Advice on Batteries........Mercrusier...

[Fiat4Fun]

Howdy,
I have a 1986 Chris Craft 210 Scorpion, that had one battery stock. The boat has been wired for two batteries, with a selector switch.

Last year, I ran on the one battery that it came with, a Trojan Deep Cycle, and I threw in my old Group 65 battery from my Jeep when I replaced it's battery. I was planning on purchasing a new battery this season.

One of my buddies, who is way more experienced in boats, told me that the batteries should be identical, as in two deep cycle batteries, or two automotive batteries, since the draw on each type is different, and the charging with the motor would have more draw on one battery than the other. Made sense, so I called up my local marine store today, and asked about batteries, and he said I should have one Deep Cycle for lights and accessories, and on high cranking amp battery to turn over the motor?
So I was a bit confused, and decided to come here for some advice. I was just going to get an Interstate deep cycle battery and be done, and then replace my older deep cycle battery that came with the boat later this year or next season so I had matching batteries. The guy I talked to today, didn't ask what motor set up I had, or any questions about the boat, and I noticed on my searches, that out boards may be different than IO. I have a 350 Mercrusier with Alpha One, if that helps!!!

Any advice would be appreciated.
Thanks
Bob

 

[AZSenza]

Re: Advice on Batteries........Mercrusier...

IF you need a deep cycle for trolling motors etc you should have 1 of each. If all you do is power a radio and lights 2 starting batteries are fine. I've had dual batteries on both my boats, I dont have need for a deep cycle and use identical marine starting batteries, both boats are 5.7 Mercs and a Bravo III and an Alpha 1. I've got 800 watts of amp and run an air compressor for toys and dont have any problems. My main concern is starting! Deep Cycles dont start as well as a starting battery but they can discharge longer to a lower state before dying on you. My 2 cents

 

[Redneckhick]

Re: Advice on Batteries........Mercrusier...

This I know. AZSenza is correct. Deep cycle batteries are made for long draw loads like trolling motors or lights and such. They are not made for short bursts of high amps like a starting battery. So you want a starting battery to start your motor and a deep cycle to run other stuff on. If you are running two batteries on a trolling motor like a 12/24 you want both of them to be deep cycle. Also as a side note you can charge a cranking battery must faster than a deep cycle. Deep cycle batteries need to be charged slow with low amps to make them last longer. Hope this helps.

 

[NYBo]

Re: Advice on Batteries........Mercrusier...

The batteries do NOT have to be of the same type.

You could compromise and go with combo starting/deep cycle batteries, but one starting and one deep cycle, or two deep cycles would also work. A starting battery isn't a good idea for the house load if you spend long periods without running the motor. Starting batteries' lives are shortened if they are regularly discharged below 80% or so.

 

[Fiat4Fun]

Re: Advice on Batteries........Mercrusier...

Thanks so much for the input.
So, just to clairfy, there is a "starting" battery that is marine grade that is different than a auto battery? I don't use a trolling motor or anything like that, but do use the stereo, and accessories out on the water. If I am not mistaken, it sounds like the best would be two marine starting batteries. Any thoughts on a Optima vs Interstate?


Does leaving the switch on both harm a battery that is at full charge while the motor is running?

Thanks for the advice.
Bob

 

[Silvertip]

Re: Advice on Batteries........Mercrusier...

Also as a side note you can charge a cranking battery must faster than a deep cycle. Deep cycle batteries need to be charged slow with low amps to make them last longer. Hope this helps.

Absolutley untrue. Deep cycle batteries can charged at up to 20% of their rated capacity. They can be charged in parallel with a starting battery just fine. Deep cycle batteries also need to be charged quickly and not left in a partially discharged state. In fact most on-board smart chargers charge at the bottom of the capacity range have 5 amp outputs and at the top of the range 20 amps.

 

[AZSenza]

Re: Advice on Batteries........Mercrusier...

We have 2 marine starting batteries, First run of the day (I charge both batteries at home when we get back and again before we go out) I start on #1 when we park, I switch to #2 and listen to the radio (with 2 amps 4 speakers and a base) for about 2-3 hours. Restart on "Both" and tow tubers for a while, then alternate 1 and 2 for subsequent starts, this is for a long day or a weekend outing, I dont swap back and forth all day long but you get the idea. I have a 7 year old battery and a 6 year old battery...Load meter says #2 is starting to get weak but its 7 years old too! This boat is used 11 months a year, with LOTS of battery cycles. Just my experience.