Alternator Load Dump

I got the term 'load dump' from MexicoWanderer.

He also basically walked me through this voltage regulator modification.

What I would do differently, well I would not order the 10 ohm 50 watt resistor and pay nearly 30$ for it, when a 50 watt 10 ohm resistor can be had for under 5$. The resistance of the 'field replacement module' was an unknown at the time however. This tricks the ECM into believeing that it is still hooked to the alternator, and into not flashing the check engine light.

I'd likely order a 10 ohm 100 watt resistor instead of the 50 for a fraction of the price I did pay. I added heatsinking to the 50 watt and all appears well a year later. It does get hot and manupulating voltage does change the ampoerage passing through the resistor, though I have not done the full battery of tests at different outputs, just put my clampmeter over a wire and dialed voltage up and down.

Function wise, There is some voltage sag as the wiring/connectors heat up. I took power for the A terminal( always on) from the alternator + stud, which then goes to circuit breaker then battery switch via doubled 6awg, then 2awg to battery terminal. Ideally this A terminal wire would be 12AWG right to battery terminal.
This doubled 6awg is an old set of jumper cables. I will replace this with 2 or 1 AWG at some point, and then the voltage sag should be less.

Before the possibility of tricking the engine computer with the resistor, I was considering influencing voltage with a DC to DC booster, but was not quite sure it would not cause the VR in the ECM to fry. I was trying to determine when and why the VR was choosing the voltages it did, as it occassionally would rocket back to 14.9v for no discernable reason.

I was always extremely irritated when the ECM's VR would choose 14.9 or 14.7 of a battery already fully charged, and than choose 13.7 on one still far from fully charged.

Now of course I choose voltage. With the dashboard digital Ammeter now reading amps into battery I basically choose 14.7v, until I know for sure the battery is full. In daytime, I can lower voltage to below my solar float setpoint of 13.6v, and the alternator amperage can goto zero as the solar provides the 8.2 amps required to run engine at idle or the 12.2 amps at 2000 rpm.

I will adjust voltage slightly for battery temperature too.

The turns counter is not really so helpful as 14.7v when battery is depleted is not the same as when it is full, but perhaps thicker copper will narrow the gap. This appears to stretch a bit more than when first installed too, so I rarely ever look to see what the turns counter reads. I'd have no issues with a non turns counting 10 turn potentiometer.

With voltmeters right next to ammeter and potentiometer, it is so easy to adjust I am not worried about the turns counter not being exact or repeatable at different amperage outputs.

50 amps max at hot idle is a factor the voltage regulator cant overcome when the loads are 60 amps. I usually can crank up the voltage at hot idle and get it to the higher voltage( field current goes way up and so did VR temperature before fan), but then when I accellerate voltage will jump well past 14.7v, and more than 30 seconds of 14.7v+ when the ECM would have chosen 13.7v fires off the check engine light and goes into limp home mode where MPG suffers until I reset the ECM by removing power. The CEL will go out on its own if I lower voltage and restart engine, but the limp home sensor settings stay active until ECM is reset.


When my 140 amp breaker tripped at sub 110 amps, It was not my first thought, and I kind of assumed the VR itself was somehow responsible, or had lost power. I drove several miles with headlights on and a battery depleted well below 50% and voltage 11.9v or so.

The I terminal is for the switched ignition 12v, and I found a wire under the dash which becomes live only after engine start. I thought this might have blown an OEM fuse so I checked those first.
But this wire also powers the fan I have attached to the heatsink on the VR, and this was still turning on after starting engine. I then probed the A terminal and found no voltage, then scolded myself for not immediately checking the 140 amp breaker.

My 14 awg fusible link on my OEm cabling was installed by an auto electric shop, whom I assume had no 10AWG fusible link, back in 2005 or so. Back then my 40/90 alternator failed and I replaced it with a 50/120, and did not charge my batteries before starting engine. The original needle ammeter went higher than I ever had seen before, and then went neutral. I was unaware of the fusible link's failure, but the Sparkies zeroed in on it immediately.

