Newbie in solar systems

goketagoketa Registered Users Posts: 9
Hello, i am new in solar systems and i would like to ask some questions.
I have a 100W solar panel for 12V
Battery 100AH open lead-liquid deep discharge SHD
Modified inverter 300W (Peak 600W)
probably will buy a pwm charge controller

My panel at best will produce 100/12 -> 8 Amper? or shall i say 100/18V -> 5.5 Amper ?

My consumption is 100-120Wh (computer ) at 230V that means it will drain 0.5AH from the battery? (of course extra power will lose from inverter operation, cable loss etc)

Another question: if i plug in tower + monitor (monitor auto-try to turn on when i plug it alone) nothing will turn on (and inverter will make a buzzzzz sound like a bee )
PSU is 500W but on run (both tower + monitor consume 100-120Wh) PSU might have 20-30% thermal loss

If i plug only the Tower it turns on (after waiting a few seconds i can plug monitor and turn it on too , and i can use some more low consumptions devices) and inverter makes no souds
Is it possible for PSU to drain instantly 500W (+20% loss -> 600W) so tower + monitor extends inverter's Peak 600W ? and a bigger inverter like 1000W would fix that problem
or it might be because the inverter is modified sine wave ?

I Should buy a charge controller with equilazer for my battery ?

Is it possible to "burn" the solar panel (wrong polarity or if the wires (before i connect them to the charger controler ) touch the ground

Inverter (if i connect revered polarity on the battery would burn its fuse) what will happen if i touch his red wire (+) with black wire (-) ? If i disconnect him from the battery it will hold some electricity, how can i remove it? (touch black wire on ground ?)

Can I attached charge controller's wire ( + - ) on inverter's (+ - ) /since it has clips and they attach easy on battery's + -

System could work without charge controller but you will have to disconnect solar panel from battery when big clouds or night exists (so battery would start "charge" the panel)?
but working without charge controller will soon destroy the battery for overcharging ?

Thanks in advances :) and sorry for newbie questions

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Welcome to the forum Goketa. Are you out of Greece?
    goketa wrote: »
    Hello, i am new in solar systems and i would like to ask some questions.
    I have a 100W solar panel for 12V
    Battery 100AH open lead-liquid deep discharge SHD
    Modified inverter 300W (Peak 600W)
    probably will buy a pwm charge controller

    I am guessing that SHD means "super heavy duty" battery? Many times, SHD and "Marine" on a battery name really do not mean Deep Cycle type battery (they are 1/2 way between a vehicle and deep cycle battery usually).

    SLI (starting/lighting/ignition) type batteries should not be cycled much below 75% state of charge (25% state of discharge). True deep cycle batteries can be cycled fairly reliably to 50% or low State of Charge.

    Normally, we like to start with your planned loads (Amps*Hours or Watts*Hour of energy used per day). But we can start with your "core" system and predict how much "useful" power it will produce per day.
    My panel at best will produce 100/12 -> 8 Amper? or shall i say 100/18V -> 5.5 Amper ?

    With a PWM controller, your panels will produce a (typical) maximum current of their Vmp rating (around 17.5 to 18.0 volts for most "12 volt" solar panels):
    • 100 Watts / 18.0 Volts Vmp = 5.56 Amperes
    My consumption is 100-120Wh (computer ) at 230V that means it will drain 0.5AH from the battery? (of course extra power will lose from inverter operation, cable loss etc)

    Opps... First mistake. And why we like to work with Watts (volts*amps) vs Amps for solar power systems. Watts is a "complete" energy unit. 100 Watt*Hours is the same for a 12 volt or 240 VAC system. With Amps, you need to know the working voltage.

    Second, need to clarify Watt*Hours--WH is an amount of energy (i.e., like 4 liters of petrol). Watts is a rate (like using 1 liter per hour).

    100-120 Watt*Hour computer... A laptop computer may use 8-30 Watts (rate). A desktop computer may use 100-300 Watts.

    And we need to know how long (how many hours) you want to run the computer... 5 hours? 10 Hours, etc....

