How Much Alternator Current Does The Engine & House Batteries Receive When Driving?

[imnprsd]

Mongobird: Thank you!

I would like to mention that I did try to install LED headlights, but I did NOT find them much better than my OEM headlights.

Then I installed the Sylvania "Ultra" Halogen Headlights and that was 200% better when it comes to lumens and "white light", but apparently take ~7A more amps for 2 bulbs. I thought this might me "recoverable" if if install LED Headlights, but now I think this is a mute point.

...Further, I doubt a 7A saving will extend the life of my alternator.

The alternative is to disconnect my DRL all together, and I do not want to do that for road safety and legal reasons, even though this option is still tempting.

So what's all this banter about? ...Well, my thinking was that if I installed LED lights then my alternator might last longer, and more importantly that would free up more current to flow to my house batteries. ...But now I believe this is definitely "over thinking" things a bit too much.

I mean, if my alternator is only putting out between 1/4 and 1/2 power... and is never running at max 160A output, and more like 45-60A, then saving 7A for two LED Headlight bulbs is mute, since I am never over loading the alternator.

Moreover, I have 400w of solar panels on my roof, and these panels output out an average o f 100A/day (Sun shinning of course)... so this this swamps my concerns about optimizing alternator current to more effectively charge my house batteries.

So you may ask, why am I so concerned? ...And my answer would be: I have a residential refrigerator, so whenever I shut off my engine I would like to think my house batteries are at 100% SOC. ...This is so I can get through the night, in a rest stop, or Walmart parking lot, or other abode, when I run my heater-blower or CPAP, and then continue on my way the next days so I can do it all over again!
Note: I travel 7K-10K miles every year so I have many overnight stays; and battery life if very important to me.

So apparently this experiment is concluded thanks to Mongobird and DavidM's comments.

Muchas gracias! ...And mahalo!

 

[Mongobird]

In my opinion, certain things are worth the price. Daytime running lights are definitely one of them from my perspective. The life cost of running them in terms of additional fuel, wear and tear on the alternator, and light bulbs it's relatively small compared to their seeming intangible benefit. One accident, even one panic stop, pays for it all.

From the standpoint of assuring a full charge on your house batteries, and your concern about that, I would look first to a smart charger which provides the profile needed for your house batteries and manages their charge. The second order enhancement I would probably make would be in the house batteries.

There are some other things you could do, particularly if you had or electrical experience than you do. For example there are relatively inexpensive power meters which I have seen on eBay, which provide monitoring of voltage, current, power being consumed, and total power being consumed. They're available in an AC and DC configurations, and I have two of the AC ones on each leg off my ground source heat pump at home. That way I can monitor how much energy I am using on my heat pump which is the largest consumer for the house. For nine years I have run my entire house and it's entire heating and cooling load off of solar power. I'm still grid-connected, and have net metering so I use the grid like a battery for the power. Technically I have two service entrances for my system, so I thought it would be easier just to monitor heat pump power consumption.

I understand the problem you want to solve, and rather than one things that you can do solving the problem, I think it would be better for you to understand electricity, the batteries, and how everything works. That is a tall order, and if you work at it casually it may take some time.

The first thing you could do is to start a log showing you're driving conditions, time spent enroute, speed enroute, house loads, etc.

You should also characterized your loads. For example your refrigerator is your big power consumer. What is the peak power draw, what is the average power draw over time given weather conditions, etc.? Keep track of additional loads on the system like running the chassis air conditioner while traveling on the road.

As you start to gather more data, and get better measurements on your current draw, and so on gaba you will get a better feel for things. At some point your concept around the use of different appliances, the amount of charge you got from the sun, and so on will become intuitive.

In my case I was studying this stuff since I was 10 years old, but it is something that someone can acquire casually, but with effort offer a much more reasonable period of time. However by continuously learning, we all enhance our neuroplasticity.

 

[imnprsd]

Actually, like most RV systems, there's not much you can do to improve on the OEM solution.

For example, I tried LED lights and did not like them. Instead I increased the power to 55W so I can see better. This defeated my goal to reduce amp use, I know, but as you implied... safety is more important.

And "no," I will not turn off my DRL... especially now that you and other have helped me understand the true load on my alternator.

And I can live with the concept of "living with what I get..." out of the engine alternator, which again is not limiting for me since I have 400W of solar on the roof. If anything, I'm concerned my house batteries are getting charged too fast.

