Class B Lithium Batteries and Solar for Off-Grid A/C Use

[scsmith63]

Newbie here....wife and I are looking at Noovo and Coachmen Beyond based on what we believe our use case will be with some boondocking/off grid use. Haven't decided on a particular model yet.

This will be our first purchase of an RV.

My question is around requiring a generator or going Lithium Battery with solar panels only. My concern is on cloudy days the Lithium Batteries may drain with heavy AC use on hot and humid days.

Noovo suggested doubling down on the Lithium batteries.

Curious about the real experiences on Lithium power consumption as it seems a 660ah battery may last 6-8 hours with heavy AC use. I read the 400 watt solar panel takes 4+ days to recharge the lithium battery.

 

[booster]

Your guess on the AC use and battery sound pretty close and you can't put enough solar on the roof of the van to recharge the batteries fast enough to run AC regularly, as even double the batteries gives two hot days and even longer to recharge from solar.

That leaves you with shore power, which you won't have if off grid, and engine charging which would take 4 hours or more of driving most days, or long periods of idling the van and fast idle.

If you want to stay offgrid for multiple days with driving, the only solution would a generator, IMO.

 

[Steve Biegler]

This is how we do it. Between the solar, driving, shore power and autostart/fast idle we have never run out of power.

 

[engnrsrule]

Booster is correct. Lithium is definitely a step up as the percent of useful power is much greater than lead acid. Roof AC is rarely useable thru an inverter on battery. What you may not realize is that most class Bs have a design feature where you can put the roof vent on med-low exhaust and crack the side windows by your bed and enjoy a lovely cooling breeze across the bed. This is the same concept as the old whole house fans common before AC.

I would generally prefer to have a generator and solar to expand boondocking flexibility. I had 300ah of lithium and 290w of solar. That could handle a few cloudy days without loosing ground, running chargers, TV, internet, compressor fridge, etc. on a 1500w inverter. To run the microwave or coffee pot, I just run the generator for a few minutes. Water heater stayed on propane if no shore power.

 

[ChristyCappello]

A friend & co camper has a class B with the Volta lithium system. With the Volta system you can run the A/C for 9 hrs without any hookups. I know travato & adventure vans makes them.
Check it out:

 

[booster]

A friend & co camper has a class B with the Volta lithium system. With the Volta system you can run the A/C for 9 hrs without any hookups. I know travato & adventure vans makes them.
Check it out:

Yep, you can do that with batteries, but for offgrid air conditioning how do you replace all that battery charge without a bunch of driving or idling?

 

[Hepstein45@gmail.com]

We have a 2020 Coachmen Beyond. We have a generator. We rarely use the A/C. When the original 600 AH AGM battery deteriorated we replaced it with a 460 AH Lithium battery. We added an additional 200 watts of solar panels for a total of 400 watts. We also added a 50 amp DC to DC charger from the alternator. We have the original 120Volt Coleman rooftop A/C. We cannot run the A/C from just the battery. We do not use the A/C when plugged in. We can run it when the generator is on but it s too loud. Even just the A/C is quite loud.
Both the solar charger and alternator charging are trickle charges. A day of driving in the sun may add 15 - 20 AH of charge. The generator will charge the battery from 40% back to 80% n 2 - 2 1/2 hours - we often do that while we are driving so the we don’t notice the noise. We have a 2000 watt inverter which will run the microwave but not a coffee maker at the same time.
So to summarize. 1) Perhaps a 12volt DC A/C will run from battery power? Perhaps it will be quieter? But a 120 Volt A/C unit needs shore or generator power and is noisy, especially while running the generator. Even a 3000 water inverter would not be big enough to run the A/C free m the batteries, regardless of size of batteries. 2) AGM batteries are really heavy and do not provide enough power to run the latest appliances such as water and room heater, They may not be enough to run an induction cooktop. Even if they have sufficient power they will not last long and it will be difficult to keep your AGM battery above the recommended 50% without being connected to shore power or running the generator. 3) our charging capability from the alternator is insufficient to recharge a battery. Perhaps newer models have better alternator charging. 4) Lithium batteries are definitely the way to go. You can easily upgrade AGM batteries to Lithium in a Coachmen Beyond. 5) A venerator makes boon docking possible- water is the limiting resource. A better alternator charging capability can negate the need for a generator.
Hope this helps.

