Expected solar output.

[Davydd]

We all need to remember that davydd uses a lot more power than many/most of the rest of us on the forum so the solar couldn't provide a meaningful part of it, especially on the short Sprinter. He also has a good cushion of battery capacity to wait for the drive.

I used to use more power since I have an all electric van, cooking with a convection oven, 2 burner induction cooktop (now a one burner though I have space for a 2 burner), huge compressor fridge/freezer, TV, etc. with no propane whatsoever. The biggest use of electricity was my electric articulating beds because I used them constantly as Lazy Boys or zero-gravity chairs. The power use was not the beds but they operated on 110v power so I left the 3,000w inverter on 24/7. That believe it or not was the biggest use of power. Now I don't have the electric beds so turn the inverter off because everything runs on 12v and I have a much smaller and more efficient fridge/freezer. Streaming with iPads for entertainment is way more efficient than TVs. I do have 6 12v USB plugs and charge two iPads, two iPhones, Apple watch and Fitbit constantly. So, yes, my van is set up to use electricity but I don't have any propane or second ICE Onan generator or solar and 552ah of lithium batteries. I've fine tuned from 800ah of batteries from experience but I think I live in the van with luxury and worry free from running out. I do have a built-in Keurig coffee maker, carry an Instant Pot, and sometimes a Ninja air fryer and rarely a Breville electric pizza oven. My freezer is still big enough to hold 4 frozen pizzas and a half-gallon of ice cream. I still can boon dock easily three days without driving. If I misjudge I can idle my engine for 6 minutes a day to re-plenish the batteries that solar on my roof can provide.

I do have a 2500 short Sprinter van. I couldn't put 800ah of AGM battery in it if I wanted to. The old Roadtreks with 800ah AGM batteries in 3500 longer vans probably exceeded the weight limit or close to it. 552ah of lithium I designed to maximize an unused space was my limit. Lithium batteries were rare in Class Bs just 7 years ago.

Avanti's comment about solar for storage is a must in a northern climate stored without shore power. The chassis battery would not survive let alone 100-200ah of house batteries. I don't have that problem even though I live in Minnesota.

 

[SteveJ-ClassB]

I have thought of a suitcase but we have no place to store one they are all just a little bit big to go under the beds or behind the driver's seat. I also worry about them walking away while we walk the dogs.

Have you looked at flexible panels? They come in smaller 50 or 60 watt sizes as well as 100 watt.

I/we have been dry camping/boondocking for about 4-5 months/year for seven years now. A couple of cheap combination locks and a cheap/light chain or wire cable has kept my portables from walking away.

 

[Msirois]

Hi to all,

i would like to add that, unless you plug to shore occasionally, relying on alternator charging unless you drive all day, you will not recharge to 100% SOC. if you have both solar and alternator/or shore you will top up your batt regularly. If your Lithium you probably don"t care as much, but if your AGM or flooded it is not good.
For me, solar is mostly for float charging. Bulk and absorption is in fact well taken care by alternator if we are on the move. If we stay put or boondock, short driving OR solar (300 W in my case) does it.

Michel
PW Plateau TS

 

[Davydd]

Hi to all,

i would like to add that, unless you plug to shore occasionally, relying on alternator charging unless you drive all day, you will not recharge to 100% SOC. if you have both solar and alternator/or shore you will top up your batt regularly. If your Lithium you probably don"t care as much, but if your AGM or flooded it is not good.
For me, solar is mostly for float charging. Bulk and absorption is in fact well taken care by alternator if we are on the move. If we stay put or boondock, short driving OR solar (300 W in my case) does it.

Michel
PW Plateau TS

I don't rely on the Mercedes Benz Sprinter alternator which limits you by MB to 40ah for the house battery. My van has a second alternator, a Delco 330 (the other popular choice is a Nations) that charges directly 220ah at high idle or 270-280ah all day at highway speeds. It most certainly charges my lithium ion battery bank to 100% and is capable to charge my 552ah battery bank in less than 2 hours driving. Yes, it would take all day on the chassis alternator or about 11 hours. There is little to no loss with a 4.0 cable to the house batteries. 4.0, BTW, is nearly 1/2" diameter of stranded copper wires more than capable of delivering the output of the alternator.

On another note, I've been saying 552ah capacity or four group 27 lithium Ion batteries. I just double checked my numbers, the Valence literature and my battery photos and each battery is rated at 144ah so I really have 576ah. I should adjust my numbers. It is still under 2 hours to charge 80% depletion. They were once in their literature 138ah batteries x 4 = 552ah.

