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Bobo87 wrote: Mon Mar 05, 2018 8:38 pm Great information NOLA. Got any recommendations for brands of marine batteries? Also, anyone have a recommendation for mounts for the second battery setup?

Thanks. I've always just used enclosed battery boxes from West Marine. As for batteries Costco has good batteries at a fair price.

AsLan7 wrote: Mon Mar 05, 2018 9:02 pm

Bobo87 wrote: Mon Mar 05, 2018 8:38 pm Great information NOLA. Got any recommendations for brands of marine batteries? Also, anyone have a recommendation for mounts for the second battery setup?

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I run Trojan batteries.

Great thread discussion here.....

viewtopic.php?f=27&t=580&start=10

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Btw, excellent input nolaboater99. One other thing to add—when switching batteries with the engine running, folks need to use caution to not turn the battery switch to the off position as this will ruin the alternator.

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Thanks AsLan. I've been boating a long time, mostly with cruisers. In my 34' Sea Ray I added an inverter and 2, 6 volt golf cart batteries wired in series to power a 110v fridge when I was not plugged in to shore power or on the generator. My last boat was a 52' Motor Yacht with twin Cat diesels. Each engine had one 8D starting battery. For the house load I had 8, 6 volt golf cart batteries, wired in series, that provided 12 volt power for some lighting but most systems in that boat were 110 volt. The 8 golf carts were also running through a Xantrex TruSine 3500 watt Inverter. I could run everything for 2 days , except air conditioners, before starting the generator to charge the batteries. These 8 batteries even had an automatic water refill system.

When you get into that much power consumption you need to know where your power is coming from and how to get it. That boat had a large power demand. Water pumps, electric flush toilets (2), water heaters (2), TV (2), DVD (2) Stereo and amp, fridge, ice maker, microwave, 3 burner stove and oven, toaster oven, bilge pumps (4), Raymarine electronics network at 2 stations including GPS, chart plotter, radar, auto pilot.... You kind of get to know this stuff.
Shawn

Thanks for all the info NOLA

Nola thats a pretty cool story! Thanks for sharing

I thought I would resurrect this thread. After spending countless hours researching, looking at the wiring of my boat and reading all of the Cobalt Chat threads I could find, this ones seems like the most appropriate place for my questions.

OK, my problem first started with my sub amp going into protect mode when cranking the stereo too high. It seemed like the amp was starving for power...at least that's my current theory. After doing some research and talking to a few folks, looking at my battery setups was step #1. I found two group 24 starter batteries in my 302, one on each side of the engine compartment. Decent specs, but seemed a bit underpowered. Found one from May 2012 (so really old), and one from Jan 2017. I have the standard battery switches (1,2 or 1+2) for both port and starboard engines (no fancy switches with ARC).

So knowing I should replace and upgrade the size of my batteries as my first step, I started researching starter vs house/deep cycle vs dual purpose batteries. One stereo guy recommended two group 27 dual purpose. Knowing that really any of these batteries, if sufficiently sized, will work, and there are a ton of opinions out there, it would seem the best combination is one starter and one deep cycle. Plus the dual purpose ones seem harder to find and are more money, but not counting them out or any suggestions. Also, it seems that group 31's are barely more money and find they mostly fit in the same trays, so will look at those too.

My problem is knowing exactly how the engines and the stereo/accessories are wired. It looks to me that both batteries are simply wired to the switches. From there I can't tell very well. There are additional wires connected to the port and starboard switch "common" posts, but for what I don't know. But if connected to "common", I think that means that whatever the switch is set to (1,2, or all), that is the battery or batteries powering everything. That's how it looks to me. Is that how it is, or am I missing something?

So if that is how it is, can I put a starter battery in position #1 and a deep cycle in position #2 and just know what to select for whatever application I need? If that's not how it's wired, how do I trace what runs off of what battery so I can replace the battery with the right kind? This does make a case for dual purpose to take the guesswork out. I will also need to know this if I end up needing to add a third battery to the stereo/deep cycle side (I have 3 amps total).

I have twin Merc 350 Mags. Does anyone know what the minimum CCA and Reserve Capacity needed for those?

I will also throw out another question after reading the threads here. There is an opinion on alternating battery 1 and 2 on different outings, etc is a good practice. I don't quite get why that's a benefit. I get placing the battery switch to #1 or #2 when floating and listening to music (preferably to the deep cycle side) in case you drain that battery too much to start the boat and having a second fresh one ready, but I don't get why you wouldn't always place it back to 1+2/All when starting and leaving so both batteries charge. That just seems like a good habit. I can see switching the battery to the starter battery for starting perhaps, but why not just use the combination power of both batteries when starting, at least with the way I think my switches are configured? Or at least always put it to 1+2/All after starting if there is an advantage to using just the starter battery for starting? That one got be scratching my head.

Like always, any help is greatly appreciated!!!

These were all the threads I read here.

viewtopic.php?p=44943
viewtopic.php?f=21&t=70&hilit=batteries
viewtopic.php?f=27&t=580
viewtopic.php?f=34&t=414

Update after some troubleshooting and taking to a local mechanic.

• My starboard battery is connected to switch position 1

• My port battery is connected to switch position to 2

• Stereo seems to be connected to position 1. When I disconnected starboard battery the stereo would not turn on unless I had the starboard switch set to 1+2. Simply in position 2 it would not work.

• Stereo does not seem to be connected to the port switch at all and will not activate by that switch alone. Must use starboard switch.

• UPDATE: This test was done when the starboard battery was disconnected. Once I reconnected the battery, the stereo will run off switch position 2 now. There must be some sort of cross circuitry to power the stereo when in position 2 when the starboard side battery is connected.

My initial thought was to then place the deep cycle House battery in position 1 on starboard side, and the cranking battery on the port side and position 2. I could always use the 1+2/All position to get the ample amount of CCA's to start the boat.

After talking to the mechanic:

• He confirmed that each battery in connected and charged separately to that respective side engine.

• He recommended to buy two cranking amps with ample CCA's (800 min CCA for any size Merc) for me since I have twins (at least one for single engine)

• If those are not adequate for my stereo config, get a third deep cycle dedicated and wired directly to my amps. He also suggest a third battery switch to be able to turn it off completely, as some amps seem to constantly draw power in his experience. He also suggest to add an isolator to read the battery charge needs for all three batteries.

• On operation, he suggest I always run one engine on switch position 1 and the other on position 2 and to avoid the 1+2 position unless needed in an emergency. Thought behind that is 1) you can isolate a bad battery faster, and 2) saves one bad battery from pulling down the good battery and less work/burn-out on the alternator/s in that condition since it's masked by the combo position. Same for single engines with two batteries supporting the position 1 on one outing and position 2 for the next.

Hope this helps anyone out there, it really helped me.

Down here in Texas most Twins are on offshore boats with outboards. Those guys seem to run 3 deep cycle or 2 start engine and one dc house with a BEP battery distribution switch.
(Sorry, can't paste the link...)

I'm researching them now for my single w/2 batteries and seem to fix the battery selection issue we deal with.

Thanks for the tip RR. I will check that out.

I failed to mention in my previous post that the mechanic was also suggesting the cranking batteries per engine due to Merc and Volvo recommendations guaranteeing enough CCA's for fuel injected engines, ECM's, etc. Especially when deep cycles batteries are typically too few of CCA's for the same battery footprint and the other comments already made on this forum. He also highly suggested not turning the battery selector switch with the engine running UNLESS you know your switch has continuous contacts FWIW.

I have a 2018 cobalt R 30 and a dead house battery. There are no specs on this battery believe it or not. How can I determine the right replacement battery? Is it a 27 or a 31?