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Hi everyone. I'm new to the club - just picked up a 2020 Metris a few days ago to replace my aging Astro.

In my Astro, I ran a 0-gauge line from my to the cargo area, and could happily draw 15-30A @ 14.0v to my heart's content at hi-idle. This was used to charge high-capacity batteries in various mobile equipment and tooling I use.

I planned on doing the same thing on my metris (maybe without the hi-idle, although if someone knows a way of doing that, I'd be glad to hear it), but then found the rabbit hole of the Metris' 'Smart' regulating alternator. I'm quite happy with the fuel efficiency this van gets, and it's a really neat trick, but I would like to find a workaround.

Does anyone have an idea about the behavior of the smart regulator, and if there's any access point in the 12v system 'ahead' of that variable regulation point?

I get that the regulator will adjust to try and charge the battery using regen when possible, or when the battery drops below 75% or so. But does anyone know if the regulation is CC, CV, or both? I'm not sure how it behaves if I try to add a large external load while driving.

Thanks!
 

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I think turning the headlights on overrides the smart charging. Might be able to fool the computer into thinking the lights are always on.
 

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Hi everyone. I'm new to the club - just picked up a 2020 Metris a few days ago to replace my aging Astro.

In my Astro, I ran a 0-gauge line from my to the cargo area, and could happily draw 15-30A @ 14.0v to my heart's content at hi-idle. This was used to charge high-capacity batteries in various mobile equipment and tooling I use.

I planned on doing the same thing on my metris (maybe without the hi-idle, although if someone knows a way of doing that, I'd be glad to hear it), but then found the rabbit hole of the Metris' 'Smart' regulating alternator. I'm quite happy with the fuel efficiency this van gets, and it's a really neat trick, but I would like to find a workaround.

Does anyone have an idea about the behavior of the smart regulator, and if there's any access point in the 12v system 'ahead' of that variable regulation point?

I get that the regulator will adjust to try and charge the battery using regen when possible, or when the battery drops below 75% or so. But does anyone know if the regulation is CC, CV, or both? I'm not sure how it behaves if I try to add a large external load while driving.

Thanks!
Smart alternators used current sensing to determine electrical load. It is a 'box' on the negative battery lead at the terminal post. It usually has a 2-3 pin connector on it. This is a 'current shunt' used to measure current. If you disconnect the small plug, it disables the shunt, making the system believe no current is flowing to which it reacts by increasing the voltage to 13.8-14V continuously. This turns the 'smart' alternators to behave like a conventional, fixed voltage alternator. You may get a dash warning to check your electrical system but if you can tolerate the light, the system should run fine otherwise.
 

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Hi everyone. I'm new to the club - just picked up a 2020 Metris a few days ago to replace my aging Astro.

In my Astro, I ran a 0-gauge line from my to the cargo area, and could happily draw 15-30A @ 14.0v to my heart's content at hi-idle. This was used to charge high-capacity batteries in various mobile equipment and tooling I use.

I planned on doing the same thing on my metris (maybe without the hi-idle, although if someone knows a way of doing that, I'd be glad to hear it), but then found the rabbit hole of the Metris' 'Smart' regulating alternator. I'm quite happy with the fuel efficiency this van gets, and it's a really neat trick, but I would like to find a workaround.

Does anyone have an idea about the behavior of the smart regulator, and if there's any access point in the 12v system 'ahead' of that variable regulation point?

I get that the regulator will adjust to try and charge the battery using regen when possible, or when the battery drops below 75% or so. But does anyone know if the regulation is CC, CV, or both? I'm not sure how it behaves if I try to add a large external load while driving.

Thanks!
I'd invest in a DC-DC Charger
 

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"Precision engineering" isn't just a sales pitch by MB. For better (usually) or for worse (yep, a few things are over engineered IMO- Crankcase Ventilation Purge Valve) you'd probably create more problems for yourself with overly creative modifications.

This is one example of an electrical modification that didn't work out so well.


I'm with focus805- get a DC to DC charger. Quite a few of us have done that with no problems. Sterling Battery to Battery Charger Install
 

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I think a DC-DC charger is absolutely critical but you still need a power supply to the charger. This can be solar, but should also be the starter battery or alternator. If the Metris "smart" alternator has a shunt that restricts power to the charger, then the charger is doing nothing while the engine is running and the starter battery is fully charged. Has anyone installed a second alternator for providing this power to the charger?
 

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That's not entirely true. A dc/DC charger steps up the current and draws from the system. It would by this point kick on the alternator when needed.
 

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That's not entirely true. A dc/DC charger steps up the current and draws from the system. It would by this point kick on the alternator when needed.
That is interesting. Is that the case for all DC-DC chargers? I'm planning on using the Renogy DCC30S.
 