I could live without shore power indefinitely but if I camped with an electric hookup I would still plug in although I can recharge my batteries from a day's use in about 1/3 to 1/2 hour of driving.

 

[Msirois]

Hi David,
I agree with you on all points. The high output alternator charging capacity that you have is great with Li batteries. But the charge acceptance from acid batteries as the SOC reaches 85% becomes so low, that even with high output it takes forever to reach 100% SOC.

 

[Davydd]

Yeah, I forgot about lead-acid batteries. I've had lithium ion batteries going on 8 years now. I've also gone through the solar panel phase with a whole roof full of solar panels (460w) that were obsolete the day I drove out of the manufacturer's facility for the first time because of the efficiency of the second alternator. As long as internal combustion engines are driving RVs the second alternator is the most efficient way to charge batteries and really the only way probably with 400ah or more house battery banks. Even built-in Onan generators (or any fuel generator) are not as efficient as under hood second alternators.

 

[RizeMaster]

We have a 200W panel on the roof. If in full sun on an average day, it allows us to run the 12V fridge, the roof fan, and water pump/lights as needed. Plus charge all the phones and tablets and cameras and stuff.

So basically no need to drive/idle/generate if there is enough sun. Being in California, and going to Utah/AZ etc there usually is enough sun most of the year.

Love having that panel.

 

[GeorgeRad]

We have a 200W panel on the roof. If in full sun on an average day, it allows us to run the 12V fridge, the roof fan, and water pump/lights as needed. Plus charge all the phones and tablets and cameras and stuff.

So basically no need to drive/idle/generate if there is enough sun. Being in California, and going to Utah/AZ etc there usually is enough sun most of the year.

Love having that panel.

We have 300W solar panels and like it a lot. As with any technologies there are pluses and minuses varying with use patterns. For us solar charging was, is, and will be a clear winner. This is an interesting article about solar trend in US RV market.

https://www.prnewswire.com/news-rel...tum-as-consumer-interest-rises-301434746.html


“PALM BEACH, Fla., Dec. 1, 2021 /PRNewswire/ -- FinancialNewsMedia.com News Commentary - There are many benefits of owning and traveling in an RV, such as flexibility, convenience, comfort, family appeal, affordability, the lure of the outdoors and adaptability. The people who cannot afford an RV or are not frequent travelers, for them, the RVs are available for the rent. People with recreational vehicles can stay overnight which is commonly known as recreational vehicle park or RV stop. More and more RV parks are expanding each year that provide many facilities. A report from ResearchAndMarkets said that: "The Recreational Vehicle (RV) Market in North America 2018-2022 is forecast to grow at a CAGR of 8.18% during the period 2018-2022. The installation of solar technology in RVs will be a key trend driving the growth of the market. With the installation of external power generators that incurred additional costs and were not environment friendly, RV manufacturers are investing in manufacturing environment-friendly vehicles with solar generators. According to the report, the substantial cost savings by using RVs over conventional modes of vacation will drive the market growth. Consumers in the market are demanding for road trips and vacations that are cost-effective. For cost-effective planning of trips, consumers can choose among options such as driving own car and staying at a hotel, owning a RV, and renting a RV." Active EV stocks in news today include: Triad Pro Innovators, Inc. (OTCPK: TPII), Volcon Inc. (NASDAQ: VLCN), Niu Technologies (NASDAQ: NIU), Volta Inc. (NYSE: VLTA), Arcimoto, Inc.® (NASDAQ: FUV).”

 

[ilmor-ClassB]

Another way of looking at it - In my experience, if you run nothing else, a 200W solar system w/ lithium batteries will keep your 3.2 CF fridge running day and night and your batteries fully charged.

 

[RizeMaster]

Another way of looking at it - In my experience, if you run nothing else, a 200W solar system w/ lithium batteries will keep your 3.2 CF fridge running day and night and your batteries fully charged.

...as long as it is exposed to the sun all day. Battery chemistry should not matter.

 

[MsNomer]

It can matter because AGM has such a severe charging curve taper.

 

[booster]

It can matter because AGM has such a severe charging curve taper.

Exactly, and most people have no idea just how severe it is. Add to that the fact that nearly no battery chargers of solar controllers are actually charging the batteries to actual full per the manufacturer's specifications, but they tell you be "fully charged" lights or 100% shown on the SOC meter. Even if you have a quality battery monitor, if it is set to the defaults or otherwise incorrectly you will get a wrong fully charged indication.


