External Regulator on Chevy "Stock" Alternator

[phantomjock]

You asked for part numbers, I can provide links and pictures , if that is OK?

I was leaning to a Single Large Amp - drop in replacement Alternator. I knew there would be some significant wiring upgrades, and wanted to charge my battery bank that I had previously installed. My battery bank is 520 Ah. I have installed 2 260Ah LiFePO4 batteries in the former generator location. These are my house supply. The Inverter?Charger is a 3000W SunGold Power unit that has had some good reviews. OK, it is not a Renology, or other brand frequently cited, but I am comfortable with the choice. I did purchase the Inverter during their Chinese New Year sale for a good discount. https://sungoldpower.com/products/30...39652729979017

Also managed to get the batteries during a Christmas discount sale.
Also available at amazon; https://www.amazon.com/ECO-WORTHY-Li...7-eb60747b8daf

Battery Charging
In addrtion to the charger for shore power charging, I had removed a 400A Alternator to Battery Charger unit from our sailboat. It literally would act like a battery charger with the charging source - a 395A alternator. It had served us well onboard and I hoped would do the same in the van. I contacted the manufacturer (Sterling Power Products) and the owner advised against it. Yes, it would work well with AGM or wet cells, but not Lithium - CRAP! But, they had a new offering in their DC2DC charger lineup; a 200 Amp unit. I worked with Ben to confirm my build out, bank size, alternator size requirements, etc.. It was going to be a "Go" with a 400 Amp alternator as the output source (hot rated). It would supply the necessary 220 amps to the B2B at idle. https://sterling-power.com/collections/new-range-bb


The only caution I have on this item; it is shipped from the UK and you take about $300 hit in shipping and duty.


ALTERNATOR
I had been checking with a number of alternator companies, including the company often suggested here. I found the frequently recommended outfit unresponsive. Perhaps they don't like email? Can't say. Another was most helpful in helping me initially choose, but in the end were unfamiliar with using a B2B and "opted out." I finally settled on a company that answered email, had an understanding of what I wanted/needed, and helped me pick my alternator. https://www.phoenix-alternator.com/h...ut-alternator/
They have "drop-in alternators of various size." They have 2 locations in Arizona, Phoenix and Tuscon and are a family-owned business (my understanding).

While waiting for the B2B to arrive, I placed my order for the alternator.

https://www.phoenix-alternator.com/p...ernator/3-ORG/ I did the deed.

High Idle
I was interested in finding a high idle mod for my 2008 Express 2500. The alternator output can hit 220 amps at 1500 RPM, so I found and added a High Idle "kit" for my 2008/6.0L Express 170P. Was even going to consider building an Arduino mock up. But, found an outfit that specializes in just what I was looking for. InPower Electronics makes the ETM68A, Electronic High Idle Throttle:
For the GM/ unit - one is on sale on eBay (last one) it is good for Gas - or Diesel. NOTE: It connects through the OBD Port, so if you are using a scan reader, you'd need to swap out.

A lot of wire and connectors, minimum 2/0 for the setup and replacing the "Big Three" for the alternator to starter, start battery, B2B, then B2B to Bank, Inverter/Charger to bank, etc, etc..

My vehicle is a 170, so I give up some cargo space with the larger Inverter/Charger, even with all the original gear removed. What would I do differently? Perhaps select a 5000BTU Aircon, then decrease the size of the Inverter, maybe drop down to a 120A B2B, and downsize to a smaller alternator. These all would require some consideration and balance. The Balancing Act as I see it is; [bi]Consumption/Capacity/Charging[/b/i]. So, it becomes; Decrease the demand, Size the Battery Bank to meet it, Choose an alternator Idle/hot rated amps matched (or slightly greater) to the B2B requirement, the Alternator/B2B matched to the Battery Bank, and the Bank sufficient to power the Inverter of choice - which could be decreased with a smaller demand, and around it goes. At some point it is, "Class. Pencils Down."

