Which battery system will work for my 75 hp 2 stroke and stereo system?

[jerseysmail]

Hello, I am new to the site but hope someone can help me out. I have a 20 foot Fisher pontoon with a 75 horse 2 stroke mercury outboard. I run a deep cycle 12 volt to run the motor and use 2 6 volt golf cart batteries connected together to make a giant 12 volt to run the stereo and accessories. The 6v batteries will last a good 18 hours with all the accessories and 600 watt amp stereo system. The only problem is i have to plug it in to my battery charger every 14-16 hours of use to charge. The deep cycle is the only battery hooked to the motor and it's charging system. Do you think I can run an isolator to charge up the deep cycle and then have it switch to the 6v batteries or will this create too much of a demand on the motors charging system trying to fill those huge batteries constantly. I also thought about yanking the deep cycle and running everything and the motor on the 2 6 volt batteries but again am afraid of hurting the motor's charging system. I don't even know how many amps the motor puts to the batteries and since it only has a pos and neg cable to the battery, I don't know how to hook it and the batteries up to the isolator. Anybody have any ideas???
Thanks in advance
Eric
jerseysmail@aol.com

 

[jimg984]

Re: Which battery system will work for my 75 hp 2 stroke and stereo system?

most of your charging should be done with a at home/or dock side charging from a 120 volt outlet. you will only get about 16 amps running at WTO from the engine

 

[Silvertip]

Re: Which battery system will work for my 75 hp 2 stroke and stereo system?

Agreed. The alternator on the engine does not have enough output to keep all three batteries topped off. You would need to run wide open for hours to accomplish that.

 

[jerseysmail]

Re: Which battery system will work for my 75 hp 2 stroke and stereo system?

Thanks...I've been trying to find out how many amps my charging system puts out. I know 2 6 volt golf cart batteries linked together to make a giant 12v will run everything all day but do you think I could get away with just those 2 baterries without using a separate starting battery? Does anyone see any problems with that or harm it could cause?

 

[Big Keepers]

Re: Which battery system will work for my 75 hp 2 stroke and stereo system?

If it were me I'd have one 12 volt deep cycle battery for the electronics and one 12 volt starting battery for the engine. Forget the 6 volt golf cart batteries. What you need are amps, not necessarily volts. Deep cycle batteries have larger amp hour capacities and starting batteries will usually provide about 500 cranking amps.

Do a search on this site for Blue Sea add a battery kit. I've posted about it numerous times. Basically the two batteries are wired independently of each other, the deep cycle has plenty of amphours to run all your electronics and the starting battery will do fine to turn that motor. When the motor is running a charging relay links both batteries to charge them at the same time. The problem with an isolator is it operates using diodes and there is a voltage drop associated with it. So while you may need 12 volts to charge your system, an isolator may only provide 11 or 10.5 volts. The relay works like a starter relay or a solenoid (which is basically what it is.) When the relay reads that amps are being delivered to one battery it closes and allows the current to flow to both batteries. The battery that requires more amps to charge itself will draw what it needs and the remainder will be drawn by the other battery. The whole set up is completed with a regular on/off switch that has an emergency setting to combine both batteries in case one has a problem and the motor won't crank.