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

[Dave Hupe]

 Sara-
I have the standard setup with a 4D battery each on #1 and #2 of the master selector switch. This is the Blue Sea battery terminal fuse holder that I installed on each of my 4D positive battery terminals https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A  .   I used a 50 amp fuse https://www.bluesea.com/products/5177/MRBF_Terminal_Fuse_-_50A in each fuse holder per instructions in the manual for my Promariner Pronautic 40 amp 1240P charger.  Specifically, the manual says " Fuse Selection - As illustrated in the diagram, each positive conductor from the charger to thebattery/battery bank must be fused. Choose a fuse that is 10 amps higher than the charger output(e.g. 60 amps, choose a fuse of 70 amps)". So, this fuses/protects between the charger and each battery.  I could easily understand where you would blow 20 amp fuses. The charger supposedly senses what each battery needs, and as you already know, can output up to 40 amps. Rarely however, does this amp output last very long.  I have watched the output quickly drop and have never detected any battery or cable heating. . Your charger also should have come with a temperature sensing cord to attach to one of the batteries.  
I don't have any experience with what you have tried with the starter battery and charger. 
Dave Hupe
1994 C320 #32_____________________________________________________________________________________________________
    On Monday, September 14, 2020, 12:34:14 PM EDT, 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