As I mentioned previously, the Alternator/B2B combo works well, as does the InPower High Idle. We did some weekend camping and all went well. I have run the 8000BTU Aircon a test only (in the driveway). All items do the job, but have not checked the amount of time for air conditioning, before charging.

Hope this helps. Your mileage may vary. Best of luck.

Cheers - Jim

[booster]

Originally Posted by phantomjock

You asked for part numbers, I can provide links and pictures , if that is OK?

I was leaning to a Single Large Amp - drop in replacement Alternator. I knew there would be some significant wiring upgrades, and wanted to charge my battery bank that I had previously installed. My battery bank is 520 Ah. I have installed 2 260Ah LiFePO4 batteries in the former generator location. These are my house supply. The Inverter?Charger is a 3000W SunGold Power unit that has had some good reviews. OK, it is not a Renology, or other brand frequently cited, but I am comfortable with the choice. I did purchase the Inverter during their Chinese New Year sale for a good discount. https://sungoldpower.com/products/30...39652729979017

Also managed to get the batteries during a Christmas discount sale.
Also available at amazon; https://www.amazon.com/ECO-WORTHY-Li...7-eb60747b8daf

Battery Charging
In addrtion to the charger for shore power charging, I had removed a 400A Alternator to Battery Charger unit from our sailboat. It literally would act like a battery charger with the charging source - a 395A alternator. It had served us well onboard and I hoped would do the same in the van. I contacted the manufacturer (Sterling Power Products) and the owner advised against it. Yes, it would work well with AGM or wet cells, but not Lithium - CRAP! But, they had a new offering in their DC2DC charger lineup; a 200 Amp unit. I worked with Ben to confirm my build out, bank size, alternator size requirements, etc.. It was going to be a "Go" with a 400 Amp alternator as the output source (hot rated). It would supply the necessary 220 amps to the B2B at idle. https://sterling-power.com/collections/new-range-bb


The only caution I have on this item; it is shipped from the UK and you take about $300 hit in shipping and duty.


ALTERNATOR
I had been checking with a number of alternator companies, including the company often suggested here. I found the frequently recommended outfit unresponsive. Perhaps they don't like email? Can't say. Another was most helpful in helping me initially choose, but in the end were unfamiliar with using a B2B and "opted out." I finally settled on a company that answered email, had an understanding of what I wanted/needed, and helped me pick my alternator. https://www.phoenix-alternator.com/h...ut-alternator/
They have "drop-in alternators of various size." They have 2 locations in Arizona, Phoenix and Tuscon and are a family-owned business (my understanding).

While waiting for the B2B to arrive, I placed my order for the alternator.

https://www.phoenix-alternator.com/p...ernator/3-ORG/ I did the deed.

High Idle
I was interested in finding a high idle mod for my 2008 Express 2500. The alternator output can hit 220 amps at 1500 RPM, so I found and added a High Idle "kit" for my 2008/6.0L Express 170P. Was even going to consider building an Arduino mock up. But, found an outfit that specializes in just what I was looking for. InPower Electronics makes the ETM68A, Electronic High Idle Throttle:
For the GM/ unit - one is on sale on eBay (last one) it is good for Gas - or Diesel. NOTE: It connects through the OBD Port, so if you are using a scan reader, you'd need to swap out.

A lot of wire and connectors, minimum 2/0 for the setup and replacing the "Big Three" for the alternator to starter, start battery, B2B, then B2B to Bank, Inverter/Charger to bank, etc, etc..

My vehicle is a 170, so I give up some cargo space with the larger Inverter/Charger, even with all the original gear removed. What would I do differently? Perhaps select a 5000BTU Aircon, then decrease the size of the Inverter, maybe drop down to a 120A B2B, and downsize to a smaller alternator. These all would require some consideration and balance. The Balancing Act as I see it is; [bi]Consumption/Capacity/Charging[/b/i]. So, it becomes; Decrease the demand, Size the Battery Bank to meet it, Choose an alternator Idle/hot rated amps matched (or slightly greater) to the B2B requirement, the Alternator/B2B matched to the Battery Bank, and the Bank sufficient to power the Inverter of choice - which could be decreased with a smaller demand, and around it goes. At some point it is, "Class. Pencils Down."

