Re: [Amel Yacht Owners] Re: Distributed vs. Conventional Electrical Systems

Ryan Meador

I believe you're supposed to fuse the battery bank as a whole, and not individual batteries.  That means one fuse for the whole bank.  The reason for this is that some subset of the fuses could blow (one could be slightly more sensitive, or one battery might supply slightly more current under load) and you wouldn't know.  You would hope that a cascading failure causes them all to blow, but it won't necessarily.  And this is bad because now you have one or more batteries isolated from the rest of the bank, yet you still have power, so you're probably not going to go look under the bunk to check the fuses.  With your battery bank now smaller than you think it is, you're likely to discharge it deeper than you intend, and the isolated battery won't be getting charged... quickly all the batteries will be ruined.

I'm a big fan of those battery terminal fuses Bill mentioned.  I installed them on my old boat after reading this excellent article (that whole site is fantastic).  I'm going to do something similar on my SM as soon as I figure out what the current rating should be; it might be possible to get away with a 300A fuse since they don't blow instantly.  As long as we're not leaning on the thruster or windlass switch for too long, I think it would be OK, but I'd love more info about the actual current draw of these systems.

SM 233 Iteration
Boston, MA, USA

On Wed, Oct 18, 2017 at 12:53 PM, James Alton lokiyawl2@... [amelyachtowners] <amelyachtowners@...> wrote:


   Is it correct that the bow thruster on the Super Maramu is 500 Amps?  And that is at 24 volts?  The thruster on my Maramu has a 100 amp breaker installed by Amel ( it has never tripped so I assume the normal draw is something below 100 amps)  and the voltage is only 12 volts so if my math is right it is about 1.5 hp which is good up to about 15 knots or so.   500 Amps at 24 volts would be about 16 hp?  Can you tell me the size of the original Amel breaker that is installed on the Super Maramu?

   Thanks for all of your past help with my Amel.  And to update you on the bow thruster leakage.  After replacing the seals as instructed, the thruster did not leak at all this season.    The thruster has also been 100% reliable thus far and is a tremendous asset IMO.

   I will consider adding some inline fuses to my boat as well just in case of a major short. 


James Alton
SV Sueno,  Maramu #220
On Oct 18, 2017, at 12:21 PM, 'Bill & Judy Rouse' yahoogroups@... [amelyachtowners] <> wrote:


I agree with Alan's point and before we sold BeBe I had decided to place 6 of the Blue Sea 5191 MRBF Terminal Fuse Blocks with a removeable Blue Sea BS5185 (150A) amp fuse on each of the 6 positive battery pairs on the positive post  of the battery and connect the the positive lead for each pair to the newly installed terminal block fuse. My assumption was that the 500 amp bow thruster would not burn individual 150 amp fuses...I may be wrong on this. The fuses are available from 50 amps to 300 amps. Since the fuses are replaceable, I was going to buy extras.

Of course, I have not tested this, so I cannot say that it works and/or whether it is the best solution.

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