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Old 10-05-2015, 03:32   #31
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Re: Fuse on house battery bank?

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Originally Posted by skipmac View Post
.....Then you run a small cable to the panel from the switch but that cable is only protected by the large fuse on the battery so depending on the size of that cable, might not be protected in a short circuit situation.
Read my post again. I said "a fused smaller wire (4 gauge?) to the panel."
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Old 10-05-2015, 03:38   #32
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Re: Fuse on house battery bank?

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Originally Posted by skipmac View Post

Also, how would you set up that one switch? If an On/Off switch then the panel and starter would always be activated together. I can't think of a simple way a 1-2-Both switch would work in this configuration.
That is the problem with 1/2/both switches - both house loads and starter are activated all the time the switch is on. This is the normal way most boats are wired when built.

My preference is individual switches for house and start with a third for emergency starting from the house bank.
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Old 10-05-2015, 05:17   #33
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Re: Fuse on house battery bank?

Somewhat related to interrupt factor : saw a burned wooden engine bed where 2 hanger bolts had been screwed into top surface to act as contacts for an ANL fuse. 8D cell went tits-up, and moisture in the bed was sufficient to attempt to conduct current. Don't be tempted to make your own bases, to save $30.
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Old 10-05-2015, 06:39   #34
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Re: Fuse on house battery bank?

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Originally Posted by BozSail View Post
From all I've read, I should have a fuse on the house battery bank and it should ideally be placed within 7 inches from the positive battery terminal. Okay, so I'm wondering, why can't I install a properly sized circuit breaker instead of a fuse? So that if I trip the breaker, I can quickly reset it instead of the hassle of changing out the fuse (and having to carry spare fuses)?

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It's been mentioned, I believe, but if you have a current large enough to blow the fuse or trip the breaker and they were properly sized in the first place, you're going to have a pretty big electrical problem to fix so being able to flip a breaker back on isn't going to be of much use. A fuse and a spare should be less expensive than the breaker anyway and properly sized, it should never blow.

You are really complicating things if you're also going to combine the battery banks for starting. The easiest way to deal with this is to put your connection to the battery combining switch before the fuse to the house wiring. That way the starting current won't be flowing through the fuse and you can ignore it for selecting the capacity of the fuse.
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Old 10-05-2015, 08:17   #35
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Re: Fuse on house battery bank?

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Originally Posted by mitiempo View Post
Read my post again. I said "a fused smaller wire (4 gauge?) to the panel."
Ah, I missed that. Apologies. Once again proved that posting late at night isn't always the best.
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Old 10-05-2015, 08:32   #36
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Re: Fuse on house battery bank?

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Originally Posted by mitiempo View Post
That is the problem with 1/2/both switches - both house loads and starter are activated all the time the switch is on. This is the normal way most boats are wired when built.

My preference is individual switches for house and start with a third for emergency starting from the house bank.
Yes a single 1-2-Both switch is problematic. There are very good solutions that use two switches that solve these problems. A very good diagram for this has been posted a few times in the past.

My setup is an On/Off fuse for the house banks with a separate, fused lead directly from the house batteries to a couple of always on loads: bilge pump and alarm, small LED panel light. Then separate hi amp fused cables from house banks and start battery to a 1-2-Both switch so I can easily choose either bank for cranking.

An alternative to this is to allow the start battery to run house loads but I thought quick access to a backup engine starting more critical. With my setup it I can move one cable or connect a jumper to connect the starting battery to run house loads if needed.
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Old 10-05-2015, 09:39   #37
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Re: Fuse on house battery bank?

Just a thought, if one bank is to low to start a motor use the other bank. If you combine them the more charged bank is both trying to start and charge the discharged bank at the same time. If you have a bad battery in the mix it will act as a load and discharge your good battery. Figure out why it wont give enough omph and fix that. Not charging not holding charge. Old sulpherated internal short battery most common problem.

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Old 10-05-2015, 10:40   #38
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Re: Fuse on house battery bank?

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Originally Posted by Badsanta View Post
Just a thought, if one bank is to low to start a motor use the other bank. If you combine them the more charged bank is both trying to start and charge the discharged bank at the same time. If you have a bad battery in the mix it will act as a load and discharge your good battery. ...............
Yep.
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Old 10-05-2015, 11:54   #39
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Re: Fuse on house battery bank?

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Originally Posted by Badsanta View Post
Just a thought, if one bank is to low to start a motor use the other bank. If you combine them the more charged bank is both trying to start and charge the discharged bank at the same time. If you have a bad battery in the mix it will act as a load and discharge your good battery. Figure out why it wont give enough omph and fix that.
This is one of the reasons I dislike 1/2/both switches. Many also do not understand its proper use and leave it on "Both" all the time. As posted a dead bank should never be paralleled with a good bank.

On my boat I have 2 separate on/off switches - one labeled start and one labeled house. I have always thought it makes no sense to have the engine circuit live when not planning to start it as happens with a 1/2/both switch.

A third switch can be installed to allow starting with the house bank or powering house loads with the start battery. It need not be with the others to avoid confusion as it's use will be very rare. A dedicated start battery that is not used for anything else rarely has an issue.

For fusing (not breakers) I regularly use 2/0 for all battery wiring and only step down in size for the panel feed. This makes for easy fuse sizing - 250 amp commonly which will not cause nuisance blows when starting even a 75 hp diesel.

For charging the switches are left totally out of it. The alternator output goes directly to the house bank - always the most in need. This is fused at the battery with an oversize fuse. This is the last place you want a nuisance blow. All other charge sources also go directly to the house bank with proper fusing. The start battery is charged with either an ACR or a battery to battery charger like an Echo Charge or Duo Charge. This makes charging of both banks fully automatic, needing no owner input.

This is a simple system that is reliable and easy to use. When on the boat the house switch is on and the start switch isn't until the engine is required.
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Old 10-05-2015, 12:04   #40
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Re: Fuse on house battery bank?

Quote:
Originally Posted by mitiempo View Post
This is one of the reasons I dislike 1/2/both switches. Many also do not understand its proper use and leave it on "Both" all the time. As posted a dead bank should never be paralleled with a good bank.

On my boat I have 2 separate on/off switches - one labeled start and one labeled house. I have always thought it makes no sense to have the engine circuit live when not planning to start it as happens with a 1/2/both switch.

A third switch can be installed to allow starting with the house bank or powering house loads with the start battery. It need not be with the others to avoid confusion as it's use will be very rare. A dedicated start battery that is not used for anything else rarely has an issue.

For fusing (not breakers) I regularly use 2/0 for all battery wiring and only step down in size for the panel feed. This makes for easy fuse sizing - 250 amp commonly which will not cause nuisance blows when starting even a 75 hp diesel.

For charging the switches are left totally out of it. The alternator output goes directly to the house bank - always the most in need. This is fused at the battery with an oversize fuse. This is the last place you want a nuisance blow. All other charge sources also go directly to the house bank with proper fusing. The start battery is charged with either an ACR or a battery to battery charger like an Echo Charge or Duo Charge. This makes charging of both banks fully automatic, needing no owner input.

This is a simple system that is reliable and easy to use. When on the boat the house switch is on and the start switch isn't until the engine is required.
Simple is better!
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Old 10-05-2015, 17:23   #41
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Re: Fuse on house battery bank?

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Simple is better!
Yes. And simplest is a battery combiner that parallels the batteries for charging and separates them for use. $100 or less.
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