Posts: 2754
Location: Mauston, Wisconsin | Your batteries don't usually just die, they are usually murdered! Mostly by misuse & lack of proper recharge or wrong battery type for the application. Sure, load the starting battery up with these modern electronics gizmo's, no problem, right? WRONG!
I looked up the two Lowrance units in question. See page 35.
http://www.lowrance.com/Root/Lowrance-Documents/US/HDS_GEN2_TOUCH_I...
Ha! Doesn't seem like much load - HDS7 (0.9A) and HDS9 (1.2A) @ 13VDC, total = ~ 2.1A. A fully charged 12V battery at rest is 12.7VDC . Why Lowrance spec's the load current at 13VDC doesn't make sense to me! But then again, I'm just an electronics/electrical engineer.
These little electronic loads are also constant watt devices, meaning they draw more current at lower voltages. Your charging battery is mean't to be at full charge ALL the time (when needed to start the motor). At ~10.8VDC these two units will be drawing about 4A.
If we average that for a 10 hr day, we are looking at a 40AH battery load@10hr rate. Ha, no problem I've got a 80AH starting battery! WRONG! A starting battery was never designed to support this kind of discharge. Just because the alternator is putting out 14VDC also doesn't mean the battery is fully charged either!
Don't forget about the other %$&# we hook up to the starting battery too. Running lights, bilge pump, stereo/radio, marine radio, etc. It all adds up through a full day of fishing, if you repeat it day to day - multiple day trips you might need jumper cables to start the motor.
Some day maybe the boat manufacturer's will actually figure out that the real fisherman need a separate battery for the navigation/sonar(s). On a large muskie boat like those used for guiding, etc. you might want 5 batteries - 36V TM (3), 12V electronics (1), and 12V starting (1). I'd even put the motor on a battery switch - A (starting) or B (electronics) or A+B (both). These also usually have a off position, so you don't have to worry about draining the battery when the boat is not in use. I installed one and a second battery for a friend in RI, after he had to call SeaTow a few times.
http://www.seatow.com/
Shep's advice is solid. Start there.
Have fun!
Al |
