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Increasing voltage from Alternator

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I might mess around with this sometime this week.

+.6 v would do me good

The second link is for float voltage, no need for it, but hooking it up to a switch wouldn't be bad. for a shtf moment while driving.

http://www.smartgaug...uk/alt_mod.html

http://www.smartgaug.../alt_float.html

alternator_02.gif

6G-ALT_wiring_GRY.gif

:morepower1:

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How to increase the charge voltage of your alternator on the cheap.

If your alternator charges at, say, 13.8 volts you may want to increase this in order to get a much higher charge current into your batteries.

The two obvious solutions are to change the alternator to a later model that already charges at a higher voltage, or to fit an external alternator controller.

This may not be necessary. Have a look at the diagram below. This shows the schematic of an internally regulated, N-Type, -VE ground alternator. This diagram covers probably in excess of 99% of alternators currently in use.

The diagram should be self explanatory but if not...

It consists of 3 stator windings. These produce the output current at AC. This is then rectified by the two diode trios connected to the B+ and B- terminals.

The third diode trio produces a DC output at the D+ terminal to operate the warning lamp and also to provide the power to the rotor.

The regulator (Reg) compares the voltage on the D+ terminal with an internal reference and then controls the output voltage (by regulating the current in the rotor which acts as an electromagnet) to maintain the output voltage the same as the internal reference voltage.

Now in many older alternators the reference was set so that the output voltage was held at 13.6 or 13.8 volts. As described elsewhere in this website this is too low.

One way to change this would be to open up the regulator and change the voltage reference or the voltage dividers. This, obviously, is not something most people can do. However there is a much simpler way.

Instead of adjusting the voltage reference inside the regulator, what would happen if we fooled the regulator into thinking the output of the alternator was at a lower voltage than it really is?

The regulator would adjust the alternator output voltage until the new voltage we fed into the regulator was correct. So if we somehow fool the regulator into thinking the alternator output voltage is 0.6 volts lower than it really is, then the regulator will adjust the output voltage to 0.6 volts higher than this. In the case of an alternator charging at 13.8 volts, this will increase the output voltage to 14.4 volts.

A diode drops a voltage of around 0.6 volts at low currents, increasing up to around 1.2 volts at high currents. So if we use a diode at low current, it will drop just about the right voltage.

If we use a diode at a higher current then the voltage drop will be higher and therefore the output voltage of the alternator will be increased by more.

By "low current, or "high current" we mean in relation to the rating of the diode. For instance a diode rated at 3 amps would drop around 0.6 volts at 0.25 amps, increasing to around 1.2 volts at 3 amps.

Now, where we are going to put this diode in the alternator, it will have to pass the full rotor field current. This will typically be upto about 4 amps or so in a moderately sized alternator. So it would seem that we need a diode that will only drop 0.6 volts when passing around 4 amps. This would imply a very large diode, maybe 20 to 30 amp rating or so.

However this is not the case. As the batteries approach the acceptance voltage the regulator will start to reduce the field current to prevent the output voltage rising too high. So when we actually need the 0.6 volt drop, it will not be passing this higher current.

A diode of around 10 amp rating turns out to be about right. This will give a new acceptance charge voltage of about 0.6 volts higher than previously.

This diagram shows the position of the new additional diode in relation to the rest of the alternator wiring.

Finding the actual electrical position is left an an excercise for the student!

It should not be at all difficiult to work out by reference to the 2 diagrams on this page.

The diode on the left is the diode that raises the charge voltage. The diode on the right is there for supression purposes. It should be the same type as the other one. Not all alternators require this diode, but there is no simple way to ascertain which do and which don't so fit it anyway.

Some experimentation may be required in order to get the correct sized diode for your particular alternator.

Some notes on this matter are in order......

The diode must be able to handle the full rotor field current and must be able to dissipate the heat that will be generated within it. This will usually mean a diode with a metal heatsink. This must obviously be electrically isolated.

Selecting different sized diodes can alter the output regulation of the alternator. A smaller diode will increase the charge voltage by more than a larger diode (due to the voltage drop varying with the diode current).

It may be found that the output voltage of the alternator falls as the charge current decreases during the acceptance cycle. This cannot be helped but it can in actual fact be an advantage. Once this stage is reached the batteries are quite well charged anyway (particularly at the new higher charge voltage) and the reducing charge voltage can help reduce water loss in the batteries. Almost a gentle float reduction in charge voltage.

Some of you may want to play with different diode ratings to get different effects.

Also consider "Schottky diodes". These have a voltage drop approximately half of normal diodes and therefore the increase in charge voltage will be roughly half as much.

