A Question For The Battery Gurus

[RGrew176]

This past week I launched my Carver for the season. Of course it would not crank as the battery that I knew was weak last season had died. I tried charging it with my battery charger but to no avail. I had to purchase a new battery. The batteries in the boat are/were NAPA Group 24 Deep Cycle batteries. There are 2 of them. I bought another NAPA Group 24 Deep Cycle to replace the dead one.

Battery #2 I also placed on my charger. When you first put a battery on the charger it does a battery check then charges if needed. The 2nd battery the charger went into check mode and within a few seconds the led gauge on the charger lit up and showed that the battery was fully charged. I had intended to buy 2 new batteries but the NAPA store only had one in stock. Since the 2nd battery seems to be in good condition I am going to start the season out with it and see how it holds up.

The location of the batteries is between the engines on this boat. The aft battery was a chore to get out because of its location so that is why I decided to replace a Group 24 battery with another Group 24. There is no way that I could muscle in or out a Group 27 or 29 where the aft battery is located. The forward battery is located far enough forward that I can easily pull out or place in.

Now to my question. If the remaining battery that I have decided to keep on should need to be replaced could I replace it with a Group 27 or 29 battery? Is it OK to mix battery sizes in this application. Can I have 1 Group 24 battery and one Group 27 or 29 battery working with the Group 24 battery. Or is it best to keep both batteries the same?

When I had my Bayliner 3055 Ciera all 4 batteries were the same Group 27's and I never had any battery problems.

Thanks in advance for your responses.

[After Taxes]

Launching and batteries! Ha. They go well together, don't they? Just yesterday I replaced my two start batteries in the Mariner, because my starboard engine battery was totally useless. The port was ok, but it's best to replace them in pairs, because the ok one will surely go soon. For this purchase, I bought Costco Kirkland 845 Marine Cranking Amps and 675 Cold Cranking Amps, group 27, marine batteries, at a very competitive price. Over the years, I've installed many brands of batteries, both cranking and deep cycle. Had never bought at Costco, but an experienced boater neighbor has had very good luck with them, so I bought those. My marina sells Interstate, which are a decent brand, however you know the drill: I can pay twice the retail price at the marina, or buy in the city for about half.

Your post leaves a few questions. It sounds like you installed a deep cycle battery, as your engine cranking battery. Is that the case? Respectfully, don't use a deep cycle for cranking.

Get a good cranking battery for your engine(s).
If twin engines and separate batteries, then generally, those two start batteries may be different brands or even size.

If your other batteries are for the house system, then they must be deep cycle batteries, and if using two batteries for house, they must be the same size and type, and preferably the same age. Use the very largest deep cycle for house, that you can cram into the space. Dual house twelve volt batteries are wired in parallel.

If you are starting fresh for the house batteries, take a look at using two or four golf cart batteries, such as Trojan six-volts, however get expert advice, as six-volts must be wired in series to produce twelve volts. Golf cart batteries provide many more amp-hours of service between charging.

I do realize many boats are wired differently, and some even share the house systems (lighting, etc.) with cranking. You need to fully understand your personal boat situation first.

Happy boating friend. I trust this helps.

[AaHubb]

Every thing I have read has recommended using the same size/type batteries in a battery bank (directly connected together). After Taxes' advice about start vs. deep cycle batteries is spot on. A start battery is built to supply a large amount of current over a short time. A deep cycle is made to supply a much smaller amount of current but over a long time frame. Although both types of batteries may have the same amp hour rating, how they achieve that is very different. There are combination start/deep cycle batteries available. Costco carries them and that is what I have in my boat for the starting bank. Using a deep cycle battery for stating may work for awhile but its life span will be greatly reduced.
..Aaron

[After Taxes]

Here's the Kirkland Signature battery I installed. 845 Marine Cranking Amps / 675 Cold Cranking Amps. I'll be happy to provide a users review this summer.

They are marketed as Canking / Deep Cycle, which I found a wee bit concerning, since I wanted purely cranking. Deep Cycle have thicker plates. My buddy swears by them for cranking over his 454 GM gas engines in a Carver 356 Aft Cabin. The price at the Oshawa Costco was 134.95. The look like an Interstate battery, with water fill caps, which I like, as I can monitor the acid levels. My previous cranking batteries were the sealed variety - yuck. Great in your auto, but I don't like sealed in a boat.

