecting them in series. 1.2 x 3 = 3.6 volts. A bit under, but will be balanced out by the fact that charged batteries always give more than the rated voltage. Can anyone help with a wiring diagram perhaps involving 6 batteries?

 

The bad batteries cannot hold any charge in cold weather and the GPS needs to be manually rebooted (takes 30 seconds) every day.

 

If the car hits a bump and there is a momentary loss of 12 V power and the battery is bad, the device would shut down and need to be restarted mid-trip.

 

Another issue is that the device loses power while being upgraded (connected via USB to computer) leading to software damage. I had to restore it 3 times already by copying the system files I backed up. Otherwise it would be bricked.

Anyway, can someone recommend an economical solution to this:


Otherwise I'll just get a busted tablet.

 

I have a copy of this model and it behaves the same way. A regular USB cable does NOT reliably provide enough power to keep it charged it seems. If you take one of those cheap cig lighter plugs to USB chargers and connect a physically compatible (fits) USB cable and run the unit in your car, you will get a net battery power loss and the unit will shut down within 2 hours. So a regular USB cable is only usable to charge the unit while it's off or to transfer data. I suspect that's why there are many of these units on eBay for sale as broken with the computer symbol: the data was damaged during an update because the battery drained to nothing before the update finished. Luckily, I backed up the data so I have successfully fixed this otherwise bricking condition.

Another problem is this thing doesn't seem to work reliably with longer USB cables. You need to use something a foot long or less to get a good data connection.

Could you clarify what you mean by the AA option? You mean like what I mentioned above about using 3 AA batteries to get 1.2v x 3 for 3.6+ volts? The problem is there is the third "charging" cable on this unit. Where would I connect that? A battery only has + and -.

 

So how do I deal with the third charge lead? The batteries will get connected to the positive and negative terminals of the GPS, but what do I do with the charger lead?