Question regarding dual batteries on powerboat

Hello all, I have a 23' VIP Vindicator with a 496 cubic inch motor. The batteries I believe were stolen out of it last year, so it has come time for a replacement. I am wondering what folks do for a battery system. I have a battery selector (1, 2, or ALL) and hookups for two batteries. Should I get two deep cycle batteries, two marine batteries, or a combination of the two? I can't remember exactly how the selector is wired, but I can wire it however it needs to be done.

Thank you for any input and help in my understanding!

 

A "marine" battery should be more ruggedly constructed, to withstand the rigors of hard, high G landings, so the innards don't collapse, so that's one consideration.

 

The deep cycle/marine dual use batteries have thicker plates than the starting type. They can output more power at a slower rate. In general, the cold cranking amps (CCA) are going to be lower. However, that rating is at 0F (-18C). Marine cranking amps(MCA) are rated at 32F (0C), since it is not likely they will get colder. Another typical installation is to have a starting battery with high MCA and a larger real deep cycle as a house battery.

 

As a general rule, starting batteries have high cranking amperes but depletes easily. It is usually wet cell type designed to be used for rapid discharge and needs to be topped up quickly when the engine has started.

House batteries that powers secondary essentials like lights, electronics, and bilge pumps are usually a deep discharge battery and is of gel cell type. Deep discharge batteries do not have the extra cranking amperes that starting batteries have.

While there is no hard and fast rule, Starting batteries are dedicated batteries. Only meant for starting the engine. House batteries, you can drain to almost zero but you still have the starting battery that can start the engine, run the alternator, and charge the batteries according to priority, which in this case is the starting battery. Once it is topped up, you can switch the alternator to charge the house batteries.

 

In general they would be acid/flooded or absorbed glass mat (AGM). Gel cell is an obsolete technology that didn't last long; they require low power charging and are sensitive to heat.

That is not correct. The batteries should not be drained below 10.5 volts to be able to get a reasonable long life.

 

I did not say voltage. but the ability to power up a device which could be a 12 v device but would barely work if the voltage is only 10 volts.
I am sure you know that voltage is a potential.

 

No, not in general. Wet cell (flooded), gel cell, absorbed glass mat (AGM), are all lead-acid batteries.

Gel cell is not an obsolete technology. Still in use, just not the best amongst its class (lead acid).

 

Oftentimes, the lack of detail or an easy answer leads the group astray.

Where is the boat located and will it see cold winters? If so, I recommend agm.

One start battery and one house battery. Ideally, the start can charge the house with a controller or acr.

Robbers love the replaced batteries and oftentimes plan to get new batteries by rapid depletion tactics. Remove batteries and get new ones next week. Best advice is to lock the battery lockers well.

If you are facing risk of theft, then get some less expensive lead acid batteries.

agms run about $250 each here for either version crank or deep..

 

Hello Shaury and welcome to the forums.

I would recommend that you find your way to a Sams Club or if that is not an option to an O'Reilly Autoparts store. Both of these retailers stock batteries made by East Penn Manufacturing. East Penn is my go to manufacturer for high quality AGM batteries. Sams Club carries a brand called Duracell, O'Reillys are called Superstart but they are all the same and made by East Penn. Just a different label on the battery case. If you're curious about East Penn.....www.eastpennmanufacturing.com

If you decide on AGM's I'd discourage buying Optimas. They were great batteries years ago but they moved their manufacturing out of the US and are no longer what they once were.

Whatever battery type you choose, use the same chemistry for both start and house batteries. If you choose AGM's use all AGM's. There is nothing wrong with flooded lead acid batteries. I've just found that good quality AGM's last longer and I like the no maintenance aspect. Just choose a size appropriate for your big block. I prefer The Group 31 size for the house bank (I use two) but that decision will be up to you.

I can tell you that I have three Duracells in my boat that have provided trouble free service for the last 8 years. They still test at about 80% of their original capacity.

If you have a few dollars to invest in your boat I'd recommend removing that "1-2-off" selector switch. A much more modern solution is a simple "on-off" selector wired in conjunction with an automatic charging relay or ACR. This arrangement "idiot proofs" the battery selection process as it is simply an on or off proposition. The ACR disconnects your boats battery banks when there is no charging current present. When you start your engine or engage a battery charger the ACR reads that there is charging current present. The ACR then connects both batteries so that both receive a charge. You can even add an indicator light to your helm panel. I have a green LED installed at the lower helm on my boat. When I open the cabin door, I just glance at the panel. When I see that green light I know my charging system is working properly and both banks are getting a charge.

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A

Undercharging will kill a set of batteries faster than anything else. It's important to keep your batteries fully charged and not to deeply discharge them. If you typically just go out for the day the OE alternator on your boat will be fine. Pick up a good three stage battery charger that you can hook up at home and your batteries will last you for many years.

You'll hear many "experts" say that boat batteries won't last more than three years or so. That is complete nonsense. Good quality modern AGM's can easily last a decade or more IF THEY ARE PROPERLY MAINTAINED and not abused (deeply discharged). Good batteries are expensive.

Good luck to you,

MIA

 

I spent 500 on two optima blue. Hope mia is wrong.

 

I hope so too. It's just that over the past four years I've only one Optima left (in my mother in laws car) that didn't fail. The first one died after 42 months, just 6 months out of warranty. Would not hold a charge no matter what I did, and I did everything I could think of to recover it. Well I suppose you can always get a bad one so I didn't think too much of it.

Then earlier this year my wife and I are on a trip to Boston. Got stranded when my 39 month old yellow top shorted internally. I've never had this happen in 40 years of driving, boating or flying. You get no warning when this happens. You shut the vehicle off and it's just completely dead on the attempted restart 5 minutes later. Typically failures like this are the result of sloppy manufacturing.

Or, maybe I'm just unlucky......

MIA

 

AGM batteries are not flooded lead acid. The plates are separated by fiberglass mat sheets that are only wetted with acid to about 85-90%. They are also a valve regulated lead acid battery (VRLA). The chemical reaction is different than in a flooded acid type. For example, the hydrogen and oxygen recombine into water. Also, they can be charged and discharged at a much higher rate than a flooded acid type. Another advantage is that if an AGM battery case is broken, there will not be an acid spill. The case may have a small amount of acid wetting the surface at the most.

 

You said "drain to zero"

 

Here we go again splitting hairs and endless debates as usual to make you feel like the guru who knows it all. Why don't you post something relevant to the topic instead of nitpicking on whatever the other forum members has to say?

 

Selecting a Marine Storage Battery | West Marine https://www.westmarine.com/WestAdvisor/Selecting-a-Marine-Storage-Battery