So after thinking about the theory of how all these power grids play with one another; and now they you and others have help me sort our a few fundamentals that slipped between the crack in my head; about 1 month ago to did what you recommended... I upgraded my shore power charger to a 17A Victron Bluetooth Charger. And now I use it instead of my Dimensions Charger when I have shore power; and I am also using it as a battery maintainer when my RV is in storage.

Adding a "smarter" charger is not exactly the subject of this thread, but I'm glad it came up, because I think it's also possible you can over charge your house batteries when your alternator and your solar power is working a peak efficiency.

And I think this situation can occur when you hit the road in the late morning or afternoon with a 40% SOC battery; and full sun powering up your solar panels to a full 18A of charge current.

Now... I might be talking out of school here, but this explanation may be the reason why my house batteries appear slightly deformed after 2 years of use? ... But again, this is just a guess.

One battery person to told me: If your batteries have bulges on the sides it's because you are over charging them, but if they are bulged on top it's because they froze during the winter. ...Is this true in your opinion?

 

[Journey cat]

Im running an 05 Winne , Journey .
Frig is run off propane .
Basically just looking to keep house batteries topped off.
From use of lights and radio ect
Ive looked at the Key Line it is rated to be 140 Amp Dual Battery Isolator is IP65 Certified
And priced at near $100
I also cane across this model " SWITCH CLUB "
for only $40 both have the same rating and sealed bottom

https://www.ebay.com/itm/12V-140A-S...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

I tought id ask if there would be any opinions of which would be the better or the same , mouse trap ?

 

[imnprsd]

Should I Use A Battery Combiner Device or VSR?

The goal of these battery combiners or VRS are to ensure your house batteries are fully charged when you get to your camp spot.

So if you are finding your batteries are not at peak SOC then maybe adding one of these devices will work well with you.

I think it was Mongobird or DavidM who said he would prefer not to use one of these devices, but he did not say why? ...But maybe now that we are addressing this subject directly we can learn more.

In my case, I talked to Keyline 5 years ago when I wanted to know more about their product. And since installed it everything has been working just great.

...But I called Keyline again in June-2020 to ask about the competition in the market and why prices have dropped 40%? ...And Keyline explained their patent expired and they did not renew it.

So that explains why you are seeing are Keyline "knock offs" and lower prices, even from Blue Sea.

I checked the Amazon reviews and there seem to be enough favorable ones to warrant a purchase, but what if these are solicited reviews and not from customer like you and me.

Keyline's VSR price is $85 without the battery cables, but that's still $46 more than the Knockoff price of $39. What you don't know is if the circuit board inside is quality controlled in the same way as the Keyline VSR? It might be and it might not.

In 5 years I have driven over 40,000 miles in my DP with the Keyline VSR with no problems whatsoever. So that's the only testimonial I can give you.

Note: You do know there are tons of so called Cummins OEM parts available on the internet, in Cummin's boxes... that are not approved Cummins supplied parts. I.e., these very same parts that look the same on the outside may not have passed Cummin's QA.

So when you buy direct from Cummins, what you are really buying, besides the part, is the assurance (or insurance) Cummins as qualified their supply chain.

Personally, I think you should stick with either Keyline VSR or get a Blue Sea battery combiner vs. the $46 savings. But I also thing your knock off will work fine, because I don't think this device gets hot. ...Now vibration failure is another concern. To bad you can I can't compare Keyline's circuit board to the knockoff? ...But what you can do is call Keyline yourself and ask them why you should buy their product over the less expensive knockoff?

https://www.keylinechargers.com/collections/all

Keyline Technical Support: (800)435-1072

 

[Journey cat]

Thanks , I have not heard of the Blue Sea either .
Ive been on the fence if I REALLY , need one though .
AS I do run the Gen set every now & then and have not ran into any other problems with batteries .
Once or twice Ive used a pre made jumper to go from Positive of both banks for a few hours or so while driving . Although , give this some serious thought !

 

[Journey cat]

Ive been doing some homework on the topic .
Ive read about the Blue Sea and a BIRD
The bird may be a more sophisticated unit
Although it falls , price wise in the middle of the other choices .
That said it's used by the coach builders .
It would be nice to know the house batteries are always charged proper .
Any comments on the BIRD ? Or should I just stick with using a KeyLine unit .

