Karisma has two parallel ‘electronic navigation systems’: an N2K system (chartplotter, wind and depth instruments) and a NMEA0183 system (two Garmin 128 GPS, one of which feeds position to the radio). both systems feed into the computer and autopilot.
The Garmin 128s are the boat’s original nav system (one was installed at the chart table when I bought the boat, and I added another in the port-side cockpit coaming shortly after purchase). These units may be old but (besides being the dedicated position system for the radio) they form a really good low-power redundancy for the amp-hungry N2K system if we should have battery power problems at sea. For this reason I want to keep the Garmins working, and I was aghast to find that the chart table unit has recently failed to get a fix.
Well, there is a suggested solution for this, which is to change the internal battery, and I can report that this works. Last week I opened the Garmin up (just a case of removing six screws in the back of the case) and wielding a 22w mains soldering iron and good quality flux core solder, was able to remove the old battery and replace it with a new one. The battery is a Panasonic 2032 with solder tabs and is available via ebay.
Below are ‘before and after’ pictures of the soldering job. Despite the units being around 20 years old the new and old batteries are identical.
Before – old battery 
After – new battery
I closed up the casing, popped the unit back onto the bulkhead above the chart table and it powered up and re-initialised, getting a fix in four or five minutes.
Replacing the battery meant the total loss of all its internal data, but because it’s connected to its twin in the cockpit, I was able to use the (now ancient) ‘Garmin/Garmin’ interface protocol to beam all my waypoints and routes back into it. So it’s now good for another 20 years’ service, and in fact it went straight onto anchor watch that very night (see next post). The radio got its position back too.
Who needs to buy new stuff eh!
Sailing Karisma 