Alternator booster diode

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Kind of clever and looks like it would work with any alt that uses a remote sense wire, eg a thin +12V wire that goes back to the voltage regulator to account for the loss on the fat wire.

This would be good if you ran a GM type sealed maintenance free battery that takes a few tenths of a volt more to charge due to its (sodium?) chemistry.
 
Good way to kill batteries and light bulbs. And what possible good could it do? If you're having issues with lights getting dim at idle, that's due to exceeding the CURRENT capacity of the alternator at low RPM, not exceeding its voltage capacity.
 
Originally Posted By: 440Magnum
Good way to kill batteries and light bulbs. And what possible good could it do? If you're having issues with lights getting dim at idle, that's due to exceeding the CURRENT capacity of the alternator at low RPM, not exceeding its voltage capacity.

I couldn't have said it better myself
 
funny,
do you know how it works?

it's a diode, and with any diode when current goes through it there is a voltage drop. Typical silicon diodes have a 0.7 volt drop all the time. Germanium diodes have a 0.3 volt drop, and there's probably a handful of other materials that have various voltage drops. The purpose of a diode usually is to prevent the backflow of electrical current, the voltage drop is a negative side effect usually. in this case they are using that voltage drop, along the voltage sensing circuit i'm guessing (they say install on ALT fuse in fuse box). So because of the voltage drop of the diode the voltage regulator sees less system voltage and increases output to maintain what it wants system voltage to be.

the only upside i can see is if you had some off-road lights and you wanted them as bright as possible.
the cons on the other hand, you're burning more fuel having the alternator output at a higher voltage. Many late model cars have implemented variable charging where the engine computer commands the alternator output to be lower which takes less effort to spin the alternator and save fuel.
And a fully charged lead-acid battery is 12.65 volts +/- a little depending on temperature. So anything above 13.0 volts will charge and maintain the battery. In hot weather having system voltage over 13.8 volts will gas the battery and kill it!
And in making the alternator output higher voltage like this, you're making the alternator work harder all the time which creates more heat in the alternator and will cause the rectifier (also diodes) within the alternator to burn out.

it is the AGM type batteries that can use a 0.1 - 0.3 volts higher charge voltage, not necessarily "GM type sealed maintenance free battery". If that type of GM battery is AGM then ok, but I wouldn't go buy a $35 diode to increase system voltage for an AGM battery. An AGM is more tolerant to higher voltages, and does not gas like a wet cell battery, but will charge and be fine on normal voltages.

the sad thing is the diode that is being used in this alternator booster, is like 50 cents. I guess packaging it into a mini blade fuse up's the cost.
 
Last edited:
It probably isn't going to cause a problem in cold weather, but is not a good idea in the summer... Since it's now winter in OZ, you'll be fine...

BTW 1 FMF is correct, silicon rectifiers are cheap, I'd think $35 was a major raping...
 
Alternators put out less in hot weather.
This works out perfectly.
Some are by design, and some by luck - the nature of resistance going up in materials when hot.
 
What is the reason a car need this to begin with? Did the original alternator or charging circuit have problem keeping up with the load? or did it have problem with components wearing out and drop the voltage?

I'd imagine a bigger alternator (more current, not higher voltage) would be the better solution to this problem.
 
The problem i have seen with similar "fixes" (there is one for for a few makes) is light bulbs seem to be very short lived. The ignition modules also get hot and burn out in some cases.

As someone pointed out this may have some bad effects on the battery also.
IMO get rid of that thing. If you were being left stranded with a flat battery find the real cause, if not your fine.
The electrical system will thank you.
 
I dont get the "alternator will cause more fuel burn" bit. Higher voltage means lower current for a given load, which means less load overall. Smart alternators drop load generation rate to reduce load on the engine overall. Current and torque should have a direct relationship - Ive heard linear, Ive heard quadratic. I dont know specifically for a car alternator, and since it is like a motor running in reverse, it makes it more complex.

There are tricks to using a diode to extend the ground voltage so that the alternator works slightly higher voltage. If we are talking 13.9 vs 14.2V, I doubt it will be a big lifetime issue on anything.

If the voltage regulator temperature correlation lets the voltage go too high, then it WILL be an issue.

If the alternator has connectivity impedance issues so it is lower than spec voltage, this may be a good option.
 
There is nothing wrong with 14.3-14.9 [warm/cold].
Over 15 and I would start being concerned. Esp when hot.

For most of us, clean all the cable ends and where they seat shiny clean, and call it a day.
 
Originally Posted By: JHZR2
I dont get the "alternator will cause more fuel burn" bit. Higher voltage means lower current for a given load, which means less load overall.


Not so for resistive loads... If you don't believe it, measure the current of a automotive lamp(bulb)at 12v and then at 15v, voltage and current will both be higher...
 
