Solar for habitat on an FMTV

[coachgeo]

so not to hijack another's thread..... starting thread here.

.... It is by no means and apples to apples comparison. If you need starting batteries and you are not putting a living space in the back the battleborn would be ideal because they are a simple drop in replacement.

Am puting former ambulance box on back of mine for habitat. Going 24v in habitat for consistency such as using the habitat battery bank to keep truck battery OEM wired bank topped up. Also my cab AC (actually a liquid chiller) is 24v. Granted this plan came about while I assumed the OEM truck battery bank was charged via the 24v side of the alternator but now understand it is 12v charge side. (or am I still misunderstanding how the FMTV alternator charges the 4 batteries?) It draws so miniscule amps (4ams at 24v) compared other options and will be massively easier and less costly to install it for cooling cab occupants compared to typical AC .

Ambo inverter was removed prior to sell so I could just as easy install a 24v-->110 inverter formerly where the other 12v one was. Useing inverter to power a cheap 110v AC unit and other 110v items. Then install step down to 12v sent into wiring of the OEM Ambo 12v system. (LED lights mostly, a few 12v sockets and a few fans). My portable liquid chiller unit (24v) and my stationary chiller unit (110v) can be used to chill sleeping cover(s), cool vest(s), poncho's etc for inside or outside use when it is more logical to just cool the person than a whole space. The 24v chiller will cool person(s) in the cab and ambo when driving. Just do not see logic in cooling whole cab or aluminum box compared to just the person(s) when your in reality just sitting inside them seat belted for long periods of time; not getting up and moving about.

Plan is for solar to also aid in powering my small home (1000w). Due to cost of batteries, have not decided yet on charge controller. Either a medium sized bank of battery for ambo and a controller that has a grid tie feature to defray power cost int he home or a larger bank that the home and/or ambo can use. I prefer the large bank... but cost esp. when factoring in annual battery replacement..... grid tie seems more logical, at least according to my friend with 30yrs in solar industry

Have a NOS military diesel fired coolant heater. Pretty sure it is 24v ignition too. It is NOS for a Duec? Plan to install in similar manner to how Eberspaecher's are are plumbed into overland truck habitats. Example plumb in ability to use it for engine/cab warming along with habitat radiant/blown heating along with small tank for hot water warming. Maybe also personal heating using above described chiller's plumbing system .


What is ya'lls suggestions on this......

Also please post what is your plans and why

 

[Aernan]

Ok the Neihoff alternator is like a dual tapped transformer. Basically it has some windings in it and you get both 12v and 24v out of it. The big thing to remember is the total amps out will be split between 12v and 24v. If you draw a lot of power (100 amps) for a long time it's going to heat up. If you make it do that for most of the lifespan you will kill the alternator quickly. They are only designed to provide some amount for some time then have a nice break. (duty cycle). Or something like 80% of load full time. I don't know the duty cycle of this part so avoid using it for 100 amp continuous duty. Also alternators are only like 50% efficient so it's not an ideal source of power.

The battery bank can be a bit hard to conceptualize. If you hook two batteries in series (like a flashlight) you add the voltage. So two 12v batteries is 24V. If you instead hook them in parallel the voltage stays the same but you add the current (amps). What they have done is hook two batteries in parallel to two batteries in parallel. So you get a total of 24v with a whole lot of cranking amps.

You can visualize the battery box this way. The two batteries closes to the edge are hooked in parallel. The wire closest to you is the main ground (negative). The next wire closer to the frame rail that connects all 4 batteries can be thought of as a 12v output. You must visualize this with the two farthest batteries just missing. So two batteries and two wires. Batteries are in parallel.

Now the next circuit is the closest (outside) wire. The positive part is the farthest wire (against the frame rail). That makes a 24v circuit. it uses all 4 batteries.

When you start the truck the 24v is used. The rest of the time only the 12v is used. That means the batteries on the outside get the most use and wear out first.

