Integrating Sterling B2B charger in RV w/Intellitec battery isolation setup

[woundedpig]

I have a 2017 Sprinter based motorhome built on the cutaway chassis.
I'm considering switching out the Intellitec components (Intellitec Isolator relay and relay delay) for a Sterling battery to battery charger in order to better tailor alternator charging for the house lithium bank, which I am going to increase to 400 AH so I can run more power hungry appliances, esp the microwave.
With the voltage drop coming via wiring from the alternator, the lithium bank does not see an appropriate bulk/absorption voltage and I'm concerned about how the alternator will fare if it is faced with a heavily depleted battery bank and the rapid charging profile of the lithium chemistry. It appears that many/most Sprinter RV manufacturers seem to be disregarding Mercedes recommendations for auxiliary battery bank size (100 AH), even with the stock Interstate batteries.
From a post on another forum where the Intellitec Isolator relay was replaced with a Blue Sea component, this relay is under the passenger seat. Not sure where the isolator relay delay is, but wonder if it is in the chassis battery compartment.

I'm still learning about DC to DC chargers like the Sterling units that allow separation and tailored charging profiles for the house bank. I read the instructions for a Sterling battery to battery charger, but I am far from clear how to integrate it in my system that has the Intellitec stuff. In integrating a Sterling in my system, it appears that the Sterling replaces the functions of these stock units.


Any thoughts?

[booster]

I haven't dug deep into all the Sterling stuff, but have looked at them several times. I think all of them are setup to drag down the alternator as far as possible so they can supply the most charging current possible.

From what we have heard of the MB systems, the biggest issue may be that the MB electronics might not like the high output that it doesn't know where it is going. A lithium battery pack of 400AH will accept much more than the stock alternator can put out, so it will be maxed out all the time, and stock alternators don't like that. High temp compensation or shutoff would be absolutely necessary, I think.

Essentially all the high charge rate systems on Sprinters use standalone secondary alternators to charge the batteries, controlled by a remote regulator to get charge profile.

[woundedpig]

My understanding is that the amp draw is limited by the Sterling units, so that even if the batteries could pull at 100 amps, a 60 amp BB1260 would limit at 60 amps, thus protecting the alternator from being overdrawn.
From their product data sheet:

"This unit will increase the vehicle’s voltage to the auxiliary battery when it is low and reduce the vehicles voltage to the auxiliary battery when it is high. It will also NOT permit high current inrush beyond the rating of the product (even under high demand loads) and so delivers the auxiliary battery system the correct voltage for different battery types (programmable) regardless off the main system voltage swings, thus, protecting the auxiliary batteries from unnecessary damage. It ensures a constant, safer and much faster charge from the system."

"As the ProBatt C current limits you do not need to rate this product to the size of your charging source - for example, the 120A model can work with a 200A alternator without causing any damage."

Still learning.........

[booster]

Originally Posted by woundedpig

My understanding is that the amp draw is limited by the Sterling units, so that even if the batteries could pull at 100 amps, a 60 amp BB1260 would limit at 60 amps, thus protecting the alternator from being overdrawn.
From their product data sheet:

"This unit will increase the vehicle’s voltage to the auxiliary battery when it is low and reduce the vehicles voltage to the auxiliary battery when it is high. It will also NOT permit high current inrush beyond the rating of the product (even under high demand loads) and so delivers the auxiliary battery system the correct voltage for different battery types (programmable) regardless off the main system voltage swings, thus, protecting the auxiliary batteries from unnecessary damage. It ensures a constant, safer and much faster charge from the system."

"As the ProBatt C current limits you do not need to rate this product to the size of your charging source - for example, the 120A model can work with a 200A alternator without causing any damage."

Still learning.........

Yes, the Sterling will stop at its max output, but if you are going to do only 60 amps, why use it. You don't need a fancy profile for lithium, just constant voltage (if it can hold it at the alternator) until you hit a voltage level, and then shut off. Normally, the low-mid 14's voltage of the stock alternator would be OK for lithium. My bet is that the Sterling would limit current if that is what you want to do, but I seriously doubt it would be able to hold voltage on a lithium pack, unless they are doing a PWM type current reduction, which in many cases just makes the voltage look like it is holding, it appears.

As you have a new, and expensive, lithium system and van, I think I would be looking at adding the extra alternator and saving headaches, and potential warranty issues. MB can't disallow you from doing the mods you are talking or void the warranty because of them, but they could make it tough to collect a warranty repair to that system if something should fail, as they could claim it was caused by the modifications.

[booster]

I would add that if you only concern is current limiting, then the 12v to 12v charger will do what you want. If you want to increase the amount you can pull out of the factory system, you really won't gain anything, I think.