As I mentioned previously, the Alternator/B2B combo works well, as does the InPower High Idle. We did some weekend camping and all went well. I have run the 8000BTU Aircon a test only (in the driveway). All items do the job, but have not checked the amount of time for air conditioning, before charging.

Hope this helps. Your mileage may vary. Best of luck.

Cheers - Jim

Are you going to just run some things on the inverter or remove the plug and wire in directly? We chose to wire the whole van off the inverter and it is very nice to have all the outlets come live on inverter sometimes.


What alternator speed do you need at the 220 amps. The spec says they will do something like 350 at "idle", but they don't spec engine speed, pulley ratio, or alternator rpm to get that so kind of a useless spec. In general, alternator companies lie and distort badly about idle rpm. DC Power rates at 2400 alternator speed at idle, which requires a 3 to 1 pulley ratio and 800 rpm idle speed. Our Chevy idles at 545rpm.


We have a 250 and a 280 amp alternator that are turned down a lot by the Ample Power regulator. We used to run two settings at 280 and 180 amps and at 545 engine rpm we would get 180 and 110 amps from the pair, to the batteries. They were also providing about 20 amps to run the van parts. They were turned down an lot as those alternators would do probably 450+amps hot at speed so 280 was loafing on max output.


I ask because big single alternators, especially in smaller cases like these are normally are very weak at the low rpms so they can get the high end very large. We are currently set at 120 and 180 amps on ours and both are about 105 and 130 amps at 545 rpm and 3 to 1 pullies.

[phantomjock]

Originally Posted by booster

Are you going to just run some things on the inverter or remove the plug and wire in directly? We chose to wire the whole van off the inverter and it is very nice to have all the outlets come live on inverter sometimes.

The same. When on shore power all the sockets are live. When on inverter, all sockets are live. The "pass thru" is a nice feature on the inverter. Our thirty years plus cruising and living aboard/abroad we have a habit of using the inverter "When/As Required." So the habit of turning it on for a microwave or laptop is nothing new. [The laptop is also setup for 12v. and the TV/Monitor soon.]

Originally Posted by booster

What alternator speed do you need at the 220 amps. The spec says they will do something like 350 at "idle", but they don't spec engine speed, pulley ratio, or alternator rpm to get that so kind of a useless spec.

Actually they do. I asked the question and they sent me a sample test sheet. Below is the serial number matched test report for my alternator:
I scanned it so I wouldn't lose it

Originally Posted by booster

In general, alternator companies lie and distort badly about idle rpm. DC Power rates at 2400 alternator speed at idle, which requires a 3 to 1 pulley ratio and 800 rpm idle speed. Our Chevy idles at 545rpm.

I won't engage in the truthfulness of specs or claims by manufacturers. As to correlating to engine RPM they were quite clear about it being 3:1 and when I checked our pulley - yep close enough. I'd need just over 700 RPM to be in a good RPM zone for charging the house bank.

Here is an ENGINE RPM vs AMPS based on my engine pulley and the actual pulley on the alternator:


Oops - I was going to add the Engine RPM to the chart - on my "to do list..."

My Chevy now idles at 1500 RPM (and can be adjusted downward in 3 steps) when I engage the InPower High Idle electronic throttle control. Your scan gauge occupies your OBD port. For our practice, I engage the B2B and the throttle control only when needed. When "underway" we turn it on and let it go. The B2B does a 3 stage drop down too, so it is not always "demanding" 200Amps.

Originally Posted by booster

We have a 250 and a 280 amp alternator that are turned down a lot by the Ample Power regulator. We used to run two settings at 280 and 180 amps and at 545 engine rpm we would get 180 and 110 amps from the pair, to the batteries. They were also providing about 20 amps to run the van parts. They were turned down an lot as those alternators would do probably 450+amps hot at speed so 280 was loafing on max output.

