View Full Version : Deep cycle vs. Starting

07-16-2007, 03:50 PM
I have two deep cycle batteries in my boat with a switch to use one for driving and the other for sitting. I had a guy ask me last weekend if my alternator properly charges a deep cycle. I think it does but my system always seems to be hanging around the 12v range (which in another post I read, should be hanging around 13v or 14v).

Question is: Is it wrong to use a deep cycle battery for tooling around, listening to music, running heater, lights, etc. or are they primarily used for just running equipment with the motor off. Should I dump one of the deep cycles and put a standard battery in its place, will my system pick up to 14v with all the stuff on? Help me out guys.

07-16-2007, 04:13 PM
I am not sure about the charge but I have a starting battery for the basic things such as lights and cranking. I then have optima blue top deep cycle for my radio and amps. I have let the radio play without the boat on for 5-6 hours and the deep cycle has never once let anything shut off. Since the starting battery is not running much with the boat is not cranked the boat fires right back up when ready. If i can find the diagram from skiers choice I will scan it in.

07-16-2007, 04:56 PM
After running the factory batt after 3 yrs w/ no secondary, and it being a deep cycle and all (it'll prolly die on me tomorrow :roll: ), Me alt says 12.8 - 13-2 volts after running the stereo (8 speakers, 500w amp) for 4-5 hrs when charging, I'd think you'd get close to the same reading. You may be putting an excessive load on yer alt.

07-16-2007, 10:20 PM
Joe Techie, wanna chime in here? Does a standard starting type battery perform better at maintaining a constant voltage with the motor running than a deep cycle? I know at night, with lights on, music playing, if I turn on the heater my PerfectPass will start to beep because of low voltage. I wonder if I would get the same result from a starter battery vs. my deep cycle.

07-16-2007, 10:37 PM
I would normally go with a starting battery and a deep cycle for the accessories. I'm seeing some information now that says some batteries are designed with to do both but you will need to look at the specs. Few links to look at.


07-17-2007, 12:07 AM
The battery in all marine applicatipns should be deep cycle due to larger cells/plates that hold more of a charge than auto batteries. If you look at the labels on both at the same time you will see a big difference in reserve time which is the life of fully charged battery has stored in case your alt lets go. If you allow your battery to "power up" allyour accesories with out running your engine you will see lower voltage readings when you first start engine as the voltage regulator senses a low charge on battery and will allow more amps and voltage to be "released"to run engine and charge batteries. If you run a regular car battery you will be left out to dry if your system runs low as you will not have enough reserve to turn over starter as they require alot of amps to spin them over

07-17-2007, 10:46 AM
As stated above - ALL your batteries should be deep cycle. When you drive your boat every day like your car - then a starter will do fine.


07-17-2007, 02:18 PM
Thanks for the input guys. I shopping for tower speakers and light combo so I may have a few questions about upgrading my alternator when that time arrives.