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

[woundedpig]

Originally Posted by BBQ

.

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

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

Help me to understand why you recommend this over a current limiting 80-120 amp B2B battery charger, for example - especially with a significant solar wattage.
I am aware of several folks with rather large lithium battery/solar installs where an auxiliary alternator was not needed. If a different battery chemistry is used for a large house bank, like AGM/lead acid, with much slower charge profiles, a second alternator makes a lot more sense as even a large bank of solar panels will charge these banks more slowly.
I'm not trying to be difficult - just want to understand

[woundedpig]

Originally Posted by avanti

It is a bit more complicated:
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.

Avanti, do you think that 600 solar watts, plus a B2B charger, could adequately support a 400 AH lithium bank in the 2017 chassis Sprinter with stock alternator.

"Sterling's recommendation :

Good rule of thumb for sizing charger to housebank is minimum 10% ampacity of HouseBank should match charger, 20% sweet spot, 30% max for customer using a lot of amps and requiring faster charging to get back to work:

10% of 400AH is 40 amp charger.

20% of 400 AH is 80 amp charger.

30% of 400 AH is 120 amp charger.

If you have 180 amp or more alt than u could go w/ 120 Amps of charging, or two bb1260 side by side.

I think a single bb1260 would be great choice for your setup."

[woundedpig]

Originally Posted by avanti

It is a bit more complicated:
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.

You may have missed a previous comment where I questioned whether there were any Class B, B+, or C mobile home manufacturers who don’t violate this OEM Sprinter spec with their stock lead acid or AGM bank.

Not sure about AdvancedRV or Roadtrek- auxiliary alternators are at least options on these, but ? Standard

David

[GeorgeRa]

I would suggest to do a balance sheet, how much energy will you be using per day and then start designing your energy sources. You mentioned microwave, will you use minutes or hours per day. I have 230Ah bank and can use microwave for my life style. Digesting your needs will make your design better.
A simple spreadsheet of your energy use per day will answer many of your questions, and only you can answer them.

[avanti]

Originally Posted by woundedpig

Avanti, do you think that 600 solar watts, plus a B2B charger, could adequately support a 400 AH lithium bank in the 2017 chassis Sprinter with stock alternator.

Dunno. Probably not if you have an I4. Alternator raw rating means little if the engine electronics don't let you use the amps.

But, I am a BIG fan of second alternators, especially if your travel style involves some driving every day. They are easy to add on the Sprinter, and will charge up your battery in a snap--rain or shine. 600 watt of solar is great, but I would definitely prioritize the second alternator over a large solar array. Even a short drive will give you a charge equal to a days solar, and far more reliably. Plus, it has the great virtue of totally taking the engine's possibly-finicky charging electronics completely out of the equation.

As for whether the upfitters are in compliance with the MB Bodybuilder's guidelines, I am really not sure what has been going on. I suspect that there have been waivers over the years, since I think the spec was historically pretty conservative. But with the modern energy management systems, the situation is getting a lot more dicy, which is one reason why second alternators are becoming more common.

[BBQ]

.

I am not sure if you are aware of the "Smart" alternator in MB.
How it works, and how it will affect your intended RV use.

I will explain it here for the benefit of the forum.

IN an effort to stretch the fuel economy of the engine,
and to give the "tiny" engine a bit "extra" power when needed,
MB would selectively shut off the alternator during certain situations,
and increase the output at other times.

For example, when you are standing at a traffic light and the engine is idling,
MB would crank up the alternator to extract as much juice from it as possible.
As soon as you lift your foot off the brakes,
MB would SHUT-OFF the alternator
saving all the engine's power for acceleration.

Other situations where the onboard computer would interfere:
Going down the hill with the brakes applied
Cruising a long stretch of highway with little load on the engine.
Going up the hill or tow-hauling
City stop-n-go driving
Your battery is full

Would this "smart" alternator affect your designed RV operation?
I don't know.

Many RV upfitters know that it would affect them. That's why they installed a second alternator so that they don't have to deal with MB's onboard computer.