As you'd recall, I am quite familiar with the Ample Power gear having been an early adopter of much of their gear (1994 AFAIR) and then the SAR V3 in 2002. We migrated to the Sterling Alternator to Battery in 2014. With the SAR V3, the 395A + 180A did a fine job charging our 1200Ah AGM bank. When you say the "van parts," I assume you mean all the Chevy overhead, e.g., headlights radiator fan, dash aircon, etc when underway.

Originally Posted by booster

I ask because big single alternators, especially in smaller cases like these are normally are very weak at the low rpms so they can get the high end very large. We are currently set at 120 and 180 amps on ours and both are about 105 and 130 amps at 545 rpm and 3 to 1 pullies.

The nice thing about this alternator, it is a 12 diode, dual plate, hairpin wound unit. What does all that mean? I guess it improves the efficiency and cooling. As I read the literature. So should be better than a "normal" automotive alternator, I gave up a long time ago on the high priced Balmar units, thinking if I need to work an alternator, I could find someone - or do it myself.

Cheers - Jim

[booster]

That explains their 350 amps at idle when cold. With a 3 to one you would be idling at nearly 1200 rpm, well over double what the Chevy does stock. At the 545 idle speed you aren't even in the test range yet at something in the 1600s alternator speed. heavily under the knee on the curve and cold it looks like it would be about 120 amps at idle and probably about 100 hot. A pretty typical curve for a big output vs case size, I think.



The big question will be how hot it will get at higher loads, and at what temp they call hot and too hot. In the limited airflow of the Chevies I found that our alternators can run at low 40s% and stay under 200-210*F and that is where I want to be. Some claim running up the 240* is OK, but I just don't see us doing that if we want reliability.



The description closely mirrors the design of the billet style DC Power alternators and they look very similar also so they may be made by DC Power on private label which is not an issue for me as they make good stuff, if they are.



So that inverter charger has a hardwired passthrough and outlets? I have never seen on like that before as the outlets usually go away when they go passthrough. Does it also have automatic neutral/ground bonding when on inverter?

[phantomjock]

Originally Posted by booster

That explains their 350 amps at idle when cold. With a 3 to one you would be idling at nearly 1200 rpm, well over double what the Chevy does stock. At the 545 idle speed you aren't even in the test range yet at something in the 1600s alternator speed. heavily under the knee on the curve and cold it looks like it would be about 120 amps at idle and probably about 100 hot. A pretty typical curve for a big output vs case size, I think.

Acknowledged. If you want performance that only comes at higher RPM, you need to generate the higher RPM. There are options, and I believe we have found one and are happy with it - to date. Here is the chart I should have posted -


You may note, I could "almost get by" at normal Idle, with a reduced output to the B2B. And the B2B does step down, but I wanted to be able to jam amps on short recharge (up to the limits) to minimize recharge time.

Originally Posted by booster

The big question will be how hot it will get at higher loads, and at what temp they call hot and too hot. In the limited airflow of the Chevies I found that our alternators can run at low 40s% and stay under 200-210*F and that is where I want to be. Some claim running up the 240* is OK, but I just don't see us doing that if we want reliability.

While on the road driving from a weekend, I was pleasantly surprised to note 210F on the alternator and under 200F in the engine bay. I attribute that to the "moderate" FL sun (88F outside) and the electric fans on the radiator. It also included the mandatory stop and go through Destin beach traffic for about 45 minutes to get to a dump site. Can't say with certainty, more test and driving to prove it out. But pleasing nonetheless.
Bottomline,I picked this alternator for several reasons:

1. Product

a. Hot Rated
b. Designed for over double the output I required (so it is not "stressed")

2. Company responsive to my inquiry

Originally Posted by booster

The description closely mirrors the design of the billet style DC Power alternators and they look very similar also so they may be made by DC Power on private label which is not an issue for me as they make good stuff, if they are.

I don't know, I didn't ask, but rebranding is common among many automotive items. Their willingness to share sample test data and answer all my questions and provide a product at a fair price was enough compared to some of the others I contacted.

Originally Posted by booster

So that inverter charger has a hardwired passthrough and outlets? I have never seen on like that before as the outlets usually go away when they go passthrough. Does it also have automatic neutral/ground bonding when on inverter?