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That is interesting. Is that the case for all DC-DC chargers? I'm planning on using the Renogy DCC30S.
I just checked the DCC30S product info...it includes a smart ignition cable for use with smart alternators. Simply tap it into the Metris smart ignition circuit in the driver's ignition fuse box. Here's a link to a helpful vid:
.
 

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I'm not specifically knowledgeable on the Metris but am on smart alternator, DC-DC chargers and lithium direct charging systems. In general, I expect Metris to generally follow typical smart charging system methods. I'm a custom camper power guy who follows the van community too.

The operation of the system and the influence of the DC-DC charger goes like this;
The purpose of the negative terminal current shunt is only to measure input to the battery (and some measure battery temperature). If the shunt is disconnected (ECU sees no current flow reported), the ECU reports an alternator fault and will revert to fixed voltage output and set a fault code. Normally driving modes in the ECU set the alternator output voltage through a pulse width signal to the alternator (GenCOM). The alternator replies with a pulse width signal to the ECU (GenMON) telling it what the duty cycle of the rotor excitation is (effectively, 'how hard it is working to produce the voltage requested'). Normal voltage is 12.4-13.0V which changes to ~13.5 when lights, heater, A/C or seat heaters are switched on. This change is not due to the current change at the battery shunt but due to the body control module reporting these changes to the ECU. Installing a DC-DC converter does not change the ECU driving modes directly but it does understand there is a higher load because the GenMON will tell it that the alternator is working harder to reach the voltage setpoint. The current shunt at the battery SHOULD not be incorrectly influenced if the DC-DC negative lead is not attached directly at the battery terminal. The negative of the converter needs to be connected on the cable side of the shunt, not the battery side. IMHO, the converter cabling should be attached right at the alternator to spare the vehicle power cabling from carrying a large, unexpected load but that is not what installation instructions say. In general, it is not possible to disable the smart control system without getting a fault indicator but the system fail-safe will only result in fixed voltage output ~13.8-14.2V, effectively making the smart alternator 'dumb'. The DC-DC converter takes power from the vehicle system at whatever voltage is produced and raises it to a voltage appropriate for the battery type and charging phase. A key to automotive reliability will be to ensure the added charge load does not overheat the alternator. At idle, there is low airflow in the alternator and at high rpm, there is low alternator efficiency, each resulting in about 35-40% CD capacity. Maximum (continuous duty) alternator capacity is ~50% in the vicinity of 5-6000 alternator rpm which is around 3:1 drive increase from engine rpm (1800-2000 engine RPM). A high idle is pretty necessary if much power is demanded. The ignition lead on the converter is what switches it on/off. I think it makes sense to install a 120C thermostatic switch ( a ~$10 mechanical device) on the back of the alternator that cuts the ignition lead, shutting off charging till it drops to ~105C. It is also desirable to install a manual disconnect switch in the cab to disable it when needing high power or experiencing high engine temperatures. I personally use an automatic thermostat on a second, 'dumb' alternator, directly charging my lithium bank to prevent thermal overload and do not alter my vehicle's electrical system.
 

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I just looked at the Renogy manual. They don't say specifically but the language used indicates to me that the device switches itself is simply operating on sensing elevated voltage in the vehicle system (probably above 13.5V) BUT, smart alternator systems operated at below that voltage frequently although the converter can still charge effectively. To keep the charger from turning on/off and provide reliable operation, they use the additional sense wire which is simply a 12V signal supplied when the ignition is on. This is less convenient (from installation effort) that voltage sensing but more reliable.
 

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That is interesting. Is that the case for all DC-DC chargers? I'm planning on using the Renogy DCC30S.
All DC based charger controllers (either solar or battery-battery charger) use some form of voltage boosting to create the higher voltages needed to charge. They do not have any direct connection to make the alternator change its behavior and can only influence the vehicle charging voltage output by being an 'unknown load' on the system that the ECU sees as a higher than normal effort being made by the alternator to satisfy the voltage demanded. Nothing 'kicks on' (or off), or changes the output voltage that is not part of the ECU drive mode programming. What makes the DC-DC work is that it can draw a lot of power at whatever voltage the alternator is delivering and boost it to what is needed..
 

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All DC based charger controllers (either solar or battery-battery charger) use some form of voltage boosting to create the higher voltages needed to charge. They do not have any direct connection to make the alternator change its behavior and can only influence the vehicle charging voltage output by being an 'unknown load' on the system that the ECU sees as a higher than normal effort being made by the alternator to satisfy the voltage demanded. Nothing 'kicks on' (or off), or changes the output voltage that is not part of the ECU drive mode programming. What makes the DC-DC work is that it can draw a lot of power at whatever voltage the alternator is delivering and boost it to what is needed..
Also interesting. Looks like the good folks at Renogy recognize the challenges associated with smart alternators and have built in capability to allow the house battery charging regardless of starter battery state. Just plug the Renogy smart ignition cable pigtail into the correct ignition fuse socket. Here’s a vid showing how in a different vehicle:
.
 