 

[Hepstein45@gmail.com]

Correction. We do run the A/C when plugged in to shore power.

 

[booster]

We have a 2020 Coachmen Beyond. We have a generator. We rarely use the A/C. When the original 600 AH AGM battery deteriorated we replaced it with a 460 AH Lithium battery. We added an additional 200 watts of solar panels for a total of 400 watts. We also added a 50 amp DC to DC charger from the alternator. We have the original 120Volt Coleman rooftop A/C. We cannot run the A/C from just the battery. We do not use the A/C when plugged in. We can run it when the generator is on but it s too loud. Even just the A/C is quite loud.
Both the solar charger and alternator charging are trickle charges. A day of driving in the sun may add 15 - 20 AH of charge. The generator will charge the battery from 40% back to 80% n 2 - 2 1/2 hours - we often do that while we are driving so the we don’t notice the noise. We have a 2000 watt inverter which will run the microwave but not a coffee maker at the same time.
So to summarize. 1) Perhaps a 12volt DC A/C will run from battery power? Perhaps it will be quieter? But a 120 Volt A/C unit needs shore or generator power and is noisy, especially while running the generator. Even a 3000 water inverter would not be big enough to run the A/C free m the batteries, regardless of size of batteries. 2) AGM batteries are really heavy and do not provide enough power to run the latest appliances such as water and room heater, They may not be enough to run an induction cooktop. Even if they have sufficient power they will not last long and it will be difficult to keep your AGM battery above the recommended 50% without being connected to shore power or running the generator. 3) our charging capability from the alternator is insufficient to recharge a battery. Perhaps newer models have better alternator charging. 4) Lithium batteries are definitely the way to go. You can easily upgrade AGM batteries to Lithium in a Coachmen Beyond. 5) A venerator makes boon docking possible- water is the limiting resource. A better alternator charging capability can negate the need for a generator.
Hope this helps.

It appears you have some things that aren't working properly in your system based on the recharging results you state.

Both the solar charger and alternator charging are trickle charges. A day of driving in the sun may add 15 - 20 AH of charge. The generator will charge the battery from 40% back to 80% n 2 - 2 1/2 hours - we often do that while we are driving so the we don’t notice the noise.

The solar and alternator charging you list should be nowhere near only being trickle charging.

Using the the old standard estimate of average solar charging gain per 100 watt of solar in good sun, you should be able to get 120ah of recharging per day and see upwards of 20 amps charge rates, especially with lithium that doesn't taper off charging much as you get toward full.

You haven't defined how many hours a typical day of driving is for you, but a common in amount is maybe 4 hours so I will use that. You should be able to get 200 amp hours of recharge in that amount of time driving.

You are missing way more power than you are getting so it really looks like would be short of power compared to the size of the system.

Your generator and shore power charging both come from the same inverter/charger you probably have and appear to most likely be about a 100 amp charger that nets the 92 amps you need for the 40-80% recharge you get that way. This would indicate the batteries are functioning as they should.

With somewhat decent sun and moderate amount of driving you should be fine if using less that 100ah per day, which is likely when not using AC.

About the only way you can lose that much charging is by having very bad settings in the two power sources that are underperforming.

I would suggest starting a new thread on the topic so we can see what equipment and what the settings are to help with trying to get it all working like it should.