Grounding/neutral bonding yes and I'm not using the outlets (provided plugs) on the inverter, but the inverter to ac wiring. All the ac goes to the panel and the panel to the services.

Cheers - Jim

[booster]

That chart looks like it is for a 3.4/3.5 ratio pulley? That would be one small diameter pulley, I think. I was worried about the small 3.0 ones we have.

[phantomjock]

I will measure in the am - in the daylight.
Regarding the DcPower alternators - I did look at those too. Lower amp output (larger pulley on the alternator), higher price, and the output data was not available.

There are a number of purveyors of alternators at various prices and output. I was pleasantly surprised that the top ones I considered (and then I bought from) actually are hands on the gear in their facility. As was Mechman, another choice, I nearly went with.

Cheers - Jim

[phantomjock]

tillard23 -
I hope this is all helpful in your decision making.
Cheers - Jim

[phantomjock]

Real quick "numbers" update.
Main pulley (Crankshaft) - nominally 150mm OD
Alternator pulley - nominally 50mm OD
3:1 Ratio.

The purveyor of the alternator does caution that the pulley should not be changed out as it wont then produce the output. Yep.

I need to clarify the chart I provided. I did a test run and took the amp output indicated on the dash (digital- not Chevy) Shown here (at rest):

I used the Chevy Tach to get the engine rpm. Noted the details and "plotted" the output. The ratio works out to something other that the size relationship of 3:1, and I have no explanation for that - and given the results i have experienced, am not concerned. New belt is tight, battery banks charging, power output is good. Life is good.

BREAK. BREAK.

Regarding the Inverter/Charger. Thought about this on my pre-dawn walkabout. The inverter has a 3 position switch. OFF - self evident; CHARGE - for use on Shore Power; INVERTER - provides house ac power from house bank. When on CHARGE, the ac sockets are powered via the pass through.


Cheers - Jim

[booster]

Yeah, the ratio is a bit of a question, I think, as there chart where they show alternator rpm and engine rpm would indicate a 3.4+ ratio.


Measuring the diameters and calculating the ratio if tough with most any belt type as you don't know what the pitch diameter really is unless you know the allowance for that particular profile of belt. PD vs OD % changes quite a bit with diameter so with quite large and quite small pullies it is easy to be off by quite a bit on the ratio.


I generally will just put a mark on each of the pullies and rotate the crankshaft to see how many times the alternator or other accessory turns compared to the damper pulley. At work, we had pitch allowances for all our belts so we could predict how much actual rpm we would gain or lose by changing pullies and that made it so much easier.

[phantomjock]

All good points and true.
I'd hate to try and cut the output too "fine" and risk not meeting the charging requirements. I believe its better to have the alternator "loaf along", than count on getting what charging is needed at the top end only. Then heat, efficiency, wear on components all become a bigger issue.

Cheers - Jim

[tlillard23]

PhantomJock-- Thanks for the info ,very good!! Will take your (and Boosters) lessons learned and move forward.



* I have the stock alternator setup. for idle rpm, I afjusted the idle rpm-vs-temp table in HP tuners, added 25 to 75 RPM in the table at higher temp in P/N. Pulls a little more air and bumps up the alternator charge just a bit. Might be useful here too. I didn't raise the D, in gear, idle for obvious reasons.

[tlillard23]

Phantomjock - One more questio.n you said you would choose the smaller BTU air conditioner, ive been thinking 5,000 would be enough. are you running your larger unit on minimal cool, and still getting sufficient cooling? or are You only referencing the load/wattage reduction?

[phantomjock]

Originally Posted by tlillard23

Phantomjock - One more questio.n you said you would choose the smaller BTU air conditioner, ive been thinking 5,000 would be enough. are you running your larger unit on minimal cool, and still getting sufficient cooling? or are You only referencing the load/wattage reduction?

Todd -
For the most part I would consider that based on the "computations" not experience. We haven't been out in the van since we've hit the high 80-low90s + humidity due to other ongoing projects. The numbers almost suggest a 3000BTU unit would be adequate - but sometimes more is better.

