Battery discharging overnight???

zuefeldt
zuefeldt Registered Users Posts: 1
HELP!!!!
Bellow is my setup. I purchased the Charge Controller and Solar Panel from Wind & Sun. I am having an issue and I suspect the Charge Controller is acting up.
Here is what I am experiencing.
1. I charge the battery fully to about 13.7 volts.
2. I have equipment that measures about .5 amps draw on the battery.
a. Equipment runs 24 hours a day.
3. All is good till day 3 when the battery drains to nothing.
a. Each day with full sun the batter seems to charge up to about 12.5 volts.
b. On cloudy days cloudy weather, it will decline slowly.
c. About day 3 it will decline to about 11.1 volts.
d. I go to bed and the next morning the batter is fully discharged.
4. I suspect the charge controller is somehow letting the solar panel discharge the battery to zero over night as there is no other device in the circuit that can use that much energy overnight. .5 Amps utility draw would not discharge 11 volts to zero in one night.

Based on the above description and the below specifications do you have any suggestions?


There was a sequence when installing the charge controller. I am not sure I followed the wiring order of connection as per the step by step instructions. Would this cause the issue? I think I may have done step 4, then step 3 and then Step 2 in that order.

INSTALLATION of SG-4 Charge Controller
1. SunGuard can be mounted in any position. It is best to mount
to a vertical surface and allow space for air flow through the
controller.
2. First connect the Battery BLACK wire (negative) to the battery.
Use either black wire since they are connected together inside
the controller.
3. Connect the RED Battery positive wire to the battery.
4. Connect the Solar array using the other BLACK wire and the
YELLOW Solar positive wire. Be very careful not to short circuit
the solar array, or the controller will be damaged.
5. SunGuard prevents reverse current leakage at night, so a
blocking diode is not required in the system.
6. A negative earth ground at the battery is recommended for
most effective lightning protection.
7. SunGuard can be mounted outdoors. Do not expose to ambient
temperatures above 60°C. Make sure that water will drain
from inside the case.

Equipment…
SunGuard 4.5 Amp 12 Volt SG-4 Solar Charge Controller
Solartech 45 Watt 12 volt Multicrystalline Solar Module
Battery = Power-Sonic 12V 35Ah U1 BATTERY MK MU-1SLD M AGM

Comments

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Battery discharging overnight???
    zuefeldt wrote: »
    HELP!!!!
    Bellow is my setup. I purchased the Charge Controller and Solar Panel from Wind & Sun. I am having an issue and I suspect the Charge Controller is acting up.
    Here is what I am experiencing.
    1. I charge the battery fully to about 13.7 volts.
    2. I have equipment that measures about .5 amps draw on the battery.
    a. Equipment runs 24 hours a day.
    3. All is good till day 3 when the battery drains to nothing.
    a. Each day with full sun the batter seems to charge up to about 12.5 volts.
    b. On cloudy days cloudy weather, it will decline slowly.
    c. About day 3 it will decline to about 11.1 volts.
    d. I go to bed and the next morning the batter is fully discharged.
    4. I suspect the charge controller is somehow letting the solar panel discharge the battery to zero over night as there is no other device in the circuit that can use that much energy overnight. .5 Amps utility draw would not discharge 11 volts to zero in one night.

    Equipment…
    SunGuard 4.5 Amp 12 Volt SG-4 Solar Charge Controller
    Solartech 45 Watt 12 volt Multicrystalline Solar Module
    Battery = Power-Sonic 12V 35Ah U1 BATTERY MK MU-1SLD M AGM

    The solar panel will deliver about 2 amps over maybe 4 hours to the battery. That is 8AH.
    The equipment is drawing .5 amp for 24 hours. That is 12AH.
    Do you see the problem here?
    as there is no other device in the circuit that can use that much energy overnight. .5 Amps utility draw would not discharge 11 volts to zero in one night.
    If the battery has been steadily drawn down each night until it is at 20%, then the 8AH drain of 16 hours of darkness will kill it easily.

    You need to at least double your panel size and also use a bigger battery.

    Look for a good off-grid calculator and start over to re-design your system. Or we can give you some instructions on how to do that.

    PS: If the 13.7 volts is measured while the battery is being charged, or just after stopping the charge (instead of waiting 4 hours with nothing connected to the battery) it is NOT at full charge.

    PPS:
    b. On cloudy days cloudy weather, it will decline slowly.
    This is telling you that on a cloudy day the panel is not even producing anywhere near the .5 amps that the load is drawing. Not surprising.
    If your load were only about 7AH per day instead of 12 AH, you might manage to squeak by, as long as you got good sun each and every day. But there would be no reserve for bad weather.
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Battery discharging overnight???

    Welcome to the forum.

    Let's do a little analysis.
    You have a steady 0.5 Amp draw on the battery, 24 hours per day. That's 12 Amp hours. That's about 34% DOD on a 35 Amp hour battery.
    You have a 45 Watt panel capable of 2.5 Amps output. To get the used 12 Amp hours from that it would need to be fully illuminated for 4.8 hours minimum. With good insolation this just might work. But it is a near thing.

    I'm going to suggest you connect a DMM to the positive lead from the charge controller to the battery and set it to measure current (10 Amp DC scale) and see what current you are actually getting. It really sounds like a typical case of chronic deficit charging; it seems to work, but by day 3 the battery has been depleted because full charge has not been given.

    If I were to pick a panel for this job it would be about 60 Watts, so that it could provide closer to a full 10% rate (3.5 Amps). Insolation is not always ideal, so panels do not always put out their full power.
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Battery discharging overnight???

    You consume 0.5A x 12V = 6W. During 24 hours, this is 144Wh.
    Your battery can hold 35AH x 12V = 420Wh.
    It takes 420/144 = 2.9 days to completely drain your battery.
    That is what you're experincing.

    Usually, manufacturers do not recommed discharging batteries more than 50%, or their life shortens.

    If your battery measures 11V it is already severely discharged, may be 3-5% left. Completely discharged battery is considered 10.75V. (10.5v for most battery manufacturers. niel)
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Battery discharging overnight???

    Definitely not nearly enough energy coming in from your panel/s to supply your usage, and since you've been allowing your battery/s to be so horribly discharged, they are unfortunately, almost certainly ruined / have it's/their life drastically shortened at best.
    Oh, and by the way, 14.5 volts more or less, depending on battery type and temperature of battery is required to actually put any useful charge in your battery. The 13.7 volts you mentioned is just a "float" voltage, preventing the battery from being further discharged.
    For best results, consider your present system a learning experience, the lessons of which will help you to move forward and build a system which will fill your needs.