 

[Snowy]

You should add Panoramic RV to your list. They are reputed to be of very high quality, and have a five year warantee. i was thinking about a Coachman Beyond before i found Panoramic. The Panoramic just seems much better built. The Noovo seems well-built (and has a 3-year warantee), but you are restricted to a RAM or a Mercedes. I would never buy a Merc Sprinter, with all their emision-system problems. The Noovo also means you must get a cassette toilet, making every dump just disgusting. I prefer a black tank. Finally, Panoramic makes a model called the Perspective built on a ford transit which i think is the best chassis for Bs right now.

Good Luck

 

[Snowy]

Also - go to the facebook pages for the coachman beyond and for the panoramic and search around for actual experience people are having with the A/C and alternator charging. I don't think it takes 4 hours driving around to charge enough to get a significant amount of A/C runtime with either rig.

 

[booster]

Also - go to the facebook pages for the coachman beyond and for the panoramic and search around for actual experience people are having with the A/C and alternator charging. I don't think it takes 4 hours driving around to charge enough to get a significant amount of A/C runtime with either rig.

I don't know if you are talking about the Hepstein45 post, or what the RV was stock, but that is what I was referring to in my post, if that is what you are addressing. It is always good to quote the comment you are replying to so there is less confusion.

In Hepstein45's post it was stated that the power system was altered with a 50 amp B to B charger and that only 15-20ah of power is added in a day of undefined hours of time driving. If you want 6-8 hours of AC time it is going to need somewhere around 600ah or more of energy to do it for most AC systems. The 15-20ah is not going to do that.

My comments of a day of 4 hours netting out 200 amp hours of engine charging is based on the limit of 50 amps from the B to B charger, and even that is only a 2-3 hours of AC time.

If you are talking about the RV in stock condition, the RV had 600ah of AGM it was stated and to get that bank full to 80% at 50 amps would take nearly 10 hours with another 4 hours plus to get to 100%. It is possible the AGMs would only run the AC until about 50% SOC depending on their voltage drop under load.

Without knowing how big and how many alternators the RV had stock it is unknown how fast it would charge, but no second alternator was mentioned, nor was OEM alternator mentioned.

The original post was a query from a non owner, scsmith63 about charging time with and without a generator and using only solar so it is assumed that driving was not in the equation, and in that case there would be no real chance of getting enough charge to run AC much at all from 400 watts of solar.

 

[booster]

For reference here is a list of the options available on a current beyond show a maxed out lithium setup. Of interest is the massive 12600ah of lithium and a 280 amp second alternator on the charging side and a 3000 watt inverter on the use. It doesn't appear that a normal generator is available with the package so driving would be essential. The limited testing we have heard about says that the second alternator will net out somewhere around 165amps average output, but that may have changed if they used a different brand that doesn't have the heat issues of older ones. Even 165 amps plus 15-20 from the solar would give around 2 hours of AC run time per hour of driving time so much more possible. It appears that there may or may not be a standard 620ah of lithium to add the package to, or it may be an intermediate update you have to also order over possibly standard AGM batteries. It is unclear on that, but on the smaller bank a gas generator appears to be stated as available. Very cryptic sales jargon, I think.

• Extra 640AH Lithionics Lithium Battery /w Internal Heater (1260AH Total w/ Li Lithium Option) (Must Have Optional Li Lithium Battery System)
• Li Lithium Battery System includes 640AH Lithionics Lithium Battery, 2nd 280amp Under Hood Alternator, multi stage voltage regulator, BMS (Battery Management System), Victron 3000W Invertor/Charger (2.8KW Gas Generator Not Included w/ Li Lithium System)
• Truma Aventa 13,500 BTU 110V A/C
• Driver & passenger upgraded seat re-covers
• Grey tank heaters
• Cozy Wrap® upgraded insulation package
• Upgraded front window covers
• New Rover 148" Roof Rack
• New KO2 Upgraded Tires w/ Black Rims
• New Rover Ladder w/ Cargo Box
• New Pull Out Pantry Behind Drivers Seat (N/A 22R

 

[scsmith63]

Appreciate the feedback....we plan on going with the dryflush Modiwell unit instead of the cassette on the Noovo

 

[ChristyCappello]

Yep, you can do that with batteries, but for offgrid air conditioning how do you replace all that battery charge without a bunch of driving or idling?