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Has anyone installed a second alternator for providing this power to the charger?
In 2017 when I was working on my van (a 2016 cargo) there were no options for the alternator. Specifically no higher amperage models, which are available for the Sprinter. As for a second one- that would be quite challenging.
 

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@MechEngrSteve do you own a Metris?
No. Long way from it. I have a 2004 F350/6.0l diesel with 2 alternators, [email protected], [email protected] dedicated to charging my 17kWh Nissan Leaf 24V battery/950W solar......DYI flatbed camper.......see @maximum.4x4.camper or search 'workingonexploring'. on YT for build and travel videos.. I spent a career in building configure to order products, many of which were power delivery related. I do a lot of teaching and consulting on building mobile power systems.
 

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In 2017 when I was working on my van (a 2016 cargo) there were no options for the alternator. Specifically no higher amperage models, which are available for the Sprinter. As for a second one- that would be quite challenging.
Also interesting. Looks like the good folks at Renogy recognize the challenges associated with smart alternators and have built in capability to allow the house battery charging regardless of starter battery state. Just plug the Renogy smart ignition cable pigtail into the correct ignition fuse socket. Here’s a vid showing how in a different vehicle:
.
I actually think what I would term 'voltage-sensitive switching' of a DC-DC converter is convenient (installation simplification) but a bad idea. There are times when the vehicle needs all of its engineer power to the wheels (hill-climbing) or when overheating needs to be relieved (low driving speed or high ambient temperatures). Just like 'turn off your A/C when climbing a hill' is advised, the same needs to be possible for the DC charger. If the charger ONLY switches on the availability of a high system voltage, the operator does not have the control needed. Ther are plenty of voltage-sensitive relays out there that handle the starter/cabin battery connection automatically. This is actually the first I have been aware that a manufacturer has this feature (but is it seems like a logical extension). I LIKE the idea that an ignition wire is needed BECAUSE it should have both a manual and thermal cutoff in series. I think a manual disable near the driver, is NECESSARY. I also think placing a thermal switch on the alternator is necessary to prevent accidentally toasting your alternator. There are NO safety mechanisms to keep you from overloading your alternator to failure. Since it is also needed to operate your vehicle, increasing the likelihood of failure is an unacceptable option because that is an immobilizing failure. I use a temp display in my cab with a thermostat (charging alternator only) and amp/volt-meters on both my engine and my battery charging alternator for exactly that reason. I have also installed systems for others using Balmar charging regulators with an alternator temperature sensor to cut back charging under high alternator temperatures. I'm pretty close to selling a kit that includes the thermal switch necessary to do this because of the mass of DC-DC chargers being used by unknowing users. There are some video clips on my Instagram of the system.
 

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No. Long way from it.
So you joined to discuss this topic? I think you had other posts suggesting people remove the shunt to force the smart alternator to be dumb. Please don't suggest that here unless you know what you are doing and are a Mercedes tech.
 

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I'm pretty close to selling a kit that includes the thermal switch necessary to do this because of the mass of DC-DC chargers being used by unknowing users. There are some video clips on my Instagram of the system.
Good luck with your sales.

I can't speak to the specifics of your arguments- most notably the possible temperature issues for the alternator. It is good to get more input from someone that specializes in this type of an install- thank you for your insight. I do not have your level of expertise or experience on various other camper projects. I followed the instruction for my Sterling charger and found out what I could about the Metris. Info was pretty sparse in early 2017 since the 2016 model year was its first year in the US.

I do know that I have not had any problems with my DC to DC charger installation after about 4 years. Or any problems with the electrical system. Maybe I was a lucky Guinea pig since I was the first one to post a thread on the subject. But quite a few other have also installed various models of DC to DC chargers. I do not recall any other forum users raising concerns after they installed a DC-DC charger, although it is entirely possible I missed a thread on the issue over my past 4+ years on this forum.

From the very unscientific sampling that participation on this forum represents, overheating of the alternator (or other electrical issues) following a DC to DC charger install does not seem to be a problem.

In my humble opinion, the experience of actual Metris owners on this forum that have installed DC to DC chargers is more definitive than your speculation about possible problems.

But I could certainly be wrong. Perhaps you do a poll asking forum members that have installed a DC to DC charger if they have had any unusual electrical problems?
 
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