Many modern chargers are charging wet cell batteries at much higher voltages than previously. 14.8 to 15 volts is becoming common. This increases the charge rate and performs a mild equalisation charge. It is not recommended that such a charge voltage be used from an alternator as the alternator does not have the ability to drop to a lower float charge the same way that a dedicated charger does. However see here to add a float voltage to enable these much higher charge voltages to be utilised safely.

One last point. If you break the circuit where the new diode is fitted this will stop all charging from the alternator. Some people have actually put a switch in here to enable a much higher than normal charge voltage to be used (by putting 2 diodes in), the owner then switches the alternator off when the batteries are considered charged. Obviously if this is forgotten, the batteries may protest somewhat. Note that switching the alternator off using this method is perfectly safe and is in no way related to disconnecting the alternator output which can destroy it.

Some people may want to take this modifcation a stage further by adding a form of float voltage. If the added diodes(s) are shorted out with a manual switch, this will force the alternator back to it's original charge voltage. So the batteries could be fully charged at the higher voltage, then the alternator switched back to it's original charge voltage to reduce excess gassing of the batteries. If this switch is replaced by a relay, this relay can be controlled by the SmartGauge high voltage alarm to automatically switch down to a lower float voltage once a certain higher charge voltage is reached. This actually comes very close to how a full 3 stage external controller works. And if you already have (or are fitting) a SmartGauge then this modification is almost free! Full details are contained here.

Happy exploring.

WARNING.... Under no circumstances must this modification be done in an attempt to overcome the voltage drop introduced by split charge diodes. The voltage drop through split charge diodes varies too much as a function of the current through them. If you attempt to use this modification to compensate for this voltage drop you will either A) Achieve nothing or B) Severely overcharge your batteries or C) Achieve next to nothing followed by overcharging your batteries! It will not work.

SmartGauge Electronics accepts no liability whatsoever for any undesired consequences of carrying out this modification. If this modification is carried out, the liability lies entirely with whoever made the modification or made the decision to carry out the modification. It is the responsibility of the person carrying out the modifications to ensure the suitability of such modifications to the installation.

We wrote this page as a benefit to you. We make no profit out of it whatsoever. Please do not ask us questions about it. We will not enter into any correspondence regarding this modification. Any emails regarding this modification or asking for further details will be ignored. Sorry.

Edited by djjdnap

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Let us know how this works out for you.

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Well went to radio shack today

got 4 rectifier diodes 50v 6A, for like 2.49$

Soldered some wire to the tips, heatshrink and electrical taped them up.

cut the wire, put the diode in between and presto change-o

well it was at 14.7, rev it a bit and highest it went was 15v. 15.2v.

although after reading some more the voltage drop of a diode is .7, but we'll see.

Edited by djjdnap

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So the missing link audio is nothing but the same as described above and thy charge $100+ for them..

I think i need to start making my own and selling them.

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My alt only "gives" me 13.6 - 13.8, I'd love to reach 14.4 v.

The max I can see is 14.13 v on the morning when it's not too hot outside. But it doesn't stay at this level for long. After some kilometers, it goes lower, until it reches 13.6 - 13.8 v, no matter if my sound system plays at full tilt or is off !!!

I'm afraid to buy an MLA or something like that for my Toyota (with a Diesel engine).

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I recently had to take my mechman alt off because of a bracket issue. Lucky for me I kept my OE alt in case anything would happen. Some things I can throw out here is that before alts are put in I charge batteries, then with O scope at the battery I set the pot on mechman harness cold start 15.1v then after car warms up it will sit at 14.8 to 14.6v.

There would be irregular voltage drops from there to 13.8 and then bounce right back up. With the OE alt in it cold starts at 14.4 car warms up and sits at 14.1v I don't know my car but I think that the computer is what adjusts the voltage and with the mechman pot there seems to be a bumping of heads. So to add to this thread your idea might be right but the computer might be regulating the voltage still.

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Crunkjuice1.

I kinda get what your saying, but I can't explain what I want to ask you about it.

Basically your saying, the extra voltage didn't do you any good because under a load your voltage would go back to the original set point? Is that it?

I've always wondered about people claiming to have voltage at 13.8, and have a .7 drop to 13.1 under a load. Then set their voltage to 14.5, and saying now after under a load they are at the same voltage they had before not under a load.

Which made no sense to me, and didn't think it worked that way.

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Crunkjuice1.

I kinda get what your saying, but I can't explain what I want to ask you about it.

Basically your saying, the extra voltage didn't do you any good because under a load your voltage would go back to the original set point? Is that it?

I've always wondered about people claiming to have voltage at 13.8, and have a .7 drop to 13.1 under a load. Then set their voltage to 14.5, and saying now after under a load they are at the same voltage they had before not under a load.

