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Old 10-12-2009, 08:32   #16

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Interesting point wrt windlass motors throwing back spikes. I've seen tech papers from LumiLed or CreeX (who make those expensive top quality LEDs used in the auto industry) stating that the intended use MUST include design for protection from 200V spikes in cars, 600V spikes in trucks, because that's how high the spikes will be from the normal starters on board. Surely a windlass motor fits somewhere into that range, so it would have the same problem.

Delco had gone to an automobile alternator design some years ago with internal avalanche devices to protect the alternators from spikes, and earned a reputation for a lemon after they found out the spike protectors failed way before the alternators normally would have, resulting in an alternator failure way too soon. Which is the mixed blessing that many designers and manufacturers have mentioned about spike protection: It needs to be kept external, outside of the devices, otherwise when it does fail it takes a whole "device" offline with it.

Since the average consumer doesn't know what a transient is and doesn't want to hear about more problems and costs....this one gets buried.

Last time I did a gut rewire on a boat, I added in an aluminum panel box in between "the instruments" and their master breaker. The box contains one crowbar fuse, one piezo alarm, and two different type of surge protectors (one zener and one zorb), set up so that any surge will either blow the fuse, set off the piezo, or get clamped before it can get out of the box.

But I don't think you could commercially market that kind of thing, who'd pay for it? "What, aren't my instruments and alternator GOOD ENOUGH?"

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Old 14-12-2009, 10:20   #17
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A capacitor reacts much faster than a battery. I would mount a 2-farad cap that has a despiking MR 2535 right to the anchor windlass motor power terminal.

I like the decade a series of electrolytic, and mica caps, using the 2-farad for an anchor windlass, 10K uf for each winch, and another 2-farad cap and MR 2535 next to the distibution panel. The final 2-farad unit with MR 2535 would be attached to the alternator terminals.

I wonder if most folks will have the same dramatic reduction in electronics problems that I have had when using this system? It's not just money and time lost in replacing blown electronics, it's where it happens and a fact that sometimes repairing and replacement is not an option.

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Old 14-12-2009, 16:55   #18

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A 2f cap without any inrush protection on it hasn't caused by any problems for you? Sometimes having a dead short (which is what the capacitor is seen as when it is first powered up) upsets things, too. That's one reason why caps are generally not used and real spike absorbers are.
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Old 28-12-2011, 13:49   #19
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Re: Answers

Originally Posted by Mexbungalows View Post
An external rectifier assembly is available and is good to 250 amps capacity. It's cost is somewhere around $400 which isn't bad considering its lifespan and how much money and trouble it will save.
You already have a rectifier bridge. Its just inside the alternator. Take it out, mount it on the bulkhead, make sure its well insulated and vibration free. In fact the heatsink that rectifier is mounted on is for dissipating heat inside the alternator casing. Once you put it outside, those diodes will be even cooler. You just have to make sure your DC + is well secured and insulated. In fact you could mount it closer to the battery bank to minimize DC cable voltage drop. And keep the 3 rectifier (AC) wires longer. AC loss is negligible.
I wonder if anyone has any results on this retrofit? I am considering doing this with one of my alternators.

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