Battery size ?
- Thread starter arcymoore
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Are these for "starting" purposes or "house" loads? 625 is your cranking amp capability.. You probably have about 75-80Ah's..I recently bought two Exide Marine batteries size #NC-24 dual purpose starting and deep cycle with a capacity of 625 amps. Should I have gone to the larger size #NC-27 ?
Depends on your load, I added a Group 31 to the set isolated from the other two and is soley for house purposes, providiing 105amp hours. This leaves the starting battery for starting and number two for running lights and backing up number 1. Probably overkill but gives us peace of mind knowing we won't run down the starter battery running auxillery stuff, and I run all house 110 plugs away from dock off an inverter.
I put in 4 6v golf cart batteries for starting and house, and 1 group 27 as backup. Might be an overkill but I get about 450Ah's from the 6v bank. I'll be able to play music allllll day long.
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Some things to think about.
A group 24 is the smallest of the standard commonly used marine group sizes.
Deep cycle batteries are far better suited than "dual purpose" batteries for "deep cycling" applications.
Your Ah's from just one of those batteries is likely between 70 & 80 amp hours.
The lowest recommended depth of discharge for deep cycle batteries is 50% your should go even less with thinner plate batteries such as dual purpose.. So if you have an 80 Ah battery you only have 40 Ah's usable. 40 Ah's may be fine for day sails but for over nights you will most likely be on the cusp of shortening your battery life.
Everything is a compromise so if you don't mind replacing batteries every couple of years then you can ignore any upgrade costs or you can bite the bullet and find a way to get a bigger bank..
Just last week I did this very upgrade for a guy who's killed two batteries this season alone. Part of it was that he did not have a shore charger and used battery power at the dock and the other part was he had just two group 24 batteries on a 32 footer, one for start/reserve and one as house bank. I took him from 65 Ah's to 160 Ah's and added a dedicated reserve bank as well. This house bank is still small by today's standards but he has no refrigeration and keeps his boat at a dock with a shore charger so it should be considerably better than the 65 Ah's he had which equated to just half that realistically.
This is not an inexpensive upgrade in the short term but in the long term the added bank longevity can pay you back. This project was about $900.00 in supplies only but included a new shore charger, combining relay, 3 new batteries, 2/0 battery cable, battery lugs, fuses battery boxes, straps etc. etc. etc.. Obviously without a charger or ACR and associated wiring you could do it for less...
Easiest thing to do is parallel your existing batteries and find a spot for a new starter/reserve battery. Should be able to do if for under $300.00 I would think..
SWG - nice set up! I am assuming your boat is old enough (like mine) that there is no holding tank under the port settee.
How are you handling charging? Do you have that set up as three banks?
How are you handling charging? Do you have that set up as three banks?
Hey Shawn!
Thanks! Actually, I based it off of a post that Maine Sail contributed a lot of his knowledge to. In fact, I think I followed a diagram that he sketched up.
It's set up as 1 bank of 4 6v batteries and then the group 27 is bank 2 (I suppose) and only used for emergencies. Both banks are hooked up to a dual charger when at the dock. A VSR relay charges both banks while the engine is running and prevents over charging as well.
Bank 1 (the 6v's) are wired to position 1 on my battery switch. They are used for starting and house loads. There are two groups of two batteries within Bank 1. Each group has two 6v batteries connected in Series...this doubles the voltage to 12v. Then the two groups are connected in Parallel...this doubles the Amps.
Maine Sail could explain it much better than I have. His post (I'll try to find it) made it very clear.
There was no water storage under that port settee. Just a couple pickups for the head. Mine is a 1976.
Thanks! Actually, I based it off of a post that Maine Sail contributed a lot of his knowledge to. In fact, I think I followed a diagram that he sketched up.
It's set up as 1 bank of 4 6v batteries and then the group 27 is bank 2 (I suppose) and only used for emergencies. Both banks are hooked up to a dual charger when at the dock. A VSR relay charges both banks while the engine is running and prevents over charging as well.