[tgregg]

Woundedpig,

In an earlier post you mention that because of the existing wiring from the alternator the lithium batteries aren't receiving the proper charge voltage.

How do you know this?

In another post you mention you have a Victron battery monitor with a shunt.

How many amps does the monitor show the lithium batteries are receiving when the alternator is charging with the lithium batteries 80 or 90 percent SOC?

I have lithium batteries installed in my Promaster RV and I charge them from the 220 amp engine alternator. No solar.

It is normal when the alternator is charging at 14.2 or 14.3 volts as measured at the alternator that the voltage measured at the batteries is low to mid 13's depending on the SOC of the batteries.

Until the batteries near full charge. Then as the charging amps begins to drop the battery voltage will rise fairly quickly to the alternator voltage.

Then it's time to stop charging the batteries.

I do that by using a Victron battery monitor to disconnect the alternator from the house batteries.

If I understand your description of the Sterling B2B, they would float the batteries at some programmable voltage in the mid 13's. I don't know how they determine the batteries are charged and I don't know if floating your batteries is not harmful. You would have to ask Battle Born.

What are the voltages and charging amps you are current experiencing?

The 4 awg wire from the alternator to the house batteries maybe be causing a voltage drop that limits the amps getting to the batteries and that might be a problem if you install the B2B.

But that maybe how the RV mfg is attempting to conform to MB's 40 amp limit.

[avanti]

Originally Posted by tgregg

But that maybe how the RV mfg is attempting to conform to MB's 40 amp limit.

This is a good point. A lot of these systems aren't exactly designed by rocket scientists, and there is a fair amount of seat-of-the-pants engineering. Moreover, they tend to evolve incrementally over time. They start out with one battery connected to a "dumb" alternator via a long run of 4AWG. Works fine. Next year, they start offering an optional second battery. Meanwhile, the OEM has upgraded to a "smarter" charging system. Then the upfitter starts offering lithium, etc etc. Meanwhile, the 4AWG is still there, limiting current. Everything still works and maybe is even still safe. Is it optimal? Probably not. But just blindly upgrading the wire might be a bad thing.

I am NOT saying that that is what you are doing (just the opposite--you are trying to deeply understand your systems). My only point is not to place too much trust on industry standard practice when making your forward-looking decisions.

[woundedpig]

Originally Posted by GeorgeRa

I would suggest to do a balance sheet, how much energy will you be using per day and then start designing your energy sources. You mentioned microwave, will you use minutes or hours per day. I have 230Ah bank and can use microwave for my life style. Digesting your needs will make your design better.
A simple spreadsheet of your energy use per day will answer many of your questions, and only you can answer them.

You say you can use microwave for your lifestyle - do you?
What capacity inverter do you have and what is your battery chemistry?

Thanks

[booster]

I was going to not get involved in this deeper, but things are getting out of order and priority, I think.

I designing or modifying any power system, you really need to follow the logical steps needed to get what you want.

One thing that certainly needs to be done is to not base what you do on what the OEM class B builders do, unless you are also willing to accept their performance level. They have been sending out vans for years with substandard, underperforming, battery damaging, systems for years.

* As has been mentioned, the very first thing you have to do is determine how much power you will be using per fay, and how big any high power uses would be (AC, hair dryer, etc).

* Once you get a feel for the above, you can look at you camping style to see how charging systems of various typed fit what you need to do. How many days in a row do you stay in one place without shore power? Is there any driving during those days? How good are the solar conditions at the times and places you go to? How long, or short, are your typical driving days, and what part of the day is the driving (time of day can be important with solar)? How often do you have shore power? Do the places you go to have no generator and no engine idling rules? Are you OK with having your van sitting idling in a campground? Do you want a generator for general use, or for emergency backup?

Until all of these questions are pretty well tied down, it will be nearly impossible to make sense of what needs to be done, and at that point you can start to determine which charging methods will fit the best, and if you need to make any compromises in your wants.

