Going Solar On My Work Van!!!

timmcbeth1984timmcbeth1984 Registered Users Posts: 6
First of all, I'm a noob at this kind of thing. Not only am i talking about solar power, but also joining a forum in itself. So I'm a double noob. Anyway, I need lots of help with an idea of going solar on my work van. It would be a pretty simple decision to make if i knew more on the subject of course but first let me fill you in on the idea. I have a Chevy Express cargo work van that i plan on running a few electric tools/equiment out of. I bought a 1000 Watt power inverter from Autozone and I am planning on buying a couple batteries to build a small bank. Well, since I only have a 105A alternator I was thinking solar panel on the roof to help out. Is this idea too far fetched? Not really sure how much wattage I'll be using with the equipment I plan to run, but the bigest piece has a 1.0HP 0.75KW electric motor that will probably run for about 30min. at a time maybe four times a day at the most and the other stuff will be a laptop, a all in one HP printer and some cordless drill type battery chargers. But nothing will be ran continuously, only when it needs to be charged up, etc. I'm not sure if solar is even the best route. Do i even need multiple batteries or maybe just get one extra battery and upgrade to the 130A alternator. If I go solar with a battery bank how much solar wattage do i need? Cost Vs. efficiency? Please help. Thanks.

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Going Solar On My Work Van!!!

    welcome to the forum,
    bluntly quit buying stuff until you've talked it out here.

    we (and you) need to know or have an idea of the wattage consumption of what loads and for how long each day.
    a few points here---
    1 the inverter you bought is most likely a cheap modsine inverter. these suffice for some things like a standard light bulb which few here recommend. most loads that are inductive like fans, motors, and compressors do best on a sine wave inverter and know that some items are known to blow out on modsine. modsine also causes a higher power consumption in many loads than a sine wave source.

    2 you do not want to employ car batteries for deep discharging applications as they won't last long being they aren't made for it.

    3 alternators often do not fully charge a battery and don't lend themselves well to parallel charging of a vehicle battery and deep cycle batteries. isolators are often recommended, but they lower the charge voltage a bit lending to further undercharging of all of the batteries. it gets complicated and there are many threads for campers and i'm quite sure many of those campers will throw in their 2 cents for your quest.
  • timmcbeth1984timmcbeth1984 Registered Users Posts: 6
    Re: Going Solar On My Work Van!!!

    Thank you for the kind greeting. So ditch the Autozone inverter, got it. So i need to figure what kind of wattage first. Some of the equipment I dont even have yet so we'll have to guess. On the many piece there's a label on the motor (In the Pic) that says 0.75Kw, thats 750 Watts right, but the Amperage and voltage readings would indicate 1035 Watts wouldn't they?
  • DillDill Solar Expert Posts: 170 ✭✭
    Re: Going Solar On My Work Van!!!
    Thank you for the kind greeting. So ditch the Autozone inverter, got it. So i need to figure what kind of wattage first. Some of the equipment I dont even have yet so we'll have to guess. On the many piece there's a label on the motor (In the Pic) that says 0.75Kw, thats 750 Watts right, but the Amperage and voltage readings would indicate 1035 Watts wouldn't they?

    yes, plus the start up surge, which can be many times the rating!
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Going Solar On My Work Van!!!

    if everything you plan to run is to be through an inverter then use a killawatt meter on those loads. it's ok to get an idea from nameplates if you've nothing better to go on, but nameplate often is higher than actuality.
    http://www.solar-electric.com/kiacpomome.html
  • Volvo FarmerVolvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    Re: Going Solar On My Work Van!!!

