Does the 4xe have a “smart alternator”?

[Jeeperz Kreeperz]

I know the 4xe doesn’t have a traditional alternator, but rather a DC to DC converter between the high and low voltage systems. However, I need to know if that OEM charging system would be considered a “smart alternator” from the standpoint of a DC to DC charger that I am installing.

I’m installing a lithium house battery in a small camper that I’ll be towing with the 4xe. I’m also adding a Renogy DCC50S DC-DC on-board battery charger with MPPT controller - which allows for either charging from the tow vehicle’s battery, or charging via solar panels, as two methods to ‘top off’ the trailer’s battery.

These lithium batteries are stupid expensive, so I don’t want to ruin one because I’m not “smarter” than my vehicle’s “alternator”

The Renogy website states:

“This Renogy DC-DC On-Board Battery Charger with MPPT is compatible with both traditional and smart alternators. For smart alternator, an IGN Port is featured to connect the Vehicle Ignition for auto-trigger once it detects the vehicle is started.”

In Googling around the web, it seems the difference between the two alternators is that smart alternators provide variable voltage for charging. Smart alternators seem to let the system hang out around 12.5V-13.5V, then hit it with higher voltage occasionally for charging. Traditional alternators, on the other hand, provide a fairly steady voltage in the 14.4V range.

Based on the voltage levels (which is all I think the Renogy DC-DC charger cares about), it appears the 4xe‘s DC-DC converter will “look like” a smart alternator.

Does anyone have any idea if my theory is correct? Or any other thoughts/suggestions?

Thanks!

Sponsored

 

[Traveller128]

It's not an alternator, but rather a DC motor/generator. It looks very similar to what we're using on our MHEV (mild hybrid) setup. Ours is slightly lower output, as it's only adding a bit less than 20HP to the motor when it's boosting. Like ours, It uses a converter to charge the 12V battery for internal systems (DC/DC converter). It's also the starter for the motor. I would think, that if you have the tow package, you could take the positive power lug in the trailer harness and use that to charge a trailer battery since that's what it's designed for (the 7 wire plug).

I sure wouldn't try to modify anything in the factory harness, or add a charger that could cause a conflict on a hybrid vehicle.

 

[Jeeperz Kreeperz]

Thanks @Traveller128 , I do have the tow package, but here’s what I’m reading on another site about this very topic:

“However, if you try charging a leisure battery at a lower voltage (around 12.5V) it will charge about as quickly as a glacier moves, or in other words, you might as well not bother. Using conventional relays on smart alternators also poses a risk as the relays and batteries won’t be rated to take the higher voltage bursts.”

So, if the DC to DC converter on the 4xe “looks like” a smart alternator to the DC to DC converter on the trailer, and I fail to use the smart alternator port on the charger, then I will get virtually no charging performance, and I risk frying some relays in the charger, or worse - damaging my lithium battery.

I’m still waiting on a reply from Renogy on this issue, and will certainly post here if/when I see an answer. But if you or anyone else has anything to add, I’m all ears!

 

[Jeeperz Kreeperz]

@Tommywear , thank you VERY MUCH for taking the time to type that explanation. Makes very good sense. And that really was my initial thought - to wire it up “as if” it is a smart alternator.

And yes, I correctly assumed I would get better support here in the forum than with Renogy

Since I’m using the 7-pin towing harness, I assume I can just use pin 4 to go to the IGN port on the Renogy charger/MPPT. As you said, the 12v signal on that IGN port is simply triggering a relay in the charger. I know your system is inside your vehicle, not in a towed trailer, and you may not have the towing package, so you may not be able to answer that with certainty. When I get some time, I’ll throw a voltmeter on pin 4, and confirm that it is working the way I think it should (i.e., only powered with ignition, NOT powered at all times). See diagram below:

 

[silverheep]

Watching the battery voltage on our 4xe, I’m inclined to think that the Renogy would see it as a “smart” alternator. I usually see it between 12.8v and 13.5v, jumping to 14v-ish when I’ve winched or otherwise drained rhe 12v battery.

 

[Senrusho]

I too have seen my battery voltage jump around between 13 and like 14.4 volts.

