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Old 13-12-2018, 19:59   #1
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Battery Switches.

I am at the stage of connecting up the 24V/240V systems on the yacht. I have a "1/2/both" switch to direct the alternator charge between the starting batteries and the house bank.

Apparently I should have a battery isolator switch to cut off the battery power when I'm not on the yacht. I would go along with that but I'd be reluctant to switch power off to the bilge pumps at any time. (I thought about the fridge/freezer too but they would drain the battery bank in no time)

Am I on the right track?

Clive
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Old 13-12-2018, 20:34   #2
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Re: Battery Switches.

Quote:
Originally Posted by coopec43 View Post
I am at the stage of connecting up the 24V/240V systems on the yacht. I have a "1/2/both" switch to direct the alternator charge between the starting batteries and the house bank.

Apparently I should have a battery isolator switch to cut off the battery power when I'm not on the yacht. I would go along with that but I'd be reluctant to switch power off to the bilge pumps at any time. (I thought about the fridge/freezer too but they would drain the battery bank in no time)

Am I on the right track?

Clive
Clive, my humble little pilothouse has 190 watts of solar panels charging six 6 volt 235 amp golf cart batteries and 2 110 amp general purpose start batteries.
The alternator is wired to the start bank thence to the house via a VSR, there are other options. Switching is through 2 four position battery switches, giving me the option of selecting the power source from either bank for either purpose. The "experts" here will decry this setup but it works!
But wait, it gets worse I only have a morningstar duo-charge PWM controller . I am able to run my fridge 24/7 without running down the batteries excessively. (I haven't used the boat much lately but have left the fridge running on the mooring, checked a couple of days a week.)
I wouldn't switch the alternator output, just the batteries. I have an always on circuit that has bilge pumps, alarm and radio memory connected, individually fused of course, and a circuit breaker in the initial circuit.
Cheers.
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Old 13-12-2018, 23:30   #3
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Re: Battery Switches.

Quote:
Originally Posted by coopec43 View Post
I am at the stage of connecting up the 24V/240V systems on the yacht. I have a "1/2/both" switch to direct the alternator charge between the starting batteries and the house bank.

Apparently I should have a battery isolator switch to cut off the battery power when I'm not on the yacht. I would go along with that but I'd be reluctant to switch power off to the bilge pumps at any time. (I thought about the fridge/freezer too but they would drain the battery bank in no time)

Am I on the right track?

Clive
You can provide a "hot" bus which has power available to it at all times from your preferred battery bank (usually the house bank). This is connected before the main isolation switch i.e. it is "hot" all the time regardless of the main isolation switch.

The hot bus can supply whatever you might want to be connected at all times e.g. bilge pumps, a clock etc.
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Old 14-12-2018, 00:02   #4
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Re: Battery Switches.

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Originally Posted by Wotname View Post
You can provide a "hot" bus which has power available to it at all times from your preferred battery bank (usually the house bank). This is connected before the main isolation switch i.e. it is "hot" all the time regardless of the main isolation switch.

The hot bus can supply whatever you might want to be connected at all times e.g. bilge pumps, a clock etc.

Thanks for that. I figured I was going to have to do something like that although I hadn't finalized my thoughts.

I've decided I will put the fridge/freezer (and video surveillance system?) on "the always on" circuit but I'll be able to override either with a switch on the instrument/circuit breaker panel.

Clive
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Old 14-12-2018, 00:05   #5
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Re: Battery Switches.

You do not want a switch on the alternator like that. Turning it to off by mistake will damage the alternator.

Yiu are required to have a switch on the batteries. Not just for leaving. But for fires etc. Every bank needs one.

The bilge pumps get wired before the switch.

Yiu have a lot of reading, studying. And Planning ahead.

Ideally the fridge is dual voltage. And runs off ac at dock. If power is lost fridge shuts off. And batteries stay full.
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Old 14-12-2018, 01:36   #6
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Re: Battery Switches.

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Originally Posted by smac999 View Post
You do not want a switch on the alternator like that. Turning it to off by mistake will damage the alternator.

Yiu are required to have a switch on the batteries. Not just for leaving. But for fires etc. Every bank needs one.

The bilge pumps get wired before the switch.

Yiu have a lot of reading, studying. And Planning ahead.

Ideally the fridge is dual voltage. And runs off ac at dock. If power is lost fridge shuts off. And batteries stay full.

I'm not sure what you mean by "You do not want a switch on the alternator like". All I've said is that I want to be able to charge the "House Bank" or switch to the "Starting Bank" .
Is there a problem with that?

"The bilge pumps get wired before the switch" That is what I intend to do and Wotname confirmed it is the way to go.

"Yiu are required to have a switch on the batteries. Not just for leaving. But for fires etc. Every bank needs one."
Well I am going to have a "hot bus" for bilge pumps (at least) so the battery will not be entirely isolated. (I'd rather risk a fire than have the yacht sink at its' moorings) Every motor on the yacht has a fuse/circuit breaker

Yiu are required to have a switch on the batteries. Not just for leaving. But for fires etc. Every bank needs one.
My starting batteries are right beside the starter motor so I don't know what can go wrong. I'm not sure there'd be anything to be gained?

Your gratuitous advice "Yiu have a lot of reading, studying. And Planning ahead" is noted but that is why I'm on this forum getting advice from knowledgeable guys who've "been there/done that".
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Old 14-12-2018, 03:14   #7
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Re: Battery Switches.