    Lets guess that you are running your 30 Watt laptop computer for 4 hours per day:
    • 30 Watts / 230 VAC = 0.13 Amps @ 230 VAC
    • 30 Watt * 1/0.85 AC inverter efficiency * 1/12 volt battery bus = 2.94 Amps @ 12 VDC from battery bank
    So--See the big difference there... At 230 VAC, 0.13 amps. At 12 VDC, 2.94 amps.

    Next, how much energy does running your computer take:
    • 30 Watts * 4 hours = 120 Watt*Hours @ 230 VAC
    • 30 Watts * 1/0.85 inverter eff * 4 hours = 141 Watts*Hours @ 12 VDC
    • 141 WH * 1/12 VDC battery bus = 11.75 Amp*Hour from the battery bank
    Using a 30 Watt laptop on a 100 AH @ 12 volt battery bank for 4 hours per day--Not too bad (use ~12% of battery capacity per day). Recommend not to discharge battery below ~50% state of charge for normal operation.

    Now, looking at your solar panel and hours per day of sun... You can use the Solar Electric Handbook to find a city near you... But assuming a minimum of 4 hours of sun per day (sunny climate, ~9 months a year minimum):
    • 100 Watt panel * 0.52 typical solar system efficiency * 4.0 hours of sun per day minimum = 208 Watt*Hours per day
    • 208 Watt*Hours per day of solar power / 30 Watt*Hours (at 230 VAC) load = ~6.9 hours of solar operation per day minimum.
    All of this is based on using a pretty efficient computer (laptop, small desktop with LED monitor, etc.).

    It sounds like you are asking about a desktop computer (closer to 100-200+ Watts * X hours per day?). May be way more power than your above system is really capable of supplying (usefully).

    See if you can find a 230 VAC type Kill-a-Watt meter (or equivalent) for your location. This will really help you understand your loads and make better design choices for an off grid / battery powered system.
    Another question: if i plug in tower + monitor (monitor auto-try to turn on when i plug it alone) nothing will turn on (and inverter will make a buzzzzz sound like a bee )
    PSU is 500W but on run (both tower + monitor consume 100-120Wh) [guessing you mean 120 Watts, not Watt*Hours] PSU might have 20-30% thermal loss

    If i plug only the Tower it turns on (after waiting a few seconds i can plug monitor and turn it on too , and i can use some more low consumptions devices) and inverter makes no sounds
    Is it possible for PSU to drain instantly 500W (+20% loss -> 600W) so tower + monitor extends inverter's Peak 600W ? and a bigger inverter like 1000W would fix that problem
    or it might be because the inverter is modified sine wave ?

    It sounds like your computer+monitor are drawing more power than the inverter can supply. The problems could include:
    • too small of DC copper cable (possibly too long): 600 Watts * 1/0.85 inverter eff * 1/10.5 volts battery cutoff = 67 Ampere maximum current flow
    • too small of Battery (more or less, your 100 AH battery can only supply a maximum of 100/5=20 amperes @ 12 volts for minutes to an hour)
    • MSW inverter--Some electronics do not like Modified Square/Sine Wave inverter outputs (may not be your problem here)
    • Inverter--May be too small to start all loads at once.
    More or less, I think you have way to large of AC load for too small of battery bank (possibly too small of AC inverter too).

    You have to go back to basics here... Either get a smaller/lower power computer or design a 5-10x larger solar power system. use a Kill-a-Watt type meter to measure your actual loads.

    Solar power is expensive. Conservation is almost always cheaper than building a larger Solar Power system.
    I Should buy a charge controller with equalizer for my battery ?

    For smaller power systems--And if you are not using a true Deep Cycle battery--Many people get along just fine with out manual equalization function. For larger systems with true deep cycle batteries, you probably should look into equalization of some sort (via solar, or plug into Utility Power once a month, etc.).
    Is it possible to "burn" the solar panel (wrong polarity or if the wires (before i connect them to the charger controller ) touch the ground

    YES! A solar panel is just a bunch of "giant diodes" that happen to generate electricity. If you connect the panel "backwards", you will get very high current flow and can very easily ruin the solar panel.
    Inverter (if i connect revered polarity on the battery would burn its fuse) what will happen if i touch his red wire (+) with black wire (-) ? If i disconnect him from the battery it will hold some electricity, how can i remove it? (touch black wire on ground ?)

