My solar works great, but is it correct?

[StarryNights]

For over a year i have been building a van, with Solar being the most interesting challenge.  Solar has been running for about a year and seems to function very well, but is entirely self built from tips studying [font=Tahoma, Verdana, Arial, sans-serif]Will Prowse videos and [/font]sites like this.  But, no professional has ever checked it over and I constantly wonder if I have any dangerous omissions!

See attached Image.  Basic design is a 24V system with eight 100 amp 3.2v LiFePo4 Fortune cells wired in series = 100amp @ 24V.  Have four 100 watt panels in 2 banks controlled by 30 amp Tracer MPPT.  Also have a 3000 watt inverter/charger and a Sterling B to B that I have as yet not had to use.  Despite living in NH where temp can drop below zero, I kept the system running last winter with my own solution of a tiny 7 watt heat tape under the battery box and $5.00 Chinese thermostat that would shut down solar charging if battery fell below 35 degrees.   Shut downs mostly only happened if outside temp got into single numbers. 

Van has no propane, use induction cooktop, and keep warm with a diesel heater.  Have no trouble running Induction and a toaster at same time. 

Although everything seems to work well, I do wake up wondering if I have overlooked something!  Comments and questions very welcomed. 

Tom

 

[nature lover]

Starry nights- The more I study solar the less I seem to know. So I can’t evaluate your whole system I’m sure the others on here will. To my amateur eyes it looks like you’re right on. I understand though that you’re using 800 amp hours battery bank and only 400 watts of solar panels. I think you might need more solar. I’ve been told the ratio should be 1 to 1 watts on panels to our ah in battery If I’m wrong somebody tell me. Again I’m an amateur but I have time to respond so I did. if it’s working that’s 99% of it isn't it? Good luck with your project.

 

[bullfrog]

What happens if the thermostat fails and charging continues below the recommended temps? Where is the battery stored? Does the diesel heater not keep the inside above 35 degrees on single digit days since no solar charging would occur at night anyway but what if your inverter charger were plugged into the grid and left on? Do they make a BMS with a battery temperature sensor that allows it to shut down charging when temps are above or below limits? I’m just learning and definitely ignorant on the new battery tech but if catastrophic battery failure can occur and is only prevented by a thermostat I would want a fail safe in the system. If nothing else another identical thermostat in series just in case one fails.

 

[StarryNights]

Nature Lover - thanks for the comments!  Actually, I have 100 amps @ 24 volts.  The 100 amp 3.2v cells are wired in series, so one adds the voltage, but the amps remain the same.  If the cells were wired parallel, it would be 800 amps, but at 3.2 volts.  Total power or Watts available is the same (Amps times volts), but few things run at 3.2 volts. 

As for battery capacity, my state of charge rarely drops below 90%.

Tom

 

[StarryNights]

Bullfrog - lots of interesting questions!

The thermostat has to be powered to close the circuit.  If it fails or gets disconnected the circuit opens and the panels get disconnected.  I have been using one of these thermostats to control a portion of my home heating system and it has performed flawlessly for 5+ years.  They definitely do make BMS with low temp control, but the one I got didn't have it.  Tests done by Will Prowse showed that low temp cutoff in these were very unreliable.  I have a lot more trust in my solution that opens the circuit if there is a failure.

The battery is stored under the bed in an insulated box.  I leave the little heat strip on 24/7 in winter.  In the daytime, assisted by sun coming through the windows, it will get the battery up to say 45 degrees, and then it will take a long time for it to cool.  The van is outside in the driveway and I wasn't living in it last winter - just testing and sometimes trying to build stuff.  The diesel heater would have kept everything warm,  but i only turned it on when I was working on the build and left it off at night. 

I could have plugged the inverter into shore power, but there was no real need because the battery SOC was almost always over 90%.  Besides, my goal is to live off-grid on BLM land this winter - and there is no shore power there! 

Tom

 

[bullfrog]

It looks like a really good system to me. Leaving the heater on is probably good as I understand those batteries don’t like staying at full charge. Sometimes we go several days in the desert with overcast days and therefore cold days and nights. I would make sure the batteries would last 3 days with the loads you have or may have with little or no charge. You will most likely want a freezer/cooler as well. If you are going to be using the inverter much you may want a bigger battery bank. Using that large of an inverter may be fine for large loads but you might consider a smaller more efficient one for smaller loads as well. With the set up you have staying at 90% doubling the battery bank should be possible and would sure help make it through the cloudy days. It looks like a really well done system to me but do some stress testing by using the loads you expect to see and a little more just to make sure you will get the results you want and the battery bank is large enough.