    Wow, if that nameplate on the electric motor is correct, you have 1.5KWhr/day in just that load. Quick back of the envelope guess is 800W of panels? Might be better to idle the van or get a little quiet generator for the times you use that big motor. Not even sure if a 130A alternator would keep up with that motor at idle though.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Going Solar On My Work Van!!!

    vf may have a good point as a small generator may fill the need better for the large loads. smaller ones may be done on the genny too, but may also be able to be done quietly through a solar arrangement. of course one could also wire an inverter to the car's electrical system while the car is running and operate some of the smaller items that way. that is what i believe your initial intention was with the large motor, but you complicated it with extra battery storage. if the alternator isn't enough then i'm afraid the genny is the answer to the large motor. tapping the electrical power of the van may prove to be more costly in gasoline for even the smaller intermittent loads than running a good generator and there are some inverter generators out there that do well on gas consumption, but cost more.

    you should still try the meter to see exactly where you stand on your loads as it will take much of the guess work out of it. the motor is claiming to be very efficient with a power factor of .99 which i would have some doubts on and less efficiency could require more power to operate the motor.
  • timmcbeth1984timmcbeth1984 Registered Users Posts: 6
    Re: Going Solar On My Work Van!!!

    Okay, just bought a Kill-A-Watt on eBay for like $13.00!!! Awesome!! So I'll be posting some wattage reading for the big motor in a couple days and the other stuff I'll try and gather up soon or take the Kill-A-Watt to the store i plan on buying the equipment from and plug them in n turn em on :p For the sake of curiosity, if I decide to put 800Watts worth of solar panels on the roof of my work van and when I figure out what kind of total wattage I'm dealing with with this setup whats the next step?
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Going Solar On My Work Van!!!

    worry about what your load requirements are first.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Going Solar On My Work Van!!!

    Using PV Watts for Fresno Ca, fixed array, flat to roof, etc:
    Month    Solar Radiation (kWh/m 2/day)
    1      2.11     
    2      3.30     
    3      4.84     
    4      6.37     
    5      7.51     
    6      8.12     
    7      8.12     
    8      7.31     
    9      5.83     
    10      4.35     
    11      2.85     
    12      1.87     
    Year      5.22      
    

    So, ignoring November thru February, the minimum sun is 4.35 hours of noontime equivalent sun per day (October).

    An 800 watt array powering AC inverter or DC based loads would generate average daily power (October) of:
    • 800 watts * 0.52 system eff * 4.35 hours = 1,810 Watt*Hours
    • 800 watts * 1/12.5 volts * 0.62 system eff * 4.35 hours = 173 Amp*Hours @ 12 volt bank

    The recommended battery bank for an 800 watt panel charging a 12 volt battery bank at 5% to 13% rate of charge would be:
    • 800 watt array * 0.77 rate of charge * 1/14.5 volt charging * 1/0.13 rate of charge = 327 AH minimum
    • 800 watt array * 0.77 rate of charge * 1/14.5 volt charging * 1/0.10 rate of charge = 425 AH @ 12 volts nominal
    • 800 watt array * 0.77 rate of charge * 1/14.5 volt charging * 1/0.05 rate of charge = 850 AH @ 12 volts maximum

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Volvo FarmerVolvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    Re: Going Solar On My Work Van!!!
    BB wrote:



    800 watts * 0.52 system eff * 4.35 hours = 1,810 Watt*Hours

    Haha! looks my back of the envelope guess was pretty close!
  • timmcbeth1984timmcbeth1984 Registered Users Posts: 6
    Re: Going Solar On My Work Van!!!

    Okay, so i got my Kill-A-Watt display today and the "Big" motor only zaps a max of 600w surge and normal @ 330wAttachment not found.. I also went to the local Sears to get an idea of kw from there battery pack chargers (4w ea. batt.), shop vacs (1200w), air compressors (est. 1200w) and grinders (300w). I'll also have a printer and laptop which together only use 65w. As an estimate, if i were to run everything all at once i figure a maximum of 4,000 Watts. On the air compressor i guessed about 1200w because they salesman at Sears couln't actually hook it up and start it so i just went by the plate Attachment not found.. It says its pretty much double the motor compared to my "Big" motor What can we figure with this new info. Obviously I wont ever be using everthing at once and honestly i'll probably only be operating only about 6 Hrs. a day, 6 days a week as an absolute maximum with a quarter of that time driving.
  • timmcbeth1984timmcbeth1984 Registered Users Posts: 6
    Re: Going Solar On My Work Van!!!

