Ordered a 100 Ah Lithium Battery

[rlsooby]

Battery management is built-in, but is that the same as charge control (i.e., not charging when it gets too cold, etc.)?

[KenjiFox]

Not quite. BMS or battery management system boards have a few basic functions. They protect against over discharge, over charge, sometimes short circuit or over draw, and very importantly they provide cell balancing.
The built in BMS in the drop in lithium (lead acid environment) batteries will not likely take temperature into consideration. Since the batteries have their own voltage management and are meant to drop into systems not meant to charge lithium batteries you may not need to use the lithium setting at all on the charge controller. There really wouldn't be a point to letting it do higher voltage equalization cycles though. I would still is the lithium setting since it disables that.

The batteries should be kept cool though for long life. General lithium tips;

Keep the batteries at about a 40% SOC (State Of Charge) and cool for periods of extended storage.
Do not let them drop below 20% SOC in typical use. Imagine you have 80AH batteries.
Check the C rating of the batteries. This is a multiplication of the capacity to find the max current draw allowed. For example if your batteries were rated 1c this would be one times the capacity in amps. 100 amps would be the max sustainable draw. Never charge above 1c no matter the rating for best life. This is lithium battery specific information. Your drop in style batteries will likely say the information directly in watts or amps.

Avoid charging the cells if they are hot. Anything over 90 degrees Fahrenheit is bad for them, and it gets worse the higher the state of charge. The worst thing for them is sitting at 100% in a hot environment.


Much of this contrasts lead acids. Never go below 50% SOC with those, always keep them fully charged at all times etc.

[John Linck]

You're gonna need a much bigger battery. Check out Tesla's powerwall units.

john

[Huck]

Originally Posted by John Linck

You're gonna need a much bigger battery. Check out Tesla's powerwall units.

john

Only if you plan on using a lot of electricity when the sun's not shining. AC will basically run off solar panels.

[rlsooby]

Thanks for the info.

[ZachO]

This should be interesting! Sounds like more pain/expense/effort than it's worth but that's because where I live, it cools off enough at night and we have low enough humidity that all this "AC" stuff is really for the weak. Of which a lot seem to be moving here because I hear no new house gets built without AC. I can't imagine what it's like where you camp but here, AC is not a requirement.

But I can definitely understand wanting to boondock and not wanting to be miserable. The few times I have camped places where it's still not humid, but 100 during the day, "cooling off" to 80 at night...sleeping is pretty awful. Out here or in the southwest there are ways to use swamp coolers, which would take a lot less power, but that won't work where it's humid.

[John Linck]

Originally Posted by Huck

Only if you plan on using a lot of electricity when the sun's not shining. AC will basically run off solar panels.

I guess it depends on your heat tolerance and how many panels you have. I am intolerant so we camp in Spring, Winter and Autumn, never in Summer. In Wisconsin solar panels are pretty useless after 6PM though the air stays warm for hours yet. Two warm bodies in a Scamp will raise the temp quite a bit too if outdoor temps are over 75 even with the fantastic fan running flat out. Before climate change Wisconsin nights could get quite chilly, but that seems rare of late. We end up camping in early Autumn on the shore of Lake Superior where zillions of gallons of ice water keep near shore temps bearable. Nights are cool and you hear the crashing surf instead of the roar of fans or AC.

YMMV, to each his own, different strokes, etc. john

Pics from the UP.

[brenware]

Please review the quality and feedback on lithium. We had two explode. Quality and proven track record on brand is key.

[JeffJ]

Kenji has solid advise! Ever try prickly heat powder and a fan? It amazing and costs very little. It worked for me while I was in the military even in the jungle with no fan and a mild breeze. Don't use it on your tender bits .

[larryc]

I'm late to this thread, but do you have a 12v A/C unit? Most are 120V AC. If yours is AC then you have to factor in the inefficiency of the inverter, which if you have a good one isn't too bad (90% efficient). But you also would have to buy and install one too, that will run you around $5000

[Huck]

Originally Posted by larryc

I'm late to this thread, but do you have a 12v A/C unit? Most are 120V AC. If yours is AC then you have to factor in the inefficiency of the inverter, which if you have a good one isn't too bad (90% efficient). But you also would have to buy and install one too, that will run you around $5000

I assume you meant $500.

[garbonz]

Emphize that drop in lithium’s that are out there not DO NOT have a solar charge controller and you definitely need one. Everyone seems to underestimate the amount of solar they will get from panels mounted on an RV, so you need to greatly oversized the solar. While the AC will only draw 400 Watts running, it will draw much more when the compressor cycles so the inverter needs to be sized accordingly.

You will need need at least 400 amphours of lithium’s or a good back up power source lie a generator. Plan on it.