These vans have a auto start feature that will run the engine for 20 minutes to charge the Volta system from what I saw on YouTube.

 

[booster]

These vans have a auto start feature that will run the engine for 20 minutes to charge the Volta system from what I saw on YouTube.

A quick look seems to say the Volta systems charge at about 6000watts. That is a quite high charge rate and is at over 50 volts so the wiring can handle it. It is about .6C charge rate on the batteries which is on the higher end of many lithium batteries these days, but I think Volta is still using the Lithium Ion vehicle chemistry so not sure what there recommendations are these days in the automotive market.

That said, an AC unit may pull 1000 watts, or maybe a bit less or more, so for every hour of AC running you would need 10 minutes of engine running at 6Kwatts. High idle or driving was stated to be needed to do that rate in the information I saw about the Volts systems.

Autostart is a common thing, but we seem to hear about it less these days for some reason. Perhaps because it often will violate "no generator" rules in campgrounds that may be for just specific times, but some are all the time. They commonly lump engine running in the same category now.

There is also the very low amount of "idling" the Mercedes recommends before needing to do a drive to prevent clogging of the DPF filter. I don't think we have ever really heard much real world testing of how accurate MB is on their recommendations though.

In any case, a van on high idle is normally quite noisy and could certainly bring noise complaints in campgrounds, especially at night or no generator hours. It appears the actual speed for the MB diesels is between 1200 and 2000 rpm so it will be loud, I think. Gas engines may be less noisy at those speeds, but not be a lot. The engine is going to be using upwards of 10 horsepower to make that much power so will be working pretty hard and generating a lot of waste heat and exhaust. Heat through the van firewall and underbody from the hot areas will cause the AC to work harder and the van to keep warming from it even when the engine is off afterwards.

I think there are still a couple of Volta system users on the forum so perhaps they could jump in and give better real world use information and how they can recharge large discharges from AC while camping without driving often.

On edit, I just looked at what really counts in this discussion, what the OP is looking at for a van and lithium system.

The OP talked about a Beyond and they appear to have a Lithionics lithium battery system, which as far as I know are all 12v systems. The second alternators used on the 12v systems will net out less than 1/2 of the wattage as the Volta 50+v system does in most cases depending on the alternator and it's cooling. You would talking about charging for close to an hour to get two hours of AC use on it if that is the case. Alternators tend to run hotter when the van is not moving so could be much less charging if that is the case for the Beyond. Also remember that this is considering the charging with no loads on it besides charging, so if the AC is running you would only get one hour of not running after an hour of charging at fast idle.

The devil is in the details and for new campers with no experience, they really don't have an idea of how much power they will be using even without the AC running. Salesman will tell you anything to get you to buy the van from them so the real information has to come from other sources like experienced campers doing similar camping patterns.

 

[Drf63]

If I may, (without derailing topic) offer ‘AC on battery runtime’ experience on my slightly bigger; 12 inch wider/longer B+ rig.

*Moderator, please move/delete if this is deemed an unwelcome topic diversion*

As others have mentioned …I too, had originally planned to purchase a Coachmen Beyond B van conversion.

While nearing the time to begin dealer negotiations, I ran across information on the Coach House Platinum 220TB …a B+ rig, of slightly larger exterior dimensions.

Fast forward to 3 years later: My 6-8 week spring/summer roadtrips have been made much more pleasant with the ability to run my rooftop AC for nearly a week on battery/incoming solar.