If one could get by with lower aircon BTUs, then the remaing services would be the microwave, and perhaps a coffee pot, etc. All these need to be calculated then balanced with inverter/battery bank/solar(?)/alternator/generator/etc..

Once I have some aircon "data" I could answer better. Outside air temp, inside temps (before & after) aircon run time, watts consumed, recharge time, etc. We don't really plan on RV Parks, but more isolated locations, and would accept low operational use of the aircon as a trade off.

From a thermo perspective, a larger BTU aircon should cool the cabin perhaps faster. But when off, the heat transfer through the "tin can" would be the same, regardless of the BTUs of the unit. I suspect the duty cycle of a smaller vs larger unit would be different in terms of watts. That is where the trick may lie.

Cheers - Jim

[booster]

Originally Posted by phantomjock

Todd -
For the most part I would consider that based on the "computations" not experience. We haven't been out in the van since we've hit the high 80-low90s + humidity due to other ongoing projects. The numbers almost suggest a 3000BTU unit would be adequate - but sometimes more is better.

If one could get by with lower aircon BTUs, then the remaing services would be the microwave, and perhaps a coffee pot, etc. All these need to be calculated then balanced with inverter/battery bank/solar(?)/alternator/generator/etc..

Once I have some aircon "data" I could answer better. Outside air temp, inside temps (before & after) aircon run time, watts consumed, recharge time, etc. We don't really plan on RV Parks, but more isolated locations, and would accept low operational use of the aircon as a trade off.

From a thermo perspective, a larger BTU aircon should cool the cabin perhaps faster. But when off, the heat transfer through the "tin can" would be the same, regardless of the BTUs of the unit. I suspect the duty cycle of a smaller vs larger unit would be different in terms of watts. That is where the trick may lie.

Cheers - Jim

There have been quite a few different discussions on various forums and lists about how much AC you need in a Chevy Roadtrek. It will vary a little from being a specific model, 170/190/210, and also on the van color though I am sure.


Some have gotten by on smallish units in 5-8K range but many others have said it just isn't enough if you live in the south, and especially if it is a humid region. I think some may have to do with how you plan on using it also. If you want to be able to cool the van down so you can sleep but just pulled into a site when it is 90+ and humid with a van that is very high thermal mass and very hot, you need as much AC as you can get. If the van has been sitting in the shade, not so much.



Our Coolcat still works fine and we just did the pull in and try to cool the van after a 320 mile drive in over 100*F. We pulled in at about 6pm and got part of the van in shade because of the low sun by then, opened the hood to let it cool better (that really helps but the latch can burn your fingers) and ran the AC until 9pm with got it to about 72* in the van. Shut it off and went to bed, but by midnight it was in the low 80's in the van which was hotter than the outdoor temp at the time. Big, hot, heavy tin can that really holds the heat.

[tlillard23]

Phantomjock - Booster -- with all of these upgrades are you still using the factor battery terminal? or something like stinger ‎SPT55302 *cheap Chinese battery cable connector I found.


*edit - although the starting battery really isn't getting much current, just wondered if the factory terminals were a failure point

[phantomjock]

From a cruising/racing background, I prefer using high grade wire ($$$) and terminal ends. I use a hydraulic press to install the terminal ends, or for larger than 2/0, the "beat-to-death" clamp-tool. You can find/use welding cable too. Its flexible and priced mid-range.
Some areas still get automotive grade wire if that is all that's on the shelf, but then I oversize. [automotive grade - not tinned, subject to corrosion]
There are extensions you can purchase for the side mount start battery. I built new ends and use those to accommodate an extra cable.

Cheers - Jim

[dicktill]

Originally Posted by phantomjock

From a cruising/racing background, I prefer using high grade wire ($$$) and terminal ends. I use a hydraulic press to install the terminal ends, or for larger than 2/0, the "beat-to-death" clamp-tool. You can find/use welding cable too. Its flexible and priced mid-range.
Some areas still get automotive grade wire if that is all that's on the shelf, but then I oversize. [automotive grade - not tinned, subject to corrosion]
There are extensions you can purchase for the side mount start battery. I built new ends and use those to accommodate an extra cable.

