My new system is working great

TXtruckerTXtrucker Solar Expert Posts: 28
After a few technical difficulties I got my new solar panel system working. My goal was to take my refrigerator and chest freezer off grid. I have 6 145w Dm Solar panels, 4 6v 220ah golf cart batteries, a Outback Fm60 charge controller and a 1800 Xantrex true sine wave inverter. The system is 12v. I let the panels charge my battery bank a full day before putting the load on them.

After the charge I plugged the refrigerator and freezer into the inverter and left it until the next morning. The charge on the battery bank was 13.8v when I plugged in the appliances. The next morning I checked the batteries and they were at 12.4v. Which according to a discharge chart is only about 60% discharged. The following day I let the system do its thing and the following morning the batteries were at 12.4v. This has repeated again for a third day.

Although I will save some money on electricity, I am very pleased with the system's ability to run these two appliances off grid. If the power goes out, which it does from time to time, I have no worries about my food going bad.

Based on the results I am getting I still have a little extra power that I could use. Hope this information is beneficial to some. I will provide additional information and answer questions if needed. Thanks

Comments

  • DillDill Solar Expert Posts: 170 ✭✭✭✭✭
    Re: My new system is working great

    do you have a battery monitor? Strongly recommended, at the very least a Trimetric 2025 is under 200 dollars with a shunt
  • ywhicywhic Solar Expert Posts: 612 ✭✭
    Re: My new system is working great

    Sounds great.. what did you end up with for panel angle?? Did you do the panels in series or just 6 in parallel??

    And what type of numbers does your Outback FM60 say?? Like Amps and kWH for the daily??

    Same panels I have so I am intrigued with what you got out of them..
  • inetdoginetdog Solar Expert Posts: 3,121 ✭✭✭✭
    Re: My new system is working great
    TXtrucker wrote: »
    The system is 12v. I let the panels charge my battery bank a full day before putting the load on them.
    After the charge I plugged the refrigerator and freezer into the inverter and left it until the next morning. The charge on the battery bank was 13.8v when I plugged in the appliances. The next morning I checked the batteries and they were at 12.4v. Which according to a discharge chart is only about 60% discharged.

    Based on the results I am getting I still have a little extra power that I could use. Thanks

    NO!

    For a standard generic Lead Acid battery at rest (very carefully defined) 12.4 volts is more like 55% SOC than 60% DOD (see below.)

    If you are discharging your batteries to 60% Depth Of Discharge (DOD) rather than down to 60% State Of Charge (SOC) then you are (not very) slowly killing your batteries.
    If you are discharging them to 60% SOC you are still killing them faster than you should given their cost.
    An acceptable level after one or more missed days of charging because of weather would be 50%. A routine day should not drive them below 80% SOC, which is 20% DOD, and about 12.6 volts on the same generic curve.
    If you were to find a use for the remaining 40% (60%?) of energy in your batteries, you would be killing them very very fast instead.

    Can you clarify whether the voltages you list were truly "at rest" voltages, where the batteries were neither charging nor loaded and had been that way for at least 20 minutes?

    You may find this paper useful in analyzing voltage measurements while the batteries are under charge or under load.
    If you measured 12.4 volts under load, then you are not nearly as bad off as I initially suggested, but still not treating your batteries well.

    If you really want to know how deeply you are discharging your batteries, you should use a hydrometer.
    SMA SB 3000, old BP panels.
  • TXtruckerTXtrucker Solar Expert Posts: 28
    Re: My new system is working great

    The panels are at a slight angle maybe 10 degrees and facing due south. I am not sure on the amps but I saw 3 kwh on the meter today when I got home. They seem to be cranking out some real good power. I put three panels in series to a breaker. Then the 2 series to the charge controller. I believe this gives me about 15 amps and 108v to the controller. These are rough numbers. I will try to get more specific in the future.
  • TXtruckerTXtrucker Solar Expert Posts: 28
    Re: My new system is working great

    When I checked the voltage this morning there was no load and no charging on the batteries and they were at 12.4v. I ordered a hydrometer last night. The batteries I am using are deep cycle batteries. Super Start GC110DT. 6v 220ah. I may be incorrect but I thought it was ok to discharge deep cycle batteries to 50% without any negative effects.
  • TXtruckerTXtrucker Solar Expert Posts: 28
    Re: My new system is working great

    Would I benefit in adding 2 more batteries to the bank? I can't add anymore panels as they are already at the peak wattage of the controller according to the manual.
  • ywhicywhic Solar Expert Posts: 612 ✭✭
    Re: My new system is working great
    TXtrucker wrote: »
    The panels are at a slight angle maybe 10 degrees and facing due south. I am not sure on the amps but I saw 3 kwh on the meter today when I got home. They seem to be cranking out some real good power. I put three panels in series to a breaker. Then the 2 series to the charge controller. I believe this gives me about 15 amps and 108v to the controller. These are rough numbers. I will try to get more specific in the future.

    Thats great numbers.. 3kw is where you should be if everything is ideal.. sounds like your panels are at a good angle for summer.. in the winter kick them up to like 45-50 (I think for your latitude though it sounds like you looked it up already.)