Which made no sense to me, and didn't think it worked that way.

With HO alt the good thing is that with a load it wouldn't drop below 14v for longer than a second But just normal driving with no radio on or even slight volume I would see my voltage meter have those sporadic drops in voltage and car kind of shuddering for a second. BUT with regular OE alt there is no pot to make adjustments but car doesn't ever idle rough at all. I have just received a new amp and sub that I will not run off stock alt but its just weird to me how the voltage is regulated. I guess I need to learn more about it. As far as what I "see" is something in my car either bumps heads with pot in harness or belt slips ever so slightly here and there.

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Yeah, I'd like learn more about alternators myself.

Sometimes it hard for me to just read info and understanding what it means without asking question. I usually like to break it down in what I got out of the info, then somebody correct me.

But maybe somebody will come in here and give some details.

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So the missing link audio is nothing but the same as described above and thy charge $100+ for them..

I think i need to start making my own and selling them.

waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay different.

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^^^ maybe a *bit different because it serves the same purpose correct?

the difference is what? they build it in to a wiring harness for you to fit to ur alt so u dont have to splice any wires.....

I mean if ur just tricking ur alt to bump up the voltage seems like the same thing to me..

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crunkjuice.

yea some cars are pcm controlled, meaning the cars computer controls the voltage, usualy newer cars.

my girls grand prix has pcm controlled alt and the voltage is all over the place, sometimes 13v sometimes 15v... she doesnt have any amps or anything

the only thing that pulls the most amps i can see is the traction control, slam on the gas and it cuts on and voltage drops to 12v easily.

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^^^ maybe a *bit different because it serves the same purpose correct?

the difference is what? they build it in to a wiring harness for you to fit to ur alt so u dont have to splice any wires.....

I mean if ur just tricking ur alt to bump up the voltage seems like the same thing to me..

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crunkjuice.

yea some cars are pcm controlled, meaning the cars computer controls the voltage, usualy newer cars.

my girls grand prix has pcm controlled alt and the voltage is all over the place, sometimes 13v sometimes 15v... she doesnt have any amps or anything

the only thing that pulls the most amps i can see is the traction control, slam on the gas and it cuts on and voltage drops to 12v easily.

Just because it could serve the same purpose doesn't meant its the same. And I'm surprised anybody would think that.

Take cheap Pyle sub, and a Fi BTL, sure they serve the same purpose, but does that mean they are the same?

Sure, the Pyle is $450 dollars cheaper, so why in the world would anybody buy a BTL if they do the exact same thing...(Reproduce bass).

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well id like to see the insides of the mla.....

and thats a good analogy...but i feel like thats comparing apples to oranges.

like saying i could buy a corolla or a f150

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I've seen inside pictures of the MLA when they first came out. I'm sure if you searched you could find some.

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you have to compare 2 products that produce the SAME results...

If a Pyle and BTL were purchased for an SPL goal and they both burped the same score, why pay more for the BTL?

That is the proper anology.

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My anology wasn't perfect but it got the point across.

Who said it has the same results? Just because voltage change doesn't mean its the same.

This way is causing the Alt to actually produce current without needing it.

I'm not sure exactly how the MLA works, but nobody can say its the same without really knowing.

But I could see a problem with batteries becoming over charged with this way.

I'm not downing this way, or praising MLA. Just saying.

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well decided im going to put a switch on it like the link suggest to get my amp to act right.

"doesnt like 15v"

i had the diode in for bought a month havent had any batt problems, wt these hotter temps it shouldnt charge that high anyway.

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I can't figure out where to put the diode..

I've read the post 10 times, still I don't get in dummy terms where to put it. Lol.

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lol well the 2cd pic is of my actual alt wiring.

as u can see the yellow wire is the sensing/checking wire because it connects to the batt wire.

it basically reads the voltage and the alternator reads it to make sure its where its supposed to be.

Now you cut that wire and put a diode in between giving a voltage drop so when the alt reads it its lower at the alt but still 14+ on the output.

so you might have to find a wiring diagram of ur alt to see which one is the sensing wire or do some hands on work and find which one is going to the battery.

If its pcm controlled idk how it would work.(usually new cars)

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Mines a 6g, and that's what you got pictured. So I guess we do have the same style alternator.

I will be trying this over the weekend.

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u ever get it hooked up?

put mines back in its the small orange wire on mines.

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So yall are doing this on the ford 6g alts?

Wouldn't this shorten the life of the alt, by causing the alt to work harder to produce the higher voltage?

And if yall are using the ford 6g alts, then what color is the wire that "senses" the batt voltage?

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