    It depends... Some DC devices are "reverse polarity protected". Fuses are generally not capable of protecting devices from reverse polarity (damage is almost instant, fuses take fraction of seconds to seconds to blow).

    For DC power systems--Always verify +/- leads before making connections. Very easy to let the "magic smoke" out of your electronics if connected wrong.

    There may be a little energy stored in the inverter DC input capacitors for a few minutes--But most people do not worry about it. You can just short the +/- input leads together if you are worried (the stored voltage/energy is usually quite low)..
    Can I attached charge controller's wire ( + - ) on inverter's (+ - ) /since it has clips and they attach easy on battery's + -

    I would suggest that all connections be ran back to the battery bus/terminals directly. "Daisy Chaining" from Charger to Inverter DC Input to Battery bank can make for less reliable operation and other issues. Each + wire that leaves the battery bus should have its own fuse/circuit breaker to prevent short circuits from causing a shorted wire from melting/causing a fire.

    For a true solar power system, don't use "clips/clamps" for DC electrical connections. These are not reliable and cannot carry much current--Use nuts+bolts and Wire Terminals to make your electrical connections.
    System could work without charge controller but you will have to disconnect solar panel from battery when big clouds or night exists (so battery would start "charge" the panel)?
    but working without charge controller will soon destroy the battery for overcharging ?

    The solar charge controller should "disconnect" (prevent reverse current flow through a "dark" solar panel) the solar array at night. It is standard for all modern solar charge controllers.

    Yes, you can connect a solar panel directly to the battery bank, but you do run the risk of over charging the battery bank and boiling it dry/damaging the plates (in the long term).
    Thanks in advances :) and sorry for newbie questions

    We also started at the same place--And learned from others.

    Our pleasure.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • goketagoketa Registered Users Posts: 9
    OMG Bill thank you very much :O (and sorry for making you to type so much)
    yes greece

    I have a kill-a-watt device that measure the W etc (power factor ... i will see it might have A too).
    About my maths
    My desktop (230V) usually consume (based on kill-a-watt) average 100W so 100W for like 3 hours per day -> 300Wh on 230Volt -> 1.3AH per day (i will have to multiply with battery's volt so its 15.6 AH (15.6% discharge per day)?
    But the solar gives 208Wh at best so i have to add another panel
    I thought it was 1.3AH so i was thinking " Oh nice 100/1.3 i can run it for 76 hours till drain out

    When i connect the wires do i have to wear plastic gloves ? (or just dont touch 2 different polarity wires at the same time)

    Ok i will have to remove clips/clamps and use nuts


    Again thank you very much Bill


    hm wrong maths i should better read you comments on wh and ah

    i had reverse thought about watt and wh

    how can i measure the % discharge of the battery?
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    You are very welcome Goketa.
    goketa wrote: »
    I have a kill-a-watt device that measure the W etc (power factor ... i will see it might have A too).

    Look for the kWH (kilo Watt*Hour) reading too... Typically you plug the device in for 24 hours and then read the kWH...

    For example, using 100 Watts * 4 hours per day usage (out of a 24 hours day):

    100 Watts * 4 Hours = 400 WH = 0.4 kWH per day.
    About my math
    My desktop (230V) usually consume (based on kill-a-watt) average 100W [just 100 Watts, not 100 Watts per Hour] so 100W for like 3 hours per day -> 300Wh on 230Volt [correct]
    -> 1.3AH per day (i will have to multiply with battery's volt so its 15.6 AH (15.6% discharge per day)?