 

[Aernan]

When designing the battery bank for the house part you should bear in mind how much power you use during a day and how many cycles you will put in your battery bank. Then you can figure out the correct minimum size for the bank and find what power sources you will use. It is possible to add capacity to a battery bank but when the weakest link (oldest battery) is done you lose access to the remaining power in your newer batteries.

 

[Ohiobenz]

Multi source off grid power on an LMTV

So my M1079 has the original 3" wall insulated box on it which I'm converting into an RV for expedition travel.
My plan is, or was, as it may change as I learn, to have the aux and main battery bank connected via a VSR, 4-300W Solar panels connected via a Victron MMPT 28VDC charge controller to the aux bank, and my 3.5kW 28VDC diesel generator as a back up - with auto start at 20? Volts and auto shutoff at 32V.
Aernan mentioned the Victron VE which I'm going to have to look into. The Tesla bank also sounds like a financially feasible battery system vs the Battleborn batteries at $1k each.

The Victron MMPT-75 worked well on my 100W solar setup on the FJ Cruiser, so I'm game to use them for other devices.

I like the option of a grid disconnect which would allow me to connect to 120VAC if parked for an extended time - and run the fridge, AC and convection cookstove.
It's the instant hot water heater that seems to be totally out of the scope of running on DC power, which has made me consider a BBQ propane tank, just for hot showers...

so fire away...

 

[Aernan]

For a good read on designing you house electrical you should read this:
https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

I would jump to section 6 which has common energy budgets for boats. It matches my needs closely.

 

[Ohiobenz]

https://www.victronenergy.com/upload/documents/schematic-vehicle-lithium-rv2-.pdf

 

[Aernan]

When looking at lithium batteries you should know there are many vendors available and you can build a pack of whatever capacity and voltage you like by assembling individual cells/batteries. The tesla is a great option because they use a unique chemistry that "resists" fires and being pulled from old cars they are substantially cheaper then full retail.

Here are some makers you may want to investigate. I too need to do more digging to get prices as well.
https://www.elitepowersolutions.com/lithium-ion-batteries/
https://www.ev-power.eu/Winston-40Ah-200Ah/
https://www.victronenergy.com/batteries/lithium-battery-24v-180ah
https://www.victronenergy.com/batteries/lithium-battery-12-8v
https://www.ev-power.eu/Winston-40Ah-200Ah/
http://www.sinopolybattery.com/en/products.aspx?cid=10
https://www.ev-power.eu/CALB-40Ah-400Ah/CALB-CA180FI-Lithium-Cell-LiFePO4-3-2V-180Ah.html

 

[Aernan]

Given the roof size and total bank capacity it is possible to run entirely on solar power. Sunpower makes som 430 watt panels and Panasonic makes some others in the 330 watt. If you cover "most" of the roof you can put 5 panels up.

330 watts x 5 panels = 1,650 or 1.65 kw. In California here we get 5-6 "sun hours" a day. 8,250 or 8.25 kw a day intake. That is ideal and panels will degrade. The great thing about solar is you can buy it in stages by adding to the string or adding another solar inverter to feed into the system.

 

[Adventure Driven]

This is what we did in case your interested, a touch overkill but have plenty of power to do whatever we want

Seth

https://www.youtube.com/watch?v=6CfneYZBWaM&list=PL_Xt8uqCZHErtT7mo7kv-DIJcdqSuqhTX&index=21


https://www.youtube.com/watch?v=xh9YacDpzng&t=6s

 

[Ohiobenz]

I'm more interested in the specifics of the control.
My system will have a 28v generator for backup.

 

[Awesomeness]

In California here we get 5-6 "sun hours" a day. 8,250 or 8.25 kw a day intake.

Keep in mind that those numbers are further reduced because the panels are not pointed directly toward the sun. At about 20 degrees off, you still make about 90%. At 45 degrees, you're down to 70%. At 60 degrees, you're at about 40%. So there is some average for the day, as the sun tracks across the sky (low angle, overhead, low angle). It moves fastest overhead, so the best power output lasts the shortest. My guess is that the average for a day is going to be like 70%.

 

[Aernan]

Should we be designing in a way to tilt the solar panels to get more power?

