12V/8AH SLA Battery with 12V/20W mono solar panel questions

MrPettit
MrPettit Registered Users Posts: 3 ✭
edited June 2017 in Solar Beginners Corner #1
I have a 12V/20W solar panel supplying power to a 12V/8.0AH/20HR SLA battery through a 12V/20A PWM Solar Charger. (I have included pictures with the specs listed)

I have a few questions, and please bare with me as I am completely new to solar energy production.

1) Is this set-up a 'decent' set-up to use for charging my cell phone and laptop? ( I eventually want to go completely solar but as of now I am starting off small and charging my electronics solely with solar power.) I have used the battery to charge my phone twice and it works fine. I have also had the whole set-up, hereafter referred to as the station, outside for a few hours today soaking up some power and all seemed to be working fine. I am a little bit of a detail oriented person and it is killing me not knowing the specifics of what all is going on while this station is charging and discharging...

2) While discharging the controller is showing that it is pushing 0.6A to my Galaxy S7, and it is charging pretty much as quickly as it does when connected to my wall charger, isn't 0.6A low? The charge controller said is pushes 5V/2A from the USB...

3) While charging (at high noon, full sunlight, in Oklahoma City, OK, with approximately 10 degrees tilt, facing relative true south) I am only showing an input current of 0.7A max. Is this right? 

4) While charging (again, with the configuration mentioned above) it started out at 12.2V and quickly made it's way to 13.0V then slowly to about 13.2. I had to bring the station inside because I, currently, am staying in an apartment complex and had to go to the store. When I returned home I put the station back outside, at approximately 4:00 pm it quickly (10 min.) jumped to 14.4V - 14.7V. I say both voltages because it kept bouncing around in that range. (The PV cutoff V is set at 14.7V, factory) When I brought the station back inside is showed 13.1V and then settled down to 12.7V when I plugged in my Galaxy S7 to charge. I am just confused on how batteries charge I guess. I know that they charge in 3 phases. But if it charges to 14.7, is it suppose to drop back down as soon as the panel loses sunlight? Is the 14.7V just while it is actively charging? 

5) Lastly, while charging out in the sun, the controller read at 30 degrees Celsius, to my understanding this is the upper limit of the 2.45V per cell... should I lower the PV cutoff limit from 14.7V to 14.4V during the summer?

I appreciate ANY help. I know there is a lot in this post but I have driven myself nuts searching the web to find answers and have found nothing...
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Comments

  • DConlyGuy
    DConlyGuy Registered Users Posts: 80 ✭✭
    #2
    # 2 your phone will decide how much amps it need not the controller #3 your getting what the panel can put out,  the numbers on the back of a panel are max rating  #4 the solar panel is to small to charge even that little battery back up to full in a day, if you hooked up a 100 watt panel to it and was getting 3 to 4 amps out of it would still take you 2 to 3 hours to charge battery full
    600 watts of solar panels,Epever 30 mppt , 2 PWHR12500W4FR battery's in 24 volt setup
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  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    edited June 2017 #3
    MrPettit said:
    1) Is this set-up a 'decent' set-up to use for charging my cell phone and laptop? 
    Yes, it is a "decent" setup.

    MrPettit said:
    2)  The charge controller said is pushes 5V/2A from the USB 
     The Charge Controller [USB Port] won't just push 2 amps, the G7 will regulate the amps flowing into the battery.

    MrPettit said:
    3)  At noon, I am only showing an input current of 0.7A max. Is this right?
     Depends upon the SOC (state-of-charge) of the 12V 8AH battery and the load. It could be right.

    MrPettit said:
    4) Charged to 14.7V, back inside it showed 13.1V, settled down to 12.7V, is it suppose to drop back down?
    Yes

    MrPettit said:
    5) 30 degrees Celsius, should I lower the PV cutoff limit from 14.7V to 14.4V during the summer?
    Yes at 30° C, you should lower the charge voltage per mfr instructions.
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  • MrPettit
    MrPettit Registered Users Posts: 3 ✭
    #4
    DConlyGuy, mvas,
    Thank you for your input. I guess it makes sense that the S7 regulates the input, wasn't thinking that one through. I have only taken it down to maybe 80% SOC and have had no problems getting it back to full today (I think), I put it outside at about 1030 and brought it in at about 1330. It was steady at 14.7V and jumping from 0.0A - 0.02A. The little indicator showed a full battery so I assume that and the readings meant that it was full...

    I just like to know the intricacies of how things work and my background in electronics is minimal, I am hoping this will dive into PV will be a great learning lesson for me. 
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  • MrPettit
    MrPettit Registered Users Posts: 3 ✭
    #5
    0.0A - 0.2A ***
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #6
    Re: point 2

    The phone charges 2a at 5v = 10w. The controller at 10w / 12v = 0.8a. The 2a on the wall wart is likely max output, the phone may not take max power for charging, so I'd say 0.6a is about right.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • myocardia
    myocardia Solar Expert Posts: 118 ✭✭✭
    edited June 2017 #7
    Estragon said:
    Re: point 2

    The phone charges 2a at 5v = 10w. The controller at 10w / 12v = 0.8a. The 2a on the wall wart is likely max output, the phone may not take max power for charging, so I'd say 0.6a is about right.
    That's all completely correct, except that his phone doesn't have the ability to charge @ 2a. The Galaxy S7 maxes out at 1.75a @ 5V (as well as ~1.5A @ 9V, as Bill says below, as long as the charger has that capability [most do not]), and since his battery was slightly over 13V, the 0.6a is pretty much perfect.
    DoD= depth of discharge= amount removed from that battery   SoC= state of charge= amount remaining in that battery
    So, 0% DoD= 100% SoC, 25% DoD= 75% SoC, 50% DoD= 50% SoC, 75% DoD= 25% SoC, 100% DoD= 0% SoC
    A/C= air conditioning AC= alternating current (what comes from the outlets in your home) DC= direct current (what batteries & solar panels use)
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #8
    For the Samsung S7 phone, it does have a fast charge USB setup. It can tell the USB power supply to output ~9 volts and it will pull around 1.4 to 1.5 amps during charge (display has to be off/on standby. If display is on, USB is set to 5.0 volts).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • myocardia
    myocardia Solar Expert Posts: 118 ✭✭✭
    #9
    BB. said:
    For the Samsung S7 phone, it does have a fast charge USB setup. It can tell the USB power supply to output ~9 volts and it will pull around 1.4 to 1.5 amps during charge (display has to be off/on standby. If display is on, USB is set to 5.0 volts).

    -Bill

    Haha, thanks for reminding me of that, Bill! I have both an S4 and an S6, both of which have the ability to do what you described, and I still got it partially wrong. I knew that there was something I was forgetting, but couldn't remember what it might have been. I'm getting old, as my daughter and my granddaughter like to occasionally remind me. :D
    DoD= depth of discharge= amount removed from that battery   SoC= state of charge= amount remaining in that battery
    So, 0% DoD= 100% SoC, 25% DoD= 75% SoC, 50% DoD= 50% SoC, 75% DoD= 25% SoC, 100% DoD= 0% SoC
    A/C= air conditioning AC= alternating current (what comes from the outlets in your home) DC= direct current (what batteries & solar panels use)
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