Navman S45 GPS is good GPS, however like all electronic battery dependent gadgets overtime the battery gets shorter and shorter and now it wont even last 5 minutes now on a good charge.
Theres no battery available online also that I coud fnd, searching for "Navman S45 battery" in Google returns very poor results. ie no battery or how to. So this will be one that I wrote. I have repacked a Nintendo DS Lite battery into the S45 as I have spares of these, but any battery with 3.7v rating of similar size is OK also.
Usual disclaimer - Follow these instructions at your own risk.
Opening your S45 will void its warranty etc. Not understanding Li-Ion battery technology will also cause a fire risk.
Getting to the Battery in Navman S45. There are four screws at the bottom and you should be able to lift it a bit.
Then you need the following tools ( hard plastic pick etc )
Now use the Pick and gently push it along the edges so that the casing will unclip itself. take your time and do not force to pull it apart.
Once off, you will need to remove the tape that is holding the speaker connection and battery.
The battery connector in the S45 is a not standard plugs. But the batter is standard Li-Ion 3.7v
Here is a picture of the OEM battery T300, Rated 720mAh.
Now you have to gently unwrap the plastic using a sharp blade ( do not apply too much pressure ) you just want to remove the wrapping.
Theres a plastic covering protecting the OEM S45 Battery, which you will need for later use to repack the new battery. You will also need the circuit that protects the battery from over/undercharging and the connector.
Now prepare the Nintendo DS Lite battery, doing the same - do not puncture the battery. The Nintendo Battery is rated 3.7V 1000mAh made in japan. How ever when i read the voltage rating with a multimeter it was reading 4.02 V.
Use a Multimeter to verify that you will re-soldering the IC from the original battery in the right way ( ie mulitmeter both read positive ) . Careful not to short ciruit the battery - they will get very hot very quick. You will need to make a clean cut with pliers.
Now prepare the new Nintendo DS Lite battery ( depending on whic battery you use - you will have to do something similar at the contact points ) Make sure you insulate the NDSL battery and just expose the solder points. Apply a bit of solder. Then also apply solder to the Circuit from the old battery.
Solder the IC that protects the battery into place, and insulate the battery wil Electrical tape.
Now place the protective plactic that covered the Ciruit and insulate it properly with electrical tape. Now place the battery back into the GPS and charge.
Do not leave the unit out of sight when test charging ( may be fire hazard if you reversed polarity or made a mistake )
Once it fully charge, you can put the Navman S45 back together. Now the Navman S45 last longer then the day I first got it.