 

[nature lover]

Tom, see I told you I was an amateur you know a lot more about it than I do. I did tell you I don’t know much didn’t I? Then I went on to prove I didn’t. Bullfrogs giving you good advice he knows a lot more about it than I do. Apparently you understood what you read and heard about solar a lot better than I did. Good luck keep us posted.

 

[Matlock]

At a glance a Q, does the sterling have a temp control shut off built-in?

 

[Camper]

What about the diesel heater.... do you like it and do you get any diesel fumes inside the van?

 

[StarryNights]

More good questions!  

Bullfrog - Battery is always powering my 130 Liter fridge, a Truckfridge TF130, their largest model. Seems to have little impact on battery life and in summer when van interior was over 90 had to turn it down because it was freezing water bottles.  12V is running LED Lights, a 12V water pump, the Diesel heater, MaxAir fan, USB fan plus phone and laptop chargers. 

The 3000 watt inverter is only switched on when needed - mainly used for cooking (induction stove, Instant Pot, toaster) and A/C power tools like compressor, skill saw, multi-tool, sander, Jig saw.  Each of these is only on for a short time.  Example: Boiling a pot of water takes about 3% of the battery, but if sun is out it recovers quickly. I do have a smaller 400 watt inverter I can use for lower-draw items like DeWalt drill battery charger plus maybe a 28" monitor/TV I am deliberating about installing. 

Doubling battery capacity is possible, but with LiFePO4 it is expensive and presently not a problem I need to solve.  If battery does get too low, I can go for a drive and it will quickly recharge with the Sterling. I look at weather forecast and don't plan high-use activities when there will be prolonged periods of little solar.

Matlock - The Sterling does come with a temp sensor, and so does the Tracer MPPT, but these only kick in if there is overheating. 

Camper - The Diesel heater is great and has no fumes inside at all.  Remember, these units are sealed and 100% of both intake and exhaust go outside.  I purchased a 2K Chinese model on eBay for about $125 and after watching lots of YouTubes did the install myself. You do hear it when it starts up (sort of a muffled jet roar) but once it gets running it throttles down and I can hardly hear anything from inside and not much outside.  

Nature Lover - you never learn unless step up and ask!  

Tom

 

[gtinseth]

Very nice diagram. I have the same solar controller and the Sterling B2B as well, although 200ah of LiFePo4 at 12v. I have a Progressive Dynamics charger for shore power and don't have much gear that runs off AC, so I don't have a big invertor. I am just finishing my Chinese diesel heater install. Great minds think alike!

That said, I wouldn't run your 12v gear off of the load connection on the solar controller. Instead have the 24 to 12 v convertor connected to the battery via a hot bus, maybe one that all the charging inputs connect to before the battery. That load connection on the epever is really meant to run a lightbulb or something else small, not all your 12v gear.

I also may have missed your battery shut off switch, good for just in case situations.

 

[Weight]

Looks good enough. I like Blue Sea buss bars to bring connections together. https://www.bluesea.com/products/category/18/5/BusBars/PowerBar
I also do not use a fuse or CB between the panels and charge controller. I do use a heavy duty switch. The main reason is to reduce voltage drop. But if the wires are sized right it is not needed as the panels have self limited current.
It seems the inverter is oversized for the rest of the system. I do very well with 2000W and 12 volts, 200+ amp hour battery. 400W solar

 

[StarryNights]

Gtinseth - Many thanks for your great comments!    I have posted my layout on a few forums and you are the first experienced user that has had comments I could really use.  What state do you live in, and what van do you have?

I did read on one forum that I should not use the 'Load' terminal on the MPPT, but since I’ve had no issues was looking for more agreement before making the change.  The 24V to 12V converter limits me to 30 amps of 12V. The Fridge is connected before the converter since it can run on 24v.  Despite being large (130 liter) it doesn't draw much and overnight might pull 7% of the battery, which is quickly [size=medium]replenished if there is morning sun.  Seems to draw about 50W when running.  12V powers LED Lights, water pump, USB charging ports plus rarely a small inverter to handle lower load items.  Highest usage seems under 15 amps or possibly 20 with fridge running.  Got a 12V USB C brick for laptop; 1 hour charge and it is good for a day.[/size]

[font=Tahoma, sans-serif]Yes, the inverter is huge and bigger than intended, but my supplier (Electric Car Parts Company - excellent) was all out of the 2K ones and made the 3K attractive.   Nice, however, and enables me to do things like run induction stove and toaster at same time.  I also can use regular 120V power tools. Since you only use most of these for a few seconds at a time, battery impact is small.  Inverter only gets turned on when needed, and I made a blinking red LED to remind me when it is on. [/font]