Originally Posted By: TFB1
Originally Posted By: JHZR2
I dont get the "alternator will cause more fuel burn" bit. Higher voltage means lower current for a given load, which means less load overall.


Not so for resistive loads... If you don't believe it, measure the current of a automotive lamp(bulb)at 12v and then at 15v, voltage and current will both be higher...


Yup, for the same fixed load, a higher voltage means more current draw. So If the alternator and battery runs at a higher voltage, then the light, the starter motor, the ignition etc will all directly or indirectly (via coil / transformer) runs at a higher voltage and draw more current.

The point is, you cannot just change the load of all the components in the car at run time. It is set at design and manufacturer time unless you swap the components out.
 
Play around on http://jgdarden.com/batteryfaq/carfaq9.htm and the voltages needed vary a few 1/10s of a volt depending on chemistry. If you wind up with the "wrong" battery in your car this could be a hack to set you right.

I bet a particular part number tail light bulb doesn't know if it's in a GM getting high 14s or a euro car getting high 13s for voltage. For all we know GM puts skinny wires in to cause a drop so it all works out.

32.gif
My volvo charges around 13.8 year round and the owners manual says to throw a battery charger on it once in a while as regular maintenance.
 
Quote:
14.3-14.9

14.3 is no problem but 14.9 is a bit much for me.
A W body i worked on had something similar installed at one time and couldn't keep light bulbs in it.
Quote:
For most of us, clean all the cable ends and where they seat shiny clean, and call it a day.

+1
 
Originally Posted By: PandaBear
Originally Posted By: TFB1
Originally Posted By: JHZR2
I dont get the "alternator will cause more fuel burn" bit. Higher voltage means lower current for a given load, which means less load overall.


Not so for resistive loads... If you don't believe it, measure the current of a automotive lamp(bulb)at 12v and then at 15v, voltage and current will both be higher...


Yup, for the same fixed load, a higher voltage means more current draw. So If the alternator and battery runs at a higher voltage, then the light, the starter motor, the ignition etc will all directly or indirectly (via coil / transformer) runs at a higher voltage and draw more current.

The point is, you cannot just change the load of all the components in the car at run time. It is set at design and manufacturer time unless you swap the components out.


Great, thanks for the clarification!
 
Originally Posted By: 1 FMF
funny,
do you know how it works?

it's a diode, and with any diode when current goes through it there is a voltage drop. Typical silicon diodes have a 0.7 volt drop all the time. Germanium diodes have a 0.3 volt drop, and there's probably a handful of other materials that have various voltage drops. The purpose of a diode usually is to prevent the backflow of electrical current, the voltage drop is a negative side effect usually. in this case they are using that voltage drop, along the voltage sensing circuit i'm guessing (they say install on ALT fuse in fuse box). So because of the voltage drop of the diode the voltage regulator sees less system voltage and increases output to maintain what it wants system voltage to be.

the only upside i can see is if you had some off-road lights and you wanted them as bright as possible.
the cons on the other hand, you're burning more fuel having the alternator output at a higher voltage. Many late model cars have implemented variable charging where the engine computer commands the alternator output to be lower which takes less effort to spin the alternator and save fuel.
And a fully charged lead-acid battery is 12.65 volts +/- a little depending on temperature. So anything above 13.0 volts will charge and maintain the battery. In hot weather having system voltage over 13.8 volts will gas the battery and kill it!
And in making the alternator output higher voltage like this, you're making the alternator work harder all the time which creates more heat in the alternator and will cause the rectifier (also diodes) within the alternator to burn out.

it is the AGM type batteries that can use a 0.1 - 0.3 volts higher charge voltage, not necessarily "GM type sealed maintenance free battery". If that type of GM battery is AGM then ok, but I wouldn't go buy a $35 diode to increase system voltage for an AGM battery. An AGM is more tolerant to higher voltages, and does not gas like a wet cell battery, but will charge and be fine on normal voltages.

the sad thing is the diode that is being used in this alternator booster, is like 50 cents. I guess packaging it into a mini blade fuse up's the cost.

Good markup for a 1n4001, eh?
 
Originally Posted By: JHZR2
Originally Posted By: PandaBear
Originally Posted By: TFB1
Originally Posted By: JHZR2
I dont get the "alternator will cause more fuel burn" bit. Higher voltage means lower current for a given load, which means less load overall.


Not so for resistive loads... If you don't believe it, measure the current of a automotive lamp(bulb)at 12v and then at 15v, voltage and current will both be higher...


Yup, for the same fixed load, a higher voltage means more current draw. So If the alternator and battery runs at a higher voltage, then the light, the starter motor, the ignition etc will all directly or indirectly (via coil / transformer) runs at a higher voltage and draw more current.

The point is, you cannot just change the load of all the components in the car at run time. It is set at design and manufacturer time unless you swap the components out.


Great, thanks for the clarification!


Yup, any time you raise system voltage, you raise system power consumption (for the same load resistance.)
 
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