Emergency Command Trailer.

AdvancedVehicle · September 2017

Hey guys new to the group. I build emergency vehicles, usually police cars, and have been tasked with a unique project for us. We have a Customer looking to build a self sustainable command trailer that is able to be deployed to disaster areas. They're looking to use solar, battery and generator power when deployed, and shore line power when at a station. The load is gonna be pretty light, a bunch of led lights, maybe a few laptop Chargers, phone Chargers, maybe a small fan, but nothing with too much demand. We would, however like to get a couple of days worth of power of need be.

We were looking at the Go Power! Solar Extreme system. This kit contains a 480 Watt solar charging kit and a 3000 Watt pure sine wave inverter system. They recommend a 400ah battery bank and now i'm looking for advice. Am I even headed the right direction with this or should I be looking for something else? Also, being in NJ, any recommendations on battery banks? I wasn't aware they were this big. Any help or a push in the right direction is greatly appreciated. Thanks in advance.

Travis
Advanced Vehicle Solutions

Estragon · September 2017

You need to define the loads. There are 3 basic numbers per load:
1. Running wattage and voltage
2. Peak wattage (for pumps, fridges, etc)
3. Running time (hours per day)

From what you've listed so far, a 3kw inverter is way too big. Some loads (eg. lights) may be DC. A 3kw inverter might take more power itself than in produces for charging phones, etc.

400ah bank isn't a problem, but it needs to be sized properly for the loads for a properly balanced system that performs as expected.

BB. · September 2017

AVS,

Welcome to the forum. Some questions,

Amp×hours or watt hours per day?

How many golf cart size batteries do you want to install?

What is the roof space for panels (no shade, vents and antennas shading of panels kills solar electric output).

12 volt wanted for dc loads (beware, deep cycle batteries see 10.5 to 15+ volts on the battery bus. You may need a 13.8 VDC output dc to dc converter --HAM radios commonly use these).

And / or a.c. power (small 300 watt 120 vac inverter ok)?

Generator? Gasoline, propane , or diesel? Size of generator?

Note: power (watts) = voltage (volts) × current (amps)

Energy = Watts × hours of use per day = WH per day

Just to give some ideas. 500-1,000 wh per day is a small system (lights, radio, laptop). 392 ah @ 12 volt battery bank, 2 days storage, 50% maximum discharge @ 1,000 wh per day)

3,300 wh per day is enough to run a small off grid home (above plus full size fridge, well pump, t.v. set, washing machine). This is good size system with 647 AH @ 24 volt battery bank and a 2,000+ watt solar array (very rough mmm numbers).

Above numbers are very rough and sorry of conservative. Just to give you an idea of the system requirements.

Using AGM or some sort of lithium ion batteries can be very nice, but they are much more expensive and in some ways, not as rugged / forgiving as flooded cell batteries.

-Bill

AdvancedVehicle · September 2017

Thanks for the quick responses.

The roof of the trailer is 8' x 16' or 8'x18' depending on model.

All of the lighting will be 12v DC, the only AC load I can imagine would be a couple of computers, printers or monitors, and USB Chargers, maybe a coffee machine. I guess the ability to run a small fridge would be nice. I would also like to be able to power a small AC, but If that pushes me over the limit, I may want to offer two seperate packages. Maybe offer them A basic package to handle a smaller load (lights, computers) and an advanced package for a bigger load (HVAC, fridge etc).

The generator they have and were hoping to use is a Honda EU3000is.

From what you were describing a 1000wh +1500wh sounds like a good start

BB. · September 2017

OK... I will design a "reasonable" off grid cabin system (i.e., reliable over time and battery state of charge). Note, for RV systems where are are weight and space limitations, many times they use 1 day of storage and 50% maximum discharge vs the 2 days of storage and 50% maximum discharge (i.e., 1/2 the size battery bank for RV). For long term usage, 25% per day usage from a battery bank allows better recharging of the battery bank (easier to recharge 25% of Lead Acid battery capacity in 1 day vs 50% of Lead Acid flooded cell battery per day--You simply need more hours of sun per day than is in a typical day--I.e., 6-10 hours of charging per day instead of ~4-6 hours of full sun).

1,500 Watt*Hours per day of AC load
1,500 WH / 12 volts ~ 125 AH @ 12 volts of DC load

Battery bank capacity:

1,500 Watt*Hours per day * 1/0.85 AC inverter eff * 2 days of storage * 1/0.50 maximum discharge * 1/12 volt battery bank = 588 AH @ 12 volt battey bank (basically 2x 6 volt golf cart batteries in series * 3 parallel strings = 6 batteries total)

Of course, there are different batteries to choose from (L16 are larger cells with higher AH ratings, and would be recommended here--But more expensive).

