Duel Battery system question

Greetings,
Boat is a 1999 2020WA - motor is a SX150 Salt Water Series II OX66 (two stroke); got it middle of June; used five times. Have always had battery switch on "both", until last weekend when I used 'both' on the way out - then switched to battery one, while anchored and using the GPS-fish finder-radio....etc.. I forgot to switch back to 'both' when I started the motor and just had "click"......motor did not even try to start. So I switched back to 'both' and motor started right up. Monday I checked batteries and battery one had about 12 volts and battery two had about 12.5 volts-both batteries are 700 CCA. Battery one has a date of November 2010 and battery two has a date of February 2011. All connections are very clean and there is a Perko-duel battery switch and a Guest Charge Pro-model 2611 battery charger in the system. Also, while the boat is on the trailer and parked in the driveway I have 'shore power' hooked up.
Okay now to my question: Can I use one Deep Cycle battery and one regular cranking battery in my system?
I am thinking that if I put a Deep Cycle battery in place of number one battery (the 'regular' battery) and just use it while NOT running the motor is should stand up better while powering stuff. Then when starting motor use battery number two or maybe both; I understand that the motor's alternator and 'shore power' will charge what ever battery/batteries are 'hooked' to it.
What do you think?
Thanks,
Patrick

You can run one deep cycle and one starting on the switch. You can turn it to both while running to charge both batteries, no problems there. Use the starting battery to start, switch to the deep cycle to run electronics while anchored.

Starting on a deep cycle will cause premature failure of a deep cycle battery due to the way they are designed. Cranking amps means nothing on a deep cycle(most don't even list it).

Obviously in a pinch(starting battery has died, or is low) and you need to start the boat, the deep cycle will start it.

eclark53520 said:

You can run one deep cycle and one starting on the switch. You can turn it to both while running to charge both batteries, no problems there. Use the starting battery to start, switch to the deep cycle to run electronics while anchored.

Starting on a deep cycle will cause premature failure of a deep cycle battery due to the way they are designed. Cranking amps means nothing on a deep cycle(most don't even list it).

Obviously in a pinch(starting battery has died, or is low) and you need to start the boat, the deep cycle will start it.

Click to expand...

So what I am seeing is............battery one (starting) - battery two (deep cycle); put switch in position 'one' to start motor, then switch to 'both' while running. After stopping motor switch to position 'two', then before starting motor put switch to position in 'one' again.....got it! I also understand that one should NEVER put switch in 'off' position while motor is running. Thanks eclark53520 for your input.

I'd be inclined to keep the starting battery for the engine and the deep cycle for your electronics- two isolated systems except with a common ground. you can use the switch to "bridge" the batteries in case the need arises. If you add an ACR - auto charging relay, the alternator can maintain the deep cycle without any manual intervention with a switch...just a different thought

Patrick, intrinsically there is no real issue with using ALL/BOTH while underway.
However, I'm one who does not believe in using this method. I want my charging system regulator to sense each bank individually, and then to predicate the charge rate accordingly.
Some will argue this point.


Also, you'd be surprised at how few Amp Hours are actually consumed during engine cranking. While the amp load may be substantial, the duration is rather short.
I've run the numbers on this many times, and always come up with very few AH required for cranking.
Amp Hours IN/OUT are our concern... not voltage alone.

Normally during engine warm up, the charging system has more than enough charge time to bring the cranking battery back up to a safe SOC.




As for a cranking battery on #1, and a deep cycle on #2, yes.... but this will depend on your usage.
If you are trolling most of the time, your engine charging system is functional.
If you are anchoring and switching from Batt #1 to Batt #2, then yes..... a deep cycle bank will serve you much better for your DS, FF, Radio or ____ since these items typically consume lower amperages, but for longer durations.

Now your cranking battery has been held in "reserve" during this time.


BTW, take each battery bank Negative independently to the main Negative connection, of which is likely at the outboard engine. This creates redundancy.


As Mark suggested, if you install one of the Blue Sea ACR units between battery banks, your ALL/BOTH charging issues go away. The ACR will do all of this for you automatically.