[woundedpig]

I know it is dangerous for a newbie without a lot of electrical know how to play devil's advocate, but here goes.
I have the lithium bank, but I also have 400 watts of solar and could easily add two more panels, with a little labor and wiring. I have the roof real estate for that. My MPPT controller was sized for an upgrade. So, the alternator is not/won't be my only source of charging.
I can get a 120 amp Sterling waterproof rated (which I don't need) B2B for just over $500. A 2nd alternator - something I wouldn't try to do myself, would cost north of $2000, I'm sure, even more, if I chose the high idle option. The Sterling's have a 4-stage charging profile, even a lithium setting, which can be customized even further. The B2B plus would charge the lithium bank under most any circumstance, and with the current limiting, protect the alternator, so I'm wondering about the expense of the 2nd alternator, even though I know it would work. I've read about the impressive charging available from these units and that many folks have the 2nd alternator only, with little or no solar.

Not trying to discount your guidance at all - very thankful for it, in fact, and you've taught me some things along the way. My mind is not made up on this at all.

[GeorgeRa]

See this related discussion on another forum, OP ended up selecting the Australian unit. OP reviewed current market offerings in a consize table. The only missing one is from Ctec like this https://www.baintech.com.au/can-i-us...art-alternator .
https://sprinter-source.com/forum/sh...ad.php?t=61720

Without knowing your schematic, I could be wrong but:

- Intellitec relays are most often used for disconnecting batteries from electrical RV system so it could work for disconnecting alternator from house batteries or not. In my case I have the factory relay connecting alternator with house batteries and Intelitec between house batteries and loads.

- Your 2017 Sprinter is most likely limited to 40A draw from the smart alternator, a lot of discussion about this subject.

- Most of B to B chargers are tuned for AGM batteries, for Li batteries the question would be how will the B to B charger know when to disconnect the charge, will BMS be smart enough to terminate the charge.

[booster]

As George says. It is highly unlikely that the solar controller and shore charger will do a good job of lithium charging, with full cutoff/restart. The solution that is the best, it appears, is for the BMS or Silverleaf type controller to handle all the charging from all the sources, so they can be reliably shut off and on when needed without hurting them or causing voltage spikes. If you have a central controller type system, you would not need to do anything with the alternator charging because the controller will disconnect (though the Intellitech maybe) when the batteries are full, and the MB stuff will still have the starting battery for reference.

Of course with the full shutoff style of control, you lose the ability of the solar to support use when the batteries have shut down after getting full, until the go down enough to start charging again.

What van and system is in place now, so we can get a feel for what you are really dealing with?

[woundedpig]

I hope I've set up Google photos correctly. Link below. I have a 2017 chassis Sprinter 3500 V6 diesel with the stock 220 amp rated alternator. Built in a cutaway chassis, so there are more storage options. Currently 200 AH lithium drop-in's but plan to increase to 400 AH. There is an Intellitec isolator solenoid relay under the passenger seat and the isolator relay delay in the chassis battery area, though I haven't looked for it yet.

https://photos.google.com/share/AF1Q...BQaGtPcm42V0dn

[booster]

Originally Posted by woundedpig

I hope I've set up Google photos correctly. Link below. I have a 2017 chassis Sprinter 3500 V6 diesel with the stock 220 amp rated alternator. Built in a cutaway chassis, so there are more storage options. Currently 200 AH lithium drop-in's but plan to increase to 400 AH. There is an Intellitec isolator solenoid relay under the passenger seat and the isolator relay delay in the chassis battery area, though I haven't looked for it yet.

https://photos.google.com/share/AF1Q...BQaGtPcm42V0dn

Whose conversion is it? Looks a lot like the Pleasure-way in that it appears to have drop in lithium batteries in it with no integrating controls.

[GeorgeRa]

Your diagram doesn’t show Li batteries, just 2 x 6V ones, most likely AGMs. Charging Li batteries is very different than AGM ones. If your van has Li perhaps you need figure out how they are charged, it is not clear.

[woundedpig]

Sorry, thought I had detailed my setup earlier, but it was incomplete. I switched out the stock lead acid batteries, which were Interstates, with drop-in BattleBorn's. The unit is manufactured by Leisure Travel Vans out of Canada. Right now I charge via a Magnum 1000 watt pure sine inverter when hooked to shore power, which isn't often. I use a custom charge algorithm which is enabled by the Magnum ARC50 remote. Many people just us the AGM2 setting with fair results. I have the solar setup I detailed earlier, which connects from the Victron MPPT solar charger directly to the + and ground busses in the back of the battery box. I have the Victron BMV 7032 battery monitor. Shunt installed in back of the battery box, which is underneath the step entry into the coach. I did the solar install. And the there is the alternator charging when on the road, which has the Intellitec components between the lithium bank and the AGM cab battery.

I plan to upgrade the Magnum to a 2000 watt unit at least.

[GeorgeRa]

Your custom profile on MRC50 is likely constant voltage and you must be monitoring SOC to terminate charging. I have the same inverter and as far as I remember it doesn’t have Li option.

