[deniseO30]

All the rewiring I did as many of you may remember? Well the cube fuses seemed ok. I wasn't overly impressed with them. Anyway. The fuse for the starter on the engine battery burned out. 125 amp, terminal loosened up "again" . with lock washers that was the cause. Any way... the new terminal is all green on the cable so I'm going to replace it with new one and get better washers on the cube terminal and go to 150 amp for the starter. I'm really tempted to leave it out. since that is what had to be done to use the engine battery again.

So it also dawned on me I need the batteries combined so the solar trickle feeds them all? (Blue Seas Isolated battery circuits switch, with acr)

 

[Maine Sail]

All the rewiring I did as many of you may remember? Well the cube fuses seemed ok. I wasn't overly impressed with them. Anyway. The fuse for the starter on the engine battery burned out. 125 amp, terminal loosened up "again" . with lock washers that was the cause. Any way... the new terminal is all green on the cable so I'm going to replace it with new one and get better washers on the cube terminal and go to 150 amp for the starter. I'm really tempted to leave it out. since that is what had to be done to use the engine battery again.

So it also dawned on me I need the batteries combined so the solar trickle feeds them all? (Blue Seas Isolated battery circuits switch, with acr)

Denise a 125A or 150A amp fuse for a starter load is a JOKE!!!! You really need 250-300A and at the smallest 200A bare minimum.... What size is your wire?

Beyond that use a nylock with the MRBF with the nylock on top of a split washer.

ANY BATTERY THAT CAN BE CALLED UPON TO EVER START A SAILBOAT AUX DIESEL NEEDS A MINIMUM 200A FUSE, BUT PREFERABLY 250-300A TO AVOID NUISANCE TRIPS....!

Once you get the right fuse in there you will have many thousands of starts and will completely forget the fuse is even there.

 

[hellosailor]

And if you have no silicon grease to schmear on the fittings to prevent them from turning green, you can always use chicken schmaltz.

With any leftover chicken schmaltz, you can make chopped liver.

 

[MarkSF]

I went with the 300A fuses for my Universal 5424. The cabling is 00, so according to the table my fuses are just about small enough to protect the cabling. 00 is rated for 280A continuous inside an engine space. I think I read you are allowed a certain rating over the continuous rating, when selecting fuses. Mainesail, do you know what that percentage is?

"the new terminal is all green on the cable". Does this mean the conductors are not tinned?

Genuinedealz.com will sell you nice cables, terminated, with tinned marine-grade wire. That's what I use, and the price was less than the bare cable at my local chandlery.

 

[deniseO30]

Hides behind sofa and softy says; "weeeell I wanted to size them closer to the load"
# 4 marine battery cable only about 4ft to starter. It's only a little 2 cylinder engine.

the terminal was loose enough to rattle. they make copper nylocs?

 

[MarkSF]

I used to have 4 gauge cabling. It starts with a lot more enthusiasm, now it has 2/0.

 

[deniseO30]

I used to have 4 gauge cabling. It starts with a lot more enthusiasm, now it has 2/0.

Well #4 can handle 136 to 160 amps load, and more on the surge

 

[Maine Sail]

Hides behind sofa and softy says; "weeeell I wanted to size them closer to the load"
# 4 marine battery cable only about 4ft to starter. It's only a little 2 cylinder engine.

the terminal was loose enough to rattle. they make copper nylocs?

What "load"? You do know a starter can draw many times it's "rating"... I have measured a 1.2kW starter at 640A during the in-rush... I have measured a 1.4kW at over 1000A in-rush. ANL, MRBF and Class T can handle brief in-rush but still need to be sized well in excess of the kW rating.. On a warm day with healthy battery & wiring you might see just 2X the rating but as the battery gets weak, marginal cable of cold temps etc. the starter load can go up..

 

[deniseO30]

load From the new 90am alternator. the terminal was loose for the starter! Could of burned, glad the fuse went

 

[eherlihy]

Hi Denise,

You should size the MRBF to the location, wire gauge and insulation temperature rating. I have AWG 2 leads with 105ºC insulation going to my batteries, and this is inside the engine room, so for me the proper size fuse for me is 178.5A - call it 175A.

