I was able to pick up an Eagle Strada 128 Portable last year. I know it's probably 10 years old but it was in good shape and had the instructions with it. It came with a battery holder that uses eight D cells. I want to swap it out for a rechargeable sealed battery. Wiring it up won't be a problem but should I be concerned with the battery amp rating? There is a 12 volt 5AH battery that fits the case and I'd like to use that when I head north in a couple of weeks. So I guess my questions are is it ok to change to a sealed battery and will it last as long or longer than the D cells?
Watch out for that rock!!!........ Oooo.... That's going to leave a mark...
your message doesnt state if your going into the BWCA ? if so leave your depth finder at home. when i was younger i bought one in after that i dont bother with them. extra weight, get lake maps that have depths marked. generally what you see above water is whats below. that doesnt help on mid lake humps but a good map and a jig on your line will tell you the depth.
IF YOUR GOING TO TRAVEL MORE THAN A FEW LAKES IN. I WOULDNT BRING ONE BUT THATS JUST ME. WITH THE WATER CLARITY UP THERE U CAN SEE WHAT YOUR IN 15' OR SHALLOWER. BUT I WOULD THINK THE CLOSED CELL ONE WOULD LAST LONGER ?
Look at the bar graph titled "Milliamp Hours Capacity". Assuming your depth finder draws around 100ma, you'll get around 16 amp hours or 160 hours use (assuming your unit works down to .8 volts/cell, or 6.4 volts, which it probably doesn't). I'd suspect it operates down to about 10 volts (1.25 volts/cell), which I'd guess would get you about half that, or 80 hours.
If you can find out from the manufacturer what the current draw of your locator is and how low of a voltage it operates at, you can get an idea of how long you can run it if you have the battery discharge curves. 5 Amp Hours doesn't mean much if you don't know how low of a voltage they measure before they call it 'dead'. I'd guess the 'D' alkaline cells will give you longer performance than the rechargeable, but they're gonna cost you more over the long run. Saving those kind of pennies doesn't matter much when you go to all the work of getting yourself out into the wilderness.
See if you can find out what voltage they spec the 5 A-H rechargeable at. Then compare with the alkaline specs. Find out how low of a voltage your locator works at, then you can make the comparison.