[C320-list] In-line fuse on battery cables

[Mark Seyler]

Sara,

I don’t have the same set-up as you do, so I'm not certain which fuse holders you have.  But my bet would be that your fuse holders are corroded, and need replacing.  (You could clean them, instead, but after 20 years it seems worth it to replace them.)

You got good advice not to just replace the 20 amp fuse with a 30 amp.  The fuse has to be sized based on the capacity of the wires and fuse holder to carry the current.  That is affected by both the size of the wire and the condition of the connections.  You can look up the capacity of the cables themselves on-line.  https://www.usawire-cable.com/pdf/nec-ampacities.pdf  But any even if the wires size is large enough, corrosion on the connections can generate the kind of heat you describe.  And it can get worse the longer it goes on.

Defender Marine has an entire web page showing different fuse holders.  https://www.defender.com/category.jsp?name=fuse-holders-and-fuse-blocks&path=-1|328|2290021&id=2290030  You should be able to match what you have by comparing to that page.  But you might need to upgrade from what you have.  I don't see any of the round in-line fuse holders that are rated for more than 30 amps.  There are other types that you could upgrade to that would take a 40 amp fuse.  You'd also want to make sure that the wires to and from the batteries are large enough to handle the extra current.

If you prefer to shop in person West Marine has similar products, but they charge more.  https://www.westmarine.com/fuse-holders 

If you get the wire size and fuse capacity ironed out, the combined house-battery/starter battery set-up should work as planned.  I think your problem was more driven by a higher capacity charger delivering more amps than you could use.  But let us know how things work out in the end.  I've learned so much about my boat from reading about how other owners solved their problems.

Mark Seyler
S/V Reality,
Catalina 320, #232
New Orleans, LA



-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of islgirl3 at aol.com
Sent: Monday, September 14, 2020 3:24 PM
To: dean at vermeire.us; C320-List at Catalina320.com; saras951 at comcast.net
Subject: Re: [C320-list] In-line fuse on battery cables

Sara,I have the same configuration as Dean, no issues. You can set the ProNautic to regulate the output. I have mine set up for 75% max output. It takes longer to charge since the output amperage is lower.
RichBarbara Rita 897


-----Original Message-----
From: dean at vermeire.us
To: C320-List at Catalina320.com
Sent: Mon, Sep 14, 2020 12:53 pm
Subject: Re: [C320-list] In-line fuse on battery cables

  I recently installed a new ProNautic 1230P (30A) and have the original
  configuration of 2 4D batteries with one on each bank. The inline fuses
  on mine are 30A.
  Everything is working great.
  Since your charger will automatically adjust the amperage up to 40A on
  a bank, I would think a 20A fuse would be easy to blow.

  On Sep 14, 2020 11:33 AM, SARA SCHROEDER <saras951 at comcast.net> wrote:

    I had reached out to the group regarding recommendations on battery
    charges, echo-chargers and solar panels.  As a reminder I have two
    4D deep cycle batteries, did not have a starter battery or
    echo-charger and my batteries were either not being fully charged or
    were losing capacity. After doing research, my helper and I ganged
    the two 4D batteries together into one house bank which became bank
    #1 and installed a new starter battery which became bank #2.  We
    also installed a new ProMariner ProNautic 12V 40 AMP battery
    charger.
    After a full weekend away from the dock, this set up turned out to
    be an epic failure.  The batteries were not being charged at all -
    either by the new charger or the alternator.  Upon further
    inspection we discovered that both the alternator and the new
    charger were blowing the 20amp in-line fuse located in the positive
    battery cable. We considered just putting in a larger fuse but Platt
    Electric recommended we not do this.
    We undid everything and reverted back to the factory settings.  One
    4D is back to house bank #1 and the second 4D is house bank #2.  The
    starter battery and echo-charger are on hold for the moment.  We
    installed new fuses in both positive cables, fired up the new
    battery charger and my batteries finally started getting a charge.
    At first the ProNautic was pumping in about 40amps but this quickly
    came down to about 20amps.  After about 30 minutes of charging my
    helper reached down and touched the in-line fuse casings. They were
    shockingly hot. We could not really even touch them.  I stayed at
    the boat to monitor them and after about 3 hours I could touch them
    and the cables themselves were "slightly" warm but not hot.
    I suspect the fuse housings are original which makes them 20 years
    old.  Does anyone have these round in-line fuse housings or is it
    just me? Have you had problems with them failing or replaced them?
    If you replaced them what did you use?  Thanks as always!
    Sara
    Wandering Star
    2000 / #707