Starting Battery Size

[Bad Obsession]

I am wondering what size starting battery to use in my boat. The current set up is starting off of a group 27 multi-purpose battery (I don't like that). I am going to re-do my house bank and then have a separtate battery for starting (#1 will be a dedicated Starting battery and #2 will be the house bank).My boat is a 1990 Catalina 30. I have a 23 HP universal diesel.I am going to use 2 group 27 batteries that are wired in parallel for my house bank. The starting battery will then sit under the quarterberth (About the same distance from the pannel that it is now). What size battery should I use for a starting battery?I am going to stay with Lead Acid Core because I want to make sure that I don't need to replace the charging system that is on my boat (battery charger that I run when I am on shore power). I also think that this should save on the initial cost to do this because I am going to have to buy 3 batteries at this point (I really hate replacing one of my house batteries that is only 1 year old but since I am parelling it with another battery the safe bet is to replace it so both batteries are the exact same).

 

[Jim Rushing]

Use the old Grp 27

for your starting battery and buy two new Grp 27's for the house bank. Your biggest problem is how you are going to recharge the starting battery. Some chargers will have the capability to recharge a third battery by itself, but most don't. You could rewire your alternater so it recharges the starting battery only. You don't use that much energy when starting the engine.

 

[Bad Obsession]

Start off of a deepcycle?

I have to replace the dual purpose battery because of age...but I have another house battery that I just bought last year and I am going to end up replacing it. Can I use the newer deep cycle as a starting battery?

 

[Jim Rushing]

All a deep Cycle means

is that it can be discharged to the 50% mark and recharged without damage. Normal batteries don't like being deeply discharged. However, you really don't discharge a battery very much when starting a engine. Using a deep cycle for a starting battery is a waste of money if you are buying the battery. You already have it and can't use it with another battery in the house bank.

 

[Don S/V ILLusion]

check this out

there is a tab off this link specifically addressing your needs called Starting off a deep cycle battery - the same logic applies to so-called dual purpose batteries,

 

[Bad Obsession]

So I can use it?

From what I am seeing I can use that 1-year-old house battery as battery #1 and use it for starting. That would save me between $55-$100. Has anyone had a problem doing this?

 

[Richard19068]

shouldn't be any problem

to use a dual purpose battery for starting a small diesel such as yours.

 

[sailaway78]

Use the deep cycle

Use the newer deep cycle for the start battery. According to some "experts" this will shorten the life of the battery. If you take care of it, it should last you quite a while. If not, you really haven't lost anything.l If it lasts a year, you have put off spending the bucks for replacement for a year. If it lasts two, same deal. It will start your engine fine. Contrary to what was previously said, and from what I have read on various battery sites, the deep cycles are not designed to put out the high amps for starting. But the little diesel you have does not require a bunch of starting amps anyway.

 

[Jim Rushing]

You Can't Use The New Grp 27

for the start battery unless you buy two more batteries. Why would you do that? House battetries need to be bought together because then the amp-voltage curves will be almost the same. To your charger, the two batteries look like one and it will charge them like there was only one battery. If the two battery curves are close together, then there isn't a problem. When you have one old battery and one new battery, one will be charged correctly and one will not.

 

[seadaddler]

Yes

No problem using the old 27 group for starting and why not buy two 6 volt for your house bank in parallel will give more than group 27.Nick

 

[Karl]

Make that in series

If you use 6 volt batteries, you have to hook two of them in series to get 12 volts, not parallel. I use US Battery, 6 volt batteries on my boat. With proper maintenance, the last set lasted almost 8 years.

 

[Jadedcrew]

House Bank

2 good quality Group 27 lead acid deep cycle batteries in parallel will give you between 170-205 amp hour capacity (average 190).2 T105 6 volt golf cart batteries in series will give you a 225 amp hour bank.You can use any of your existing Group 27's as a starting battery. Deep cycle batteries don't like that kind of service, but will work, then replace it when it gets tired. You could use a group 24 for starting as well.

