Zap Stop - Fact or Fiction ?

[courageous cat]

Zener Diode as Voltage Regulator Tutorial
Here a good read on this subject

[cwyckham]

So I have an MC-614 which is sensing voltage directly off the batteries (and is connected directly to the house bank through a fuse). I was thinking that the balmar TSP I have installed would protect the diodes if I blew the fuse, but it sounds like it's not doing me any good at all as the external reg will keep driving the field higher and higher anyways and will burn through the zener diode.

Is this right? If I blow a fuse, do I fry my alternator? Not that I should be blowing the fuse too often.

The alternator that I have has an optional internal regulator (balmar 60 series), so maybe I'll throw the TSP in a drawer in case I ever need to bypass the external, but even then it sounds like it's pretty useless to me.

Do I have this right?

[Stu Jackson]

Sounds like you're confusing the regulator wiring with the alternator output.

[Dsanduril]

The MC-614 has a red power wire at position 2 and a red, fused battery sensing wire at position 9. Are you talking about blowing the fuse in the sense wire? The MC-614 will stop operating if the sense wire is disconnected (i.e. if the fuse blows). Are you worried that the regulator will see that as zero voltage and so drive the alternator to full output? The MC-614 is built to prevent that (in fact, sometimes won't run when connected to a severely discharged battery, as the voltage it senses is too low). That, at least, is how it is supposed to work according to Balmar.

The death of alternator diodes is when the alternator output gets disconnected from the battery while the alternator is putting out power. Imagine you have 50-100A coming out of the alternator, you open the battery switch, and all of a sudden that power has no place to go. It causes a voltage rise in the alternator, which kills the diodes. The TSP is intended to ground that voltage rise before the output diodes die.

You can shut off the field current (which is what the regulator controls) pretty much any time you want. Just turns off the alternator, no big deal. Without the field current the alternator just sits there and spins, and does nothing. Since the MC-614 is designed to kill the field current when it senses no voltage that should be what happens presuming it is all operating properly, and the TSP has nothing to do with it on the regulator side.

[senormechanico]

I disagree about a Zener diode being a one shot device in this scenario.
True the peak current could be significant, but it's of very short duration.
Most semiconductors have short term current ratings that are orders of magnitude greater than their continuous ratings.

A typical silicon diode rated at 2 amps or so has an instantaneous rating of 60 amps.

[cwyckham]

Originally Posted by Dsanduril

The MC-614 has a red power wire at position 2 and a red, fused battery sensing wire at position 9. Are you talking about blowing the fuse in the sense wire? The MC-614 will stop operating if the sense wire is disconnected (i.e. if the fuse blows). Are you worried that the regulator will see that as zero voltage and so drive the alternator to full output? The MC-614 is built to prevent that (in fact, sometimes won't run when connected to a severely discharged battery, as the voltage it senses is too low). That, at least, is how it is supposed to work according to Balmar.

The death of alternator diodes is when the alternator output gets disconnected from the battery while the alternator is putting out power. Imagine you have 50-100A coming out of the alternator, you open the battery switch, and all of a sudden that power has no place to go. It causes a voltage rise in the alternator, which kills the diodes. The TSP is intended to ground that voltage rise before the output diodes die.

You can shut off the field current (which is what the regulator controls) pretty much any time you want. Just turns off the alternator, no big deal. Without the field current the alternator just sits there and spins, and does nothing. Since the MC-614 is designed to kill the field current when it senses no voltage that should be what happens presuming it is all operating properly, and the TSP has nothing to do with it on the regulator side.

Sorry if I was unclear. I was thinking originally that the TSP would have some utility if the large fuse (150 A) on the alternator output to the battery blew. It sounds like a) it won't help and b) it's unlikely I'll blow that fuse anyways. If that fuse goes, then I can kiss my diodes goodbye, with or without a TSP, from what I'm reading.

[Stu Jackson]

Yes, that's right.

And your quoted post is true, too. How do I know? because each and every one of the factory crimps on my Balmar MC-612 failed at one time or another. The indication was that the tachometer stopped working.

The design i=of the external regulators is pretty much fail-safe.

It's only the interruption of the AO that'll give ya grief.

Good luck, got it now?

[cwyckham]

I've only had the alternator/regulator installed for a couple weeks, and I can tell you one wire that doesn't fail gracefully when it breaks!

After only about 15 hours of use, I came downstairs to find the battery voltage at 17, then the field started cycling up and down.

