Good overview of lithium batteries and a solar/lithium upgrade on a larger RV
Clearly not a Class B but the 4 part blog post on their upgrade by the Wheeling It folks provides one of the best summaries of solar and lithium battery info I have seen. Just scale down the solar panels for a Class B. Here is part 1 and you can find the remaining 3 parts on their website...
Very interesting article. Good find. Only a couple of little "nits". The no Peukert thing in lithium is pretty true, but the statements about high loads reducing the capacity of AGMs is really not correct. At a higher load, you will shut off sooner (AH wise) than at low loads because of voltage drop, not loss of capacity. If you were at the 20 hour rate at the end of the discharge, so less voltage drop, you would get the same capacity as if you ran the 20 hour rate the whole time. They also make a big deal about the lithium charge rate being so very high, which it is, but they have about 100 amps max of solar, and a 125 amp charger, so they really aren't going to get faster charge rates than they would with AGMs, which would accept that much. The exception comes at the end of charge, which they mentioned as "no absorption" when the charge current drops fast and the time to finish is long. In almost all the RV systems we have seen, the charging systems aren't big enough to make the lithiums charge faster, when in bulk, but the not needing to get full, and being able to charge at high rate to the very end is the big advantage.
I wish they would have gone into a bit of detail about what actually controls their charging, beyond the BMS. The Blue Sky and the Magnum remotes both have the capability to control charge based on amps or SOC, although only the Magnum will do a full shutoff when full like is recommended for lithium by most now. The Blue Sky would go into float, which is not recommended on full lithium batteries. They mentioned setting charge timers, so they may not be using amps or state of charge from the power sources. Maybe the Elite power monitor thing takes care of that, and there was a shunt shown in the pix. To me this is one of the "missing links" in the lithium systems that is rarely mentioned. They may be just letting the batteries charge to high voltage limit of the BMS and then shutting off the sources. It would be nice to know, though. They also didn't mention any engine charging controls.
Clearly not a Class B but the 4 part blog post on their upgrade by the Wheeling It folks provides one of the best summaries of solar and lithium battery info I have seen. Just scale it all down for a Class B. Here is part 1 and you can find the remaining 3 parts on their website...
Scale it down? ETreks and Advanced RVs have already exceeded what they put in.
They are using the Elite system Advanced RV has been using. Without getting into detail I am pretty sure ARVs system is more sophisticated.
Advanced RV's Solar Womp that was designed for the owners to boondock 5 days in the August Nevada desert at Burning Man has 1200w solar.
We have been out almost 7 weeks in the southwest. February solar performance was little benefit with short days and low sun angle. It is getting better in March but still totally questionable with flat panels on a roof. The have to be angled perpendicular to the sun and track to be of use in the winter. Late March is our limit in the southwest. One more week in Tucson and then we head north.
The larger the battery bank the less benefit you get from solar. The dual alternator is the best thing you can have in a B. AGM or li-ion it charges faster since shore power and Onan generators or single chassis alternators have much lower input. This should be a standard with Bs and eliminate the Onan. Quieter, less weight, space saving, fuel saving, more versatile, probably more fail safe and less maintenance.
We have mostly been camping off grid. Orientation of a B to maximize sun protection such as try to never face south with your front windshield is important. East west with passenger side on the north is best because an awning can't block low sun angles. You quickly learn to appreciate dispersed desert camping where you can orient perfectly or even adjust during the day.
__________________ Davydd
2021 Advanced RV 144 custom Sprinter
2015 Advanced RV Extended body Sprinter
2011 Great West Van Legend Sprinter
2005 Pleasure-way Plateau TS Sprinter
Maybe I should have been more clear, how about "scale down the solar panels", does that work for you?
I got the idea somewhere that the basic battery management features in the ARV were handled by the Elite BMS shown in this system with the addition of the CAN interface to connect to the other battery management features implemented in the overall coach control system. Does ARV use a custom version of this BMS or some other system or the standard version?
Maybe I should have been more clear, how about "scale down the solar panels", does that work for you?