We here all the time from RV owners that they "get full batteries every day", but all of the ones I have actually seen the data of their charging systems, they actually rarely do. About the only time folks actually get truly full is if they drive a long day with alternator voltage high enough, or if they have solar that hold absorption voltage long enough which they normally do not. Both of those ways a charging will also overcharge the batteries, which actually worse for them, so you need to know when the get full and have a way to disconnect the charging, unless you have the very rare solar controller that charges by amps stage changes.



Depending on the size of the battery charger and battery bank, when the charger changes from bulk charge to absorption the batteries will somewhere in the 70-90% full in most cases. One oddity is that the bigger the charger (in amps) compared to the battery bank capacity, the lower the SOC will be when it goes from bulk to absorption.


Once you are in absorption and the current starts to taper it will normally take upwards of 6-8 hours of hold time in absorption before going to float to meet the battery manufacturers spec for full charge, which will be in amps per 100ah of capacity shown in a % or directly in amps.

 

[jakegw2]

I have 340W of solar. The amount it outputs depends heavily on the angle of the sun - both from a time of day and time of year perspective. The peak output I ever observed from the system was in FL in July. Up in the NE even at noon in the summer I have not seen that same peak amount.

So here is one data point for you. A few weeks ago I was doing some work on my camper on a sunny day in the mid afternoon with my LiFEPO4 batteries about 70% full. I have both a PWM and MPPT charge controllers that I can choose between with a selector switch (long story as to why - I wouldn't build it this way if I was starting from scratch but I ended up here because it allowed me to reuse parts I had and get the complete functionality I wanted).

With my MPPT charger I was getting 19.7A at 14.6v = 287W. When I switched to my PWM charger I got about 14A at 14.6V = 204W. Note that neither of these are close to the rated 340W of my array.

The peak reading I got in FL in the summer (when I only had the PWM charge controller) was 19.9A at 14.6v = 290W. If I had had the MPPT controller back then I just might have hit the rated 340W output!

I don't track the output very closely so I do not have many data points to share - similar to Davydd's experience, we drive our camper somewhere almost every day and that is enough to bring the batteries at 100% charge. Solar didn't turn out to contribute much to our camping experience. If I had to do it again I would just have gotten a single panel with a PWM controller - just enough to counteract parasitic drain during storage and left it at that.

 

[SteveJ-ClassB]

With my MPPT charger I was getting 19.7A at 14.6v = 287W. When I switched to my PWM charger I got about 14A at 14.6V = 204W. Note that neither of these are close to the rated 340W of my array.

Interesting and cool to have a real data point. If I may, what is the incoming voltage to the controller? I'm thinking with the PWM in the mix you have a nominal 12 volts, correct?

 

[jakegw2]

Incoming voltage at the panels is typically 21.8v without any load. With the MPPT controller the MPP panel voltage usually ends up being 18v (+/- about 0.2v). With the PWM controller the panel voltage is pulled down to the same as the battery voltage.

With LiFEPO4 the system voltage is about 13.6v (floating* voltage for LiFEPO4). This operates all my nominally 12v house systems just fine.

For LiFEPO4 chemistry 14.6v is needed to deliver a full charge with 13.6v being the float voltage. This differs from AGM which typically has a full charge voltage of 14.4 and float voltage of ~13.6v

*LiFEPO4 doesn't really need a float voltage since it has almost no current leakage. However, since it can't be turned off on most chargers it is good to keep it about the same as the battery's full-charge voltage which is 13.6v. This has the added benefit that whenever a load is placed on the system it will be drawn from the charger, not the batteries, keeping them at 100% charge.

 

[booster]

Incoming voltage at the panels is typically 21.8v without any load. With the MPPT controller the MPP panel voltage usually ends up being 18v (+/- about 0.2v). With the PWM controller the panel voltage is pulled down to the same as the battery voltage.

With LiFEPO4 the system voltage is about 13.6v (floating* voltage for LiFEPO4). This operates all my nominally 12v house systems just fine.

For LiFEPO4 chemistry 14.6v is needed to deliver a full charge with 13.6v being the float voltage. This differs from AGM which typically has a full charge voltage of 14.4 and float voltage of ~13.6v

*LiFEPO4 doesn't really need a float voltage since it has almost no current leakage. However, since it can't be turned off on most chargers it is good to keep it about the same as the battery's full-charge voltage which is 13.6v. This has the added benefit that whenever a load is placed on the system it will be drawn from the charger, not the batteries, keeping them at 100% charge.

This is just about textbook for a modern 12v moncrystalline panel. Open circuit about 21.7v and maximum power point (where an MPPT controller wants it to run) of 17.7v.