Bank 1 (the 6v's) are wired to position 1 on my battery switch. They are used for starting and house loads. There are two groups of two batteries within Bank 1. Each group has two 6v batteries connected in Series...this doubles the voltage to 12v. Then the two groups are connected in Parallel...this doubles the Amps.
Maine Sail could explain it much better than I have. His post (I'll try to find it) made it very clear.
There was no water storage under that port settee. Just a couple pickups for the head. Mine is a 1976.
SWG, Your explanation is fine..makes sense to me, but that is a LOT of amp hours you have there!
And the port side set up sounds about right..Mine is a 1977, and I only have the single 17 gal. water tank on the stbd side & the two holes in the hull for the head lines in the forward half of the port settee. A couple years later, Catalina started putting a 17 gal tank in the port settee and made it for black water, right in the same spot where your batteries are, which is why I was asking.
I've moved my batteries over to the stbd settee, and eventually plan to add the 2nd 17 gal. tank to port for more fresh water (I built a custom v-berth tank modeled after the Catalina design as the holding tank since it is 25 gal.)
In the area where the batteries were on our boat originally, I mounted a large piece of PVC board using the existing long bolts that hold the table support (if you make the dinette into a bed.) This makes it real easy to mount stuff and move it around without drilling additional holes in the fiberglass (of which the P.O. already had made plenty.) Now, I have the oil filter & fresh water pump there, and eventually will mount the HX & coolant resevoir when I get the time to convert the A4 to FWC.
I have a single Gr27 for house & a Gr24 for 'start/emergency', but I have modest electrical requirements...if I ever added something like a fridge or more power hungry electronics, I may need more Amp hours some day.
Always nice to see & discuss other setups to get some ideas. Thanks!
Here's a pic of that same area in my boat...the wiring job is a work in progress, so things are not all tidied up yet.
And the port side set up sounds about right..Mine is a 1977, and I only have the single 17 gal. water tank on the stbd side & the two holes in the hull for the head lines in the forward half of the port settee. A couple years later, Catalina started putting a 17 gal tank in the port settee and made it for black water, right in the same spot where your batteries are, which is why I was asking.
I've moved my batteries over to the stbd settee, and eventually plan to add the 2nd 17 gal. tank to port for more fresh water (I built a custom v-berth tank modeled after the Catalina design as the holding tank since it is 25 gal.)
In the area where the batteries were on our boat originally, I mounted a large piece of PVC board using the existing long bolts that hold the table support (if you make the dinette into a bed.) This makes it real easy to mount stuff and move it around without drilling additional holes in the fiberglass (of which the P.O. already had made plenty.) Now, I have the oil filter & fresh water pump there, and eventually will mount the HX & coolant resevoir when I get the time to convert the A4 to FWC.
I have a single Gr27 for house & a Gr24 for 'start/emergency', but I have modest electrical requirements...if I ever added something like a fridge or more power hungry electronics, I may need more Amp hours some day.
Always nice to see & discuss other setups to get some ideas. Thanks!
Here's a pic of that same area in my boat...the wiring job is a work in progress, so things are not all tidied up yet.
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I'd like to again say, Thanks to Stu and MaineSail for their excellent advice and clear guidance on boat maintainance and repairs, particularly for our Catalina 30. Here's another gem relating to battery banks; don't forget your MRBF's!
http://www.sailnet.com/forums/electrical-systems/64546-fusing-your-batteries-another-option.html
Rob
http://www.sailnet.com/forums/electrical-systems/64546-fusing-your-batteries-another-option.html
Rob
Electrical 101: http://c34.org/bbs/index.php/topic,5977.0.html
With lots of links, many to Maine Sail's contributions.
Thanks, and happy reading.
Stu
With lots of links, many to Maine Sail's contributions.
Thanks, and happy reading.
Stu
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