    *Just a little extra piece of info* I've been runing a bussiness from my van for about a year now without any help from any big equipment like I've been describing. These pieces of equipment are additions/investments that will make everything run more effeciently and increase productivity, but are not neccessary. That being said, the frequency of operation of most of these pieces will be minimal. For the "Big" motor probably a Max of 1 hr / day. The shop vac and the compressor only 1hr / week.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Going Solar On My Work Van!!!

    The problem is several fold...

    First, you have supply the peak/starting power.

    Second you have to supply the running power * hours of use per day.

    Third, you have to recharge that use, ideally, in the next day's worth of charging (driving, sun, etc.).

    Frequently, the starting load support requires a very large battery bank.

    And sustaining 1 HP (800-1,200 watts) for one hour requires a fair amount of battery (battery is typically 2-4x larger than "daily load" for long life).

    So--all of a sudden, you have a the requirement for a large/heavy flooded cell lead acid battery bank. Unless you choose an alternative such as AGM (very good surge/high current support) or something exotic (some sort of lithium based chemistry--Expensive, light weight, small size).

    And, especially for flooded cell (and a lesser degree AGM), you need a pretty hefty charging source because of the large battery bank.

    Which gets us back to your basic needs... If a "quiet" battery based power source is important, and you have the money/room/capacity to install--Then we can talk battery options.

    If, however, price/space/weight is at a premium, and these loads are sporadic (i.e., 1 hour a week at a time, vs 10 minutes a day x 6 days a week), then a genset may be the more cost effective solution (i.e., you already have the noise of a compressor or shop vac--so a relatively quiet genset like a Honda eu or Yamaha inverter/generator is the not worse thing in the world).

    If you require, for example 1,500 watts for 1 hour per day (air compressor, etc.), we can at least pencil out a battery bank and see what it looks like.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • timmcbeth1984timmcbeth1984 Registered Users Posts: 6
    Re: Going Solar On My Work Van!!!

    Please forgive me for being such a noob. Let me try to make sense of this, 1500w for 1 hr per day is alot to supply so I'd need a big reservoir of power (Big Battery Bank). And since that reservoir needs to be refilled as close as possible to where it began by the next day i'd need a hefty charging source. A ton of solar panels would do the trick right? But since you can only charge at a certain optimum rate, doesn't that limit the ammount of input wattage to the batteries from the pannels or atleast make it pointless to have over a certain ammount of pannels? So lets say 1500w/hr per day is what i'll be using, then how many and how big of a battery bank would i need? And lets say i could only fit like a 350w array on the roof what other options do i have to sufficiently charge up the bank the rest of the way? Could i use a second alternator and the solar array to charge the bank at the same time?
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: Going Solar On My Work Van!!!
    Please forgive me for being such a noob. Let me try to make sense of this, 1500w for 1 hr per day is alot to supply so I'd need a big reservoir of power (Big Battery Bank).

    Not that big. Two T105 golf cart batteries should do it. (Or AGM equivalents; pricier but longer lasting and higher power.)
    And since that reservoir needs to be refilled as close as possible to where it began by the next day i'd need a hefty charging source.

    Not if you have a while to charge. 1500 watts for an hour is the same energy as 150 watts for 10 hours. (Or 300 watts for 5 hours etc)
    A ton of solar panels would do the trick right? But since you can only charge at a certain optimum rate, doesn't that limit the ammount of input wattage to the batteries from the pannels or atleast make it pointless to have over a certain ammount of pannels? So lets say 1500w/hr per day is what i'll be using, then how many and how big of a battery bank would i need? And lets say i could only fit like a 350w array on the roof what other options do i have to sufficiently charge up the bank the rest of the way? Could i use a second alternator and the solar array to charge the bank at the same time?

    Why do you want to go solar? Solar systems are expensive, will make your van topheavy, will reduce your gas mileage and add to the likelihood of leaks. If you drive your van regularly then just use the alternator. Cheap and efficient. You'll need to run some heavy gauge wire to the alternator and install a battery switch (not a diode isolator, a switch) so you don't kill your starter battery. The second alternator will also work well but is generally not necessary; your alternator will already put out ~1000 watts.