Then, to charge the battery bank, we use 5% to 13% rate of charge typically for solar. 5% is good for weekend/seasonal usage, 10% or higher rate of charge is recommended for full time off grid (lead acid batteries are expensive and solar panels are "cheap". More panels generally give you happier battery bank).

588 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 554 Watt array minimum
588 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 1,107 Watt array nominal
588 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 1,439 Watt array "cost effective" maximum

Then there is sizing the array based on how much power you use... Your location, and the tilt of the array will affect the "hours of sun" per day... For your trailer, you can mount flat (first chart) or tilt to face noon-time sun:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Trenton
Average Solar Insolation figures

Measured in kWh/m2/day onto a horizontal surface:

Jan	Feb	Mar	Apr	May	Jun
1.92	2.71	3.69	4.57	5.21	5.61
Jul	Aug	Sep	Oct	Nov	Dec
5.51	4.97	4.15	3.13	2.07	1.66

Trenton
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel where the angle is adjusted each month to get optimum sunlight.

Jan	Feb	Mar	Apr	May	Jun
3.35	3.91	4.41	4.82	5.16	5.63
Jul	Aug	Sep	Oct	Nov	Dec
5.38	5.13	4.70	4.30	3.38	3.10

Your summer sun (in Trenton) does not do too much better with a tilting array (lots of clouds in summer?). In winter, you get amost 2x as much sun... So you have to decide if tilting the array is worth the engineer/expense. Say your minimum solar day is 3 hours of sun (the rest, make up with genset when needed):

1,500 WH per day * 1/0.52 off grid AC system eff * 1/3.0 hours of sun per day = 962 Watt array "break even" on 3 hours of sun per day

For the number of panels, just sq ft wise (using random, less expensive, solar panels):
SolarWorld SW-285 Mono All Black

Pmax: 285 Watts
Voc: 39.2 Volts
Vmp: 32.0 Volts
Isc: 9.52 Amps
Imp: 9.0 Amps
Silicon type: Monocrystalline
Efficiency: 17%

Amphenol UTX locking connectors
Weight: 39.7 Pounds
Dimensions: 65.95" x 39.4" x 1.30"

And your trailer is:

8 feet = 96 inches

16 feet = 192 inches

You may fit a maximum of ~2 wide by 3 panel long for ~6 panels or ~1,710 Watt array

That is a pretty good size array and would, if we use 3 hours of sun as our minimum baseline, produce something like:

1,710 Watt array * 0.52 off grid AC system eff * 3.0 hours of sun per day = 2,668 Watt*Hours per day @ 3 hours per day of "average" sun

BB. · September 2017

So--Does the above look "interesting" and we can continue? Or bigger/smaller/wrong city/etc.? This is, relatively, a conservative design.

If you need more panels, there are folks that have done various folding panel designs (watch for wind damage/flipping of vehicle in high winds). For example:

http://www.mobilesolarpower.net/
https://www.google.com/search?q=trailer+mounted+solar+power+system&source=lnms&tbm=isch

-Bill

mike95490 · September 2017

At least you are open to using a generator, there will be some cloudy days.
First size up your loads Thusly:
5 radio chargers @ 20w=100w x 16 hours = 1600 watt hours
1 Fridge = 1,300 watt hours
2 desktop computers & monitor @ 190w x 2 = 380w x 12hrs = 4560wh
2 laptop computers @ 90W x 2 = 180w x 12hr = 2160wh (I'd spend the $$ for laptops and toss the desktop idea)
Interior lighting 10w x 6 = 60w x 12hr = 720wh

First
Add up all the watt hours for all your gear - then x2 = the PV array size / 4 hrs , if you want to not run generator on sunny days
(gosh that's really clumsy to write out properly)
Second
Add up all the watt hours for all your gear - then x3. That will = the wh your battery bank needs to be
I'm thinking a 48V bank would be required.

Most of the time the batteries will be sitting, degrading till they expire after 5 years. They will need to be on Float charge until you deploy, and then change the charger to Cyclic duty.

Estragon · September 2017

Okay, we're getting somewhere. The "B" system has a coffee maker, fridge, and maybe air conditioning. It comes down to loads. The rest of the system flows from there.