Tried to diagnose for a while, then just shut down the ignition. When we were at anchor and I could get into the engine compartment I found the regulator ground wire to be broken right at the crimp. My fault for installing with no strain relief. Not a graceful fail, but then, I don't know how they would design it to know it had no ground.

[hellosailor]

My understanding goes with mechanico and contrary to what stu says about this one. Yes, a continuous overload would blow up the diode, or any spike absorbing device. But we're looking to clamp transients that may be on the order of 1000V for a couple of microseconds, and a properly selected diode or other spike protection device should be able to take typically several hundred or thousand hits on that scale. They don't heat up and explode instantly, you need to keep the load on them way longer than one spike incident.

[Maine Sail]

Originally Posted by cwyckham

So I have an MC-614 which is sensing voltage directly off the batteries (and is connected directly to the house bank through a fuse). I was thinking that the balmar TSP I have installed would protect the diodes if I blew the fuse, but it sounds like it's not doing me any good at all as the external reg will keep driving the field higher and higher anyways and will burn through the zener diode.

Is this right? If I blow a fuse, do I fry my alternator? Not that I should be blowing the fuse too often.

The alternator that I have has an optional internal regulator (balmar 60 series), so maybe I'll throw the TSP in a drawer in case I ever need to bypass the external, but even then it sounds like it's pretty useless to me.

Do I have this right?

The TSP has a fuse where the Zap Stop did not. Problem is your system will continue to work even when you blow the TSP fuse. No one checks it before they hit the key... The next time you pass through off the diodes are no longer protected because the fuse has already done its job. I've had a few cases where boats were equipped with Zap Stop devices that stopped the "zap" once but failed to the second time.


Also if your alternator regulator is sensing the bank then you ideally need to route the alt to that same bank too. If the alt can be "switched" to direct flow elsewhere, like a second bank, the reg will not see a voltage rise on the bank being sensed and continue to pump the voltage and you can cook the battery. I see this scenario quite frequently. So, alt output and sensing need to go to ideally go to the same bank otherwise you can run a risk of cooking one bank....

As always if you wire the alt direct to the house bank it should have a fuse as close to the battery bank as possible. I also install an engine room "service" switch for the alt output so when working on the engine the bank can be isolated. This switch is in the engine bay or hidden elsewhere so "Uncle Bob" does not reach down and turn it....

[cwyckham]

Originally Posted by Maine Sail

The TSP has a fuse where the Zap Stop did not. Problem is your system will continue to work even when you blow the TSP fuse. No one checks it before they hit the key... The next time you pass through off the diodes are no longer protected because the fuse has already done its job. I've had a few cases where boats were equipped with Zap Stop devices that stopped the "zap" once but failed to the second time.


Also if your alternator regulator is sensing the bank then you ideally need to route the alt to that same bank too. If the alt can be "switched" to direct flow elsewhere, like a second bank, the reg will not see a voltage rise on the bank being sensed and continue to pump the voltage and you can cook the battery. I see this scenario quite frequently. So, alt output and sensing need to go to ideally go to the same bank otherwise you can run a risk of cooking one bank....

As always if you wire the alt direct to the house bank it should have a fuse as close to the battery bank as possible. I also install an engine room "service" switch for the alt output so when working on the engine the bank can be isolated. This switch is in the engine bay or hidden elsewhere so "Uncle Bob" does not reach down and turn it....

Yes, my regulator sense wire and my alternator output cable both go to the same (house) bank, the latter through a 150A fuse. I've also now moved my alternator ground wire to the batteries instead of the alternator to reduce vibrations and stresses. My starter battery is fed by the echo function of my Xantrex shore charger.

Service switch would be a great idea. Right now I have to pull the fuse.

[Maine Sail]

Originally Posted by cwyckham

Yes, my regulator sense wire and my alternator output cable both go to the same (house) bank, the latter through a 150A fuse. I've also now moved my alternator ground wire to the batteries instead of the alternator to reduce vibrations and stresses. My starter battery is fed by the echo function of my Xantrex shore charger.

Service switch would be a great idea. Right now I have to pull the fuse.

Cool, just wanted to make sure you would be a battery cooker.... I see it more than I should so I try to mention it when I suspect there could be a possibility..

[cwyckham]

Originally Posted by Maine Sail

Cool, just wanted to make sure you would be a battery cooker.... I see it more than I should so I try to mention it when I suspect there could be a possibility..

I appreciate it. I installed it myself, so anything is possible! I still need to figure you a way to improve the physical install a bit (not enough swing to tighten belt)