 

[Journey cat]

IMNPRSD ,
Thank you for the heads up on this devise .
I purchased one . All i have to do now is install it .
I have wanted to do something like this for some time now . Im sure it will make an improvement !

 

[imnprsd]

You are welcome.

Other Tips:

* I attached several feet of solar wire (6AWG I think) to each Keyline post, but did not clip the length to fit. (Not yet.)

* I installed the Keyline to the sidewall in the battery bay. The screws poked out the other side, but I saw no problem with that.

* You then pull out your battery tray and cut the wires to their proper length. Note: The excess wire will drape in front of both battery banks, which is just fine.

* Remember to attach to only the (+) terminals, but not just any (+) terminal in the bank. You want the same terminal your alternator connects to on the engine/chassis battery bank; and you want the same terminal your inverter/charger connects to on the house battery bank. Note: There is no negative wire!

== END.


Suggestion For The Road: I carry a 3' long battery cable with me for back-up. Why? Well, one day my alternator failed on the highway, and after my alternator light turned on, and I pulled off the highway... and my engine stalled-out. Why?

Answer: The shorted diodes in the alternator sucked the life out of the chassis batteries, to the point there was not enough voltage for the ECM.

...but when I attached the single 3' long battery cable between my chassis and house battery, it effectively worked like the "Boost Solenoid" that is "on" all the time.

...I started the engine and drove 50 miles to a repair station to get my alternator replaced. So that 3' battery cable saved me from a tow!!!

Note: I think at that time I had 79,000 miles on my coach. (Which is typical useful life for a Leece-Neville/Prestolite alternator from what I hear.)

==> So while I would not suggest everyone carry a spare alternator, I do highly recommend you carry 3' long battery cable ($12 or less at Walmart) to jump your house battery bank to your engine/chassis battery bank in time of need.

 

[Mongobird]

...but when I attached the single 3' long battery cable between my chassis and house battery, it effectively worked like the "Boost Solenoid" that is "on" all the time.

...

==> So while I would not suggest everyone carry a spare alternator, I do highly recommend you carry 3' long battery cable ($12 or less at Walmart) to jump your house battery bank to your engine/chassis battery bank in time of need.

I had the alternator die on my 2004 Meridian driving it home several hundred miles after buying it. I used the boost switch. Boy was my left arm tired from holding it. A mechanic at Freightliner told me people shove toothpicks into the switch. It was a new rig to me, and I had no tools or anything else. I now have a popsicle stick I could adapt if necessary.

Regarding the 3' jumper...I think it's a good idea to have any kind of jumper, but I would be reticent to drive around with something which could pop off and hit the chassis and ground out the house batteries.

Duct tape might be helpful.

 

[Journey cat]

I also carry a 3 foot battery cable for just that purpose !
I appreciate your information on installation.
Being me I was thinking , mind you . Of , on my 05 Journey .
With circuit breakers and solenoids up front over the generator.
To install it there as it would offer added protection to the elements ,
BY taping on to the Aux solenoid as both banks terminate there and the wire back to the batteries is - LARGE .
After reading your info I do think Ill do it your way also , which was my original thought . As I wanted to eliminate additional wire in that area .
I just gave it a second look and other than additional wire , there is plenty of room to do a neat install.

 

[imnprsd]

Alternator Video

I found this video posted by CreativePart in another thread about alternators and Lithium Battery charging, but it also answers some general questions realative to this thread.

I particularly like the comments about alternator only being 50% efficient, but the video also went on to say ~50% of the inefficiency is lost to heat.

Consequently, this implies a 160A rated alternator is only good for about 80A. This seams to jive with what other people are saying, but apparently deep cycle lead acid batteries inherently "limit" the charging current, unlike lithium batteries, so the heat loss is less in lead acid batteries.

So, I think this video is saying you can't just flip over to lithium ion batteries without considering what affects that upgrade will have on your alternator. (I hope I said that right?)


Thanks CreativePart!

 

[Mongobird]

There's a trade-off between efficiency, longevity, and cost.

Most automotive alternators are about 55% efficient. Some are 60. This is using contemporary data for cars in about the last six model years.

It is easy to build alternators there are up to about 90 to 95% efficient, however the windings are much denser, and their reliability and longevity in automotive or RV applications takes a hit.

