ConFused

[Albanach]

Looking for some advice on what size fuse I should use to protect my batteries or what’s downstream from them. They are a bank of 150 A each in parallel and are being used for starting the engine and as house power. Engine is a 25MPBXC. The fuses are the ones right next to the batteries/battery posts.

Have found many articles in the search forums that go into great detail of the science involved and are obviously written by experts and well meaning contributors. However, I find myself in the end looking at options that seem to range from 30 A to 300 A.

The Catalina manual shows a 20 A fuse for a 205 A battery capacity. The to be replaced fuse on one of the batteries appears to be 30 A.

Can anyone out there help with a plain answer? What do you have on your 310?

 

[trainmanjess]

hello

yes... this issue can be very confusing... I get lost in translation too... I have a friend who helped ... I installed a 30 amp fuse for the house battery bank, and a 20 amp fuse for the starter battery..... along with the house bank, I installed a 30 amp solar controller... then each circuit has it's own fuse in the switch panel... it may seem redundant, but safety is important....

for the solar controller, the solar panels come into it, then go to the house banks, then there is another set of wires that go out to the switch panel to power it... the solar controller also controls the power from the house banks to the boat as a back up 30 amp fuse too... if it draws more than 30 amps, it shunts the power relay and shuts down...



sincerely
Jess

 

[woodster]

try here http://www.pbase.com/mainecruising/battery_fusing

 

[Stu Jackson]

In addition to woodster's link:

Battery Fuse Sizing with tables (from Maine Sail)

http://forums.sbo.sailboatowners.com/showthread.php?t=130775

Perhaps the same material in a slightly different format.

 

[rpwillia]

Battery Fuses

I installed Blue Sea Systems battery fuses. I used the Terminal Fuse Block Single Stud (30-300 amperes – P/N 5191) to mount the fuses along with 200 amp Marine Rated Battery Fuse(s) (MRBF) [P/N 5187].

I recall I had a discussion with MS on this.

 

[JK_Boston_Catalina310]

You don't fuse based on the battery size. The fuse is based on the wire size from the bank to the starter. For our boats that's a 1/0 gauge wire factory. According to the http://assets.bluesea.com/files/resources/reference/20010.pdfBlue Sea Systems sizing chart this size wire should be protected with a 300 amp fuse if single wire or 200 amp fuse if a bundled wire. According to ABYC code the fuse on a starting circuit should be within 7 inches of the battery.

The factory setup is two 4D batteries in parallel. With the 1/2/both/off switch you can start off of either battery. So both batteries should be protected by fuses.

I have 250 amp blue sea systems ANL fuses protecting my batteries.

I have tried some of the cheaper brands in the past and they just don't work as well. I won't buy anything but blue sea systems at the moment (that could change see Maine Sail's 800 pound gorilla post). I have used other brand holders and they are ok but won't bother shopping those again. Just get he blue sea system stuff.

All that said if you don't have fuse holders in place I would just go with terminal blocks due to the easy of installation.

Good luck and fair winds,

Jesse

 

[Albanach]

Thanks, rpwillia and JK_Boston. Your info was what I needed. It confirms my purchase of a Blue Sea system with 200 A ANL fuse for the battery in question (can’t use the MRBF in my setup). Boston, your link to the Blue Sea chart was the clincher ( I had forgotten about that) as it gives the only reference to bundled wires I have found so far. Have also taken into consideration here some of Maine Sail’s comments.

Mind you, I am still slightly curious, why Catalina’s manual shows a 20 A fuse.

 

[pk104]

Could you be looking at the 20amp fuses between the batteries and the battery charger that are shown in the manual?