Cheers - Jim

For all my large DC circuits, I use and swear by:

1) Ancor (or similar) tinned marine wire: e.g. https://defender.com/en_us/ancor-mar...3724&615=36068

2) FTZ terminals which allow double crimping: e.g. https://shop.sailboatowners.com/prod.php?2502

3) proper FTZ crimping tool: e.g. https://www.ebay.com/itm/26628217912...3ABFBMwrTOxqdi

4) ... and a couple of layers of heat shrink tape (preloaded on cable before adding terminal)

P.S.: I also use Ancor triplex wires for all the AC circuits: e.g. https://www.zoro.com/ancor-triplex-c...20non%20zombie

[tlillard23]

PHantomjock - maybe I missed it, what are you using for the B2B and does this alternator play nice with the starting battery? what electronics do you need for that?

[phantomjock]

PHantomjock - maybe I missed it, what are you using for the B2B and does this alternator play nice with the starting battery? what electronics do you need for that?

Todd -

I'll try to answer the question without getting into my approach as a system of systems: Consumption, Capacity, Charging, Components, Connections, and of course - Costs.

The quick answer is:

Our House Bank is 520Ah. It is supported by a 200A Sterling Power Products B2B (model BB12200) https://sterling-power.com/products/...42182886850749
The alternator is 420A (Hot Rated) 12 Diode, hairpin, and idle speed for charging while in camp is set using a High Idle kit. Our system does not include solar or a generator (GenSet).

Some details on our choices to ensure the alternator plays nice with both house and start battery banks. It depends on the size and type of house batteries. As I understand the physics, each has its pros and cons. Our use plan is based on dry camping with no external charging (shore power). If you use a GenSet or solar panels - those devices could change the approach.

AGM and Flooded batteries:

1. Dual alternators with smart regulation: Each charges a bank independently. Many proponents point to the [i]safety of redundancy/i] as an important feature. In the Chevy RT, the second alternator installation is a PITA.
2. Single Alternator: An HEHR/Powerline Isolator/Combiner works, as in the original RT installation. A better option is removing it and using a Blue Sea ACR. The ACR is fairly simple to install. The pass through of wire through the firewall can be complicated - but it’s do-able. An advantage of the Blue Sea ACR is its ability to jump the start battery from the house bank. Also, you can run it in automatic or manual mode. I found it useful, but no longer use it in my new configuration.
3. Alternator sizing: Alternator size will determine how long you'll need to run the engine to recharge the AGM/Flooded batteries. Be sure to use the "Hot Rated" output to maximize the charging profile and duration of output over time. NOTE: the charging profile of AGMs is such that the last 10%+ is slow going and to top up to 100% will take a while. Solar would help that top up to happen.

Lithium House Bank:

1. Dual alternators and smart regulation can have a place in this application. Just ensure the second alternator (house) has the capacity to fill the charge-demanding lithium bank. If the bank demands more than the alternator can give, alternator burn-out can occur.
2. Single alternator: the focus of your Battery to Battery question. Our setup is a 520aH lithium bank and 420A (Hot Rated) alternator. We use a 200A Sterling Power Products B2B. With the High Idle kit, we can output 200-220 amps from the single alternator to charge the lithium house and sealed start battery banks. Once topped up, the B2B goes into stand-by and you are done.
A B2B charging device does all the magic. But, not without matching all the components. It provides a charge to both the house and starting battery banks, with initial priority being the start battery. Then, when the start battery is full, it internally switches all output to the house bank. NOTE: a lithium battery will take all the alternator can give and if not adequately sized, the alternator will burn out. So, if you are recharging at idle, you need a hot rated alternator to ensure it has the minimum output required for your lithium bank.

More information than you requested, but I wanted to clarify as best as I could and maybe answer other questions at the same time. Based on my observation and installation, YMMV. Hope it proves useful. I have some images in the previous pots on this thread than may help this "word picture."

Cheers - Jim