[Huck]

Originally Posted by garbonz

Emphize that drop in lithium’s that are out there not DO NOT have a solar charge controller and you definitely need one. Everyone seems to underestimate the amount of solar they will get from panels mounted on an RV, so you need to greatly oversized the solar. While the AC will only draw 400 Watts running, it will draw much more when the compressor cycles so the inverter needs to be sized accordingly.

You will need need at least 400 amphours of lithium’s or a good back up power source lie a generator. Plan on it.

My plan is to have the trailer cool enough to fall to sleep plus another couple of hours. After that I will make do with fans.

You left out that the ac compressor doesn't run continuously, so sometimes it's drawing zero. I will have 600w of solar panels on the roof plus a 100w semi-portable panel. Worse case I spend $150 and buy another 100w panel (and a y cable) giving me 800w.

People focus on the batteries, but during sunny days the AC is running off solar.

[Donna D.]

Originally Posted by Huck

People focus on the batteries, but during sunny days the AC is running off solar.

No, solar doesn't run anything. It's function is to charge the batteries. IF you don't have enough amp hours in your batteries, it won't matter how much solar you have.

[mszabo]

Not going to happen, buy a generator.
It will be cheaper.
That setup won’t run a coffee pot.

[Donna D.]

I've been following the travels and technology of Technomadia for years. Want to know about lithium batteries? Lithium Ion Batteries for RV Motorhome House System - LFP / LiFePO4 | Technomadia


How about solar?: Solar Electrical Systems for RVs | Technomadia
The (Almost) Fantasy of Solar-Powered RV Air Conditioning

[Jon Vermilye]

I have to agree with Donna & others - I think you are being overly optimistic on your expectations of solar. For one thing, unless your tilt the rooftop panels the proper angle for the area you are in & have the van parked with the bottom of them aimed south, you will be lucky to get 1/2 the rated wattage of the panels. If it is possible to run the AC directly from the solar panels, what happens when a cloud, another RV, or something shadows the panel. Your batteries are going to have to come into play for the system to work.

Another problem is even if it was possible to connect the solar controller output directly to the AC, you can't both charge the batteries & run the AC if your panels just meet the minimum wattage for the AC. How do you plan to put back in the batteries what you take out?

I dry camp with 320 watts of roof top solar tilted at the correct angle for Quartzsite, AZ, and can (and during the middle of December & January) add a 160 watt portable panel. I don't run an AC, but do use 40 - 50 amp hours per day. No problem keeping up on sunny days, but one or two with heavy clouds will have me down to 70% - 80%. This year I did 73 days in a row of dry camping (I've done as many as 91 when I had my Escape 17 & 195 Watts of solar), so I have had some experience at long time living without hookups.

I hope it works for you, but it is quite an investment for a couple of hours of cold air...

[ShelbyM]

Good links in post 36, they've done the math.

[Huck]

Check out Jim's video. He now runs 2 5000 btu air conditioners with 1185w of solar and only 3 225 Ah AGM batteries. How does he do it? He runs the AC during the day, not at night. Exactly what I am planning, except I might run for a couple hours at night.

https://www.youtube.com/watch?v=9ezFMgUH7pU

Here's the more detailed version.

https://www.youtube.com/watch?v=cCZVAX-c4co&t=306s

And one more. Matches my configuration 800w solar, 500w ac.

https://www.youtube.com/watch?v=eUN0wKDxbaA

[Choosethisday]

I've learned a lot reading the advice of all of you and appreciate all the advice much. So since this is one of my few areas of expertise please allow me to help where I can. I'm a licensed electrical inspector with a degree in electronics. I've done a great deal of work with solar, batteries, and power control and conversion and have even built from scratch some of the control systems myself.

First, for deep cycle lead based batteries where weight is an issue we figure .8 pounds per amp hour for 12 volt batteries. This isn't exact but is close. So 3 225 ah 12v batteries would weigh over 500 pounds. This might be okay for larger trailers but would be too much for smaller ones. A lithium system would be much lighter but also much more expensive.

Second, you absolutely must use a specialized charge controller for most common lithium based batteries, and also NiMH systems. Many/most of the larger AH rated battery packs come with a build in charge controller so this wouldn't be an issue. When installed where a fire might be life threatening and one wants to go with Lithium I would strongly suggest lithium iron phosphate systems. While not using a dedicated controller can still destroy even these systems there is almost no danger of a fire from improper charging/discharging. Lithium ion systems can be okay if they come in a listed package with a built in charge controller but otherwise I would not use even them in this situation although possiby tongue mounted might be okay.
Third, at least here in the Northwest in the job I have. we only like to use solar when there is no reasonable way to connect to the grid. If we do have to go solar, unless the installation is for a non critical installation, we figure at least a 400% overbuild unless we have sun tracking where we still need at least 200%.
A number of years ago, in a small motor home, I used two AGM batteries with an inverter with a small generator. To run a 500 watt AC I had to run the generator about half the time I used the AC. Except for the noise, this is the way I would go again except I would use an inverter generator to lower the noise.