AdvancedVehicle · September 2017

> @BB. said:
> So--Does the above look "interesting" and we can continue? Or
> bigger/smaller/wrong city/etc.? This is, relatively, a conservative
> design.
>
> If you need more panels, there are folks that have done
> various folding panel designs (watch for wind damage/flipping of vehicle
> in high winds). For example:
>
> http://www.mobilesolarpower.net/
> https://www.google.com/search?q=trailer+mounted+solar+power+system&source=lnms&tbm=isch
>
> -Bill

Yes this sounds pretty spot on!

BB. · September 2017

OK. Then need to look at how you use the power... A 1,500 WH per day system, running 24 hours per day would be capable of supplying:

1,500 WH per day / 24 hours per day = 62.5 Watt average load

As you can see, this is not very much power/energy. For example, a small laptop will take from around 8 watts to 60 watts... With ~30 Watts being fairly typical for an average lower power laptop running all the time. Add some USB and radio chargers, there goes another handful of Watts. If you want to run from an AC inverter, here is a pretty nice 300 Watt 12 volt TSW inverter with standby and remote on/off that draws 6 Watts just being turned on (standby mode uses much less power, and checks about once per second for an over 6 Watt AC load, then turns on). This is a fairly feature rich AC inverter for a smaller/12 volt unit:

https://www.solar-electric.com/morningstar-si-300-115v-ul-inverter.html

If you ran this inverter just by itself 24x7 hours per day, that is 10% of your total available energy per day (6 watts out of 62.5 watt continuous available power).

Watts, add another 3-6 Watts of LED 12 hours per day (6 Watts * 6 Watts is 36 WH per day).

Any loads that run 24 hours per day usually end up being very significant for solar power systems. For a cabin/small home, most of the energy is used in the evening--That is 5 hours per night, or ~1,500 watts*hours per night / 5 hours per night = ~300 Watt average load.

If you have a sunny day and use significant power between 9am and 3pm, a 1,710 WH array gives you 2,668 WH per day with 3 hours of sun on a tilted array--So you have some extra power to play with.

And to finish it up, just some numbers on what a 588 AH battery bank can support (6x 6 volt @ 200 AH flooded cell "golf cart" batteries give you 12 volts @ ~600 AH battery bank). Of course, in general, you only want to discharge a lead acid battery to ~50% state of charge for long life. For this usage you could discharge to 20% state of charge if you recharge the battery quickly with the genset--You have very few cycles per year (emergency/fair/etc. usage--Batteries will "age out" before they cycle out, or they will be killed by miss-use:

588 AH * 12 volts * 0.85 AC inverter eff * 1/24 hours per day usage = 250 Watts (24 hour discharge until battery bank dead--"gentle usage")
588 AH * 12 volts * 0.85 AC inverter eff * 1/8 hours discharge rate = 750 Watts (maximum continuous discharge. 8 hours until dead--Actually probably closer to 7 hours--The faster you discharge a battery bank, the less "apparent capacity it has")
588 AH * 12 volts * 0.85 AC inverter eff * 1/5 hours discharge rate = 1,200 Watts (maximum power for minutes or an hour)
588 AH * 12 volts * 0.85 AC inverter eff * 1/2.5 hours discharge rate = 2,399 Watts peak power (for a few seconds, like starting a well pump)

While the battery bank is capable--The limitations for your needs are the 24x7 operation. And you can see why I suggest only a small/efficient 120 VAC TSW inverter. The battery bank could support upwards of 750 Watt to 1,200 Watt AC inverter--Any significant hours of use will use up your daily energy harvest by 1-2 hours of usage, and empty the battery bank in ~4-7 hours of usage at full power.

Since you will have an AC genset... Then a nice AC battery charger will be a big help. Roughly, a good range for a genset charger is ~10% to 20-25% of battery AH:

588 AH * 10% rate of charge = 58 amp charger
588 AH * 25% rate of charge = 147 amp charger

A very nice battery charger (you can put two together for more current) is this one from Xantrex (very generator friendly):

http://www.xantrex.com/power-products/battery-chargers/truecharge-2-2.aspx

It is a wide ranging AC input (96-265 VAC)--Very nice for getting "any power" (genset with poor regulation, long power run of 240 VAC power, etc.). It is also "Power Factor Corrected" (more or less, it uses AC current more efficiently, very important for running off of a small AC genset).

Roughly, the current draw for the TC2 charger at 60 amps charging:

60 amps * 14.75 volts charging * 1/0.90 TC2 charging eff * 1/115 VAC input = ~8.4 amps @ 120 volt circuit
8.4 amps AC * 115 VAC * 1/0.80% genset derating = 1,208 VA rated genset (i.e., nice with a Honda eu2000i or similar genset).