An alternator is merely a power source. They're not really designed as battery chargers, although they are used as that. AGM and flooded batteries tend to increase their charge impedance, reducing charging current, as they get to a higher charge state. Most lithium battery packages do not, and it is actually a desired attribute for them to have a low impedance all the way up to a full charge.

Solar charging lithium ion batteries presenting a low impedance to the power source, namely the alternator, can lead to overheating as the previously mentioned video shows, when the system it's not designed to match the power source with the power sink.

They changing impedance profile of AGM and flooded batteries is also a factor in not getting them fully charged during short run times. The amount of power which they will accept steadily reduces as they get closer to fully charged.

Lithium ion chargers are designed to counteract this and take advantage of the battery chemistry to keep power acceptance at a high rate.

As a side note, the design RPM of an alternator and engine can be modified. Usually this is accomplished with a different sized pulley on the alternator. I have done this on rally cars, and on ag equipment. Usually an alternator spinning at higher RPM will wear out the brushes faster, however there are more expensive brushless designs available. Piston engine aircraft with gasoline engines oh, it is easy to size the pulley because the engine RPMs are relatively constant and the alternator can easily be run in a range to optimize cooling and efficiency. Turbine engines tend to use a different arrangement, normally with a DC starter generator, which is a completely different design. aircraft have the advantage that they power plants typically run in a very narrow range of RPMs while cruising.

Back to RVs. If one wants to optimize charging when using a generator or traveling on the road using the propulsion alternator, it would be highly desirable to use a smart charger which modifies the charge profile optimize power absorbed by the battery, and longevity of the battery. Given different battery types, varying temperatures, and varying engine speed, it is difficult optimize battery charging with conventional alternators.

 

[Journey cat]

This is all very interesting .
I chose to retain the original style Battery's .Group 31 Wet cells
I find them ample for my needs and pocket as I keep a close eye on maintenance

I took your advise and mounted the KeyLine in the battery compartment . Using marine grade cable I had from boating days . I chose to use two colors , Red going to the Start bank and Green to the House bank . To eliminate future confusion of which goes where .
Its going to take some time to get familiar with its operation though .
I need to mention , I use a Deltran 5 amp tender when coach is not in use .
That being said , It charges when , Engine is running . And both banks were at float level .
So I turned on the inverter , run the microwave oven for a few minutes . Turn on the TV for a few hours also to lower the level of charge on the House bank .
Al is well at this point .As Im getting familiar with its use .
A couple days pass and I decide to use the Tender to on the Start bank only .
Low and behold when House bank reaches cut in level . Red light of KeyLine
came on . Sort of like 2-4-1 charging of the Tender !
IM sure it all well , and do believe KeyLine will be a good item to have on the coach .

 

[imnprsd]

2-4-1 charging

Absolutely!

This is one reason I installed the Victron 17A (not the 25A option) so it can act as a battery maintainer for both house and engine batteries a la Keyline VSR (Voltage Sensitive Relay) that combined both battery banks together in storage and when I am camped with shore power. ...I just fish the Victron power cord out the bedroom window... and plug the window gap with a towel... and plug the Victron into shore power.

That said, when I'm camping with shore power, I turn "off" my Dimensions Inverter/Charger and plug the Victron 17A charger into my bedroom wall socket. I'm trying this out to see if my house batteries will last longer; and I have since come to understand a 17A charger over 3 days will fully recharge my 430AH of house battery storage bank AND take care of the 120AH/day I am using to power up my fluorescent lights in the galley and living room, and the 12V bathroom lights.

Note: They now sell LED-round bathroom lights for cheap, so that is going to be my next upgrade; and then I will replace my 3ft kitchen fluorescent lights with LEDs.

And when I need 100A of battery charger, for over night charging, then I will turn my Dimension Inverter/Charger on and unplug the Vicron. (Which is almost never for me.) So by NOT using the charger in my Dimensions Inveter, I hope to extend the life of this unit and avoid a $2500 bill to upgrade to a PSW inverter/charger I really don't need. So the Victron is also insurance against premature inverter/charger failure; and I'm pretty sure these Dimension units only fail on the charger side 95% of the time.

As a bonus that Victron also gives me a bluetooth cell phone App I can use to see how many amps my Victron is putting out over time. And this is nice to know too.

