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Catalina/Capri 25/250 Sailor's Forums

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Battery Selector Switch Question

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RickStevens
1st Mate

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USA
62 Posts

Initially Posted - 02/18/2006 : 11:37:00

I'm sitting here working on my ever-growing C25 wish list. One item is an upgraded electrical panel. I've picked up a LOT of good tips in this forum, but I haven't yet found this particular item discussed.

I am thinking of replacing my "1/2/On/Off" battery selector switch with a simple "On/Off" main breaker switch. "On" will always control both batteries, and "Off" will be... Off! I have a Honda BF9.9 outboard with electric/pull start (the alternator on the engine puts out 6 - 12 amps) so engine starting and charging shouldn't be a problem. I am putting in 2 deep cycle marine batteries and a permanently mounted charger in the next couple of weeks, so the switch will be controlling 2 of the same type of battery.

Does anybody on the forum have any experience with this, or any warnings to share? I managed to fry one of my batteries a few weeks ago due to a faulty portable charger

, so I'm a little sensitive about this whole subject right now and don't want to mess things up.

"Not Renamed Yet" - '82/C25/SK/TR

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 02/18/2006 : 11:57:48

Rick S,

If you haven't done so already, I suggest reading the [[url="http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorListView?storeId=10001&langId=-1&catalogId=10001"]west Marine Advisors[/url]], particularly the one titled [[url="http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/creatingabatterysystem.htm"]Creating a Reliable Battery System[/url]], which discusses your very question, "replacing my "1/2/On/Off" battery selector switch with a simple "On/Off" main breaker switch." (Yes, they suggest not designing an up to date sailboat electrical system around a traditional [OFF/1/BOTH/2] selector switch.) One thing I might add -- I don't consider it a really good idea to leave lead-acid batteries connected in parallel when they're not being charged or discharged. Unless they are in identical condition, it's my understanding the weaker one will 'pull down' the stronger one. One way to deal with this would be to use a [[url="http://www.yandina.com/combInfo.htm"]Battery Combiner[/url]] which can be set up to automatically parallel your batteries when they are either being charged, or in use. Otherwise, it will isolate them from each other. I can provide you a link to an example schematic if this isn't clear.

-- Leon Sisson

Edited by - on

danandlu
Navigator

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USA
175 Posts

Response Posted - 02/18/2006 : 12:03:05

Rick,

Even though I am electrically challenged I found this article very interesting. I currently have no alternator (pull start) and only 1 battery, as simple as it can be. I may upgrade after this first season.

http://www.amplepower.com/primer/prefer/index.html

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 02/18/2006 : 13:27:15

There are a number of books available on our links page that specifically address some of these issues. I'd recommend gettin one or all of them. I myself do now know enough to speak about this intelligently, but anytime I need a reference, I'm pullout out my 12v bible for boats.

Duane

Edited by - on

ct95949
Captain

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Aruba
300 Posts

Response Posted - 02/18/2006 : 17:40:45

Both of my house batterys have their own switch which when off completly disconnects them from everything else except the bilge pump.They are common 120V light switches.
I had similar problems with an old charger but after installing a Guest three stage-two battery charger last winter the batterys have never been low and they're only charged when I'm at the boat.

Edited by - ct95949 on 02/18/2006 17:56:49

sweetcraft
Admiral

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USA
816 Posts

Response Posted - 02/18/2006 : 22:20:20

I started the discussion way back about using an isolator with the orginal btry switch 1/2/both/off. It was the cost in 79 in making the decision to go with the isolator and I have not had a problem. I did also install breakers, 40 amp, at each battery to protect the positive leads to the isolator. The breakers are small and low cost and have to be reset if opened, they can't come back on. Both batteries are in boxes so that nothing can fall in and cause a short. I have cruised for 4 to 5 weeks without discharging either battery. Isn't there a sign that says a fire at sea can ruin your whole day?

Edited by - on

HudsonM1
1st Mate

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USA
41 Posts

Response Posted - 02/20/2006 : 21:54:51

In case some of you haven't seen this, Blue Sea Systems just came out with a nifty new switch. http://www.bluesea.com/

Unless I'm misunderstanding the discription, it looks like it allows you to follow the West Marine Advisor schematic that keeps all banks isolated, but you only have to buy one switch - not 3.

Edited by - on

oldsalt
Admiral

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USA
578 Posts

Response Posted - 02/21/2006 : 03:26:44

Craig,

Common 120 volt AC light switches aren't rated for the level of DC current at 12 volts DC they need to be able to handle on your boat and may pose a risk of fire in the case of an overload or a short circuit.

Neither can they accept adequately sized wiring for a 12 volt DC system under their terminals since they're rated for # 12 AWG and they won't resist internal corrosion that may cause further heating.

Using them aboard your vessel doesn't seem like a safe proposition to me.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 02/21/2006 : 08:47:03

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by HudsonM1
 In case some of you haven't seen this, Blue Sea Systems just came out with a nifty new switch. http://www.bluesea.com/

Unless I'm misunderstanding the discription, it looks like it allows you to follow the West Marine Advisor schematic that keeps all banks isolated, but you only have to buy one switch - not 3.

<hr height="1" noshade id="quote"></blockquote id="quote">
Our boats do not use start batteries, that is for inboard systems. I don't believe this new switch brings anything to our table.