Being already locked in to the drop in style lithium batteries will certainly limit some of you choices in equipment and such. Covering all the "best practices", at least the current ones, can be a very difficult task when using a collection of parts for different vendors, and this is especially true of lithium. Lithium has the, very different from other batteries, full shut off/rebulk when down charging profile which can be hard to get to play nice with things like solar that can overvoltage the system if they are disconnected from the battery reference. They also have the need to have shutoff recovery methods if the shut off from over/under temperature or voltage, and maybe heaters depending on where you are.

All of the above, I think, is why we are starting to see the intergrated systems like the new Xantrex (which we don't yet know how well it is done) or the central controlling systems that Victron appears to be selling now that all work together (I don't think anyone here has fully researched their capability yet).

[Davydd]

To answer some questions. A second alternator is an option for Roadtreks. It is standard for Advanced RV since almost the inception of the company 5 years ago. They have abandoned the Nations alternator for the Delco alternator. I've had both in my Class B and it is night and day. For one, fast and full charging at 280 minimum amps for a solid hour while driving. I have an 800ah lithium ion battery bank. I have full use of my B electrically 24/7 same as one would have if plugged into shore power. It is all electric including all 120v outlets, coffee maker, microwave/convection oven, induction cooktop and compressor refrigerator. No propane.

Advanced RV is going into their 3rd generation with the Volta 48v system. That alternator charges twice the rate what I have. Coupled with their new more efficient air conditioner I'm guessing they are attempting true alr conditioning all the time or close to it. It depends if they can now get through a night in a campground with restricted generator hours. The Nations alternator had a death spiral in that they determined in the field it could not keep up with the air conditioning. I don't use my air conditioning much at all so have no desires about needing it as I avoid traveling in the south in the summer. Maybe I will know more in May when I attend Advanced Fest. Right now I am not worrying about it. By then I will also know more about the new 2019 Sprinters.

When you have an 800ah lithium battery bank and fast charging, solar doesn't do much in the equation. It probably would when your RV is not in use and being stored. Now I store in a garage and am considering not installing solar on my next RV.

[GeorgeRa]

Originally Posted by woundedpig

You say you can use microwave for your lifestyle - do you?
What capacity inverter do you have and what is your battery chemistry?
Thanks

I have 230Ah lead acid AGM battery bank charged by:
1. Shore power/Magnum MMS1012
2. 300W PV/Morningstar MPPT charge controller.
3. Alternator via MB relay (modification coming).

Microwave is 600W unit drawing about 95A so 15 min run would reduce charge from 100% SOC down to 90% SOC, doable, but we camp, use stoves, barbeque, camp fire, not trying to extend household lifestyle to camping.

In recent years I noticed two fads in the RV World:

1. Li, more lithium, more volts, in my view it will stay with new adapters unless someone will come out with an integrated package which will not cost ½ of a new RV. Mickey Mouse style homebrewed installation can be very dangerous.
2. Compressor fridges, well proven in marine world (Danfoss), efficient, reliable, completely insensitive to level, this is not fad anymore, it will stay.

Enjoy you RV, learn what needs to be improved, stay away from jumping to conclusion mode (sorry to have some fun with the video), and get a compressor fridge if you don’t have one yet.

https://www.youtube.com/watch?v=xRxqY4wuTHw

[nebulight]

I wrote up a long post, but of course my PC crashed and lost my post. Bottom line is address what type of electrical needs you have before going crazy with your electrical system as others in this post have said. I did the math about using a microwave oven for 5-10 minutes on a 400ah pack which is around 5kwh of stored energy. Using a microwave for that amount of time with that large of a battery bank will have a tiny dent in your over all capacity of the bank. I have 400ah of lifepo4 and I use a microwave, induction cooktop and electric kettle for boiling water. I also have a solenoid to connect my house battery to the starting battery via a switch and I NEVER turn it on because my 300w of solar do a well enough job to recharge my battery even if I've got a few days of cloud cover because I won't be using near enough power to get the batteries to even half.

Now if you run your AC or any electric heat or hot water, then yes, having a fast charge alternator will help as those loads won't last very long on 400ah.