My point is that... Yes, my residential refrigerator uses a lot of amps/day, but so does all my 12V lights I did not consider before I installed the Victron for ~$140 on Amazon. So you can think of this Victron as a super-duper battery tender, plus bluetooth! So that's a 2-5-1 deal and so far it's working out great!

 

[Journey cat]

That Victron is nice unit !
I already have the golf ball sized LED's in the Bath room over the sink .
And have LED's in most all other places also.
Frig is on Propane except when on shore power .
Yup we have to baby that Dimensions unit for sure .
Purchased 5 new Batteries in January . I had a mix of old & new before and want to keep them in the best of shape .
I do watch some TV at night , after my other half goes to sleep . And in the AM I use the inverter to make coffee , ect.
And the KeyLine will take care of the Batteries , as I hit the road !

 

[Journey cat]

IMNSPRSD
In regards to use if a KeyLine . Which I know you have for several years .
I came across this comment .
What is your opinion on this statement .

Those KeyLine Chargers or only good to connect to start batteries together. They have no way to control the current to the second battery. 140Amps is to much current to charge deep cycle batteries, also if your idling when you start up it will overheat your alternator .

 

[Mongobird]

So a little independent from this thread I have been pondering my 04 Meridian electrical system.

It turns out that I have a high end aftermarket charger installed by the first owner of the rig, and that was disconnected. It is a quasi smart charger. I like the newer ones, so it may not get used. I am thinking about that.

In the 120 volt area, I found to my chagrin that the engine heater runs off the inverter if turned on, and shore power is lost. So that can wear down your house battery.

It also turns out that the main breaker on the main panel will not stop that from happening.

Along with this, I found that even if the main breaker is off, and the AUX BATT is off, there are still things which draw significant power. The microwave, anything plugged into the 120 v circuit for the microwave including the engine heater. Yep that engine heater bothers me.

Another thing that bothers me is that running the generator will not charge the chassis batteries, in the stock wiring configuration. There is an easy work-around. The Boost momentary contact switch will put the house and chassis batteries in parallel. Not a perfect configuration, but it allows charging of the chassis batteries while the genset runs, which I think is a good idea. As for the momentary aspect of that switch, I found that a tie wrap shoved under the switch works great, and removes easily, and is readily noticed. I also contacted Winnebago and was told that the contactor (relay to some) controlled by the Boost switch is rated for continuous duty.

So for near term, I will use the Dimensions to charge the house battery, and jury rig a smart charger to keep the chassis batteries charging when desired. Most of the time.

Since I still have AGM (house) and flooded cells (chassis), I can readily bridge the battery systems. Probably not a good practice with LiIon chemistries. But I don't have to deal with that right now.

The chassis smart charger will also run when the genset is running to charge the chassis batteries. I like that better than just letting the chassis batteries die down over several days until the propulsion engine gets fired up (an then perhaps needing a Boost switch activation to get it going).

Also to aid in starting, for now, I am trying to remember to use the Boost switch on initial crank.

In the end, I want smart chargers, which will properly condition the respective batteries. I also would really like a charger charging the battery, rather than the alternator. That would be better for any type of chemistry. I just don't know the end-game so I don't know what my end solution will be.

But the prior owner said the batteries were 3 years old, and that was last year. So if his information is accurate, they are 4 years into whatever life they will have, and time will show what plays out. Meanwhile I am trying to be prepared for different chemistries, and I am trying to better understand things that do not make allot of sense to me, like running a 120V engine heater off an inverter. If it's that cold, perhaps the genset should be fired up for preheat and to top the batteries (with the Boost switch forced on) for the start.

Unfortunately, I have flown planes which have much more complex electrical systems, so I have little to complain about.

 

[imnprsd]

Mongobird: I can't follow your thoughts this time. All I can say, FYI, is that I used to own a Beach Baron B-55 and K-model Bonanza and these small planes the electrical systems were primitive if you ask me. (Radios don't count.) So I guessing you were a professional pilot?

...Which would be something, because typically a pilot can't fix anything, and you sound like you can fix everything. So good show!

JourneyCat: About the Keyline 140A rated Voltage Sensitive Relay (VSR) aka battery isolator. This is how I think it goes:

* The Keyline is a passive device. It only acts like a switch. A smart-relay if you will. But what magic is does inside the box is why you can't just take a pair of jumper cable and connect the engine battery bank to the house battery bank and "call it good."

