I'm not trained or fully understand the technology. I understand that I could completely destroy my SatNav or other undisclosed risks to me and my surroundings. Even though my SatNav appears to work now I may be damaging it slowly. You get the idea. Use info at your own risk. I welcome your thoughts and comments.
Garmin C550 SatNav battery replacement.
The batt
ery died in my Garmin C550 SatNav and it would only work via the 12v car charger. I looked up the replacement batteries and they were from £18.00 to silly money, plus I would have to wait for delivery. I decided to use some old AA NiMH rechargeable batteries I had lying around and after a trip to Maplin and £1.40 I fixed it. Here's how....The factory battery in mine was a Li-ion 3.7v 2200mah so I thought that 3 x AA NiMH would work, based on AA NiMH rechargeable batteries being 1.2v x 3 = 3.6v the NiMH batteries I used are 1300mah so x 3 = 3900mah. Now in my head 3.6v is close enough to 3.7v and 3900mah offers a good increase in power. If I'm remember correctly voltage is important to get right. The 3900mah is ok being over as the device will only take the power it needs. If you read this and understand electronics I would be interested to know if this is correct.
What I used: (You don't need everything and can use and adapt as you see fit)
- Small philips screwdriver
- Soldering iron and solder
- 3 x AA NiMH rechargeable batteries
- A 3 AA battery carriage (Maplin YR61 £0.79p)
- 9v PP3 battery connector (Maplin HF28 £0.59p)

- Insulation tape
1. Take off the front silver plastic surround from the SatNav, Just prise it off.
2. Undo the 4 cross head screws and split the unit apart gently.
3. Remove old battery and then remove the circuit board that is attached directly to the battery. The circuit board has tags that connect to the battery. I removed these from the battery terminals with a screwdriver.
4. Solder the 9v PP3 battery connector to the circuit board keeping the palarity correct.
5. Put the 3 x AA batteries in to the battery carrier.
6. Connect the 9v PP3 connector to the battery carrier and put the battery carrier in the SatNav
7. Reassembly.
8. Test and enjoy.
Points to note/check:
- The unit will only switch on when it is together as it automatically switch's off when you open it. The unit has a terminal that only forms a circuit when the unit is together. So put back together to test or it won't work.
- No sound / won't charge. I had this problem at first. It turned out that the circuit ribbon that joins the two sections of the unit together had been pulled about too much and when I removed and refitted this all was well.
- I had cut the battery wires as I was messing with the old battery trying to take it apart to see if it was made of smaller cells while it was still connected and it suddenly heated up so I quickly cut the wires and through it outside. You hopefully won't need to do that. ;)
Circuit board that is attached to the battery.
Cleaned up from above and PP3 connector
soldered on.
Same as above pic.
Fits like a glove.
The terminal that turns the unit off when
opened.