Yeah, I know …that sounds like an outrageous exaggeration or bold-faced lie. It’s not, and I can provide the receipts (Victron BMV 712 SOC screenshots, if desired)

Specific hardware: Dreiha Atmos 4.4 rooftop AC, SoftACStart module, 1920ah LiFePO4 battery bank (six 320ah Li Time batteries), 1040w rooftop solar (four Renogy 200w Shadowflux anti-shading panels & two of their 120w SF Anti-shading models), Two separate Victron Solar controllers, Victron Multiplus II 3K 12v unit, Victron 12-50 XS DC DC charger.

The most vital part of this performance equation is the unique ‘dehumidifier mode’ of the Dreiha AC. Rather than a continuously operating compressor …it alternates between a compressor phase and plenum fan distribution phase, dramatically reducing energy draw. (Somewhat like a variable speed mini-split)

When ALL moisture is removed from my rig’s interior, 86 degrees (the HIGHEST temp setpoint) in dehumidifier mode …effectively feels like the low to mid 70’s.

Occasionally, when I need more/faster cooling …I drop the setpoint to 80 degrees (75 is the lowest I’ve ever used)

Before the recent upgrade in battery bank/solar, the prior setup (600ah LiFePO4, 600w solar) was able to run the same Dreiha Atmos 4.4 rooftop AC for 2 days on battery/incoming solar.

The compressor phase requires about 90a, however …the energy needed for the plenum distribution fan is only about 3-5a.

During midday/afternoon sun exposure, the two separate arrays roughly pull between 50-60a …reducing the AC compressor phase draw by 2/3… and actually REPLACING 40+ amps in the plenum distribution fan phase.

Running the AC 7.5 hours overnight with the Starlink Mini on 24/7 …I routinely see just a 3-5 percent drop in SOC. When stationary, the solar arrays can regularly generate a 15 percent charge to the battery bank.

When travelling, the 48-50a from the DC DC charger can easily compensate for rain/cloudy non-solar collecting days.

I have an onboard Onan 4K generator, but it is much louder than the Onan QG 2800i model that the Beyond is equipped standard with. Therefore, I’d rather just use the 6.8l V-10 engine to safely IDLE-charge the batteries without issue ..fuel economy is basically a wash between the Onan and V-10.

The new AC unit was a direct fit replacement for the Dometic Penguin II AC requiring no special accomodation.

 

[booster]

Drf63, I am a numbers and data person, so appreciate the detailed information. There are certain parts of it in this discussion that are more important than others but all are useful.

First off for AC on batteries and solar is the size of the output of the solar array and 1040watts is too large for what can be fit on most class B vans but on a C can be done. Also mentioned was a 15% gain if SOC from solar alone. These would be normal amounts of gain for that size bank using the fairly accurate average for output in good sun conditions of 30ah per 100watts of solar capacity so makes sense. It is 312ah in amp hours. At the stated 90amps of draw of the AC that would give you about 3.5 hours per day of AC time when the compressor is running. The rest of the usage would have to be made up from the batteries, generator, or you preferred engine idling if you are parked and not driving at all.

With the above known, the rest is on the batteries to make up and a 1920ah bank is huge. Assuming an 80% drawdown to be conservative that would give 1536ah of usable power. In "nearly a week" of 6 days that would give you another 256 amp hours a day to use or another 2.8 hours of compressor on AC running.

All of this would show 6.3 hours of compressor on time per day max in good sun and 80% drawdown, but with no other power use. Moderate power using campers like us use 50-100ah per day of capacity depending on the temperature (frig use) and amount of indoor cooking. If you use 90ah per day it would cost you an hour of AC compressor on time. You may be higher than that with the AC circulating fan on continuously as our CoolCat uses about 10 amps when on fan only and that would use 240ah per day. It would be interesting to know what the average AC on, regardless of compressor on or off, time is and how much power it draws.