    Be careful here... You are going the "wrong direction".
    • Watts = Voltage * Current = Watts (a rate, like liters per hour)
    • Watt*Hours = Voltage * Amps * Hours = Total Energy used (like using 4 liters of fuel).
    This is why Amp*Hours gets confusing... if you ignore "Voltage", you have "garbage" numbers for energy usage. Many times, AH is just fine, because in a car or boat, everthing is running at 12 VDC so you do not have any "voltage/energy conversions" to mix up the calcuations.
    • 100 Watts / 230 VAC = 0.434 Amps (on your 230 VAC wiring)
    • 100 Watts / 12 VDC = 8.33 Amps (ignoring AC Inverter losses) (on your 12 VDC wiring)
    If you had a 230 VAC "battery", then the 1.3 AH could make some sense. However, you have a 12 VDC "real battery"--And that is where we need to "know" the Amps and Amp*Hours:
    • Amp*Hours@230vac = .434 Amps * 3 Hours = 1.302 AH @ 230 VAC (if you had a 230 VAC battery that would be its AH used)
    • Amp*Hours@12vdc = 8.33 Amps * 3 Hours = 24.99 AH @ 12 VDC from "real" 12 VDC Battery bank (excluding inverter losses)
    But the solar gives 208Wh at best so i have to add another panel

    The 100 AH battery can reasonably (reliably) supply for a bit less than 4 hours:
    • 100 AH * 0.85 AC inverter eff * 12 volts * 1/8 hour discharge rate = 127.5 Watt @ 230 VAC load (reliably for 3+ hours)
    If you try to pull any more ~127.5 watts, the Lead Acid battery will not be happy (run lower output voltage, less efficiently, shorter life).

    There are other types of batteries (like Lithium Ion, AGM lead acid batteries, etc.) that can supply a higher amount of current (Amperes) for a small battery...
    I thought it was 1.3AH so i was thinking " Oh nice 100/1.3 i can run it for 76 hours till drain out

    Nope--A common mistake. AH*Voltage = Watt*Hours.

    X Amp * 230 VAC >> X Amp * 12 VDC
    When i connect the wires do i have to wear plastic gloves ? (or just don't touch 2 different polarity wires at the same time)

    For electric shock. Assuming you are not standing in the Mediterranean (salt water sea) while doing your electrical work, 12 VDC is not going to shock you. 24 VDC to 40 VDC--Usually safe if you have dry hands (you may get a little shock if your hands are wet). Over 40-60 Volts is "unsafe" to work on live unless you know what you are doing (insulated gloves, kill power, etc.).

    PLEASE NOTE: The above is talking about "touch safe" electrical voltage. We also have to worry about current.

    If you put >~0.005 amps (5 milliamps) or so directly through your heart, you can stop your heart. So, that is the first concern, high enough voltage and left hand holding + and right and holding -, the current goes right through your heart. That is one reason technicians only work on live circuits with one hand.

    Doctors have also learned that you may survive an initial shock, only to die hours/day later (electricians that get a 120/240 VAC shock can be put in the hospital for observation in the USA).

    Next--The issue of higher amounts of current and voltage. Lead Acid batteries can output 100 amps or more into a dead short (large battery banks can output 1,000's of Amperes into a dead short). Think Arc Welder.

    Roughly over 12 Volts, the arc of a short circuit can "sustain" (think electric arc welder). With higher voltage/larger AH rated battery banks (and large building AC power systems), there is something called "ARC FLASH"... This is literately an electrical explosion.

    I believe he survived this Arc Flash...

    You will not have this problem with smaller battery banks--But is is not unusual to "spot weld" a dropped wrench on top of a battery on a larger battery bank.

    Always be real careful around battery banks (remove jewelery, wear face shield, insulate wrenches and screw drivers, etc.).
    Ok i will have to remove clips/clamps and use nuts

    Only reliable way to go.

    Have fun!
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • unseenoneunseenone Solar Expert Posts: 61
    The % discharge or more commonly State of Charge (SOC) of the battery. This is measured by the open circuit voltage. In the following example a specific AGM battery, so check your manufacturer specifications. This can be checked against the specifications of the battery maker. I'll put an example here, courtesy of fullriverdcbattery.com for example.
    Attachment not found.
  • goketagoketa Registered Users Posts: 9
    I love you guys :) i am really thankful
  • goketagoketa Registered Users Posts: 9
    If i go for vacation and i know for 10-15 days wouldn't use the system is it better to disconnect solar and charge controller from battery? Or its no difference (inverter will be off )
  • Alaska ManAlaska Man Solar Expert Posts: 252 ✭✭
    Leave your panels and controller connected, disconnect everything that will draw power. Inverter, direct wired loads, etc. I have a main disconnect, pull the lever and it separates the battery from all power draws.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Always turn off loads.