* A rating of 140A does not mean the Keyline is producing current. It's just a switch.

* And since our typical 160A RV alternator is only 50% efficient it will never exceed the 140A rating or get anywhere close, because even a dead battery has a lot of internal resistance. (And I'm not going to touch the capacitance and inductance and other stuff about battery physics, because it's pretty involved and I don't fully understand it.)

* What I can says is that the Keyline VSR senses voltage and allows current to pass to the other battery bank.

* Current can pass in either direction. So when I'm driving and the alternator is a higher voltage than the house battery bank, current will flow from the engine battery to the house battery... if the house battery will accept it.

* And when I am in the sun, and the solar panels are charging my house batteries above 13.4V, or the house battery charge is working, then current flows from the house batteries to the engine battery.

* And get this: Just yesterday I picked up my RV from a 197 Day Storage slumber, and the Victron Charger/Maintainer, that I connected to my house batteries, kept both my house and my engine batteries fully charged. Thanks to the KeyLine VSR and my new Victron 17A Charger I mentioned in earlier posts. (See picture.)

Note: The Victron was putting out 14.2V, but it was only passing 0.5A/day, to both my house and my engine battery bank, which is really good, so I know I don't have any shorts!

...So, the Keyline VSR took care of my engine batteries!

* The Victron 17A Charger is now my primary charger (say bye-bye Dimensions Charger); and the Victron is also a Battery Maintainer.

==> When I returned to pickup my RV yesterday, the engine just fired right up after a 7 month slumber!!! WOOHOO! Last time I had to call a tow truck to jump start my dead batteries!!! Thank you Victron and Keyline!!!

SIDE COMMENTS: When I picked up my RV afer almost 7 months of charging on the Victron battery maintainer, at 14.2V and .5A/Day, all my house battery cells were still full of water!

...Which I thought might be a problem, but apparently not when you have 2 banks of batteries joined by the Keyline VSR.

So, I don't plan to use the Victron "storage mode" next time I put the RV in storage. I.e., I just plug the Victron in and the Keyline VSR distributes the charge, which BTW, I don't think the BIRD or Amp-L or other OEM chassis chargers will do since they only manage the alternator output. (At least I think these devices are no good for battery maintaining, but I'm not sure? Who knows?)

==> So if you ask me, the KeyLine VSR is a superior product.

BATTERY TALK

* The thing about batteries is that a battery will RESIST charge; and so you can't force current into a battery if the battery if full and there is no where for the electrons to go.

* In this why a battery is a 2.1V storage cell when full, which is why a battery will never read more than 12.6V, since there are 6 cells. And when you see 12.8V you are picking up "surface charge."

* So when the Keyline VSR only open the gate at ~13.4V volts then it becomes a fight to where the current will go... or not... when the opposing battery is full... and that energy is lost to heat for the most part.

* Moreover, current prefers the the least path of resistance, but when you have two battery banks connected together, what happens when the engine batteries are full and the house batteries are at 50% SOC or dead?

==> My guess is this. The VSR does not care. And in terms of seeing too much current flowing out of an alternator, it's not a problem, because all that resistance inside both battery banks.

==> So, there is no way a 160A alternator burn up, or the VSR will fry, because the battery banks will not accept that much charge.

SIDE COMMENT ABOUT CHARGERS: They say your can safely charge a deep cycle battery by 1/4 of it's storage capacity. So 420AH of house batteries can receive 100A if you are looking for fastest rapid charge, but this will also shorten the life of your battery. So why do it if you are not in a hurry. And if you have 8 hours to charge a battery and you are trying to replenish 200AH, then you only need a 25A charger, theoretically, but 50A would be better. ...And what would be better than that is 17A for 2-3 days of charging! So this is my new game plan.

* My Dimensions charger is rated 100A, but the most I have ever seen it charge is 40A. This is because the battery will not accept a 100A. And frankly, as I just explained, there is no reason to rapid charge a battery when you have 3+ days of camping to do in an RV park.

Note: 100% SOC is practically unattainable except for your first day on the road, then with each charge cycle on the road, you have to live with 90% or less as you your batteries start to get old. So don't believe what you see on your SOC meter or volt meter if that's how you determine SOC.