Have once AC circuit in the trailer running from 300 Watt inverter. Have a second one that runs from the genset. And you can put in a transfer switch (manual or automatic relay) that switches from the 300 Watt inverter to the genset/remote power trailer input.

And to give an idea of fuel usage:

eu2000i--1,600 Watts will run ~4-9+ hours per gallon of gasoline (1.1 gallon fuel tank)
eu3000i--2,600 Watts and will run 3.5 to 7.7 hours (1.6 gallon fuel tank)

I like to run the loads from the AC inverter (smaller wiring, use ac receptacles instead of cigarette lighter plugs--Although, it is common to run Anderson Power Pole connectors for 12 volts with HAM radio systems. Remember a deep cycle battery bank will operate around 11.5 to 15.5+ volts (discharged+loads to charging voltage)--That is a pretty wide range for many 12 volt devices. We have had a few reports of laptop chargers that have failed at ~15 volts.

Some HAM suggestions:

http://www.qsl.net/w2vtm/powerpole.html (DC power connectors--Power Pole)
http://www.dcpwr.com/shop/ (example of off the shelf Power Pole connector blocks)
https://www.solar-electric.com/kiacpomome.html (Kill-a-Watt meter to measure AC power/energy usage)
http://www.rc-electronics-usa.com/ (DC Amp*Hour/Watt*Hour meter)
https://www.solar-electric.com/bogart-engineering-tm-2030-rv-battery-monitor.html (battery monitor)
https://www.victronenergy.com/battery-monitors (nicer battery monitor, one model has alarm output)
https://www.solar-electric.com/mnbcm.html (simple volt meter based only--above use current shunts to measure battery current)

Obviously, lots of details to go--Just want to suggest that you measure your loads (Kill-a-Watt meter for AC loads, Doc Watson for DC loads--Or similar meters) to see what your "useful" energy usage is.

-Bill

AdvancedVehicle · September 2017

Wow outstanding write up Bob, I really appreciate it. Checking out all of the links now. I need to gather a final list of everything I need total, so I can get it all priced out and ordered. I will be sending you a few bucks for your time as well.
Also, Our need for 24 hour use isn't as important as it sounds. I can see very few, if any things needed to be run for 24 hours.

BB. · September 2017

I am just a volunteer here. No donations needed.

Our host who pays the bills for three from is Northern Arizona Wind & Sun:

https://www.solar-electric.com/

They are a full service retailer/wholesaler. They cash give you a parts list through a configured and tested system.

Feel free to ask more questions. The first design can go easier with help.

-Bill

BB. · September 2017

Also, let us know how it all works out, with pictures.

-Bill

myocardia · September 2017

AdvancedVehicle said:

Thanks for the quick responses.

The roof of the trailer is 8' x 16' or 8'x18' depending on model.

All of the lighting will be 12v DC, the only AC load I can imagine would be a couple of computers, printers or monitors, and USB Chargers, maybe a coffee machine. I guess the ability to run a small fridge would be nice. I would also like to be able to power a small AC, but If that pushes me over the limit, I may want to offer two seperate packages. Maybe offer them A basic package to handle a smaller load (lights, computers) and an advanced package for a bigger load (HVAC, fridge etc).

The generator they have and were hoping to use is a Honda EU3000is.

From what you were describing a 1000wh +1500wh sounds like a good start

I guess you weren't aware, but newer laser printers may only use ~20 watts in standby, but use 400-800 watts while printing. 500-600 watts is pretty average use while printing, Pretty much the faster they are able to print, the more power they use. The power usage occurs because laser printers have to heat the roller to be able to print, and heating with electricity is extremely non-efficient. This is for every brand of printer that uses toner, instead of liquid ink. The same applies to any and every copy machine, which of course also use toner and a heated roller. BTW. Inkjet printers usually use roughly 1 watt in standby, and 15-20 while printing. Also, older desktop computers use can easily use 100 watts each, at idle.

Of course, all of the above combined, even while printing, uses next to nothing, compared to coffee makers and air conditioners. Coffee makes use right around 1,000 watts anytime that the power switch is in the on position, and I've never personally seen an office worker who knew that coffee makers have power switches. While 1,000 watts for 10 minutes while brewing 10-12 cups is no big deal, 1,000 watts 8-12 hours per day can't be done on battery power.

Emergency Command Trailer.

Comments

Trenton
Average Solar Insolation figures

Trenton
Average Solar Insolation figures

Categories

Emergency Command Trailer.

Comments

TrentonAverage Solar Insolation figures

TrentonAverage Solar Insolation figures

Categories

Trenton
Average Solar Insolation figures

Trenton
Average Solar Insolation figures