 

[av8or]

Just wondering the outcome of this, as I’m looking to do the same. The smart charging system is almost worthless for charging a trailer battery, it might even be a detriment as in maybe since the trailer battery is at 13+ volts and the Jeeps charging system and battery are happy at 12.7, it’s possible that the Jeep is actually stealing power from the trailer.

 

[Jeeperz Kreeperz]

@av8or I decided not to install a DC to DC charger for the time being. I have a NOCO 120V charger for when I’m in my garage or at a campsite with shore power. Then I‘ve picked up an MPPT, and will add some solar panels for when I’m off grid.

For reference, I asked Renogy for some clarification on the issue, and this was their response, which contains a helpful chart showing the voltage cut in and cut out points for this particular Renogy DC-DC charger:

“Our technicians have replied that DCC50S 12V 50A DC-DC On-Board Battery Charger with MPPT is connected or not connected to the IGN wire to distinguish between the Traditional Alternator and Smart Alternator, which will operate at different voltages. If Traditional Alternator is connected to IGN wire, DC-DC Battery Charger will think it is Smart Engine and will charge the rear battery according to the charging logic of Smart Engine, which may cause the front battery to be over discharged.

In addition, please refer to the picture as below”

 

[av8or]

I’m puzzled by all this, I have never had a vehicle with smart charging before. When I travel several days in a row, it seems like the Jeep is actually stealing power from my trailer, and maybe it is, if the trailer battery has higher voltage than the Jeep. It’s hard to believe that with 190 watts of solar on the roof and a lithium battery I’m better off parked than driving!

 

[Senrusho]

Are you still running the genesis kit? I'm trying to figure out if I will have to do anything special to mine to hook solar up to my genesis kit.

 

[VKSheridan]

I’m puzzled by all this, I have never had a vehicle with smart charging before. When I travel several days in a row, it seems like the Jeep is actually stealing power from my trailer, and maybe it is, if the trailer battery has higher voltage than the Jeep. It’s hard to believe that with 190 watts of solar on the roof and a lithium battery I’m better off parked than driving!

@av8or, you might be surprised. I thought the same thing. Having been taught 14.7 VDC is a good frame of reference for automotive charging systems, the whole “smart alternator“ thing seemed like a great example of over-engineering.

Pop the hood on just about any car built in the past decade or so and look at the negative post on the battery. Attached will be a thing that looks like a shunt. If it’s there, your car either has a smart alternator or some dude installed a shunt for an aftermarket ammeter.

In Jeep terms, this shunt is called your Intelligent Battery Sensor (IBS) and its job is to give inputs measuring voltage (SOC), state of health (SOH) and temperature to your Powertrain Control Module (PCM).

Your PCM takes all this information and creates a dynamic charge profile for your system. In this system with these batteries at “X” volts, how much amperage flows and at what temperature? How long does it take for the amperage to fall to its average factor and how does that change with time and temperature? At the current temperature, what amperage will be needed at what voltage to achieve full charge? There’s more calculations but you get the drift.

A conventional alternator doesn’t care. It’s rated at 14.6 volts up to 60 amps. At 14.6 volts, it will push as many amps as the batteries and cable can take (up to its rated limit). Once the resistance in the battery grows (fully charged), the voltage stays the same but the amperage drops.

On your Jeep, it’s a whole different world. Your PCM decides the alternator’s voltage and amperage output by strengthening/weakening the control voltage in your alternator.

If you’re sane, you're probably asking why.

Well, it’s because your old school alternator was at its happiest pumping out amperage. When it couldn’t because the battery was fully charged, it would still try (holding hard and fast at 14.7 volts). In time, an engineer realized unchaperoned alternators were a solid contributor to adding needless load to the engine, wear to the belt, more exhaust out the pipe, heat in the circuit and trips to the fuel pump.

Introducing the smart alternator….

If your batteries are charged, there’s no need to hold system voltage at 14.7 volts. Its not like the batteries can get “fuller than full”. At 12.6-12.7, the batteries are full. That is why you are seeing “crap” voltage on your voltage gauge. 12.6 volts has been the target all along yet we are confused when we actually see it. Toss all the old “14.7“ rules out, your smart alternator can and will hit just under 16 VDC if the PCM commands it.