[Viper]

Good advice guys. I agree with all the above in that one should not mix battery types and sizes within the same bank. Ideally the batteries in a bank should also be of the same age however that isn't always practical.

I'm not crazy about dual purpose batteries. In spite of OEM claims, they are a compromise at best between a good start battery and a good deep cycle battery. The construction requirements of each type a very different. What makes for a good starting design makes for poor deep cycle construction. The result is a compromise to end up with a battery that will serve both duties albeit less efficiently than their single duty counterparts. Having said that, one has little choice when faced with OEM wiring that utilizes the same bank to start an engine and run house loads. It's a poor design, and I wish boat manufacturer's would stop cheaping out by wiring things up this way. Anybody with this type of setup should have this on their bucket list of upgrades to isolate house loads from the engine banks.

I've never used Kirkland brand batteries. Curious to see how they work out. I don't use anything less than 1000MCA/800CCA for gassers now. Diesels are a different story of course; typically 31 group heavy duty. The only smaller rating I use is for generator applications. I typically go with 800MCA for those unless it's an older Onan MCCK with no starter where the generator windings are used to turn the engine over. For those, I also use the 1000MCA.

[RGrew176]

For the record I have heard that Deep Cycle batteries may not be the best for cranking and starting. My experience however differs somewhat. My last boat a 1999 Bayliner 3055 Ciera had a 4 battery setup. I wanted the 4 batteries because I spent a lot of weekends on the hook. In 2005 I started the season with 1 dead battery.

I decided to replace all 4 of them. I purchased 4 Sears Diehard Deep Cycle batteries. I bought them just after launch in April of 2005. Every year at launch they never failed to start my boat. As the seasons progressed I often wondered will the boat start this year. I was really surprised in 2011 when they cranked as normal and the boat engines fired up. They were still going strong after 7 seasons of use.

I guess the question is, how many CCA's do you need when the weather is warm enough for boating. I agree you really need the CCA's to start your car when it is -10* in January. I am not poo pooing what anyone here posted. My Carver has a 2 battery setup. To be honest I am not sure which battery is for starting and which one is the house battery. As it is set up currently there is one positive cable from each engine going to the aft battery and from the other engine going to the forward battery. It may be they are both used for starting and house usage. There is a negative cable running from the aft to the forward battery.

I really don't want to mess with the setup as it works and my boat starts when I turn the key. I will need to spend more time going over the owners manual and see if I have any wiring diagrams that may show how the setup should be.

I want to say thanks to each of you for the information you posted.

[Viper]

There's no question a deep cycle battery will start your engines, and probably do it for many years. The question is how many more years would you get out of them if they are used for house loads only. How much of a higher risk of failure is there when using them for cranking loads? I've replaced more deep cycle batteries in cranking banks than any other type of battery, likely for this very reason. You certainly don't want one to fail because of a shorted cell due to constant loads it's not designed to deliver when you're trying to haul anchor on a Sunday evening to head home. It's just a matter of using hardware as it was designed to be used so you can hope of achieving the life span/duty cylces it was intended to have. With the costs of running a boat these days, that's pretty important IMO.

Two schools of thought when it comes to available power IMO; EFI engine computers do not like voltage drops very much during cranking, it could cause some weird symptoms hense Merc's recommendation of 1000MCA minimum for big blocks like 454s. I simply err on the side of caution and use the benchmark for all gassers now. While carbed engines don't have ECMs to worry about, they usually don't start as easily as their EFI counterparts and because of their vintage, they typically use a different starter design that draws more amperage, so for that, I feel more comfortable with the higher CCA and have experienced way better results.

While warm temps aid in helping engines start easier, they're still boats, and they typically sit for days or weeks without being started unlike a car that is used on a daily basis. That makes a huge difference. Also consider that it's unlikely you'll get the CCA spec during regular use as this declines over time. In warmer temps, the natural discharge rate increases so when one considers all these factors, the highest CCA you can get for the footprint/battery group, the better.