 

[Awesomeness]

Should we be designing in a way to tilt the solar panels to get more power?

It all depends how much power you need or want. My point is mostly that solar numbers are dangerously deceiving. Between the losses from aging (typically a loss of around 10% in the first few years, then remains fairly constant), not pointing directly at (e.g. tracking) the sun, inverting DC power back to 120V AC, etc., you can easily lose the majority (>50%) of the power generating capability of the solar system before you've even plugged something into it.

That means you either need to drastically oversize your system, drastically undersize your consuming devices, work hard ($$$) to mitigate the losses, and/or have a backup means of power (e.g. alternator, generator, etc.). You can't just read the box of the panel and go "Oh, three 500W panels will run this 1500W A/C."

 

[Mike929]

I'm curious about the controller and converters you would use based on your experience?
Best to go 120v appliances that are cheap and easy to replace, or try to build with DC based appliances and avoid conversion loses.

In my case, I assume I can get 4 large panels on a 15' box.

Secondly, how do you handle hail? In north Texas, you can count on large hail on average, every 7ish years.

 

[Awesomeness]

None of these problems are just as simple as "which one is better?". Like your question about AC or DC appliances points out, there are numerous trade-offs and you have to choose which is best for your budget/use/skills/etc.

Peak inverter efficiency can be over 90%, but poor efficiency can be pretty terrible too. The inverter itself also draws power (even when supplying no power). So an oversized inverter (which draws more) can itself be a drain on the system if not working very hard. (For example, you have a big inverter that eats 100W itself, and then you only draw 100W of AC to charge your phone... it's costing you 200W!)

Another consideration is that AC power suffers less loss traveling through wires than DC. So if you have long wire runs, and an efficient, appropriately sized inverter, it is possible to have AC be overall more efficient than DC.

The trouble with all of this topic is that if not done competently, it is easily possible to make huge mistakes, and end up with a system with terrible efficiency and capabilities. Sometimes you can do projects and get away with "shade tree engineering", mostly by brute forcing the issue and just overkilling it. With solar though, you are really designing a very performance-restricted system, because power input is so low. So the margin for error is very small.

 

[Mike929]

Are there any references you would suggest, or possible people could list there systems noting strengths and weaknesses. I.e. a steel soldiers reference guide w/ known examples.

Just a thought. I have no issues researching, I would just like to avoid the expense of redesigning an initial solution if at all possible.

 

[Awesomeness]

I don't have any suggestions for this type of use because all my solar knowledge comes from other non-vehicle related engineering projects that I've worked on that included solar capabilities.

Personally though, I would start by looking at what most RVs are doing. It's reasonable to assume that they've already tried all the tricks and that whatever they have settled on is a smart direction to start heading. Think about whatever line of work you are/were in. How many times did you roll your eyes when some new guy came along with a bunch of naive ideas about how they were going to do it different and better? They were probably talking about a bunch of the things you yourself tried when you were a newbie. Obviously, there are sometimes good reasons to go a different way, and new things that come along, but they are rare.

 

[coachgeo]

PS.... since this bulletin board is mostly; not all, but still mostly inhabited by folk interested in preserving military trucks there is not so much Overlanding truck build info in here. Nothing wrong with that, its just not the direction this board headed. Admit though there seems to be a bit more folk interested in Overlanding expedition in this forum than others forums of SS....

Anyway..... long story short...... this subject is so massively discussed over at ExpeditionPortal.com it has its on forum dedicated to it. You'll find ton of your answers there and would be a great place to start. But please do bounce what you learn there off us too.... there is enough here with overlanding desires it would be great to learn from one another.

 

[Aernan]

I have discovered the crowds don't entirely overlap. But you can find me over there and I would be happy to discuss the electrical complexities of designing a house on wheels.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[coachgeo]

recent articles on this subject

http://www.truckcamperadventure.com...ake-on-the-ultimate-electrical-system-part-1/
http://www.truckcamperadventure.com...ake-on-the-ultimate-electrical-system-part-2/