    If the system is new and/or you don't trust it (yet), you can disconnect the charge controller for up to roughly 30 days (again no loads on flooded cell battery bank) without much harm to the batteries.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    I should add, if your system needs to run small loads while gone, that is why you built the system. But be aware of the weather, a week or two of bad weather can reduce the output of the system to 50% or even below 5% of its normal output.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • goketagoketa Registered Users Posts: 9
    Only inverter draws power from the battery (and i always turn inverter off when I finish the work on the computer) (charge controller doesn't give any 12V load)
    the only "draw" is batterie's discharge from time passing - hope charge controller self-consumption for operation is drawn from solar and not the battery-.
    So its better to have the solar and charge controller on the battery (nothing else) so it would charge the small amount of energy loss from battery self-discharge ? (than disconnect the battery and reconnect after 15-20 days and start charging to restore the energy loss due to storing)

    (dont know if i used correctly the words draw and load :) )

    PS thanks again for fast answers :)
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    If you trust the charge controller is doing what you need, leave it connected.

    Make sure you don't "boil" the batteries dry (expose plates) while you are gone.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • goketagoketa Registered Users Posts: 9
    how much "fat" the cable much be for 80W panel ( "12" V , 4.74 A) (2 meter long )
    When i touch with multimeter the charger's output for battery i read battery's Volt (12,78V ) shouldn't i read the charging Volt ? (14 Volt)
    charge controller is a Wellsee "MPPT" when there isn't much sunlight on panel charging-led is flickering (<<charge battery with constant volt>>) multimeter read on charger's inputs from solar different values of volt 14,xx 16,xx 15,xx 17,xx (not constant)
    When there is much sunlight on the panel charge led is on (<<battery is been charged strongly>>) multimeter reads constant value of 13,XX volt on charger's inputs from solar.
  • scrubjaysnestscrubjaysnest Solar Expert Posts: 175 ✭✭✭
    goketa wrote: »
    how much "fat" the cable much be for 80W panel ( "12" V , 4.74 A) (2 meter long )
    When i touch with multimeter the charger's output for battery i read battery's Volt (12,78V ) shouldn't i read the charging Volt ? (14 Volt)
    charge controller is a Wellsee "MPPT" when there isn't much sunlight on panel charging-led is flickering (<<charge battery with constant volt>>) multimeter read on charger's inputs from solar different values of volt 14,xx 16,xx 15,xx 17,xx (not constant)
    When there is much sunlight on the panel charge led is on (<<battery is been charged strongly>>) multimeter reads constant value of 13,XX volt on charger's inputs from solar.

    Not sure what your asking on the cable, wire size? For a 2 meter length I like to use 10 AWG, don't remember for sure but think that is 5mm2 cable. Some one else here will chime in on the size.

    My system is a little different, PWM cc so what I measure may be somewhat different then yours. Full sun conditions, during boost phase; CC input ~ battery voltage. As the batteries take a charge the CC input will rise to panel Vmp, for me that is 18.1 volts. CC output will rise to 14.5 volts and stay there until CC switches to absorb mode. During absorb mode CC input ~ Vmp or again 18.1 volts. CC output = 14.9 volts. Float mode: CC input 18.1 volts, CC output =13.34 volts. I would expect to see something similar on yours if your 80 watt panel has a Vmp of 17 to 18 volts. Output values of the CC should be similar for a lead acid battery, but will be lower if the CC is set for Gel or AGM. Clouds passing across the sun can have enough impact on CC input to cause the output volts to decrease. Your manual for the CC should define the different led modes. Hope this helps some.
  • goketagoketa Registered Users Posts: 9
    Manual:
    Red led off -> no charge
    Red led flickering -> charge battery with constant volt
    Red led continously ON -> Charge battery strongly

    my wires are 2.5mm² but as i see is acceptable for 2% loss
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