Strangely the original 10AWG link did not blow as designed, and still tested fine , with no load.

I've been meaning to properly replace it, but with the parallel circuit it has not been an issue since.

I did use 14 or 12AWG wire to the I terminal of the voltage regulator, but this wire carries so little current this was several degrees of overkill.

So overall I love the modification, and it is working quite well, even with the voltage sag at high amperages. It can be improved with thicker copper.

As for tricking an internally regulated alternator, I do not know how one bypasses the internal VR and wires up an external VR like the transpo540HD in its place.

Tricking the ECM and installing the 540HD on an externally regulated alternator is likely cakework in comparison to modifying an internally regulted alternator for external regulation.

Lance neville 8MR external regulation modification

What I really love about the VR modification is I can stop the belt squealing when cold and wet by lowering the voltage, and of course I can now visibly see the difference in amperage the battery accepts at different chosen voltages. 3x more amps at 14.7v vs 13.7v is not insignificant.

I am a retired automotive engineer and worked on electrical systems and EFI.

In my occupation a "load dump" was when an inductive load (ignition coil, fuel injector, large solenoid) was turned off (load dump). The collapsing of the magnetic field caused a high voltage "kick back" (back electromotive force, EMF). Depending on the size of the inductor, This spike could be quite hogh, potentially damaging other electronics.

Typically zener diodes were used to direct this voltage to ground through a resistor.

Landyacht

Please tell me more about your

"Transpo540HD adjustable voltage regulator modification still working awesome"

I am installing a home brew alternator voltage regulator modification. My 140amp Delco alternator uses the "S" terminal to determine the output voltage, normally the alternator puts out a constant 14.9Vdc without any temperature or SOC compensation.

I have a DCtoDC Boost device with via a switched connection (normal or override operation) to the "S" terminal. This device supplies an adjustable higher than expected voltage fooling the regulator to reduce it's output.

How does your system operate?
Where did you get it?

Thanks for the info

Edit - Found the links to the older threads but would still like to hear how things are working now and what if anything you might do different

Update located here http://www.cheaprvliving.com/forums/Thread-Your-Vehicles-voltage-regulator?page=2

Yeah, having an accurate ammeter is a nice thing to have in a vehicle. Jeesh, the cars of olden days had good ammeters in them, how did we lose the track?

That 14 AWG fusible link thing has me worried. Are you drawing off power to the house battery before the fusible link? From the alternator directly, IIRC. Memory fails, occasionally.

Blue Seas may be selling the Marine version of those Bussman breakers. They are almost identical to the shore-used type but the contact studs are in front with little rubber booties. If that isn't the case, I'll take your word on it. Stranger things have happened in the Marine supply world.

The Cb I bought, in 2012, is branded 'Absolute' and is the pushbuttonj disconnect/ lever reconnect type similar in appearance to Bussman's hi amp series.

I noticed when I added it, my maximum idle amps at the time were reduced by ~5.

I was noticing that Blueseas has relabbelled cooper/Bussman products and added some extra price to them.

I used to use the lever to see how much amperage increased when I switched the lever and closed the thicker parallel circuit with depleted house battery.
Much was dependent on how hot the 14awg fusible link in OEM circuit was at the time of switching.

Anyway I am glad that I finally had reason to move Hall effect sensor to a battery cable, and thaat I did not fully reassemble until I was sure I did not have to flip the sensor over( I did). Most all the mystery of how much total amperage the alternator was making disappeared a while back, but today was the hardest I pushed it with lights blower motor and a thirsty battery, and enough rpms to maintain 90+ amps output.

Now my dashboard mounted digital ammeter will show amps into or out of battery only.

Yes, get a good breaker. I'm liking the Bussman Hiwatt manual trip breakers. You can use them as a switch, too. They also come in sealed marine variety if you need to spend more money.