Rectifier negative post keeps breaking - Suggestions needed

[Ostinato]

I have two engines each equipped with a 150 amp Series 6 Balmar alternator. They both have 0000 wire attached to them.

In October 2013 the port engine alternator's negative stud broke. I replaced the rectifier and changed how the negative and positive wires ran to it so that the wire would vibrate along with engine more easily. But while doing routine maintenance this week I noticed the negative stud on the same alternator broke again. The break appears to show fatigue at the bend. Essentially I got two sailing seasons out of it.

I have checked with Balmar and while they have experienced a several of these failures over the last year, their specs have not changed and their suppliers say nothing has changed on their end. The positive stud shows no issues nor does the starboard engine alternator.

I am now about to replace the rectifier again and am looking for suggestions on how to reduce the strain on this stud. I have thought of adding a short length of lighter wire between the 0000 and the stud or trying to reinforce the stud at the bend but would like to see what other ideas there are.

[lonesoldier0408]

Anyway to run a shorter cable to the block, then a separate cable from the block to bus bar/battery.? Prevent fatigue from vibration and cable weight.


Still surrounded by anchors.

[Ostinato]

The 0000 is run run back to the house bank and isolated from the engine but the terminal suggestion is a good one and refines how I might do this. Thanks.

[HappyMdRSailor]

Looks like 5 separate wires are not enough to support it... Add a few more...

I kid... Maybe find yourself a small block of phenolic or other hi temp insulating material and use it as a support block? Something like 1" wide with a small "channel" cut in it that fits the width of the terminal and wedged in there???

Just throwing things against the wall looking to see what sticks...

[unclemack]

If the 0000 lug were at the bottom of the post rather than the top maybe it would have less leverage to vibrate/bend/fatigue the post bracket.

Perhaps a simple cable tie to a strong point would move the vibration away from the post?
Keep a couple of spare rectifiers on board too?

That post bracket is certainly flimsy and oddly shaped - dissipation of heat is the only reason that springs to mind for such a design.


I'd be interested to learn Balmar's reasoning

[twinboat]

Agree with a solid mounted, insulated battery stud, nearby on the engine. Run a short 4/0 cable to it, then all of the grounds from there.

4/0, that's a big alternator ground. Are the using 4/0 on the positive side ?

If I recall, I used 2 gauge on my 150 amp alternator.

[rwidman]

Originally Posted by Ostinato

....... I have thought of adding a short length of lighter wire between the 0000 and the stud ...........

A lighter gauge cable will reduce the current carrying capacity of the entire circuit. Don't do that if you need the capacity you currently have.

Are you using marine grade wire? Many fine strands? The stiffer the wire, the more vibration is passed on to the terminal.

[MCOS]

It appears from the photo that the rectifier frame is in contact with the alternator husing. If this is the case you can use any of the mounting bolts as terminals and continue to use the rectifier without the terminal.

[deblen]

http://www.sunforceproducts.com/Supp...ctionTable.pdf

[dmalcol1]

0000 wire is good to carry at least 300 amp at 30 degrees Celsius you could go with a smaller #2, 85 degrees Celsius rated wire as long as engine room stays at or below 30 degrees Celsius. If engine room temperature is greater then derate factor must be applied to wire current carrying capacity.

[Rockyscience]

Hi, I think this will solve your vibe problems.
4 AWG Welding Cable Class M UL/CSA | WireAndCableToGo.com

[donradcliffe]

The stud is breaking, not the wire, because it was never designed to hold that much vibrating weight. Use a smaller wire. If your balmar is externally regulated with battery voltage sensing, you don't need to worry about voltage drop.

[tim m]

you need to get a handful of wire ties and install strain relief to take the vibration from your heavy cables and tie them off so the vibration is absorbed away from the B - tang on your six series alternator.

no silly guys for me just good business!

[Ostinato]

These are some really good thoughts. The positive is 0000 also. This wire size was selected because there is 25 foot (+/-) run to the battery bank and I didn't want to loose more 3%. I'll check to see if the rectifier is in contact with the alternator housing and report back If so, as suggested, I may able to rig an alternate stud or connect elsewhere. The exploded view for the regulated is not clear on this. Thanks.

[LaT]

I think MCOS advice is good.
Otherwise a flat short cable with very fine strands to a terminal separate from the motor will fix it.