Newbie PV/batt/AC design questions for military truck RV...

frankson
frankson Registered Users Posts: 22
Got a 5-ton diesel M934A2 expandable van, similar to this...

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Currently re-insulating inside as a full-time off-grid home.
Also, will paint reflective paint atop roof & will utilize some
moveable shading on any sun exposed sides of the vehicle.

With it's poor mileage, it won't be driven often, but rather
parked & lived-in for many months at a time, including in
Texas summer heat. I'd guesstimate it'll be occupied most
all evenings and only 24 hrs/day for half the week, at most.

Electric loads; LED lighting, small portable ice maker to
infrequently feed small super insulated ice chest, bread
maker twice a week, small microwave infrequently, and
12 vdc laptop, radios, fans. Water useage is all gravity
feed, stove is propane, solar oven whenever possible,
rare space heating needs would be either via smallest
marine diesel heater or propane.

Biggest load will be smallest efficient window AC available
that'll do job. For sleeping, we are talking about 50 sq ft
or 325 cu ft partitioned off quarters. AC window unit at top
center front in overhang allows directing AC exclusively into
there at night. Total open living area, including bunk area,
not taken up by storage space for supplies, water, galley,
head, etc. works out to about 150 sq feet or 975 cu ft.

Also, have Solar Chill 1412XP Evaporative Cooler to utilize
instead if/when humidity low, which is not often enough
here in central Texas.

While truck is 24 vdc, I'm not looking at trying to tie into
its batteries. Nor, ever charge house batteries via truck.

Components I'm starting with...

6 Kyocera KD-135-SX-UPU, 135 watt 12v, 2B mounted atop rig.

4 Lifeline GPL-8DL AGM battery bank, about 1000 amps total.

Dedicated 5.5 hp diesel driven DC battery charger, which can
put out either 180 amps in 12 vdc or 160 amps 24 vdc.

BTW, DC genny on underside of truck and battery bank inside
with window air conditioner and evaporative cooler and other
loads will all be in close proximity and I've lots of free welding
wiring here, so choice to wire 12 or 24 vdc can be based much
less upon cost of wire size/lengths.

I have no illusions that six panels and 1000 amp battery bank
are sufficient for running AC continuously. And, swamp cooler
will often be ineffective to use instead when too high humidity.

When AC required, I'd ideally like to be able to, at least, bulk up
battery bank right before bed time via diesel DC charger, shut it
down, and then not exceed a battery bank draw down past 50%
with running AC on lowest setting at night. Then, fire it up again
briefly in the morning for quick bulk charge and let panels bring it
up to nearer 100% the rest of the way during the day, hopefully
sunny, especially when I'm gone and no loads then on system.

Appreciate any thoughts on above; good/bad/ugly, or creative
enhancements to reducing loads or maximizing energy production,
along with any specific recommendations you might have for...

- Do I set up system and batteries for 12 vdc or 24 vdc? A lot of
my daily use LED lighting, fans, laptop, etc., are already 12vdc.

- PV charger size make/model and best connections for tying in
together six KD-135-SX-UPU to it. I won't be adding more PV's,
though I might fool with a small wind genny sometime, if both
gotten cheap and I found myself on windy TX coast for a spell.

- Inverter size make/model

- Battery charger for if/when I have free shore power available.

- Any creative ideas to tilt mount PV panels, ideally all together as set

- Best radiant reflective roof paint, if for waterproofing, too, even better

- Efficient, smallish, AC unit for mounting in top front overhang of van

I know that selecting and settling on Air Conditioner, thus knowing its
running amp draw and starting surge, should come first to best select
inverter, but you might could help narrow down inverters for me here,
if no specific air conditioner recommendations to go along with it, too.

Thank you anyone for any suggestions here.

Comments

  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Newbie PV/batt/AC design questions for military truck RV...

    Lets start with first things first. You need to add up all your loads for a typical daily consumption to get to the battery sizing question.
    Then once you settle on the battery sizing you can determine your charging requirements be it solar, generator ...

    As far as AC units the mini splits seem to garner lots of support here, they just work pretty effectively. What kind of BTU load do you link you will need?
  • frankson
    frankson Registered Users Posts: 22
    Re: Newbie PV/batt/AC design questions for military truck RV...
    solar_dave wrote: »
    Lets start with first things first. You need to add up all your loads for a typical daily consumption to get to the battery sizing question.
    Then once you settle on the battery sizing you can determine your charging requirements be it solar, generator ...

    As far as AC units the mini splits seem to garner lots of support here, they just work pretty effectively. What kind of BTU load do you link you will need?
    True enough, I'm trying to guesstimate load times and anticipate all of that, not easy.

