RV solar with generator backup?

[PNW_Steve]

Hey Everyone,

Thanks again for making such a great resource available to us. I really appreciate the mods for working to keep up the quality of information here.

I do browse some of the other boards for entertainment

I came across a question on another board that raises some questions about my RV installation.

"Basically I have to run the genny in my RV to get them to 100%. I found that running it in the morning to bring them up to 80% screws up my Victron CC by making the starting voltage the cc see's higher and shortens the absorb charge to maybe an hour or two when it should have been on absorb for 6 hours. "

I will be traveling in my RV for up to 3-4 months at a time. I will be dry camping the majority of the time.

Given the space, weight and financial limitations I have come to the conclusion that I will have to run my generator to support my larger loads. Typically a coffee maker, hair dryer and microwave.

Since my largest daily loads occur in the morning I had planned on about an hour of runtime each morning to handle the big loads and getting a head start on the days battery charging.

After reading the question above, I am questioning my plan.

Any suggestions as to how to avoid the issue that he had?

Thanks.

[NCmountainsOffgrid]

I'm not sure your battery charging by using the generator in the a.m. is any different than most of the rest of us RV or motorhome owners.... the driving time allows the alternator to charge the house batteries, the solar provides charging when parked, at least during sun hours, and the generator is used when none of these others are available, usually the night and early a.m.

as for whether the house batteries get charged 'fully' every time you run the generator, I would say 'don't sweat it', especially in the early a.m. since solar will be coming into play soon enough(if you have any). Depending on your nightly usage of power, you may want your generator to run longer for more of a 'fuller' charge, but if you have an AGS(auto gen starter) module, then you can allow it to crank and run the generator during the night, if needed, such as when the batteries fall below 12.0 volts or so.

we find that having the generator run overnight is not as big of an issue, if you don't want it to - you can set your Inverter's LBCO level to 11.5 or so, and turn off the AGS - this will provide enough power during the bedtime hours, but can limit the generator starting during the overnight hours - if the Volts fall below the 11.5 setting, the inverter will simply shut off until it has 12.0 of power again, usually after you've started the generator in the morning. Your fridge will keep your good nice and cool until then - it's usually only several hours during the very early morning hours anyway. Some of us don't mind the generator running whenever it needs to, and some of us would rather not 'hear' it during sleeping hours.... : )

btw, I've never looked at our generator to 'fully' charge the batteries, since they can and may require many hours of constant run time will all the available amps going to the charger - during that time you may be limited on the other things you can do at the same time, such as air conditioners, and other heavier draw items - though your generator may be large enough and well suited to do it all, it just depends.

the quote you gave sounds like someone is concerned that their solar charge controller is not reacting correctly - that may be, but that is a solar issue, not a generator one. Solar is probably going to have a hard time ever 'fully' charging your RV's House battery bank - but it will depend on the number of batteries you have, and the sizing of the solar system - as well the aforementioned 'sun hours'. Most RVrs typically find that solar is really just a way to offset generator run time, not do away with it. For example, if it's really hot, you'll need to run your generator anyway to run your air conditioners - so solar then is a moot point since it is not really any aid while the generator is running, yet it's right in the middle of the day when the 'sun hours' are at their best - loosing the one thing you have solar for - solar power.
Solar is not really the 'dream' solution so many may think - though it certainly can have it's place in an off-grid lifestyle, especially if you can afford to have less of the 'amenities' you might normally have while on shore power or the generator.

[Mike90250]

That's how I run my backup generator on cloudy days, a couple hours in the AM, before the sun gets going, and then if there is any sun behind clouds, it tops off the batteries. Having set points properly configured is critical.
Using a generator to hit the final 20% of charge takes hours and wastes fuel

[Bala]

There is not really a set and forget. I know running the genset in the morning messes with my controllers but its all 12 years old so I just change things as I need to.

You should? come to understand your system and its state of charge at the end of the day and in the morning depending on what the weather was like and what your usage was.

After a while you will just know if you need to change settings, run the genset or do nothing but relax.

Like Mike said, set points are critical but may need changing a little or lots.

[PNW_Steve]

That's how I run my backup generator on cloudy days, a couple hours in the AM, before the sun gets going, and then if there is any sun behind clouds, it tops off the batteries. Having set points properly configured is critical.
Using a generator to hit the final 20% of charge takes hours and wastes fuel

Thanks.

My want is to avoid the issue that the gent who asked the original question.

Apparently the shore power charger was causing some conflict with the charge controller.

[PNW_Steve]

I'm not sure your battery charging by using the generator in the a.m. is any different than most of the rest of us RV or motorhome owners.... the driving time allows the alternator to charge the house batteries, the solar provides charging when parked, at least during sun hours, and the generator is used when none of these others are available, usually the night and early a.m.

.

Thanks for the reply.

I am not sure you have a clear picture of what I am doing.

I am relatively certain that the alternator won't be doing much charging while driving given that I have a 12 volt alternator and a 24 volt battery.

I am fairly certain that solar, assuming daytime travel, will charge while I am driving.

I am also fairly certain that the Iota DLS-40 charger will charge the batteries while I am running the generator or connected to shore power.

Thanks again.

[PNW_Steve]

My intent has been to run the generator in the morning for an hour or so to get a start on the days charging and support my coffee maker. Then let the solar take over for the rest of the day.

I would like to avoid the issues that Bala and the other gent have mentioned regarding the shore charger, run in the morning, causing issues with the solar charge controller.

[NCmountainsOffgrid]

I am relatively certain that the alternator won't be doing much charging while driving given that I have a 12 volt alternator and a 24 volt battery.



