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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

battery isolater

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f_sondergaard
1st Mate

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USA
92 Posts

Initially Posted - 06/03/2002 : 13:29:57

Has anyone had any experience with a battery isolator? West Marine sells it and I believe you can hook it up, and charge more than one battery with your alternator. We have a 15hp honda 4-stroke. West Marine tech line says it can be done. Any experience from our fellow 25 owners?? Thanks!

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 06/03/2002 : 16:21:48

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
Has anyone had any experience with a battery isolator? West Marine sells it and I believe you can hook it up, and charge more than one battery with your alternator. We have a 15hp honda 4-stroke. West Marine tech line says it can be done. Any experience from our fellow 25 owners?? Thanks!

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I use one currently. It is wired from my battery charger to the isolator to the batteries. I would assume you just replace the charger with the alternator???

Just make sure you use inline fuses so you don't blow an alternator or a battery.

dw

Duane Wolff
"The Flying Wasp"
C-25, #401 std,sk
Chief Measurer C-25/250 National Assn.
<img src="http://im1.shutterfly.com/procserv/47b2dc20b3127cce9cd2f45b211a0000004010" border=0>

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Steve
1st Mate

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USA
87 Posts

Response Posted - 06/03/2002 : 16:45:02

This may be something I'm interested in. How do these things work? Are they charging each battery individually, or together? How much do they cost? Do they work OK if the two batteries are at different levels of charge?

This might save me a trip or two, at least.

Thanks,
Steve
"Island Time"
87 WK Tall Rig

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 06/04/2002 : 08:33:18

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
This may be something I'm interested in. How do these things work? Are they charging each battery individually, or together? How much do they cost? Do they work OK if the two batteries are at different levels of charge?

This might save me a trip or two, at least.

Thanks,
Steve
"Island Time"
87 WK Tall Rig
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

The basic premise behind them, and one of our electrical guru's could really assist with a definition, is that they charge each battery in the bank individually without allowing a battery with a lesser charge to suck juice out of its brother.

http://www.sailnet.com/store/departments.cfm?id=296

DW

Duane Wolff
"The Flying Wasp"
C-25, #401 std,sk
Chief Measurer C-25/250 National Assn.
<img src="http://im1.shutterfly.com/procserv/47b2dc20b3127cce9cd2f45b211a0000004010" border=0>

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dgabel
1st Mate

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USA
75 Posts

Response Posted - 06/04/2002 : 11:14:09

This is what they do.

They have a set of switches inside the box and some means of sensing charging voltage, and voltage of each battery. The one I have uses relays.

When the outside source (charger, alternator) goes higher than the voltage of the battery(ies) the switch connects the output of the source to the input of the battery, charging the battery. If both batteries have lower voltage than the charger, then both batteries get charged. The switches keep the batteries isolated when the charging source is not higher than the battery voltage, so that one battery cannot drain the other.

The newer ones from West Marine use solid-state switches (basically silicon diodes). Older ones use relays, like mine.

It seems to work just fine, so far. This is the first year that I've had it. I'll know more at the end of the season.

Dave Gabel
Walkure
Sail #1485
Northport, NY

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Steve
1st Mate

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USA
87 Posts

Response Posted - 06/04/2002 : 12:18:05

Dave,

Thanks for the info. I usually go down to the boat, charge one battery, go down the next day, etc. Last summer, my boat was about an hour away so it was a pain. I've never liked leaving a charger on the boat any longer than I have too. I'll go by West Marine and pick up an isolater.

Just when I thought there was nothing else I could buy for this boat ...

Steve
"Island Time"
87 WK TR

Edited by - on

Steve
1st Mate

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USA
87 Posts

Response Posted - 06/04/2002 : 12:19:34

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 06/04/2002 : 13:32:44

Dave,

So I have a six amp charger and two batteries. What size isolator should I be using? Is 70 amp enough?

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f_sondergaard
1st Mate

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USA
92 Posts

Response Posted - 06/04/2002 : 16:50:22

Thanks for the interest and the information on this topic. I am going to go and buy a isolater and hook up all three of my batteries. I will let yall know if it works or not.

Thanks again.

Jason & Fran
Gentle Breeze
Southport, NC

Edited by - f_sondergaard on 06/04/2002 16:51:43

Edited by - f_sondergaard on 06/04/2002 16:52:45

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Daniel
1st Mate

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78 Posts

Response Posted - 06/06/2002 : 18:25:35

What size fuses would you recommend? I am using the West Marine 50A isolator but don't have fuses in the lines... yet. I'd like to get them in ASAP.

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Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 06/07/2002 : 08:13:20

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>
What size fuses would you recommend? I am using the West Marine 50A isolator but don't have fuses in the lines... yet. I'd like to get them in ASAP.
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote>

I am speaking from the hip here, so make sure to get a second opinion, but it is my general understanding that you want your fuses to be rated higher than your charger and that is all you need.

dw

Duane Wolff
"The Flying Wasp"
C-25, #401 std,sk
Chief Measurer C-25/250 National Assn.
<img src="http://im1.shutterfly.com/procserv/47b1ce23b3127cce9b043565af3d0000004010" border=0>

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dgabel
1st Mate

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USA
75 Posts

Response Posted - 06/11/2002 : 17:52:21

First, if you have a six-amp charger, then you will find that the 70-amp isolator is really overkill. I believe West sells a 50-A model, and that should be adequate. I got an older model last year that uses relays, and can handle 70 A. It's more than enough to charge two batteries. Mine charge from the outboard, and the documentation on that engine does not say how much current the alternator puts out, but the wires attached are only 4-gauge. The Boatowner' Illustrated Handbook of Wiring, by Charlie Wing, says that inside engine spaces the max allowable current for this wire is 61 A. Because I am not using shore power, and am only charging with my outboard's alternator, I am convinced that I will never see that much current in those wires, so I am sure that the 70-A isolator I have will work fine. I believe that a 50-A isolator would work as well, and I believe (but I cannot guarantee) that that size will be fine for your purpose. If you're at a dock and are using shore power, find out what the capacity of the circuit is. It has a breaker on it, and the rating of the breaker is the rating of the circuit. You can't carry more current than that breaker will pass.

Fuses. You size the fuze to protect the wiring. So you have to figure out what wire sizes you're dealing with. To do that, you need to know what current you're going to carry. There are charts in any sailboat wiring book (see my note above) that tell you what size wire you need for what current. Then you pick a fuse that will open when the current exceeds the rated current for the wire you're using. Fuses (and circuit breakers) are safety devices that protect you from overheating the wiring and starting a fire.

If you are dealing with wire that's already in the boat, the owner's manual lists wire gauges for what went in the factory design. You can use those to determine what size fuse you would need.

Dave Gabel
Walkure
Sail 1484

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