Dual vs triple bridge alternator remote rectifiers

[Ostinato]

I am considering installing a remote rectifiers for my Balmar series 6 150 amp alternators. Quickitifier comes in versions - one is a dual bridge and is rated for 210 amps; the other is a triple bridge and is rated for 420 amps. https://alternatorparts.com/quicktif...rectifier.html



Aside from the rated amperage differences are there any other advantages to the triple bridge rectifier? For instance, will they run cooler or last longer? Thanks.

[tanglewood]

Originally Posted by Ostinato

I am considering installing a remote rectifiers for my Balmar series 6 150 amp alternators. Quickitifier comes in versions - one is a dual bridge and is rated for 210 amps; the other is a triple bridge and is rated for 420 amps. https://alternatorparts.com/quicktif...rectifier.html



Aside from the rated amperage differences are there any other advantages to the triple bridge rectifier? For instance, will they run cooler or last longer? Thanks.

No clue what they mean by that, and the web site is pretty incoherent.

[hellosailor]

It sounds like their "double" kit is actually just one external bridge rectifier, which is installed in parallel with your existing internal diodes (diode frame, array, rectifier, call it what you will) and expected to politely share the load with them, or to take the load off them by working more efficiently.

And their "triple" system is nothing more than two of those, two external rectifiers still installed in parallel, so they can carry more current and spread out the heat load.

I have to suspect that whether multiple rectifiers (diodes) are going to share loads and play together nicely is going to depend on technical specs, the length of the wiring runs, and a couple of other un-obvious things. So my reservation about this is that, compared to a simple external rectifier, how well is this one going to play with the existing internal one?

Wouldn't it be more effective to just use an external rectifier (diode array) and regulator, and just get that entire load out of the alternator, but leave the option to switch back to the internals as a hot spare?

[Ostinato]

Originally Posted by hellosailor

…..but leave the option to switch back to the internals as a hot spare?

How would you do that - by reconnecting the internal rectifier? But you said "hot" so that must not be right.

Actually I never envisioned the device as being much more than an external rectifier which is actually what they call themselves some place on their home page.

I am sure you are right about the extra rectifier/diodes in the 420 operating in parallel. From the website the "420" has 12 transistors while "210" has 6. Not about load sharing though.

[EngNate]

IMO this is mostly "fluff", and spending your money on other things will lead to a greater return in terms of enjoying your boat. Not that what they're saying isn't (mostly) true, or what they're selling doesn't work, but that the rectifiers built into a quality alternator are just not that problematic. They do fail on occasion, but not more frequently than brushes wear out. I'd say that any claim of a performance improvement is doubtful.

[Q Xopa]

Originally Posted by EngNate

IMO this is mostly "fluff", and spending your money on other things will lead to a greater return in terms of enjoying your boat. Not that what they're saying isn't (mostly) true, or what they're selling doesn't work, but that the rectifiers built into a quality alternator are just not that problematic. They do fail on occasion, but not more frequently than brushes wear out. I'd say that any claim of a performance improvement is doubtful.

External Recitfiers arent really a reliability thing.
Its more a case of getting some of the heat generated by rectifying out of the Alternator so we can get more current output before they heat limit regulate or melt.

[rgleason]

Maine Sail's MarineHowTo website has an excellent article about Alternators. External Rectifiers are necessary to enable small case alternators to run continuously at higher amps due to the heat that has been removed from the alternator by moving the rectifiers to an external location. Otherwise the small case alternators generally will be restricted to lower continuous output ratings due to high temperatures.

[johnjuliano]

Originally Posted by rgleason

Maine Sail's MarineHowTo website has an excellent article about Alternators.

Could you post a link?

[rbk]

https://marinehowto.com/category/electrical/

Two things if you're considering an external regulator.
1) is it programmable? 2)Can it compensate for voltage drop and temp?

You've taken the time to install a nice alternator, why not pair it with what it was designed for and get the most power and life out of your investment?

[hellosailor]

ostinato-
It might or might not be feasible, you'd need a way (switch or plug) to go from the internals to the externals and revert back again. Either by running extra wires, or if there was external access to the diode connection points.

johnj, rbk-
Not to be confused with regulators, the question here is external rectifier diodes. Both will suffer when a less expensive automotive design is used, as opposed to a large-frame alternator or one with external regulator. But these days, car alternators of 150-200A capacity are common. Not rated at that for continuous duty, but still twice what the "old" high power alternators used to be.