Just to rephrase your question: You want to have Li charge controller between alternator and house battery bank, correct? As already recommended by Booster, with multiple charging sources your best option is likely a single charge control/termination system.

At most you have 40A on 2017 Sprinter, (Avanti – correct?), check on your Magnum monitor or Victron, is it really worth your effort for occasionally used engine alternator.

While you reengineering your RV, I wish you best enjoying your new RV as is, but, be careful with more and mighty power, it can easily go bum-bum.

[woundedpig]

You raise good points about the Magnum-
The Magnum ARC50 has a custom charging selection that allows a good lithium algorithm.

Per manual:
Custom selection allows you to individually adjust the Float (Range: 12.0-16.0V), Absorb (Range: 12.0-16.0V), and Equalization (12.0-16.0V) charge voltage settings and to set an equalization time for your batteries. Minimum equalization time 10 minutes, at voltage no less than the Absorb setting.
Of course, lithium batteries shouldn’t receive an equalization.
The Magnum inverter charger does not have a specific lithium algorithm, but the AGM2 setting charges the batteries fairly well, though most folks find a benefit from solar to finish topping off the batteries, because of a peculiarity in the default behavior of the Magnum.
Per the manual:
Once Charger mode has been enabled, the unit waits and displays “Charging” to determine the charge routine. If the DC voltage is low (≤12.8 VDC), the charger initiates bulk charging. If the DC voltage is high (≥12.9 VDC), the charger skips the Bulk and Absorb charging stages and go directly to the final charge stage (Float or Silent). So the Magnum assumes that your batteries are either AGM or LA.
I just use the AGM2 setting for the BB’s, because it will not overcharge, and I can use solar to top off the bank.

[GeorgeRa]

I have noticed similar topics on the Sprinter forum. Folks there often ask questions regarding feedback for their DIY electrical systems and some typical starting points are energy balance and a shot of actual schematic. What you listed is not a diagram of your system so it is difficult to provide a feedback. There are 4AWG wires connecting 200A relay, a mixed bag.

Due to capacity limitation of smart alternators there are folks turning to auxiliary alternators sometimes called under hood generators.
Assuming your modification questions are almost in line with DIY work I would suggest starting with:
1. Good energy balance, in and out of your battery bank.
2. Actual electrical or block diagram representing your plan.

[BBQ]

.

MB uses smart alternators.

not sure they have installed the same in the cutaway.
I don't see why they would make it differently.

[Boxster1971]

wonderpig - you may find these two technical bulletins from the Daimler Vans Upfitter site useful.

https://www.upfitterportal.com/en-us/

The first one confirms that the Sprinter alternator regulator is equipped with a LIN (Local Interface Network) interface. The characteristics of the LIN alternators are fixed in the engine control unit (ECU).

The other details how to add additional batteries to a Sprinter.

Enjoy,
- - Mike

[woundedpig]

Thanks, I was able to find those references yesterday. Not sure what to make of the 40 amp current limitation mentioned in the Additional batteries pdf. I've seen that in other posts on several forums. Is any B or C motorhome manufacturer in compliance with that spec with their coach bank? The Intellitec components in my Unity are basically a voltage controlled switch to make sure the chassis bank is charged and not drawn down by the coach power consumption. I can see no current limitation device on the schematic.
Can someone explain the implications of the Sprinter alternator regulator being equipped with a LIN (Local Interface Network) interface? With the amps output chart in the pdf on the alternator, should it not be possible to pass 60, 80 amps or more to a house battery bank. People who have installed battery monitors routinely report that level of amps going into their house battery bank, especially early on when significantly depleted, and especially with lithium banks.
Thanks for any thoughts. I wish I were an engineer and not a retired pediatric ICU physician sometimes- but only really at times like this. But it was fun taking care of all this kids for many years.

[BBQ]

.

You need a 2nd alternator. AKA the underhood generator.

Most of the RV use the stock alternator for trickle charging only.

[avanti]

Originally Posted by Boxster1971

The first one confirms that the Sprinter [SIZE=4][SIZE=2]alternator regulator is equipped with a LIN (Local Interface Network) interface. [SIZE=4]The characteristics of the LIN alternators are fixed in the engine control unit (ECU).

It is a bit more complicated:
It is true that Sprinters have had LIN-based alternators for quite a while now. However, they never did anything fancy with it until 2014, and then only with the 14 engine. It (and only it) comes with option E33, and has an "Intelligent Battery Sensor (IBS)", which monitors "various battery status parameters such as current, voltage and temperature of the vehicle battery." This is used to implement various energy-saving strategies, such as only charging the battery when the vehicle is coasting or braking.

As far as I can tell, you can get away with larger current draws with the V6 engine (understanding that you are violating an OEM spec). But when I tried to do so with my I4, the results were not very good. This led me to add a second engine alternator. Most of the upfitters are doing the same these days.