[VT-VX] How To Increase Alternator Output Voltage

[Immortality]

@immortality my apologies for dragging this off topic. I like the concept but still don't understand the why or where the benefit is. So as not to detract from the how to I will leave it as it stands and people can draw their own conclusions.

No problem. Intelligent debate is always welcome and helps everybody expand their knowledge.

 

[Pollushon]

As long as the alternator is not at its maximum capability. You only have a certain number of windings cutting through a certain field strength. The alternator can only generate X amount of power.

When you are at that limit you are at that limit.

If it is cabale of producing 100A at 14V (1.4kW) it will only be able to produce 93A at 15V. That is one of the fundamental laws of electricity.

in your lithium example you are increasing the available power to enable it.

You're not factoring resistance in the equation. Straight up ohms law says you're correct but once the diode is added the circuit resistance is changed

 

[Immortality]

As for the reason, this is one example of increased system voltage. Fuel pump output (in PSI) Vs system voltage.

 

[Jolls]

You're not factoring resistance in the equation. Straight up ohms law says you're correct but once the diode is added the circuit resistance is changed

It was in the OP. The resistance causes the VD because it consumes power (current side) so the regulatior increases the field current, which consumes more power (current) and the overall output (voltage side) increases by the amount of the voltage drop. The power consumed by the component theoretically remains the same (higher voltage/less current).

So you are consuming power in a couple of places to increase the voltage. It is a zero sum game as the restances and current consumed - along with the increase in voltage means there is less current available to servide the system. So in summary every resistance you add consumes power and increases the power demand. The more you add the less power is available for use; once it reaches capacity of the alternator you can't make more.

Everyone should be under no misconseption. You can increase the voltages/currentd only if the demand on the system is less that the maximum capacity of the alternator. In essence there is an amount of power availble to shift around - increasing current to overcome additional resistances increasing voltage to do whatever. It is when you are at the limits of the alternator that it matters - the laws of physics means any increase in voltage at this point means performance will be compromised.

Fuel pump output (in PSI) Vs system voltage.

Now that makes some sense - provided the flow rate/pressure is at capacity and is affecting performance. So the real benefit is increased performance from some motors - providing adequate power is available in the system.

The downside is increased heat and potentially shortened component life. A worthwhile tradeoff?

I tend to be a little more pragmatic - a higher output pump that is fit for purpose at the nominal voltage perhaps.

I get the intent now; and undestand why some may consider this a worthwhile mod. Thanks.

 

[shane_3800]

It was in the OP. The resistance causes the VD because it consumes power (current side) so the regulatior increases the field current, which consumes more power (current) and the overall output (voltage side) increases by the amount of the voltage drop. The power consumed by the component theoretically remains the same (higher voltage/less current).

So you are consuming power in a couple of places to increase the voltage. It is a zero sum game as the restances and current consumed - along with the increase in voltage means there is less current available to servide the system. So in summary every resistance you add consumes power and increases the power demand. The more you add the less power is available for use; once it reaches capacity of the alternator you can't make more.

Everyone should be under no misconseption. You can increase the voltages/currentd only if the demand on the system is less that the maximum capacity of the alternator. In essence there is an amount of power availble to shift around - increasing current to overcome additional resistances increasing voltage to do whatever. It is when you are at the limits of the alternator that it matters - the laws of physics means any increase in voltage at this point means performance will be compromised.



Now that makes some sense - provided the flow rate/pressure is at capacity and is affecting performance. So the real benefit is increased performance from some motors - providing adequate power is available in the system.

The downside is increased heat and potentially shortened component life. A worthwhile tradeoff?

I tend to be a little more pragmatic - a higher output pump that is fit for purpose at the nominal voltage perhaps.

I get the intent now; and undestand why some may consider this a worthwhile mod. Thanks.

You are talking in current again. You have to look at it in watts.

 

[Skylarking]

As is, nominally, the alternator provides power to the cars systems and also recharges the battery. If the battery voltage is high, the alternator will pump less power into the battery (as it sees a lower load). If the battery voltage is lower, the alternator will pump more power into the battery (as it sees a high load) That’s because as power is pulled from the battery, the battery voltage will drop (as everyone who has checked voltage at crank can attest to). Also, as power is pumped into the battery by the alternator, engine load is increased (cause power ain’t free which is why smart EFI systems increase idle speed when there is engine load).

So, if you trick the alternator into thinking the battery voltage is lower than what it is, by adding a diode in series with the sence wire giving a 0.6v drop, then the alternator will increase voltage output and current to pump more power into the battery (thinking its more flat or has a higher load than it actually has). If the battery is already fully charged, the consequence of doing this is that the battery may be overcharge and thus start to boil on a long drive.

Talk of increasing voltage in isolation to battery charge and load issues, to allow a fuel pump to push higher pressures may be a bit misguided without doing a lot more tests at various engine rpm and various electrical loads to ensure you won’t kill your battery on long drives. As for the alternator, I’m sure it’s designed with some headroom so should be able to cope with a bit of extra load associated with such mods. The question is will the batter cope on a 4 hour drive across state...