    I did rough numbers on mine (using todays test) and came up with 3150 watts.. (or 3.1kWH).. sounds like yours..

    I would say add 2 more batteries to the mix if you can afford it.. don't wait too long to do it so all the batteries are close in date..

    That would give you some wiggle room.. 660ah from the 440ah you have.. figure your pumping 45 amps/hour into the bank.. right now your at C10 charge rate.. you'll be at like a C14.5 if you up the bank.. tough call on the charge end.. granted you would have the reserve.. though it may take longer to bring it back up.. (these are my thoughts, others will be along to correct me)..
  • inetdoginetdog Solar Expert Posts: 3,121 ✭✭✭✭
    Re: My new system is working great
    TXtrucker wrote: »
    When I checked the voltage this morning there was no load and no charging on the batteries and they were at 12.4v. I ordered a hydrometer last night. The batteries I am using are deep cycle batteries. Super Start GC110DT. 6v 220ah. I may be incorrect but I thought it was ok to discharge deep cycle batteries to 50% without any negative effects.

    Those batteries may be listed as deep cycle, but none of the measurements I found in a very quick Internet search confirm or disprove that. The may well be hybrid batteries.
    Even if they are true deep cycle, going down to 50% SOC will reduce the number of charge/discharge cycles you can get from them quite a bit over lower discharge percentages. You should get the numbers on the actual number of cycles predicted at that DOD and make a calculation of how soon you will need to replace the batteries. Then compare the cost of new batteries to the price you would have paid to your utility for the same amount of electric power. That might be an eye opener.
    Just adding one or two batteries to the six you have now will not make a big difference. And getting more panels would only charge them faster, not reduce the DOD from overnight operation.
    SMA SB 3000, old BP panels.
  • PhotowhitPhotowhit Solar Expert Posts: 4,276 ✭✭✭✭
    Re: My new system is working great
    inetdog wrote: »
    For a standard generic Lead Acid battery at rest (very carefully defined) 12.4 volts is more like 55% SOC than 60% DOD (see below.).

    That's NOT right, I'd say likely your actually above 80% charged, largely depending on when in the morning your checking.

    Battery FAQ's Here.

    There is a nice chart in red, green and yellow about a 2/3 down the screen.

    The problem with using voltage is all the variable factors, fully charged with the battery in float and your around 14 volts, at rest, for 2-3 hours, fully charged your at 12.7, likely the last action was discharging running a compressor and if that happened with in 1/2 hour of checking the voltage, your batteries might not have returned to rest and show lower, if they are hooked up to charge controller and it's bright daylight, even w/o the sun shining on the panels, your charging so you might be lower than 80% at 12.4. not bright sunlight and no compressors running, new electronic thermometers use a small amount of electric, so you have a small draw, but your inverter isn't in search mode(also a small draw) so instead of the inverter using .5 amps it's usine 1.5 amps....

    Yes, a hydrometer will help cut through the confusion, but you can learn to live with a volt meter and understanding of how your system works, don't make any big jumps, likely your OK for now, more interest stuff coming up as the days shorten and your charging less, but the ambient temperaturs should make refridgeration easier, so different loads and different charging...

    Someone will come along now and recomend a battery meter... I'll just say notice the enviroment, several warm cloudy days... might run the charger...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • TXtruckerTXtrucker Solar Expert Posts: 28
    Re: My new system is working great

    I only have 4 batteries in the bank. Also, this project was not done to save money on the electricity bill, but to get these 2 appliances off the grid in case of a power failure. We have power failures here often because of thunderstorms and the occasional ice storm.

    Here are some numbers from the charge controller. I don't understand all of them, but maybe someone here does.
    Today's readings:
    245ah 3.3kwh
    60Vp 56.3Ap .74kwp
    max 14.8v
    min 11.9v
    abs 2:01
    float 5:30

    Yesterday's readings

    265ah 3.6kwh
    60vp 61.5ap .83kwp
    max 14.6v
    min 11.8v
    abs 2:02
    float 4:79

    Hope this helps
  • TXtruckerTXtrucker Solar Expert Posts: 28
    Re: My new system is working great

    Some additional information. The appliances are in a climate controlled environment of 69 degrees. This help to keep the compressors from running all the time.
  • TXtruckerTXtrucker Solar Expert Posts: 28
    Re: My new system is working great

    I was using that very same chart as a point of reference. According to it I am ok. time will tell. When I get my hydrometer I will check the batteries.
  • ywhicywhic Solar Expert Posts: 612 ✭✭
    Re: My new system is working great

    The numbers look great and give me HIGH HOPES..

    Whats your battery settings??

    Absorb 14.4, 14.6, 14.8?? Float 13.4, 13.6, 13.8??
  • inetdoginetdog Solar Expert Posts: 3,121 ✭✭✭✭
    Re: My new system is working great
    TXtrucker wrote: »
    I only have 4 batteries in the bank. Also, this project was not done to save money on the electricity bill, but to get these 2 appliances off the grid in case of a power failure. We have power failures here often because of thunderstorms and the occasional ice storm.

