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Extending battery life of 3.7 volt GPS

Discussion in 'Power Electronics' started by vassock, Feb 12, 2016.

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  1. vassock

    vassock

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    Nov 30, 2015
    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
     
  2. HellasTechn

    HellasTechn

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    Apr 14, 2013
    The third lead is the charge lead.
     
  3. Gryd3

    Gryd3

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    875
    Jun 25, 2014
    3rd wire is usually either a temperature sensor, or a digital signal wire.
    You can increase battery size, but may get unexpected results. Does the GPS have an external power jack? (You can often buy External Batteries that plug into this jack and won't require any modifications to the GPS case... heck, you could wire it to the car)
     
    davenn likes this.
  4. HellasTechn

    HellasTechn

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    Apr 14, 2013
    that is one way to do it if you dont mind it being bulky. Or just look for a better quality battery ? We can not say for sure if we dont know the unit you are talking about and it's battery pack.
     
  5. HellasTechn

    HellasTechn

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    Apr 14, 2013
    It may be the case but i have seen battery packs for GPS using it to charge the battery.
     
    Gryd3 likes this.
  6. vassock

    vassock

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    Nov 30, 2015
    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?
     
  7. HellasTechn

    HellasTechn

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    Apr 14, 2013
    That should not be a problem because normally 3.6 rated cells give 4.1 to 4.2 volts at full charge while the 1.2V would probably give about 1.5 each. So that should be ok. The problem when useing the 1.2V eneloop batterys would be the different type of charger that the eneloop will probably require.

    I personally wouldn't go with a mod like that.
     
  8. HellasTechn

    HellasTechn

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    Apr 14, 2013
    Why do you think it affects it's reliability? I would say that it could only affect its run time.
     
  9. vassock

    vassock

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    Nov 30, 2015
    The bad batteries cannot hold any charge in cold weather and the GPS needs to be manually rebooted (takes 30 seconds) every day.
     
  10. HellasTechn

    HellasTechn

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    Apr 14, 2013
    So it affects it's run time and internal memmory, not it's reliability, right ?
     
  11. vassock

    vassock

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    Nov 30, 2015
    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.
     
  12. vassock

    vassock

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    Nov 30, 2015
    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.
     
  13. HellasTechn

    HellasTechn

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    Apr 14, 2013
    Could it be that the USB jack on your GPS is damaged ?
     
  14. cjdelphi

    cjdelphi

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    Oct 26, 2011
    You could go for the aa option and use a boost converter to ensure a constant voltage to the device
     
  15. vassock

    vassock

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    Nov 30, 2015
    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 -.
     
  16. vassock

    vassock

    33
    0
    Nov 30, 2015
    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?
     
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