[Davydd]

We are using more and more the convection oven feature of our microwave as we get comfortable in its use. Also we just bought an Instant Pot and I predict it will get a lot of use as well. The induction cooktop is pretty efficient. You can boil water for instance a lot sooner than a propane burner. The FitRV had a video on this. Don't get me wrong. We still camp and grill outdoors on charcoal or over a fire. I've made pizzas in a Dutch oven on charcoal. Steaks, brats and burgers are still the best that way. We no longer use propane burner camp stoves because with a portable induction cooktop and Instant Pot we can set up outdoors and we have the electrical capacity. And if you want to use your home recipes, bake, slow cook and prepare dinners like home you are going to use a lot of electricity.

Also, having a large compressor separate door refrigerator/freezer becomes necessary just to store half gallon containers of ice cream and previously prepared pizza dough.

If you are full time or go out for more than a month cooking normal is priceless, IMO.

[GeorgeRa]

Originally Posted by Davydd

We are using more and more the convection oven feature of our microwave as we get comfortable in its use. Also we just bought an Instant Pot and I predict it will get a lot of use as well. The induction cooktop is pretty efficient. You can boil water for instance a lot sooner than a propane burner. The FitRV had a video on this. Don't get me wrong. We still camp and grill outdoors on charcoal or over a fire. I've made pizzas in a Dutch oven on charcoal. Steaks, brats and burgers are still the best that way. We no longer use propane burner camp stoves because with a portable induction cooktop and Instant Pot we can set up outdoors and we have the electrical capacity. And if you want to use your home recipes, bake, slow cook and prepare dinners like home you are going to use a lot of electricity.

Also, having a large compressor separate door refrigerator/freezer becomes necessary just to store half gallon containers of ice cream and previously prepared pizza dough.

If you are full time or go out for more than a month cooking normal is priceless, IMO.

Just to make sure OP understands that your high capacity system was done from the ground up by folks doing van conversions for living and have experience with Li systems. He is asking questions about modification from lead acid system, possibly dangerous if not done absolutely right. I am sure you don’t fear of fire in your van and you most likely don’t have a 4AWG charge wire.

[BBQ]

Originally Posted by GeorgeRa

Just to make sure OP understands that your high capacity system was done from the ground up by folks doing van conversions for living and have experience with Li systems. He is asking questions about modification from lead acid system, possibly dangerous if not done absolutely right. I am sure you don’t fear of fire in your van and you most likely don’t have a 4AWG charge wire.

>possibly dangerous

+1

... especially when some installations are getting up into the kilowatt territory. One tiny oops can zap you silly.

[booster]

You would not likely ever get "zapped" by any RV lithium system as the voltages are too low. You would have to be on the AC side, which we have always had to deal with. The danger comes from the large amount of amps, and their energy from those amps. Get a short across something and it can heat up enough very quickly to start a fire, or blister your hand if it is a wrench or jewelry. Internal shorts to any of the systems could also be source of fire if not properly fused and protected.

This does not change the fact that I agree with the warnings. With all the extra controls and hardware needed for lithium, you really do need to know what you are doing and make sure all the parts will work together properly.

[woundedpig]

Someone mentioned wiring size. What AWG is used from the alternator to the battery in the Sprinter? In my LTV 4 AWG is used from the starter battery to the voltage sensing relay (VSR) and then on to the coach battery. The total distance from battery to battery is less than 8-9 feet.
I'm still trying to understand this, but all the B2B charger manufacturers list wire sizing as an advantage to their systems because of the way the chargers work. Perhaps they mean on the house charging side, where voltage can be boosted to whatever the set algorithm demands, sort of similar to MPPT solar charger design.