I got the idea somewhere that the basic battery management features in the ARV were handled by the Elite BMS shown in this system with the addition of the CAN interface to connect to the other battery management features implemented in the overall coach control system. Does ARV use a custom version of this BMS or some other system or the standard version?
They use the Elite BMS and it is customizable. For instance when everyone was talking about it was bad to leave li-ion batteries fully charged I had explained long ago ARV could manage charging input from three sources simultaneously (shore, alternator, solar) which could charge the batteries at well over 300 amps. When charging reaches around 90% state of charge it puts on the brakes so to speak to gradually slow down charging. When SOC reaches 99% it stops altogether and until battery uses drop it to 90% it doesn't charge again. That includes sitting with shore power or solar. At the other end it permanently blocks out the last 20% SOC so you cannot fully deplete your batteries. There is no AGM battery kludge to protect them. It's almost noon and 80 degrees under the Arizona sun. The battery temperature is 74 degrees. 96 degrees earlier in Palm Springs and the batteries stayed in the 80s. Winter temperature swing cycles in the southwest and temperature lag keep them cool. Conversely this trip when we were below freezing constantly for nearly a week all the way down to zero the batteries stayed maintained above 41 degrees on the road boondocking as they did in the Minnesota winter plugged into shore power. In essence from 0 to 96 degrees or any temperature any RVer with common sense is willing to tolerate ARV's management system is doing its job.
I read completely that first installment. There was nothing new in it that hasn't been discussed here. What big RVs do that sit snowbird style is different than what Class B users do with greater mobility. For instance I am not sure a dual alternator would be smart if you don't drive.
Solar? Didn't I say Solar Womp had 1200w? Doesn't Campskunk's Roadtrek have more than WheelingIt?
__________________ Davydd
2021 Advanced RV 144 custom Sprinter
2015 Advanced RV Extended body Sprinter
2011 Great West Van Legend Sprinter
2005 Pleasure-way Plateau TS Sprinter
I'll give it one more try to see if I can be more clear...
For a Class B you would not be able to fit the 15 100 watt panels that they use on your roof but you could use high capacity panels to maximize wattage for the limited area available...
Greg, OK, OK. Solar panels are for those that park and sit. In the desert winter southwest they have to be directional to be of any benefit. That part is not very B applicable. Their battery part? Nothing new there. For someone wanting a quick tutorial the piece is fine.
If you think I am online a lot today this my sit and relax do nothing day in the desert boondocking. I at least have an understanding how all this stuff works. Biggest disappointment today? 204 campsites in this rather nice NFS campground on Lake Roosevelt and not a single other B.
__________________ Davydd
2021 Advanced RV 144 custom Sprinter
2015 Advanced RV Extended body Sprinter
2011 Great West Van Legend Sprinter
2005 Pleasure-way Plateau TS Sprinter
For instance when everyone was talking about it was bad to leave li-ion batteries fully charged I had explained long ago ARV could manage charging input from three sources simultaneously (shore, alternator, solar) which could charge the batteries at well over 300 amps.When charging reaches around 90% state of charge it puts on the brakes so to speak to gradually slow down charging. When SOC reaches 99% it stops altogether and until battery uses drop it to 90% it doesn't charge again.
IIRC, this was an programming update that ARV put in on one of your trips back for updates. Originally, I think it was on continuous full charge even when full. Several here thought the continuous charge was not a good idea and were told it was not an issue at the time.
Clearly not a Class B but the 4 part blog post on their upgrade by the Wheeling It folks provides one of the best summaries of solar and lithium battery info I have seen. Just scale down the solar panels for a Class B. Here is part 1 and you can find the remaining 3 parts on their website...
Yes - good overview. I also like the linked article on the new Hybrid Inverters. However I think their statement that "Lithium DON’T Lose Capacity At Low Temps" is a bit misleading. Lithium batteries do suffer some loss in capacity at cold temps, just not as much as AGMs. The data is a little hard to find. When I did my research for a battery upgrade I dug up a lot of data on Lithium batteries. The chart below, from Sandia Labs report shows the typical loss at low temps. I've also attached a copy of the full report for those interested.
