Furuno CR2450 3V Lithium Battery for GP1650 (001-428-240-00)

The Furuno GP1650 has been running on helms for years, and like a lot of chartplotters from its era, it leans on a small internal battery to hold onto your settings. That's what this part is. A CR2450 lithium coin cell, 3 volts, the exact backup cell Furuno spec'd for the GP1650 and GP1650F. It isn't the main power source. The unit runs off your boat's 12-volt supply. This little cell just keeps the memory alive when everything's switched off at the dock. Think of it as the plotter's memory keeper, nothing more, nothing less.

How do you know yours is going? The tell is almost always the same. You fire up the plotter and your waypoints are gone, or the clock has reset, or the whole thing boots like it just came out of the box. On a lot of GP1650s that shows up somewhere around the six to eight year mark, which is right on schedule for a coin cell that's been quietly holding memory that whole time. If your unit powers up fine but forgets everything the moment you cut power, a fresh battery is the first thing to try.

This is a CR2450, and that number matters. It's a specific coin cell size, not the same as the smaller cells you'll find in a car key fob or a bathroom scale. Don't guess and grab whatever 3-volt button cell is in the junk drawer. Use the CR2450 that's spec'd for the job so it seats right and holds memory the way the GP1650 expects. It's the difference between a battery that works and one that rattles around loose or won't make solid contact at all.

Now, the install. This isn't a slide-out tray like your TV remote. The backup cell lives on the GP1650's main board, so getting to it means opening the case and working around the electronics inside. Most folks who tackle it themselves desolder the old cell and fit the new one in its place. Take your time with the ribbon cable when you open things up. It's easy to stress or tear if you pry the case too far, and that turns a cheap battery job into a much bigger repair. If you're not comfortable with a soldering iron near a circuit board, there's no shame in handing it to a tech.

Two things worth calling out. First, watch your polarity on the way back in. Get the cell in backwards and you can wipe the settings memory instead of restoring it. Second, this is a boat, and boats live in salt air. If your GP1650 is mounted at an open console that catches spray, check the battery contacts for corrosion while you're in there. A light touch of dielectric grease on the terminals helps keep the connection clean for years.

Here's a bit of dock wisdom. If your GP1650 is the only plotter at the helm and you rely on waypoints you can't easily re-enter, think about swapping the backup cell before it strands you, not after. A coin cell gives you very little warning. It holds memory fine right up until the day it doesn't. Doing the swap on a quiet weekend at the slip beats losing a season of fishing spots the first cold morning the battery finally gives out. It's a few dollars of insurance for years of saved data.

And to be clear about what this doesn't fit. The GP1650 and GP1650F are their own generation. This backup cell is spec'd for those units, not for Furuno's later NavNet plotters, which handle memory differently. If you're working on a GP1650 or GP1650F, this is your part. Order it, do the swap, and get your waypoints back where they belong.