If one has a dual battery setup, using diodes to isolate the start battery from a fridge (or accessories) battery, then these diodes create a 0.6v drop so adding a diode to the alternator sense wire can compensate for the battery isolator voltage drop. The rest of the cars systems will see much the same as it did before the battery isolator was added (and the isolator will dissipate quite some heat if you’ve seen the heat sinks the isolators diodes are bolted to). In these cases, usually 4x4’s, their standard alternators don’t seem to have any issue keeping two big car batteries charged.

 

[Immortality]

This mod is certainly not new and I'm not claiming credit for it. I've simply adapted it to my car.

The Commodore alternator is nominally rated at 14.4 volts and I'm now seeing about 14.8 volts at the alternator or about 14.7 volts at the battery. .3-.4 volt increase from nominal isn't a huge variation and considering this is an older vehicle with some degradation in the original wiring system I'm mostly restoring what has been lost with just a little extra on top.

I am also led to believe that modern batteries ,especially the calcium hybrid batteries do like a slightly higher charging voltage. I also avoid sealed for life batteries and occasionally check the battery fluid levels to ensure peak performance and increased life span. I got almost a decade from a previous battery that got used and abused in a daily driver.....

Electrical components generally have a reasonable tolerance for voltage variation, it's not like I'm running a 16 volt battery/system.

Time will tell but I'm not worried.

 

[shane_3800]

This mod is certainly not new and I'm not claiming credit for it. I've simply adapted it to my car.

The Commodore alternator is nominally rated at 14.4 volts and I'm now seeing about 14.8 volts at the alternator or about 14.7 volts at the battery. .3-.4 volt increase from nominal isn't a huge variation and considering this is an older vehicle with some degradation in the original wiring system I'm mostly restoring what has been lost with just a little extra on top.

I am also led to believe that modern batteries ,especially the calcium hybrid batteries do like a slightly higher charging voltage. I also avoid sealed for life batteries and occasionally check the battery fluid levels to ensure peak performance and increased life span. I got almost a decade from a previous battery that got used and abused in a daily driver.....

Electrical components generally have a reasonable tolerance for voltage variation, it's not like I'm running a 16 volt battery/system.

Time will tell but I'm not worried.

10y out of a battery is good. The fleet landcruisers we get at work get about 8 out of theirs. Most cars get 5 to 6 years out of the first then 2 to 3 years out of aftermarket batteries.
Well that's in Canberra where we get big temp swings.
The MF batteries go okay I've seen some last 5 to 6 years under the right conditions. They aren't sealed they have a matrix on top that lets the gas out but not the fluid.

 

[Jolls]

You are talking in current again. You have to look at it in watts.

Mate I have spoken about watts, ohms, amps and volts and the interrelationship between them. I understand the system fully - I have been trying to understand why you would want to do it.

@immortality and @Pollushon have provided the only credible reasons for considering this mod. The remainder of the explanations show a lack of understanding of the electrical system. You can't magic additional power - you can manipulate the available power but any increase in one component has a corresponding effect on another. You can take that at the macro and micro level.

When your car is running all electrical systems in the car are drawing their respective voltages 'sagging' the system, pulling that voltage down. Your alternator pushes 14v to keep the battery at that max charge and help fuel those systems but if the systems running from said battery are pushing it hard it the battery might might not reach its full charge during your drive because it's only combating the drain. The extra .6v are buffer not only for the sag but to keep the battery at max and extend its life

@Pollushon I don't disagree with the premise - we could argue the physics but to what end, The alternate side of your outline above on a healthy system is overcharging the battery. Opposite side of the same coin.

Based on yours and Immortality's examples I understand why you would consider it. I agree that .6V isn't a huge deal; but, I am certainly of the opinion that a healthy system will cope well without modification.

If the system, or components of the system, are struggling, or you think it may struggle because it is at or near to its limits, I recommend upgrading the component or the alternator. I note @immortality has already gone down this route. Each to their own. I have no doubt that anyone following this thread has been exposed to both sides of the discussion and can make an informed decision.

For mine this mod is a neat way to extend the life of a failing charging system.

 

[shane_3800]

Mate I have spoken about watts, ohms, amps and volts and the interrelationship between them. I understand the system fully - I have been trying to understand why you would want to do it.

@immortality and @Pollushon have provided the only credible reasons for considering this mod. The remainder of the explanations show a lack of understanding of the electrical system. You can't magic additional power - you can manipulate the available power but any increase in one component has a corresponding effect on another. You can take that at the macro and micro level.



@Pollushon I don't disagree with the premise - we could argue the physics but to what end, The alternate side of your outline above on a healthy system is overcharging the battery. Opposite side of the same coin.

Based on yours and Immortality's examples I understand why you would consider it. I agree that .6V isn't a huge deal; but, I am certainly of the opinion that a healthy system will cope well without modification.

If the system, or components of the system, are struggling, or you think it may struggle because it is at or near to its limits, I recommend upgrading the component or the alternator. I note @immortality has already gone down this route. Each to their own. I have no doubt that anyone following this thread has been exposed to both sides of the discussion and can make an informed decision.

For mine this mod is a neat way to extend the life of a failing charging system.

I told you. If you have a 65amp alt @12v compare that to a 65amp alt @13v the 13v one has more wattage.
I don't know how much more you want me to explain.
I'm not as articulate as both of them as I'm a mechanic I didn't go on through school. So you get my raw words.