Dual Battery Question

S

Slippery When Wet

New Member
Jan 19, 2010
422
St Croix River, MN
Boat Info
2003 Crownline 230EX
Engines
5.0 MPI Mercruiser, Bravo III
OK, so I have a nOOb question about dual batteries. I bought my 2002 SeaRay 225 Weekender last August. I took the batteries out before storing for the winter and I did not pay attention to which one was which because I did not realize they were different. The guy I bought the boat from said one of the batteries was "almost new".....well, not really, the newer looking one is a Dual-purpose battery that was bought in June of 2007 and the Starting battery is not dated but looks much older. Well, I put the battery charger on them and the older one didn't seem to fully charge and the newer one did, but after leaving the charger on it overnight, I noticed water on top and running off it the next day, so it must have boiled over. But it showed charged. Well, the last thing I want or need is to have battery issues while out on the river, so I went and bought 2 brand new Interstate batteries. One starting and one deep cycle. $225 for both. :wow:

Now for my question: Is battery #1, as marked on the cable, the starting battery and #2 the aux battery? It is hard for me to tell because the cables go to the battery switch which is hidden very well, not easy to follow the cables. I suppose I could experiment by hooking up #1 only and seeing if the starter has power, but I thought I would ask here first. It's kind of a pain to get in there so I really don't want to get them backwards and have to switch them.

Thanks!
 
Not sure about your boat so can you get the wiring diagram and see what cable numbering goes where? You may be able to get one from the Sea Ray site to download.
 
Theoretically, yes the #1 is probably the starting battery. Hook up one battery and check it out.
 
When all else fails....RTFM! :grin:

The manual states that both batteries power the starter and the accessories and you should turn off the stronger one (based on Voltmeter readings) to save it for starting while engine is off and you are running accessories. So, I guess I will hook the cranking/starting battery to #1 and the Deep cycle to #2 and shut off #1 while engine is off and I am running accessories. :thumbsup:
 
The one with more wires running from it should be the house battery. The starting battery should not have any extra wiring except the charging wires (thin) going to both batteries and you should be able to track them to the charger on board.

The PO may have made some changes however so the above may vary with your hook up...

You should see some heavy gauge wiring going from the staring battery to the starter also...
 
More than likely, you should have two starting batteries, but the PO put in a deep cycle for running accessories while the engine is off. That's a good idea, and your method of turning off your starting battery when the engine isn't running is correct. However, you do not want to charge your deep cycle battery from the alternator, so you must have #2 turn off while the engine is running. Deep cycle batteries will not last long when charging off the alternator. or you may have an on board charger rigged up somehow that doesn't allow the alternator to directly put juice to the deep cycle.

Anybody ever seen anything like this? I have two starting batteries, and two deep cycle batteries. The only reason for my deep cycles is to run my inverter. They require hooking up to shorepower and a battery charger to charge. They're not hooked to the battery switch, so they don't charge by running the engine. But it would be nice to be able to charge them while on the water.

Slippery-I didn't mean to try to answer your question with a question. But I thought we could both get some more advice from experienced skippers out there.
 
I didn't know you shouldn't charge a deep cycle off the alt. Is that because it charges it too fast?

I have an August 2008 deep cycle that I have been charging this way. It's worked so far but have I shortened its life?
 
KRB64 said:
I didn't know you shouldn't charge a deep cycle off the alt. Is that because it charges it too fast?

I have an August 2008 deep cycle that I have been charging this way. It's worked so far but have I shortened its life?
Click to expand...

I've been running the same way since the PO said that he always set the switch to both batteries. From what I understand deep cycle batteries should be run down and then charged all the way back up. I guess I'll turn off the deep cycle while underway and charge it up at home if it was used.
 
It really doesn't matter which battery is #1 or #2 as long as you know which is which. I assume that your battery switch has "1", "2", "Both", and "Off" on it like mine does. Hook your starting battery up to cable #1. Turn the battery switch to #1 and you should have power to the 12v system (radio, water pump, etc...) as well as be able to start your engine. Turn the switch to "Both". Everything should still work. Nothing should work with the switch in position #1 or "Off". Turn the switch to "Off" and move the battery to cable #2. Now, everything should work with the switch in position #2, or "Both". Nothing should work in position "1", or "Off".
 
Holy cow this sounds difficult. "Switch to this while running, when you stop switch to that, don't do this, do that, blah". Do yourself a favor and buy this battery switch and your batteries and battery switch will never cross your mind again - http://www.boemarine.com/Products/7650/Default.aspx

I had one of the old 1/2/Both Switches on my first boat and I would go crazy trying to keep up with which battery to use when. Now, any boat that I am even remotely associated with using or advising the owner or owning gets one of these switch setups.
 
My Deep Cycle battery is on #1 and my Cranking Battery is on #2. I set my switch to "Both" while starting and running the engine. I switch it to #1 while I am using the accessories with engine off (to save the #2 Cranking battery for starting). I switch it to "Off" when the boat is not in use.

If I shorten the life of the Deep Cycle battery, oh well, next time I will get a dual-purpose battery for both.
 
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