I am also fairly certain that the Iota DLS-40 charger will charge the batteries while I am running the generator or connected to shore power.

Thanks again.

hmmmm....very interesting to have an RV/motorhome with a 24v House battery or bank...

maybe let us in on the year/make/model of your RV, and how many batteries you have, and what Volts they are, as well as their connection(series,parallel,both),
and even what Volts your Inverter/Charger(make/model) is set to charge them at....

I would also suppose that you have your solar wired at 24volts, of course...

: )

[Mike90250]

Thanks.

My want is to avoid the issue that the gent who asked the original question.

Apparently the shore power charger was causing some conflict with the charge controller.

Wired correctly, there should be no issue.

No shore power. : the SP charger has no idea if you are running the RV engine or the PV panels charging the battery.
On shore power : Do instructions state "Never start your engine while on shore power " I doubt it. Engine alternator should not cook SP , neither should PV panels.

[PNW_Steve]

hmmmm....very interesting to have an RV/motorhome with a 24v House battery or bank...

maybe let us in on the year/make/model of your RV, and how many batteries you have, and what Volts they are, as well as their connection(series,parallel,both),
and even what Volts your Inverter/Charger(make/model) is set to charge them at....

I would also suppose that you have your solar wired at 24volts, of course...

: )

Not sure how it is relevant but here goes:

2002 Bluebird A3RE

4x L-16 batteries in series.


inverter is a Xantrex Prosine 1800/24

Charger is an Iota DLS-27-40

Solar is not 24 volt. Closer to 75 volts.

[PNW_Steve]

Wired correctly, there should be no issue.

No shore power. : the SP charger has no idea if you are running the RV engine or the PV panels charging the battery.
On shore power : Do instructions state "Never start your engine while on shore power " I doubt it. Engine alternator should not cook SP , neither should PV panels.

Not sure that I understand your response .

The shore charger and the solar charge controller both connect directly to the battery bank (with o/c protection) engine and alternator should have no effect. Did you mean generator?

That is the root of my question. I have heard from a couple of folks that generator run time in the morning has "confused " their charge controller causing erratic behavior.
I would like to avoid duplicating their problems

[NCmountainsOffgrid]

yes, everything IS relevent... I'm not sure how anyone could come to a conclusion that a generator run time, while charging your battery bank in the a.m., would have any effect on your solar charge controller - but if that 'person' has an issue, it sounds more like it's their own charge controller...

why is your battery bank running at 24v versus 12v? was this as the factory in
Ft.Valley Ga built it? I used to live near Bluebird/Wonderlodge...

so you're feeding 75volts of solar into a 24v charge controller? I don't imagine this setup was from the factory.

[PNW_Steve]

yes, everything IS relevent... I'm not sure how anyone could come to a conclusion that a generator run time, while charging your battery bank in the a.m., would have any effect on your solar charge controller - but if that 'person' has an issue, it sounds more like it's their own charge controller...

why is your battery bank running at 24v versus 12v? was this as the factory in
Ft.Valley Ga built it? I used to live near Bluebird/Wonderlodge...

so you're feeding 75volts of solar into a 24v charge controller? I don't imagine this setup was from the factory.

OK,. I have read two accounts of the problem and want to avoid having the same.

Why 24v? Because 12 volts is impractical for a system of this capacity . There are some great stickies on here that give a better explanation than I can.


No, it didn't come from Georgia this way.

[Mike90250]

......

That is the root of my question. I have heard from a couple of folks that generator run time in the morning has "confused " their charge controller causing erratic behavior.
I would like to avoid duplicating their problems

A properly configured setup, cannot confuse or burn out a charge controller. Many things can do that, but not in a proper setup

Example - my system has XW inverter, Classic MPPT Controller, Morningstar MPPT controller, Iota Charger and an antique generator. All gear was carefully selected for over a year, to match loads and appliances, before I bought anything. Nothing has interacted poorly, except for a bad batch of diesel fuel from chevron. Not understand how things are supposed to work and violating operation conditions can fry things.

I tried to look up your charge controller ( Bluebird A3RE ), but your model number didn't match anything on the india web page. With 75V of PV, I hope it is a MPPT style controller.

[NCmountainsOffgrid]

now we're getting somewhere, these were very beautiful high-end coaches 'back in the day'... and can make a great 'home' even now...

I would wonder if the stock unit came with a more standard 12v system, versus 24v, which is not common in the industry... if so, I would wonder why someone had gone to the trouble to change it. With 4 parallel 6v house batteries, making a 24v output, it makes sense, but the amp hours are now half(?) of what most other 12v rvs have usage of, with the same size and number of batteries, which sounds more like what you want when you want more 'time' off-grid without the generator running. Maybe it comes out equally in the end though - it sounds like it's only really done to match a 24v solar output.

But, I suppose if your usage is really as you say, minimal and mostly in the a.m., then maybe it will work just fine. Your generator will most likely always be in play, used in the a.m., and probably late night before bed, etc. If you have enough solar to offset most of your usage during sun hours, then you'll probably not need the generator unless you need the air conditioners.

All in all, I don't think that your worries about what someone else has mentioned about the charge controller being affected by the generator is warranted. There's really no 'connection' between the two, other than the battery bank itself. I imagine also that the charge controller has settings to customize the stages of charging, which may be why the other owner was not seeing the length of time they expected, if their internal settings were not correct. Maybe they had it set at 80% and did not realize it.


Travel, park where you want, and enjoy! You'll do just fine.