Edited by - on

ct95949
Captain

Members Avatar

Aruba
300 Posts

Response Posted - 02/21/2006 : 09:12:11

Hi Mark
I'm no electrician but this was my reasoning when installing these switches on my house batterys.My biggest house wire is 10 gauge(30 amps) which runs from the batterys,to the switches,then to the main panel.12 volts x 30 amps=360 watts,120V x 30 amps=3600 watts.I realize these switches are only rated at 15 amps but that is still 1800 watts,more than enough to handle the heat in this 12V current?

There are many sizes of 10 gauge eye terminals so wire size at the switch was no problem.To avoid corrosion I coated all the connections with liquid tape.I would like to add fuses or links at the batterys for further protection.

These switches have been in place for three years with no apparent problems but my electrical experiance is certainly limited and I would like to know if I'm missing something.
Thanks,Craig

Edited by - ct95949 on 02/21/2006 09:15:34

RickStevens
1st Mate

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USA
62 Posts

Response Posted - 02/21/2006 : 15:10:14

Based on all the info here, plus the shared links (and lots of other reading), I am likely going the way of the Isolator/Automatic Charging Relay with multiple switches. The switch setup I'm looking at is based on this quote from the West Marine advisor pages:

<blockquote id="quote">quote:<hr height="1" noshade id="quote">...consider using three OFF-ON battery switches as follows: one switch to connect your starting battery to your starter circuit; one switch to connect your house battery to your boat's distribution panel; and one switch to parallel your battery systems if either battery fails.... With this set-up, you simply turn your engine and house switches to the ON position whenever you are onboard, whether anchored, starting your engine, or sailing. The battery parallel switch remains OFF unless there is a complete failure of either battery bank or you have run your starting battery down trying to crank a reluctant engine.<hr height="1" noshade id="quote"></blockquote id="quote">

The charging relay will allow me to use the Honda's alternator to make sure both batteries are topped off. The addition of a quality hard-mounted shore charger should keep me ready to go. I'm still debating the merits of a 10A vs. 20A charger - leaning heavily toward the 20A - but the combination of this, the ACR, and stand-alone switches seems to provide both redundancy and simplicity of operation.

One major difference: Since I am getting 2 new batteries my plan is to make them both deep-cycle types instead of having one specifically for engine starts. My existing, weak-as-a-kitten #1 battery

has done a fine job with this engine, so I'm not convinced this application needs a dedicated starting battery. At least, that's the plan.

As always, thanks to all.

Edited by - on

oldsalt
Admiral

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USA
578 Posts

Response Posted - 02/21/2006 : 18:45:55

Craig,

Without getting into specifics, the basis of your calculations are incorrect.

At any rate, when designing your system, you have to provide for the short circuit current which is available at any point in the system, rather than the anticipated calculated load.

Don't let the low voltage fool you, your battery bank can crank out heavy amperage which will produce an incredible amount of heat instantly if you have a short in your system and you will have a fire. The voltage may be low but there is a considerable amount of energy in the system.

All of the #10 AWG wiring connected to your system should be properly fused and your battery switches need to be sized and designed for a DC low voltage marine system. The toggle switches used in home wiring are incapable of fulfilling these requirements and are extremely dangerous to have aboard.

You should also use only tinned, marine grade wire preferably with soldered type eye terminals rather than the crimp on type. Poor connections are an additional source of heat and voltage drop. Covering up crimp ons only hides the problems.

By the way, the longer the run from the batteries, the heavier the wiring needs to be to minimize voltage drop.

The fact that you haven't had any serious probelms in the last three years sort of reminds me of what the mutual funds tell you: "past results are no guarantee of future performance".

Seriously, I am a licenced electrician and engineer and I hope you correct the wiring system on your vessel before you encounter the catastrophic failure which is almost certain to happen in the future. And when it does happen, the whole event will occur in seconds, without warning. I don't know if your as old a salt as me, but if you are; think "flashbulb".

Someone posted a link to a site that sells marine wiring with a listing of proper sizes.

There is also an excellent book on marine wiring which someone mentioned on this site. Of course, I can't recall the name.

It would be worthwhile to research the above references and gain some insight into how to proceed.

Afterwards, you can rewire your vessel with a proper main battery switch, marine circuit breaker or fuse panel, and wire it all up with the proper wire and terminations.

I hope this helps and best of luck.

Regards,

Mark

By the way, I'm very, very, surprised that nobody else here chimed into the discussion of how your boat is wired.

Edited by - on

Frank Hopper
Past Commodore

Members Avatar

Pitcairn Island
6776 Posts

Response Posted - 02/21/2006 : 19:04:58

http://www.ancorproducts.com

No comments? We like pretty lights! Bright light, bright light!

Edited by - on

ct95949
Captain

Members Avatar

Aruba
300 Posts

Response Posted - 02/21/2006 : 20:19:51

Thanks Mark
My system is not quite as bad as that.
All the wiring and terminals I've installed are Ancor marine grade.My main panel is the newer Catalina model with breakers.I have a Cat battery dissconnect switch for the outboard battery.There are many in line fuses but I do need some at the batterys.I know a short in any system causes a tremendous amount of heat and the possibility of fire but I still don't know why these switches won't handle the normal load passing through them.I have other simple 12V toggles that are not as heavy,are those wrong too? I will heed your advise about getting a book and doing some research.
Thanks,Craig

Edited by - on

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