I don't think I would run the lithium up to 14.6v all the time and hold them there. Latest best data would seem to indicate that will not be good for them. Many, because of this, seem to be charging at 13.8-14.0v and then holding there if the charger can't do a full cutoff to preserve battery life and capacity. Lithium is still the wild west of battery types, so the data changes constantly, so nobody knows what is just right, but they really have narrowed down from the pure "just drop in to replace lead acid and no need to change anything" days.

 

[Davydd]

Jakegw2, I wouldn't know my data point since I can fully re-charge my batteries in approximately less than 1/2 hour driving and I probably use more electricity than the average Class B since I have no propane whatsoever. I just know that 460watts of solar panels didn't move the needle to make a wit's difference especially in the winter where we tend to camp in two week intervals about annually in Texas in a campground. Other than that 3 days is about our endurance.

Booster, Lithium to me is not still the wild west of battery types. I've had them for 8 years and know of just one example of 10 years in an RV. They are everywhere in all types of uses. They are 40% lighter of AGMs and come in drop in battery case types now for easy replacement though I suspect I would never have to. I have 4 group 27s packed with 576ah. My first ARV was a built up 16 modules of 800ah of lithium under the van that I could not possibly service myself. I couldn't get that in AGM batteries in my van design weight or space wise. Heck, I remember when lead-acid where you needed to top off with water was all you could get under the hood chassis and house.

The point is one can have large battery banks diminishing the capability of solar ever charging them fully. The early Roadtrek 800ah AGMs were a disaster. That is why I didn't put solar in my current van. If you see my roof in the air conditioning thread you can see I couldn't get much or any solar on my roof anyway.

I usually use about 120ah maximum in a days use with an all electric van. I've cut that down from my previous van of where I was using about 200ah where I had the inverter on all the time for convenience to operate my articulating beds on 110v and a twice as large less efficient refrigerator/freezer.

If I could get 200w of solar on our roof which I doubt I could replenish as much as 60ah in a day maximum. I doubt I could do that once a year in South Padre Island in February where we have a two week reservation this winter. Probably about 40ah in a day maximum or 1/3rd needed. I would have to drive periodically with the second alternator in that 2 week period which I would do anyway on the 5 mile long island or across the bay exploring, going to restaurants and shopping. That's why I said negligible or diddly.

 

[@Michael]

Lithium is still the wild west of battery types, so the data changes constantly, so nobody knows what is just right,

Lithium to me is not still the wild west of battery types.

I wouldn't necessarily call it the wild west, but the DIY'er certainly has to pay very close attention to the charge/discharge parameters of the LiFePo4 class of batteries, as the various manufacturers each have their own recommendations. Some are very specific as to charge profile, others are not. The vendor of one my LiFePo4's is confident enough in their BMS that they suggest I could simply set my charge at 15 volts and walk away - the BMS will automatically turn on and off the separate banks of charge and discharge mosfets as appropriate. (No idea how they got that to work, not going to test it.) Another vendor says it's just fine to use a default AGM charge profile. Some batteries have active balancers, others need to periodically be fully charged so the stay balanced. Some allow low-rate charging at freezing temps, others do not. Some have low temperature cutoff, others do not.

Buying a pre-engineered solution like Davydd bypasses that issue. No doubt ARV knows what they are doing.

 

[booster]

I wouldn't necessarily call it the wild west, but the DIY'er certainly has to pay very close attention to the charge/discharge parameters of the LiFePo4 class of batteries, as the various manufacturers each have their own recommendations. Some are very specific as to charge profile, others are not. The vendor of one my LiFePo4's is confident enough in their BMS that they suggest I could simply set my charge at 15 volts and walk away - the BMS will automatically turn on and off the separate banks of charge and discharge mosfets as appropriate. (No idea how they got that to work, not going to test it.) Another vendor says it's just fine to use a default AGM charge profile. Some batteries have active balancers, others need to periodically be fully charged so the stay balanced. Some allow low-rate charging at freezing temps, others do not. Some have low temperature cutoff, others do not.

Buying a pre-engineered solution like Davydd bypasses that issue. No doubt ARV knows what they are doing.

When I was referring to Wild West, I was referring to all the different and often, I think, outrageous claims that some of the vendors and manufacturers make or made in the past. Battleborn used to be one of the worst that way, even, but they have gotten better lately.


It can be very difficult for non technical people to filter through all the claims and recommendations to try to figure out just what is correct and what isn't, and even then there are still a lot of unsettled things related to the care and feeding of lithium IMO.

 

[ilmor-ClassB]

...as long as it is exposed to the sun all day. Battery chemistry should not matter.

Yes, you are correct.