I think the key is that you are running at an 85* setpoint, as that is very high by most standards even with low humidity, IMO. It will use very much less power, though. It is not clear if you run the AC or only at night like many campers do. Do you have a way to see the daily power use in the monitoring equipment? That would be very interesting to know as you have about 600ah per day to use with solar and batteries in good sun conditions. You also mention running the RV engine as preferred if power is needed, which I would agree with as you likely have a second alternator so can charge must faster than the generator will in most cases and may be quieter. Do you ever have to run the engine in real use? Assuming you use the battery capacity after a week of camping how are recharging the capacity to be able to do another week? We are somewhat different than many B campers in that we like over 3 week stays in places so that is important to us, for instance. You have a class C, so may be different also.

All of this just boils down to what it always is for power use in our RVs, Power in plus reserve capacity VS Power out. We all have to stay within those limits is a way we are comfortable with.

 

[Drf63]

I’m on the road right now, returning home after a 2.5 week northeastern tour of the states …so I’ll provide some quick answers to your questions and address the others requiring data screenshots later.

Yes, I agree that 1000w of rooftop solar is challenging to mount on a large B van conversion, or compact 23’ class C. (I had to accept a small amount of panel overhang on the DS)

** Pictures and full write-up RE ‘On-battery AC runtime testing’ are contained in my recent post at the IRV2.COM forum **

Because a 22’ Coachmen Beyond is so close in size to a 23’ Coach House Platinum 220TB …RV consumers aware of this, will often ‘cross shop’ comparing the two categories.

That is the rationale for posting here, and perhaps the knowledge of the added rooftop solar potential of a small Class C (in addition to the increased cargo/interior living space) offers some buyers more practicality for their intended use case.

Yes, the AC was left on 24 hours during the testing. I never use it in any other mode than ‘dehumidifier’, because of the extreme energy efficiency.

Do I run the engine in ‘real use?’

Unsure of what that means…

No, I do not have a secondary alternator …just the oem spec 150/155a unit. I run one Victron 12-50XS DC DC charger. As I’d mentioned, even after installing a muffler, the Onan 4K generator is still too loud …so I prefer idling the V-10. I mostly boondock, so nobody is nearby, to be potentially offended.

On travel days, naturally the V-10 is running in ‘real use’ and sending 48-50a to the battery bank (if needed). The solar is often in ‘float mode’ unless I put an unusually heavy load on the bank.

I’ve never seen the SOC lower than 74%. I think that occurred after a couple of days of poor solar conditions, constant AC, microwave, 32’ HDTV, gadget charging and 24/7 Starlink usage.

If I somehow needed the most RAPID charging available, I could idle the engine while also running the Onan generator, for a total of about 125-140a.

I also have a 3rd Victron solar controller (rarely used) that allows input from two 220w portable Eco Flow solar panels. Since the upgrade, I no longer carry the portable panels …I honestly don’t need what they provide anymore.

 

[booster]

I think I can't get around the power in/power out thing. The only way I could see you maintaining at 74% SOC over 6 days with the power use listed would be if you drove often, idled the engine (that is the "running the engine in real use"), or ran the generator. 50 amps of alternator charging will only give 1/4 of your battery capacity in a 10 hour drive and even with generator and shore on would only get to about 75% of rated battery capacity. I think the discrepancy must be in the charging side of the mentioned 6 days of use with more than just solar being used, unless I am reading something incorrectly.

Are you able to see and copy out a 24 hour SOC graph from the history of the monitoring system? I think it would be very interesting for all of us to see.

Our solar and battery capacity are very close to being 1/3 of yours at 300 watts and 618ah, and we get similar results to what you list, but without any AC use. Assuming you have similar non AC as we do, you would get an extra 200ah of charge a day in good sun or less in the rain, shade or heavily clouded. We break even to slightly gain on sunny days and can lose maybe 30ah of charge in poor solar conditions. That gets me back to having 200ah of capacity to run the AC with compressor on of two hours minus what it uses on fan only so would give very little cooling time. We never plug in except for using AC, and I have the second alternator charging on a on/switch so even if we drive we don't get and charge unless needed and that is fairly rare.