* LiFe04 batteries have lower internal resistance, and can be charged at a faster rate, so you need to use a battery isolator when connecting to your alternator, unless the LiFe04 has BIM circuitry built in. And even then you probably should use a battery isolator, because I really would not trust the BIM to protect my $2,000+ bank of LiFe04 batteries when a battery isolator is only $75-$150. (Depending on the brand.) (Go Victron and get bluetooth monitoring too, and therefore you don't need to spend money on a battery display inside your RV.)

Note: I have yet to go to LiFe04 so I'm just sharing what I think I know. And there is much you can read about this elsewhere, so I'm going to get off this topic.

* The folks at Keyline told me you can use their VSR between FLA engine batteries and LiFe04 house batteries, but I can't recommend that until I try it myself. In theory it should be okay, but I don't like being the first on the block to try this stuff... when it comes to batteries and inverters.

MY BATTERY UPGRADE PATH IN CASE YOU ARE THINKING ABOUT LiFeO4?

If I decide to go to LiFe04, I'm not going to dump my old FLA power grid.

I see no reason to do so. It's paid for, it's reliable, and my Dimensions quasi-sign inverter is solid.

...But, if I keep RVing and start doing some BLM camping, which I have never done before; and if want more AH of battery storage, my plan will be to build a separate LiFe04 power grid that is completely separate from my current 12V FLA power grid and inverter. And I think this setup will be the most cost effective too.

So why am I doing this? Well, I think, if my residential refrigerator is using half my daily battery (100AH/day) then why not split it off from the FLA grid and build a separate 24V grid, with a separate 24V inverter, and just just use the LiFeO4 bank to power the refrigerator, and maybe 1 extra outlet inside for my TV and computer?

This will double my AH storage and my budget is $1,700. (TBD) ...Unless they come out with a DC-Air Conditioner that is reasonably priced, and more efficient, then I might spend more. (TBD)

==> Remember, if you are dry camping where you need to run your AC then you have to run your generator, and at that point all this tech talk about LiFeO4 is a "don't care subject." I.e., all that money spent on solar and LiFeO4 and going green is for bragging rights that doesn't mean a thing if you have to run your generator to power that AC.

Same goes for wind power! So wake up America! There are no "green jobs" coming. And all us RVers know it! ...But that Keyline VSR and Victron 17A Charger is a winner if you ask me!

 

[Mongobird]

imnprsd, I am sorry that my explanation was Byzantine. Simply put I think that a smart charger is a better way to charge batteries than to use an alternator alone. And I agree that charging over a period of time is far preferable to a rapid charge.

There are two differences in my thinking, and the first is that I would like to treat each battery bank individually. AGM and FLA have different charge characteristics. Let them each have their own charge manager. If that charge manager can do things like pulsing them for sulfation management, that is good.

The second aspect is that I have not determined the suite of requirements for my so-called smart charger. I think I would like it to be able to charge as high as 50 amps on demand, but normally I would like a much lower rate.

Since I have not fully determined my requirements, and since I have developed an interim workaround, I have not picked any hardware. You have, and it works for you. And your solution has some very nice features. I am just not there yet.

I am also new to this game. I really don't like camping, but the the DW does, and last year I had promised her a trip to Rome, a trip to Bay of Fundy, and relented to take a cruise with her, none of which happened. So from my perspective the acquisition of the '04 Meridian was a consolation for her and a new hobby for me.

As a sidebar, I assume that by efficiency of the alternator, you mean the efficiency of converting mechanical energy to electrical energy. Indeed many alternators are in the 50 to 60% efficient range. Certainly in the vintage of motorhome that I have. Some alternators, such as one that I have on one of my cars have much denser windings and approach 70% efficiency. But that is only a factor as we look at mechanical power taken from the engine to run the alternator.

And alternator is merely a power source, and not necessarily ideally matched with the power drain of charging batteries. This is why I would like an independent charger for each separate bank of batteries.

And in this thread of long discourse, another tangent is how long do alternators last for most people on their RVs. My Meridian was bought with 80,000 on it, and the alternator failed driving it home. While I didn't have complete maintenance records, the alternator I took off was an aftermarket brand. So the existing alternator when I bought it was at least the second alternator. It failed due to the brushes wearing out. One of the bearings has a little bit of slop, so I'm not sure if I will re-brush the alternator or a more thorough rebuild. But I am surprised that in 80,000 mi the rig had gone through two alternators.