 

[Steve Dion]

Optima

Think about an Optima. They will charge just fine with your current charger. They are vibration resistant and pack a big punch in a small package.

 

[Bad Obsession]

Space is the problem

THe problem with the golfcart batteries is space. It will take up signifigantly more space than 1 extra group 27. The current set up is just 1 dual purpose battery (#1) and one deep cycle battery (#2 housebank). The extra group 27 will give me a lot more capacity then I already had. I don't have a refridgerator so my main electronics are GPS, VHF, Autohelm (Raymarine S1 wheel pilot), Car stereo, and any lights that I may run in the boat.As far as bang for my buck, I think that the best solution is to move the starting battery to the new location and add the second group 27 where my starting battery (Currently an older dual purpose Group 27) sits. There is only enough room in the current battery storage area for 2 group 27 batteries. I wish I could stretch it to fit 2 group 31 batteries but I don't think that I can (I will measure a lot more but I don't think it will fit).Just to up the house bank I am looking at buying two new group 27 deep cycle batteries, a ground cable that will run about 50", and 1 18 hot cable to use to parellel the housebank. I have enough from the switch to the new place for the starting battery to work. I have to make a flat spot with wood, fiberglass, and resin for the starting battery.The main thing would be to use the 1 year old group 27 deep cycle that is currently on the boat as a starting battery. Will this work or do I have to buy a third battery that is a starting battery?

 

[Paul F]

charging

Looks like you have it handled as far as the batteries are concerned. For the charging set up take a look at using a combiner to hook the house batteries and starter battery together. Charge the house bank first and then when charged the combiner will connect the starter battery and charge it. All this is automatic there are no switches to remember, just hook it up and forget it. The cost will be about as much as the money you saved by not buying a third battery - that's boating.

 

[Taylor]

Trojan summary flyer

Here's a link to a Trojan Battery flyer:http://www.trojan-battery.com/ProductLiterature/pdf/rvflier.pdfOne thing to note on the sheet is that Trojan *does* quote cranking performance for their deep cycle batteries - a 105AH group 27 Deep Cycle has 530 CCA while a 105AH Dual Purpose group 27 has 630 CCA. For their 85AH batteries its 440 CCA vs 550. BTW - my experience with T105's from Trojan is that this is a fabulous battery.

 

[seadaddler]

Yes Yes Yes 

You can use the group 27 for starting battery for sure,that's what I did on my old boat which also had two group 27,onewas for start and one for house bank.When one went bad I used the good one for start and added two 6 voltfor house bank.What ever you have room for 6 volt or group 27 or group 31,it doesn'tsound like you need that much house bank with no ref which is the big draw.Nick

 

[Jadedcrew]

Space

Here are some measurements from the Trojan Battery site.T105 6 volt 10 3/8 L, 7 1/8 W, 10 7/8 H, 62 lbs., 225 AH (20 hour rate).G27 AGM 12 V 12 L, 6 5/8 W, 9 3/16 H, 67 lbs., 100 AH.G27 acid 12V, 12 3/4 L, 6 3/4 W, 9 3/4 H, 55 lbs., 105 AH.

 

[Bad Obsession]

The reason is..

The reason that I want to upgrade the housebank is that I am considering doing an overnight run down the bay towards Hampton, this summer. I want to be able to run my items, including the running lights, without worrying about killing the battery. I am going to also add a battery monitor into the housebank so that I can keep track of what is going on.

 

[Don S/V ILLusion]

energy review

Haven't read all the preceding stuff so excuse me if this is redundant.If you have a specific purpose as you describe, why not do a simple review of how much power everything on the boat draws over a 24 hr period?Doing so will give you max draw from the house bank while away from shore power and also give you a good approximation of how to size your house bank such that you don't draw over 50% of the capacity before recharging. It's too easy to intuitively pick the wrong size bank capacity without first trying to figure your typical usage.