Quote:
Originally Posted by coopec43 View Post
I am at the stage of connecting up the 24V/240V systems on the yacht. I have a "1/2/both" switch to direct the alternator charge between the starting batteries and the house bank.

..........
Clive
The problem that smac999 refers to concerns having the 1/2/both/off switch in the alternator circuit.
The potential problem lies with being able to inadvertently turn the alternator to the "OFF" position while the alternator is charging. This might (and often does) cause the diodes in the alternator to fail. I won't go into the reasons now but if you want, I can explain later .

Some don't like having a switch that can be turned "OFF" in the alternator circuit however personally I am quite OK with it but you have to be alert and remember never to turn it "OFF" while the alternator is charging.

EDIT: if you forget and blow the alternator diodes, you only forget once!
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Old 14-12-2018, 03:42   #8
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Re: Battery Switches.

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Originally Posted by Wotname View Post
The problem that smac999 refers to concerns having the 1/2/both/off switch in the alternator circuit.
The potential problem lies with being able to inadvertently turn the alternator to the "OFF" position while the alternator is charging. This might (and often does) cause the diodes in the alternator to fail. I won't go into the reasons now but if you want, I can explain later .

Some don't like having a switch that can be turned "OFF" in the alternator circuit however personally I am quite OK with it but you have to be alert and remember never to turn it "OFF" while the alternator is charging.

EDIT: if you forget and blow the alternator diodes, you only forget once!

Thanks for that.

Yes I was aware that damage could be done if the alternator was charging but the switch was OFF. In fact I probably would not switch from bank to bank while the alternator was charging just in case damage was done while it was momentarily between banks (maybe an overkill I suppose)

I just had a look at all the battery switches on eBay and they are 1/2/both/OFF. In the morning I'll check to see if there are any alternatives. What I want is 1, 2, 1&2 but no OFF but I can't find anything like that.

What a pity there isn't a post for OFF then I could wire that post to 1 (or 2).

Clive
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Old 14-12-2018, 03:53   #9
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Re: Battery Switches.

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Originally Posted by coopec43 View Post
Thanks for that.

Yes I was aware that damage could be done if the alternator was charging but the switch was OFF. In fact I probably would not switch from bank to bank while the alternator was charging just in case damage was done while it was momentarily between banks (maybe an overkill I suppose)

I just had a look at all the battery switches on eBay and they are 1/2/both/OFF. In the morning I'll check to see if there are any alternatives.

Clive
Most (all?) proper marine 1/2/both/off switches have "make before break" contact switching between the 1/2/both positions. Make before break means the contacts are never open circuit as you switch from 1/2/both. Of course they open circuit in the OFF position
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Old 14-12-2018, 04:05   #10
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Re: Battery Switches.

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Originally Posted by Wotname View Post

Some don't like having a switch that can be turned "OFF" in the alternator circuit however personally I am quite OK with it but you have to be alert and remember never to turn it "OFF" while the alternator is charging.

I'm encouraged after a quick look. Blue Seas have 2, 3 and 4 terminal switches. Maybe the 4 terminal switch will suit my purpose?
(I'll have to investigate further but it is encouraging that there is a choice)

https://www.bluesea.com/resources/17...l_Applications


I need to investigate further.


Clive
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Old 14-12-2018, 05:18   #11
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Re: Battery Switches.

Hardwire alt output - and all other significant charge sources - to House directly. That is the one that needs 99% of your care.

Put an ACR / VSR between House and Starter, even a little Echo Charger will do, but Blue Sea ML 500A one is the bulletproof best, last forever.

Rewire the 1/2/B to be a "feed Load from" switch, and use for starter cranking and Bilge pumps.

Leaving it on Both position risks requiring a jump start.
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Old 14-12-2018, 06:25   #12
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Re: Battery Switches.

Good discussions here
https://forums.sailboatowners.com/in...usings.137615/

http://forums.sailboatowners.com/ind...-2#post-891581
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Old 14-12-2018, 16:27   #13
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Re: Battery Switches.


John

I sometimes wonder where I'd be, building the yacht, without the Internet and advice from people like you, Wotname (and many others).

Thanks for those links: I most certainly will look at them in the next few days.

Clive
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Old 14-12-2018, 17:01   #14
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Re: Battery Switches.

Clive,


The dumb DCP switch and how to wire an alternator are covered here:


Electrical Systems 101


For example:


Installing Battery Selector Switches (the "posts" in the back don't physically match with the switch positions on the front) Batteries and a factory (?) mis-wired battery selector switch


Happy reading & learning.
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Old 14-12-2018, 20:04   #15
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Re: Battery Switches.

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Originally Posted by coopec43 View Post
My starting batteries are right beside the starter motor so I don't know what can go wrong. I'm not sure there'd be anything to be gained.

I did a fire survey on a boat 2 weeks ago. He started the engine. The starter relay stuck. And the starter motor kept cranking. He turned off his battery switch. The lights went off , the engine kept cranking. Because the engine was not on the switch. After a short time the battery wires melted and failed. Stoping power to the starter. His batteries were also right beside his engine.

As I said. By code. Every battery needs one. And they need to be able to be shut off from outside the engine room so you don't have to enter it.


As for the alternator. There are proper products to use . Like a blue sea acr. Or a victron Argo fet isolator. A 1-2-all switch is not.
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