    Sorry, I was not clear enough in original post...

    Limiting factors are I won't be able to add any more PV's than the six KD-135-SX-UPU's,
    nor any more batteries beyond the four Lifeline GPL-8DL AGM's, about 1000 amps total.

    And, thus, need to make the best of maximizing system within those strict limitations,
    mostly with help from diesel dc genny, but hopefully also with some guidance to both
    correctly select the remaining components I'd inquired about and any suggestions to
    minimize loads further while maximizing efficiency.

    There's things this system will and won't ever do, given PV & batt limitations, I'm just here
    inquiring of any component & design suggestions & recommendations to make the most of it.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Newbie PV/batt/AC design questions for military truck RV...

    The incredibly long and involved mini-split thread: http://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-%28inverter-variable-speed%29

    This could be a good application for one.

    As spec'd, you'll probably have about 2 kW hours AC to work with from those panels. That's not too bad; I run the whole cabin off 2.4 kW hours. No A/C, but a full size electric 'frige (major power user).

    The panels alone are not going to charge 1000 Amp hours of battery. They would support about half that @ 12 VDC (on their own). As for whether you should pick 12 Volt or 24, you need to work out what sort of Watt hours you need to store and what the maximum AC Watts will be. If the latter is continuously above 1.2 k then 24 Volts starts to look attractive (lower DC current). Otherwise the easy availability of 12 Volt equipment makes the choice. Do not put in 24 Volt and then "tap half" to get 12 VDC; the battery bank will be unbalanced and its life shortened.

    According to my info, your batteries are 255 Amp hours each. If you parallel all four (not good to have lots of batteries in parallel) you'd have 1020 Amp hours @ 12 Volts and a peak charge current potential that just touches the 5% recommended minimum. With your diesel gen back-up, this looks viable.
  • frankson
    frankson Registered Users Posts: 22
    Re: Newbie PV/batt/AC design questions for military truck RV...
    The incredibly long and involved mini-split thread: http://forum.solar-electric.com/showthread.php?5104-Sanyo-mini-split-AC-%28inverter-variable-speed%29

    This could be a good application for one.

    As spec'd, you'll probably have about 2 kW hours AC to work with from those panels. That's not too bad; I run the whole cabin off 2.4 kW hours. No A/C, but a full size electric 'frige (major power user).

    The panels alone are not going to charge 1000 Amp hours of battery. They would support about half that @ 12 VDC (on their own). As for whether you should pick 12 Volt or 24, you need to work out what sort of Watt hours you need to store and what the maximum AC Watts will be. If the latter is continuously above 1.2 k then 24 Volts starts to look attractive (lower DC current). Otherwise the easy availability of 12 Volt equipment makes the choice. Do not put in 24 Volt and then "tap half" to get 12 VDC; the battery bank will be unbalanced and its life shortened.

    According to my info, your batteries are 255 Amp hours each. If you parallel all four (not good to have lots of batteries in parallel) you'd have 1020 Amp hours @ 12 Volts and a peak charge current potential that just touches the 5% recommended minimum. With your diesel gen back-up, this looks viable.

    Thanks, Cariboocoot, and 'yes' had waded through that mini-split thread yesterday before posting, along with dozens of others.

    Tons of great info here!

    Reality is, I'll probably end up running any typical small AC window unit with dc charger on more often than just solely via batteries.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Newbie PV/batt/AC design questions for military truck RV...
    frankson wrote: »
    small portable ice maker to infrequently feed small super insulated ice chest, bread maker twice a week, small microwave infrequently, and 12 vdc laptop, radios, fans.

    What ice maker is that? Does it really use less energy than a small super efficient fridge?
    Do I set up system and batteries for 12 vdc or 24 vdc? A lot of my daily use LED lighting, fans, laptop, etc., are already 12vdc.
    I faced the same issue when I set up my system. I gave up the 12 volt loads in favor of 115 volt loads and a 24 volt system. If you have loads over 1000 watts you would be better off with a 24 volt system. My large loads are only a few hours/week (laundry, vacuum, etc) but my large inverter/charger (20 watt no load draw) is on 24/7. That is NOT efficient because often my only load is a 5 watt LED bulb. The solution (not yet implemented) will be to add a second small inverter for 24/7 use, in which case I will turn on the large inverter only when needed.

    Whether a two inverter solution will work for you may depend on your refrigeration... 115 volt refrigeration will need to draw current 24/7 and will be too much load for a small inverter. My solution was to use a DC fridge. Fridges that use the Danfoss compressor (Sundanzer, Steca, Sunfrost, etc) will work on either 12 or 24 volts DC.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i