The more I read about voltage sensing relays (VSR) and dual battery systems, plus smart alternators, the more it seems to me that VSR's have no place anymore in a more modern van electrical system. I still am unable to find out whether the current V6 MB sprinter engine has the same smart alternator technology as the I4 engine. As someone said, MB is not very much into sharing information. From the alternator document on the up fitter page, I know that the V6 has the 220 amp battery and that

"A new generation of regulators are used in the Sprinter. The alternator regulator is equipped with a LIN (Local Interface Network) interface.
The characteristics of the LIN alternators are fixed in the engine control unit – for this reason aftermarket alternators can not be retrofitted.
The only available alternator for the Sprinter starting model year 2010 is 220 Amp alternator (standard equipment).
No D+ (engine running positive signal) output is available at alternator with LIN Bus technology, only at the body builder connector EK1 (see Body Builder Book) under driver seat."


I am going to speak with both the Austin Sportmobile place in Austin and the MB dealership with the highest volume of Sprinter sales and support to see if I can l earn anything. Sportmobile says they do lithium installs, but only with auxiliary alternator setups. I'd like to know what they do in lead acid or AGM house bank setups.

Some more info that I found..

Nice piece on smart alternator/regen braking - some data collection on a 2013 Ford Transit. Wild voltage readings during the drive cycle.

https://photos.google.com/photo/AF1Q...S83-yi9CLBqbJq


https://www.12voltplanet.co.uk/auxil...ternators.html

https://caravanchronicles.com/2017/0...nd-motorhomes/


https://www.linkedin.com/pulse/intro...oltage-russell

[avanti]

Originally Posted by woundedpig

Someone mentioned wiring size. What AWG is used from the alternator to the battery in the Sprinter?

This strikes me as a dangerous question. I don't know what size it is, but if you are considering pulling anything like the number of amps for which this question might plausibly be relevant, you are wandering into territory best avoided.

In my LTV 4 AWG is used from the starter battery to the voltage sensing relay (VSR) and then on to the coach battery. The total distance from battery to battery is less than 8-9 feet.
I'm still trying to understand this, but all the B2B charger manufacturers list wire sizing as an advantage to their systems because of the way the chargers work. Perhaps they mean on the house charging side, where voltage can be boosted to whatever the set algorithm demands, sort of similar to MPPT solar charger design.

Just guessing, but many such systems have "sense" inputs that measure the voltage at the battery, rather than at the charger. This allows the system to automatically compensate for the voltage loss in the wire runs. This, in turn, permits you to downsize the wires, just so long as the ampacity rating is adequate for safety.

I still am unable to find out whether the current V6 MB sprinter engine has the same smart alternator technology as the I4 engine.

I am 99% certain that the V6 still does NOT have this feature. You can tell for sure by looking on your van's build sheet. As I said above, the feature code is E33. It will show on the build sheet if you have it. You can also look at the battery. Vehicles with option E33 have a sensor on the positive battery terminal (in addition to the squib on the negative terminal, which all modern Sprinters have).

As someone said, MB is not very much into sharing information. From the alternator document on the up fitter page, I know that the V6 has the 220 amp battery and that

"A new generation of regulators are used in the Sprinter. The alternator regulator is equipped with a LIN (Local Interface Network) interface.
The characteristics of the LIN alternators are fixed in the engine control unit – for this reason aftermarket alternators can not be retrofitted.
The only available alternator for the Sprinter starting model year 2010 is 220 Amp alternator (standard equipment).
No D+ (engine running positive signal) output is available at alternator with LIN Bus technology, only at the body builder connector EK1 (see Body Builder Book) under driver seat."

Yes. All Sprinters have had LIN-based alternators for a long time. That doesn't mean that they have done much with them on the V6.
Also, note that just because they use a 220amp alternator, it doesn't mean that they are expecting upfitters to take off large amounts of current. Those alternators are meant primarily to to support several large loads built into the Sprinter, such as the injector heaters and especially the electrical pre-heater in the HVAC system. The ECU knows when these loads are on and can use the LIN to nudge up the alternator output to compensate.

[woundedpig]

Originally Posted by avanti

This strikes me as a dangerous question. I don't know what size it is, but if you are considering pulling anything like the number of amps for which this question might plausibly be relevant, you are wandering into territory best avoided..

Good grief, Not to worry - my question was for my own edification. I just would like to know what is there