If you’re still sane, you're probably asking why. Keep in mind most sane folk don’t mourn the end of diode popping, battery eating, heat generating, radio interfering devices but let’s assume youre more nostalgic than nuts….

Introducing ESS……

If you’re in stop and go traffic, cranking that starter repeatedly sucks the juice. You're giving the PCM just a few seconds of run-time (while running your 6000 watt boom box) to restore the state of charge (SOC) of your batteries. By kicking up the strength of your alternator’s windings, the PCM can increase both the amperage (SOH) and the voltage (SOC) without charring your cables using the temperature sensing in that shunt. In fact, if you’re racing light to light, the PCM can use the alternator as an engine brake by increasing the strength of the windings AND take that energy to reduce the charge time of your batteries in anticipation of the next ESS opportunity.

Regenerative braking via fan belt….Who would have thought.

Even if your car doesn’t have crazy ESS stuff, the smart alternator still makes sense. It gives your batteries what they need, not just a generic output.

Back to your trailer. Measure the voltage before you connect it and measure it after a long drive. I bet it stays the same unless you sat with the engine off with your foot on the brake pedal….. LOL

Lastly, assuming your trailer wiring and battery are good, the voltage on the trailer battery after that long trip will be exactly the same as your Jeep’s battery. Roughly 12.6 VDC if your PCM properly graduated PCM school…..

Hope this helps! Errrrrr, what was the question?

 

[Jeeperz Kreeperz]

Are you still running the genesis kit? I'm trying to figure out if I will have to do anything special to mine to hook solar up to my genesis kit.

Yes, I still have the Genesis kit in the Jeep. I haven’t picked up the portable solar panels yet, but my plan was to set up the same connector on both the trailer lithium battery, and at the front grill of the Jeep. That way I can use the same panels to power up either the trailer battery or the Genesis aux battery.

Genesis explains how this is done here:

How can I hook up solar panels?

Most people want to use solar panels to be able to run their accessories for as long as possible with the engine off. You can connect the solar charge controller directly to our power and ground bus bars. The solar charge will go into your aux battery first to replace the power used by your accessories. As long as the panel is big enough to keep up with the demand and charge up the battery, then our smart isolator will link them together, and the solar will flow over to the cranking battery as well.

Watch the video!

 

[Senrusho]

Yes, I still have the Genesis kit in the Jeep. I haven’t picked up the portable solar panels yet, but my plan was to set up the same connector on both the trailer lithium battery, and at the front grill of the Jeep. That way I can use the same panels to power up either the trailer battery or the Genesis aux battery.

Genesis explains how this is done here:

How can I hook up solar panels?

Most people want to use solar panels to be able to run their accessories for as long as possible with the engine off. You can connect the solar charge controller directly to our power and ground bus bars. The solar charge will go into your aux battery first to replace the power used by your accessories. As long as the panel is big enough to keep up with the demand and charge up the battery, then our smart isolator will link them together, and the solar will flow over to the cranking battery as well.

Watch the video!

Okay, so then all I need is a MPPT charge controller and a panel. Is the smart alternator thing only a worry for dc-dc chargers for aux batteries set up elsewhere that need to be charged by the vehicle.

 

[Jeeperz Kreeperz]

Okay, so then all I need is a MPPT charge controller and a panel. Is the smart alternator thing only a worry for dc-dc chargers for aux batteries set up elsewhere that need to be charged by the vehicle.

That is my understanding - that the solar panel and MPPT are all that is needed to charge the battery under your hood - this appears to be the solution whether that battery is a factory AGM, an aftermarket deep cycle, or a dual battery setup like Genesis.

And yes, my concern at the start of this thread about the 4xe LV battery voltage “looking like” a smart alternator was mainly related to how much (or how little) voltage would be seen by the DC to DC charger in my trailer, and thus whether I should tell a Renogy DC-DC charger that it is connected to a “Smart Alternator” on the 4xe, just to fool it into charging using that particular charging profile.

 

[huey_atx]

Take a look at the "Battery Current Sensors" section of this month's Rock Auto newsletter. It was news to me. Is this something we would need to adjust for? I’ve got a winch & a couple of lights & trailer lights all directly connected to my battery.

https://www.rockauto.com/Newsletter/

Sponsored