Verifying the operation of dual alternators

My link was just an example of what is out there canned solution. There are no shortage of them out there. Then too use a pair of 200 Amp DC shunts and amplify the output using a pair of these easily programmed for 0 to 50 mV = 4 to 20 mA = 2 to 10 volts or 1 to 5 volts. I have used the in numerous applications. They run about $100 per copy from Inor USA.


Ron

How about a sould system? .

Click to expand...

I am not sure what a sould system is but a sound system that can burn down a pair of 150 amp alternators and ruin a set of diesel truck batteries plus can fit into a four door version or less of the F350 series would clearly be of a financial outlay value that would make the $800 repair bill for two alternators and batteries seem like nothing.

My guess is still with some auxiliary device that has a very heavy power demand like a hydraulic power pack unit for an after market attachment or work system.

tcmtech said:

I am not sure what a sould system is but a sound system that can burn down a pair of 150 amp alternators and ruin a set of diesel truck batteries plus can fit into a four door version or less of the F350 series would clearly be of a financial outlay value that would make the $800 repair bill for two alternators and batteries seem like nothing.

My guess is still with some auxiliary device that has a very heavy power demand like a hydraulic power pack unit for an after market attachment or work system.

Click to expand...

Sorry for the spelling. Fixed.
A good set of subs could use that much.

tcmtech said:

To me this sounds like needless worry and what if thinking for a problem that doesn't really exist. There is no logical reason to isolate the outputs of the two alternators with diodes in the first place being that alternators initially produce three phase alternating current that gets ran through a set of rectifier diodes to turn it into DC power that the vehicles electrical system works on. The reverse power flow blocking function is already built into them.

There are a few million Ford diesel vehicles that run single 100 amp or less alternators for dual battery sets without problems relating to burning out alternators so concerning yourself over a odd coincidence of two battery's and two alternators going out in short succession of each other is needless worry in my view.

My concern comes from why does the F350 have dual alternators on it any way? What is the excessive electrical load that justifies them? Normally a dual alternator setup is only required fore fire and rescue or ambulance type vehicle applications. After that the reasons for having them drastically drops off.

Is there an electrically lifted dump box, snow plow attachment, winch, or some other electric device that draws hundreds of amps for extended periods that puts regular high loads on the electrical system?

Click to expand...

The truck has a a full size plow setup with highly tinted windows and extra lighting and other accessories. It doesn't matter if you think the problem doesn't exist. According to the physical evidence that's what happened. It does not appear to us or the shop the second alternator has been operating for a while (based on corrosion and wear). Meanwhile both batteries and the first alternator are dead. The alternators are stock. Stock installed, stock Ford parts. The dealer and shop both note this is a common situation with the dual battery and/or dual alternator systems when the batteries are weak and the loads high. I'm not sure why your information notes it differently. To stay on target, are you aware of any other options for detecting when one alternator has failed when two are connected parallel?

The "back feed" reference is from the fact that both alternators are connected in parallel. Yes the field of alt 2 does not see any voltage from alt 1 (unless the output regulator has failed in such a way as to allow it, but we aren't speaking of that failure not does it matter in this discussion). The output of the regulators each see the output voltage of the other. The idea here, as others have noted, is to detect when one has failed. The original idea was to place a diode in series with each regulator output to provide isolation and be able to detect the output voltage of each. Though doable, it may not be the most feasible option. I will be looking for DC current sensor options as well.

You could just read the warning light voltages.

The alternators already have the main rectifiers, so if you measure the voltages on the thee AC windings on each alternator you would be able to see if one alternator stops. If you just need to measure the peak voltage from each alternator, you would connect three diodes from the AC windings and measure the voltage after the diodes.

Well the warning light terminal has those three diodes already fitted. http://www.tb-training.co.uk/images/Image138.gif

I'll have to look again, but I don't think your drawing matches well with the wires that are available on the new alternators, without disassembling it. I though when we installed it we only had to attach one wire, the positive terminal; obviously the negative was connecting through the chassis. Perhaps this truck doesn't have the warning light (pictured) wired; thus there is a terminal available but not used. I'll have to double check for any extra unconnected terminals.

From post #16

Have you looked up the alternators? Maybe thay have something built in.

Click to expand...

The truck has a a full size plow setup with highly tinted windows and extra lighting and other accessories. It doesn't matter if you think the problem doesn't exist. According to the physical evidence that's what happened. It does not appear to us or the shop the second alternator has been operating for a while (based on corrosion and wear). Meanwhile both batteries and the first alternator are dead. The alternators are stock. Stock installed, stock Ford parts. The dealer and shop both note this is a common situation with the dual battery and/or dual alternator systems when the batteries are weak and the loads high. I'm not sure why your information notes it differently. To stay on target, are you aware of any other options for detecting when one alternator has failed when two are connected parallel?

I though when we installed it we only had to attach one wire, the positive terminal; obviously the negative was connecting through the chassis.

Click to expand...

I figured so much. My guess is that since you are running the stock automotive starting type batteries in a high load and deep discharge aplication that is what killed them. Anyone here can tell you that automotive batteries live short lives in high discharge applications like what yours are doing which is why yours died.
For high drain and discharge applications like running a snow plow power pack you should be using a good quality set of heavy duty marine deep batterys. They are built to handle that type of loads and deep discharge cycling like what your plow does to them whereas automotive starting batterys are not and will not hold up to it.