    That makes perfect sense, and also justifies going even deeper toward the red than for an off-grid use.
    In that sense, you do have energy to spare and can look at other loads you may want or need to run when the grid is down.
    However, once you have made your measurements and gotten used to your new system, you may want to put the appliances back on the grid when you are home and make a provision to switch them to battery when needed. That will keep your batteries in the best condition to serve you when the grid goes down. If you are going to be away for a day or more, putting them on the inverter full time may be cheaper than investing in an automatic transfer switch.
    SMA SB 3000, old BP panels.
  • TXtruckerTXtrucker Solar Expert Posts: 28
    Re: My new system is working great

    I have the controller set at 14.4 bulk and 13.2 float. I think my system is set up good. I will watch it over time to see how it performs. Thanks for all the information.
  • DillDill Solar Expert Posts: 170 ✭✭✭✭✭
    Re: My new system is working great

    the minimum of 11.9 volts would be a little concerning to me. Probably occurring when there is a big draw, but still..
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: My new system is working great

    Having had banks of GC-2's with 4 to 14 batteries and having Link Meters with shunts and counting AMP's in and out, I'v come to the point where just use Voltage now. 50% DOD on a new bank will be about 12.1 volts, as the bank ages it will drop to 11.9 and when it's time to replace it's about 11.7 > volts. The Life span of GC-2's is about 4-5 years and about 700 + , 50 % cycles. I have seen them stretched to 6 or 7 years, but they do not have the capacity to take any deep discharges and drop voltage fast.

    Usually about the 4 th year you'll begin to see positive post protrusion and some case distortion from repeated charge cycles. Checking the SG is important and EQ'ing as necessary will help keeping them in going longer.

    Batteries are expendable, use them or lose them. Reported voltage is dependent on cabling sizing and the dip and recovery of the battery and the size load, a momentary large load easily will drop any battery bank.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: My new system is working great
    Having had banks of GC-2's with 4 to 14 batteries and having Link Meters with shunts and counting AMP's in and out, I'v come to the point where just use Voltage now. 50% DOD on a new bank will be about 12.1 volts, as the bank ages it will drop to 11.9 and when it's time to replace it's about 11.7 > volts. The Life span of GC-2's is about 4-5 years and about 700 + , 50 % cycles. I have seen them stretched to 6 or 7 years, but they do not have the capacity to take any deep discharges and drop voltage fast.

    Usually about the 4 th year you'll begin to see positive post protrusion and some case distortion from repeated charge cycles. Checking the SG is important and EQ'ing as necessary will help keeping them in going longer.

    Batteries are expendable, use them or lose them. Reported voltage is dependent on cabling sizing and the dip and recovery of the battery and the size load, a momentary large load easily will drop any battery bank.

    i have to remind that these voltages are at rest voltages. the batteries while used even lightly for some time will draw down a bit and if a big load goes on, even for a short while, the voltages can be drawn down beyond the at rest voltages and is normal under the peukert effect. this means that the batteries aren't necessarily in a state of being on their way out depending on the loads presented to them.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: My new system is working great

    Yes Neil, they are at " Rest " voltages. The Amp Hours used were measured Out / In with shunt type meters with the proper calibration over the life of the battries. The point I was trying to make is that the Voltage at 50 % DOD changes over time as the capacity of the bank changes due to age, sulfation and bad maintenance, bad connections, undersize cables. Parasitic loads can be the worse over time.

    A Refrigerator just having two defrost cycles during the battery discharge cycle ( before recharging ) will throw you way off. My Refrigerator will pull 90 amps @ 12 volts for about 10 minutes each defrost cycle, then it has to restart. With a small bank you have to really watch. Of course a bigger bank has to be replenished.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: My new system is working great

    i wasn't reminding you in particular even though i had quoted you as i wanted those readers to remember those were at rest voltages. we are in full agreement that it goes downhill from there, be it big loads, age, etc. or a combo of those factors drawing the working voltages down further.
  • PhotowhitPhotowhit Solar Expert Posts: 4,276 ✭✭✭✭
    Re: My new system is working great
    .... The Amp Hours used were measured Out / In with shunt type meters with the proper calibration over the life of the battries. The point I was trying to make is that the Voltage at 50 % DOD changes over time....

    Not my experience, I think what your seeing is a reduction of battery capacity which is reflected in an your battery meter, so for the 50% DOD, as the battery ages, the capacity becomes less so the 110 amps discharge which use to represent 50% capacity, becomes 60% and then 70%...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,486 ✭✭✭
    Re: My new system is working great
    Photowhit wrote: »
    Not my experience, I think what your seeing is a reduction of battery capacity which is reflected in an your battery meter, so for the 50% DOD, as the battery ages, the capacity becomes less so the 110 amps discharge which use to represent 50% capacity, becomes 60% and then 70%...
    True, and the 12.1 volts that use to represent 50 % becomes 12 volts and 60 % and then 11.9 and 70 % and so on. Just two ways of measuring it.
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