[font=Tahoma, sans-serif][font=Tahoma, sans-serif]Sterling B to B: Did you wire in the trigger to shut down if the BMS protection activates?  Always wondered if i did this right.[/font][/font]

[font=Tahoma, sans-serif]Chinese Diesel Heater - mine works great, have next to no fuel pump noise and no smoke. After a lot of reading and YouTubes, took about 8 hours over 2 days to install (i'm old and don't bend well any more).  Curious to hear how yours works![/font]

[font=Tahoma, sans-serif]More in next post - get 404 error if longer[/font]

 

[StarryNights]

The diesel heater I got is the 2K model, smaller, uses less fuel and reviewers said it put out enough heat. It came with the simple rotary controller and have since picked up a more advanced one with a long-range wireless remote and things like altitude adjustment - plus remote has AAA batteries instead of hard to find 24v ones.

Battery shut off: You are correct, it is not shown!  Will Prowse did not have one in the plan I used.  I do have the switch and was about to install when had some concern about shutting down battery without 1st disconnecting solar.  MPPT not supposed to like this. Think I have an automatic solution and it is on the list to fix this week.

Again, many thanks for your comments and look forward to hearing more about your install.

Tom

 

[gtinseth]

I have a Subaru powered 87 Vanagon Syncro, not a poptop and no camper interior, just the queen Z-bed. Our home base is in northwestern California. 

I tore apart the entire charging setup when the diesel heater project started. You learn from each project, and with the limited space, I needed to condense and reorganize. Under the rear seat storage contains the batteries, the solar charger, the shore charger/convertor, the diesel heater and all the circuitry and ducting for all those things. The Sterling B2B is under the passenger seat near the starter battery. I haven't wired it to communicate with the batteries BMS, but it is the LiFePO4 aware model so it should know what to do if I have it programmed correctly. On the roof are the solar panels on Yakima bars with L-shaped canoe mounts. Ahead of that is a Warrior Products safari rack with LED exterior lighting for the sides and front. That is where the hi-lift and other recovery gear lives.

I power a Costway 55qt frig, lots of LED lighting and USB and DC cig lighter style outlets and of course the heater, which takes 10 amps during startup and shutdown for a minute or three. For the heater, I upgraded to the aftermarket Afterburner controller made by Ray Jones in Australia. Gives me much more control and many more options including wifi and bluetooth connectivity. I have the 5 KW heater, which is too big, but the new controller lets me throttle it down pretty well without sooting up. I have a 10" android head unit in the dash which is wifi connected to the LTE modem/router and to a gps antenna. We have Calyx, Google Fi, and Verizon to choose from and will probably add ATT at some point. No big antennas yet, just MIMO patches, but maybe in the next network upgrade. Both the wife and I are on Zoom a lot and so connectivity is pretty important as is reliable power. 

The biggest downside to all of it is the fact that it is a 34 year old vehicle. Sometime I am going to have to face the fact it is time to get a vehicle made in this century. I do know it inside out and have touched just about every possible spot on it, so I can fix things, but I'd rather they didn't break. A modern vehicle with modern systems. What a concept.

 

[bullfrog]

I like you and many others came from VW buses (except in our case it was many years ago) to wanting something we didn’t have to fix that required only regular maintenance, was able to cruse at today’s highway speeds and hopefully get decent milage. Unfortunately they don’t make a Prius type vehicle that fits two older overweight people with some disabilities which means you need more room as well, so you end up compromising. Even though I have never owned a Prius I have owned several other Toyotas which have proven to be ultra reliable. The Prius even now can provide climate control as well as have an inverter installed large enough to power a house. It is one of the best as far as fuel mileage vehicles offered. If the Prius just had more ground clearance, was designed (battery wise) to last over 300,000 miles, cost less to purchase I would own one. If Toyota would get into larger vans (Class B size) with this drivetrain, even if it got 15 miles per gallon, I think it would be a perfect vehicle for many. We currently own a Sequoia with over 250,000 miles and if you could stand up in it I would be building it out. Maybe put a VW pop top on it and tow a Prius! Lol!!!

 

[bullfrog]

I had to laugh as I can’t tell you how many times I said “A modern vehicle with modern systems. What a concept!” yet now I am building a 1987 Suburban to pull a homebuilt trailer with lots and solar and a 1987 Samurai on it due to wanting something cheap and easy to fix! Lol!!! What a hypocrite I am! Lol!!!

 

[gtinseth]

Heh, I had a 1992 Suburban that I wish I never sold. Funny how we all travel similar paths to get to somewhere we are happy, or mostly so.

This has taken this thread astray. I am sorry about that.