With electronics, you derate the life expectancy of the parts by 1/2 for every 10 degree temperature rise, typically with 68F/20C as the nominal operating point. So as you go from 68F to the ~180F of an engine block that the alternator is attached to, 70-80-90-100-110-120-130-140-150-160-170-180 degrees, you've already cut the life expectancy of the diodes and everything else in half--eleven times. So "normal" has cut the life 1/2;1/4;1/8;1/16;1/32;1/64;1/128;1/256;1/512;1/1024....Down to about one thousandth of what the life of those components could be?

Even with fans and getting off the engine block...put an IR thermometer on the alternator case and check out the temp it is operating at.

So using heavier components, big heat sinks, separate fans, all can and does make a real difference *if* there's a heavier than intended load on the original system, which after all was built to sell for a price, not necessarily for performance.

[EngNate]

Silicon Diodes (rectifiers) have a characteristic voltage drop (a loss in the alternator system), and a negative temperature coefficient - the voltage drop goes down as temp goes up. Losses in the rectifiers are lower when hot.

Rectifiers can be connected in parallel, and if taken from the same manufacture lot they will share current, more or less. When units with different voltage drops are paralleled the load will be carried predominantly through the lower drop diode.

The external rectifier add-on will only by small coincidence even closely match. Optimally, the diodes used will be chosen so that they will take over from the internals. A small improvement in performance - a few more amps available at x rpm, could be realized. Schottky rectifiers are a type with lower voltage drop than standard diodes, but are significantly more expensive. I read the product info the other day, and don't think I saw any of this although a lot of electrical terminology was thrown around.

The rectifiers are the first in line in the cooling air flow in the alternator. Most of the heat is produced in the stator, and its frame is the outside of the housing, that does get hot but the back end is much cooler.

Check out the fan on your high power or non-stock alternator. Does it have straight or angled blades? If angled they must turn in the specified direction - forming arrows in the direction of rotation. Angled blade fans move more air than straight ones which can turn either direction. Often upgrade alternators are supplied with these.

[Ostinato]

Engnate: What if the internal rectifier is by passed or removed then the parallel issue is eliminated - correct?

My purpose in doing will be to extend the life of the rectifier and to maximize amperage output. Do you think there is a better way?

[EngNate]

If there's to be a performance advantage the externals must have a lower voltage drop than the original ones and if so it won't matter if they are disconnected or not, as long as they aren't faulty/shorted. It may or may not be practical physically depending on the alternator construction.


Many multimeters have a diode test function, which measures the voltage drop, and both the alternator and external rectifier can be checked if you have it in hand. Possibly the sellers of the product will provide it, they or the actual makers surely know, the typical value is always in the part datasheet. If it isn't lower than the more or less standard .65V there won't be any performance to be gained, only the likelihood or possibility of lower failure rate due to heat. There is yet another consideration to that still. The product uses a computer fan - the whole thing is conveniently made in a PC power supply enclosure. The fan can fail unseen and its not a favorable environment for it.

[RaymondR]

Originally Posted by rgleason

Maine Sail's MarineHowTo website has an excellent article about Alternators. External Rectifiers are necessary to enable small case alternators to run continuously at higher amps due to the heat that has been removed from the alternator by moving the rectifiers to an external location. Otherwise the small case alternators generally will be restricted to lower continuous output ratings due to high temperatures.

Sounds like a good capability to have when so many of us use the engine alternator, which is designed to bring the voltage of a cranking battery of limited amp hours back up fairly quickly, to charge high amp hours house batteries where the output amps are high a much longer period before the voltage increases.

[Ostinato]

Engnate - You’re right the fan could fail and needs to be checked for type bearing it uses and rated hours but at this point I am not sure based on my experience that it’ll be more frequent than I have been experiencing rectifier failure. I plan on adding a heat sink as well.

Question: When two rectifiers are rigged in parralell and a diode in one fails such as in the model 420 will the other one in theory pickup the load?