Observing the lithium batteries I have they do heat up some when charging. I believe with lithium batteries, the electrons don't disappear so the capacity is still there when warmed. I had small lithium batteries on my motorcycles, in the winter the starter would crank slow till enough load time to self warm themselves, then it would crank over normally. I'm talking about a lithium battery the size of a pack of cigarettes and a 1000cc motorcycle engine.
IIRC, this was an programming update that ARV put in on one of your trips back for updates. Originally, I think it was on continuous full charge even when full. Several here thought the continuous charge was not a good idea and were told it was not an issue at the time.
Correct. It stopped charging at 99% whether alternator was running, plugged into shore power or solar panels sitting under full sun but would trickle charge as energy was used. I don't know the full story why they changed it but it doesn't exist in a 60% SOC as a few thought was so great. Point being they have that technology and programming capability. Anyone else doing it? I'm guessing battery longevity but who knows? At the rate I am traveling I may never know. I'll wear my B out long before the batteries. I already need new tires after 14 months.
__________________ Davydd
2021 Advanced RV 144 custom Sprinter
2015 Advanced RV Extended body Sprinter
2011 Great West Van Legend Sprinter
2005 Pleasure-way Plateau TS Sprinter
I posted this as a good overview of batteries and solar power for someone who wants an initial introduction to the topic. No more, no less... ... I guess it was a worthwhile post...
Thanks Greg! Yes it was a great post. Always nice to get another view on experience with solar and Li batteries. Also noted that the Wheelingit couple, Nina and Paul, are both engineers and Nina writes in an easy to understand style. They are both self professed geeks and it will be good to follow their experience since they intend to post more data.
For the DIY'ers lithium batteries currently runs about $6 an AH(12v). About half or less of what the MFG's charge. So if you are running 200ah of lead batteries, a 120AH lithium bank would provide more power that charges faster and lasts a long time for about $800, not to mention the space and weight savings.
For the DIY'ers lithium batteries currently runs about $6 an AH(12v). About half or less of what the MFG's charge. So if you are running 200ah of lead batteries, a 120AH lithium bank would provide more power that charges faster and lasts a long time for about $800, not to mention the space and weight savings.
The cost of a complete system using GBS components is of course somewhat higher. For instance, how much cheaper would a DIY complete 200 amp hour system be than the $2000 price shown here...
A mini BMS and modules, contractor, fuse cost about $200 total and will accommodate most any size battery bank. The mini BMS will also control two peripheral units such as a charger or solar controller. $65. Its getting more affordable and almost a no brainer for the DIYer at these costs.
A mini BMS and modules, contractor, fuse cost about $200 total and will accommodate most any size battery bank. The mini BMS will also control two peripheral units such as a charger or solar controller. $65. Its getting more affordable and almost a no brainer for the DIYer at these costs.
And what would be a reliable source for a high quality 200 ah lithium battery bank for $1200 ($6 per ah)?
Have been utilizing solar as full time RV'ers for 8 years. Have had a 34' 5th wheel with 1400 W of panels (90 V to controller) and 9 kW-hrs of LFP (48 V nominal). We just purchased a 2002 Roadtrek 190 to go places in Yucatan and Canada where a 5th wheel will not go (and if it does go, it might not return) Son is in solar (for 25 years) and is fabricating a solar system for the Roadtrek. This will be a 315 W and a 100 W panel (require different controllers), 360 amp-hr (12 V nominal) LFP battery suite (4.5 kW hrs). He is putting in a 2 kW PSWI and will run shore power through battery charger so that the AC in van will be through battery to inverter. This has proven critical in the 5th wheel since AC in Mexico (notably Yucatan which is the only place we have hooked in Mexico, back when we only had about 700 W of solar) can vary from 80 V to 150 V and this can destroy electronics (burned out micro-waves in Baja and Yucatan before he put in the battery chargers).
We were able run the energy hog Dometic A/C (2200 W actual draw) for 4 hours with combination of solar and battery suite. The A/C on the Roadtrek draws less than 1 kW so A/C may be possible for a few hours.
Reed and Elaine
Good overview of lithium batteries and a solar/lithium upgrade on a larger RV
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