To me thats where the problem originated. If the one alternator was showing physical corrosion and age it probably just gave up on life like alternators do when they get old leaving the heavy loading for the other alternator to deal with which shortened its remaining life. If they were both stock alternators installed at the same time one dieing of old age would be a good indicator the second one was simply not too far behind it.

How old is the truck and with how many miles on it?
How old where the alternators and is alternator burnout a regular ocurance on this truck?

Because you are using an alternator the charging current is not DC but pulses or "AC". I believe a AC current probe or current transformer will give you an idea of what the charging current is. I know it will not be accurate but it will indicate if current is flowing and about how much. There will be no extra power lost by using a AC current transformer. I should get my coat on and try it on my truck. It will just clip on over the wire and read the ripple in the current.

tcmtech said:

I figured so much. My guess is that since you are running the stock automotive starting type batteries in a high load and deep discharge aplication that is what killed them. Anyone here can tell you that automotive batteries live short lives in high discharge applications like what yours are doing which is why yours died.
For high drain and discharge applications like running a snow plow power pack you should be using a good quality set of heavy duty marine deep batterys. They are built to handle that type of loads and deep discharge cycling like what your plow does to them whereas automotive starting batterys are not and will not hold up to it.

To me thats where the problem originated. If the one alternator was showing physical corrosion and age it probably just gave up on life like alternators do when they get old leaving the heavy loading for the other alternator to deal with which shortened its remaining life. If they were both stock alternators installed at the same time one dieing of old age would be a good indicator the second one was simply not too far behind it.

How old is the truck and with how many miles on it?
How old where the alternators and is alternator burnout a regular ocurance on this truck?

Click to expand...

Deep discharge application? There is no point in time when the electrical system is under load while the engine is not running (unless he leaves the lights on when he gets home, then he's just being a twit and we're not going to worry about that.) The truck is a 2006 with almost 70k. The alternators are stock and have not been changed since he acquired the truck a couple years back. The batteries are not original, but he has not changed them since he's had the truck. (ie., the batteries are newer than the alternators). The system has high load but the batteries have no reason to discharge to the point where there is a need for a deep cycle battery.

ronsimpson said:

Because you are using an alternator the charging current is not DC but pulses or "AC". I believe a AC current probe or current transformer will give you an idea of what the charging current is. I know it will not be accurate but it will indicate if current is flowing and about how much. There will be no extra power lost by using a AC current transformer. I should get my coat on and try it on my truck. It will just clip on over the wire and read the ripple in the current.

Click to expand...

I thought generators had the AC output. There have been are two types of power generation systems in cars; generators and alternators. I thought generators were AC-ish and alternators were DC-ish. Honestly, of the top of my head I can't remember all the details.

Here is what I know from experience and many here will be able to confirm as well.

First off being its an F350 it most likely is running a larger and heavier snow plow model which would likely also have a larger capacity power pack unit on it, From what I could find online and from a few larger personal units I own I can attest to them having a 300 - 450 amp power draw on a 12 volt system when operating.

Although your alternators maybe rated at 150 amp each that rating only applies when they are at their higher end of thier operating RPM's which is most often seen at engine speeds associated with highway driving. Plowing snow is at the opposite end of that and is mainly short bursts of medium RPM's at best with lots of stop and start time near idle RPM's while shifting from forward to reverse and back where the alternators output is at its lowest which can often times be 1/3 to 1/2 their peak rated outputs at best.

BTW I have owned and worked on Fords all my life personally have never found any of their alternators to capable of running anywhere near their rated amp capacity while maintaining a proper system voltage especially at or near idle speeds.
Given that the alternators are working more often than not at speed well below their peak output range coupled with what could be a 50 amp continuous load made by the vehical itself leaving them with considerably less than enough reserve output to keep up.

From that I would expect even with combined outputs they may have only been producing 100 - 150 amps reserve power on average where as a heavily used snow plow would be pulling 300 - 450 amps at a fairly high duty cycle which could very well have an average amp load exceeding the alternators average output thus causing the batteries to have to make up the difference which is what runs them down too far causing their short life and eventual failure.
Once the first unit failed failed the second unit was no where close to being able to keep up with the average load which is most likely what brought the batterys down to damaging levels enough times to ruin them.

That is why I suggested the use of deep cylce batteries over normal automotive starting batteries.

Alternators put out alternating current which is why they have a rectifier set in them. Generators use brushes so they only need a mechanical disconnectcal disconect relay, which was found in the old regulator box that is associated with them.

Follow my logic?

generation/alternator
http://en.wikipedia.org/wiki/Alternator
http://www.tb-training.co.uk/images/Image138.gif
From the links, it looks like alternators are AC in nature and in the case of cars (trucks) use internal diodes (rectifiers) to get DC. I think you can see ripple current.

Put one of these on each alternators output then you can know the exact voltage and current they are running at at any time.

**broken link removed**

Or a pair of these mounted in the dash.

**broken link removed**

tcmtech, Nice find.

When you only have to work 2 - 5 hours a day out of a 12 hour shift you get lots of free time to spend on the internet looking around!

That and I have bought similar meter sets for other home projects before as well.

tcmtech said:

Put one of these on each alternators output then you can know the exact voltage and current they are running at at any time.

**broken link removed**

Or a pair of these mounted in the dash.

**broken link removed**

Click to expand...

I like that meter, wounder how accurate it is.

When you only have to work 2 - 5 hours a day out of a 12 hour shift you get lots of free time to spend on the internet looking around!

Click to expand...

You work to hard take a brake. LOL