    Or just get a generator and an inverter/charger.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Going Solar On My Work Van!!!

    OK--We can do a few rule of thumb sizings... Assuming a flooded cell battery (aka golf cart or similar deep cycle battery/bank):

    First, surge current. Motors can take upwards of 5x their running current for starting. Compressors can be very hard starting loads. I have converted compressors to "unloaded" types (when the compressor stops, unloads the pressure until it gets turning again--it can help).

    But lets assume 2,500 watts of starting load. A flooded cell battery can supply (reliably) about C/2.5 (or C*0.40) of its rated AH capacity as a surge current (note, we use the "20 Hour" discharge rate for our various rules of thumb):
    • 2,500 watts * 1/12 volts nominal * 1/0.85 inverter eff * 2.5 max current surge = 613 AH @ 12 volt battery bank

    Or, about 6 golf cart batteries in series/parallel (i.e., 2 batteries in series x 3 strings in parallel for 12 volts @ 660 AH assuming 6v @ 220 AH battery). For higher power systems, I would be suggesting a 24 volt system (i.e., ~330 AH @ 24 volt system--same weight of lead/volume of battery--just arranged differently for higher voltage/lower AH rating--same power Power=Volts*Amps; you double the voltage and 1/2 the current for same power).

    Could you get by with less--possibly. It is very hard to predict how well an inverter will start a heavy load like a compressor, and how much battery bank it will need to make it start. Again--just rule of thumb design.

    Next, how deep to discharge the battery bank. A good starting point is to discharge a battery by 25% for 2 days of backup power (no sun) and 50% maximum discharge. But for a portable setup where you will recharge the next day (or not need the power the next day), you could discharge to 50% for one day (i.e., RV where weight/space is limited, and if the batteries last two years--you will still be happy).

    So, 1,500 watt AC load for 1 hour and 50% battery discharge (minimum bank size):
    • 1,500 Watt * 1/0.85 inverter eff * 1/0.50 * 1/12 volts = 294 AH @ 12 volt bank

    Or, ~1/2 of AH at 147 AH @ 24 volts (same/similar batteries, just rearranged for higher voltage/lower AH bank--same power).

    Another limit is a C/8 discharge rate (flooded cell)... If you discharge faster, batteries can heat up and be less efficient (apparent capacity is less at high discharge rates).

    Based on discharge rate:
    • 1,500 watt*hours * 1/12 volts * 1/0.85 inverter eff * 8 rate of discharge = 1,177 AH @ 12 volt battery bank

    (or ~588 AH @ 24 volt).

    So, now we have several, wildly different battery bank designs based on different aspects of assume battery function.

    AGM's have much higher surge/sustained current capabilities (discharging and charging), so you could used a much smaller AH battery--In theory they will even support C*4 (at least one brand--Concord Lifeline). Or the 294 AH @ 12 volt battery bank sizing.

    Just to give you an idea about the current required... A 1,250 watt inverter (2,500 watt surge rating or 2x rated load for some inverters) on a 12 volt battery bank should have wiring/breaker/fusing rated for:
    • 1,250 watts * 1/0.85 inverter eff * 1/10.5 battery cutoff * 1.25 NEC derating = 175 amp circuit minimum rating

    I am sorry I cannot be more specific--There are a lot of unknowns and motors/compressors/inverter/etc. all have different requirements/capabilities.

    You may end up "over designing" to get it to work first time--Or find somebody with experience with a similar setup (or suggestions for equipment variations that would work for your needs).

    Then there is the hold charging issue--But once we have the loads/bank defined, then the charging can be discussed with more clarity.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: Going Solar On My Work Van!!!

    You may be able to run the laptop and printer with out the inverter.
    I have seen DC/DC voltage boosters on ebay for charging laptops off 12v power.

    If you want to run a compressor you can do what I did. I run a compressor with my suburbans battery power, to get around the problem of the AC motor start up load on an inverter I just got a big 12v air compressor and run it straight off battery power.

    Cordless power tool chargers should work ok off a cheap power inverter.
    You may want to see if your cordless tool manufacturer offers a DC/DC vehicle charger.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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