Look at the table below, and find your wire gauge, then find the insulation, and read what should be your fuse rating.
(Posting this image from Maine Sail's site);

[EDIT] If sized too small, you WILL blow fuses as your battery voltage drops. You know that the voltage will drop as you spend a night at anchor, and use the batteries. Voltage down means current up to produce the same power to the starter motor.

 

[Maine Sail]

Hi Denise,

You should size the MRBF to the location, wire gauge and insulation temperature rating. I have AWG 2 leads with 105ºC insulation going to my batteries, and this is inside the engine room, so for me the proper size fuse for me is 178.5A - call it 175A.

Look at the table below, and find your wire gauge, then find the insulation, and read what should be your fuse rating.
(Posting this image from Maine Sail's site);

[EDIT] If sized too small, you WILL blow fuses as your battery voltage drops. You know that the voltage will drop as you spend a night at anchor, and use the batteries. Voltage down means current up to produce the same power to the starter motor.

Yep and voltage drop across the wire only compounds battery sag.

If need be you can go to 150% of that table which on 4GA 105C wire is about 240A..

On another note ANY FUSE is ALWAYS SAFER than NO FUSE !!!!

I have blown a 300A MRBF fuse on 15' of 8GA wire and the wire never even got a chance to get warm to the touch.. Way out of ABYC specs and I am not recommending it but fuse so you don't have nuisance trips. If this requires upsizing the piddly 70's wire builders used so be it. Catalina now uses 1/0 or 2/0 on the same size engines they did in the 70's & 80's when they were using 4GA.......

 

[eherlihy]

These charts are also relevant: they show that MRBF fuses WILL support higher amperages than their nominal rating for short (< 10 sec) periods of time;

Recommended Fuse Range; (200A for ~8 sec)

Fuses that Denise used; (not so good, 200A for ~1.1 sec)

 

[Maine Sail]

This chart is also relevant: it shows that the fuses WILL support higher amperages than their nominal rating for short (< 10 sec) periods of time;

ANL, Class T and MRBF fuses are intended for motor starting loads and to get you well past the in-rush but they still need to be sized larger than the continuous average in order to not "nuisance trip"...

If you look at the 125A and the 300A MRBF you will note that the 300A can handle 200A for approx 10 full seconds but the 125A fuse can barely get beyond 1 second at 200A.. Even the 200A fuse can handle about 8 seconds at 200A. This window on the 125A fuse is simply too short for a starter motor....

 

[deniseO30]

thanks gents, no need to beat me up! The 125 handled quite a few starts without a problem. I know, it's not will it fail, just when, I'd love to see the real time amps on my starter. It turns the engine over quite easily. And if the engine bat gets low, the house bank comes in thanks to the ACR. Love how it all works. just the starter is the bugaboo.

As i said it's 2 cylinder and all the #4 wire runs are short. (less then 6ft) For now, I'lll get a 175 cube and keep a spare. Maybe change the starter cable to #2. AGAIN. the terminal was very very loose. Like a 1/16" play. which was the 1st real cause.

a regular amprobe type clamp on meter will not give me DC amp reading right?

I may change all the cables to #2. but it's all $ related of course.

 

[aa3jy]

a regular amprobe type clamp on meter will not give me DC amp reading right?

If its rated for DC amps it should

 

[MarkSF]

A 5 ft length of 1/0 cable, terminated at both ends, is $31 at Genuinedealz.com, with free shipping. Just saying.

No, I don't own the company!

But I did use them to make new cables between my batteries, switch, and starter. They even use the proper 4-jawed crimper.

 

[deniseO30]

Yes Mark thank you, I've been using them for most of my wiring and related purchases. Great outfit too!

 

[MarkSF]

I think my problem was not so much with the wire guage, but the quality. The original Bristol cabling was fine. But someone added a second battery bank, and did a crap job. The cabling wasn't tinned, and the crimps on the terminals were badly done. The terminals weren't tinned, either. Finally, no heat shrink at the terminals.

 

[deniseO30]

Mine had a mix of re purposed jumper cables and non marine cable.

 

[deniseO30]

I'm going to borrow a DC clamp on amp meter! I want to see this "mega amp" draw my little starter is claimed to be drawing on startup!