Solar problems. Please help!

I'm pretty stoked you guys have a forum here. Hopefully, you and the members here will be able to help me out with my problem.

I have a cabin that we visit a couple times per month. When I got there on Friday night, the six batteries (2 month old Centennial 6 volts) were reading around 13.5 volts. We used very little lighting over the weekend as we were working on my neighbors cabin most of the weekend so we weren't even in ours except for at night. Sunday morning we wake up to dead batteries. Volt meter was reading 9.0 volts. Even if we left a light on (which we didn't) I wouldn't think it would kill six 6 volts.

So, I checked the volts at the charge controller(coming in and out) and on the solar panel terminals themselves. Everything was at 9.0 volts. If I disconnect the solar panel from the charge controller the panel reads 20.0 volts.

We didn't leave until 4pm Sunday and the batts were still reading 9.0 volts. The system was turned off all day.

Any ideas?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    Re: Solar problems. Please help!

    If the Solar Charge Controller is a standard PWM controller--then the fact that the panels were about the same voltage as the batteries indicates that the charge controller appropriately (directly connecting the solar panels to the battery to charge).

    At this point, if possible, you should bring a DVM, generator, and battery charger to the cabin.

    First, measure the current output by your solar panels during full sun--should be near their Imp rated voltage. Next, you should disconnect the solar panels from the charge controller and check for a current path (lights left on, something plugged in, and also check if the solar charge controller is draining the battery bank).

    If you find the problem or not, next you should but the battery bank on charge and get it up to at least 75% state of charge (if you have time, fully charge the bank). You can use a hydrometer to check all of the cells--if you find one or two cells that are very high or very low wrt to the others--then you may have a bad battery (shorted cell can discharge the entire bank--open cell can prevent string from charging) or cable/connection.

    In any case, the longer you let the batteries set at 75% or less State Of Charge--the more the batteries are being damaged/ruined (sulfates in a discharged battery begin to harden within a few hours when below ~75% state of charge).

    If the batteries set at 9 volts until next weekend--there is a good chance that you will need to replace them (assuming that the solar charger is not working properly or the unknown load / bad cable / bad battery has not been fixed).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Solar problems. Please help!

    Most charge controllers will not turn back on at under 10 volts as they cannot determine for sure what the correct battery voltage is.

    You may have to bypass the controller for a few minutes and run the panels direct to the battery to get them up to around 10.5 volts or so and then hookup the controller normally.

    However, I would try to find out what drained the batteries so badly first.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar problems. Please help!
    Windsun wrote: »
    Most charge controllers will not turn back on at under 10 volts as they cannot determine for sure what the correct battery voltage is.

    You may have to bypass the controller for a few minutes and run the panels direct to the battery to get them up to around 10.5 volts or so and then hookup the controller normally.

    However, I would try to find out what drained the batteries so badly first.

    What could possibly drain six 6-volt batteries that fast? We had a small boom box radio and 3 flourescent light bulbs running for about 4 hours. Where could the power go?
  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Solar problems. Please help!

    Look for a direct short, burnt wire damaged insulation. but as of your story so far the fact is it seems strange ? To help Chance, list your complete system... Batteries...PV Panels.. Charge Controller make model, Im aware or certain CC that can lock up a bit like a PC at times. and all possible loads, lights only or other items as well. The more information you give the better likelehood of help u will receive. Also check all battery connections everywhere and I mean everywhere. !! look for good tight joints and lack of corrosion. Fuses or Circuit Breakers all OK. To discharge as badly so quickly on your arrival seems to indicate your load draw whilst u where there was matched by no solar input whatsover.

    HTH Plus I agree with previous post in that the sooner you replenish your BB hours or days in stead of weeks is crucial.

    Nigel
  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    Re: Solar problems. Please help!

    One possible reason for the "crash"... If you have been running deficit charging (not fully charging the batteries after every use)--it is possible that you have been charging 10% less every trip--and the last one took your batteries from 10% charge to 0%...

    You did not give the size of your solar panels and other specifics--Another reason to check the state of charge of your battery bank once in a while--to make sure that they are getting 100% charged (and equalized with flooded cell batteries) at least once in a while.

    Many systems (not saying yours) end up with deficit charging and the owners don't realize it for months or until the weather turns bad or more visitors come by and burn more power than normal.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Solar problems. Please help!
    BB. wrote: »
    One possible reason for the "crash"... If you have been running deficit charging (not fully charging the batteries after every use)--it is possible that you have been charging 10% less every trip--and the last one took your batteries from 10% charge to 0%...

    You did not give the size of your solar panels and other specifics--Another reason to check the state of charge of your battery bank once in a while--to make sure that they are getting 100% charged (and equalized with flooded cell batteries) at least once in a while.

    Many systems (not saying yours) end up with deficit charging and the owners don't realize it for months or until the weather turns bad or more visitors come by and burn more power than normal.

    -Bill
    I said in my opening post that when I got there, I went to turn on the inverter and checked the volt meter that read 13+ volts. It the batts were only at 10% wouldn't it have read in the 11.5 range?

    I have an anolog volt meter (need to get a digi one) that is wired into the inverter terminals where the battery bank also is wired into. Is this the best place to wire it so I can monitor my batts at any time?

    The solar panels were already there when we bought the place 7 years ago. They look pretty old and have no labels on them. There's four panels mounted together and each one measures about 8" wide by 4' long. The CC is made by ASC Specialty Concepts, model number ASC-12/16. I can't remember what the inverter is.

    Here's another question, shouldn't inverters shut off after they get to a certain voltage preventing total battery drainage? Mine shut off but only after the batts were totally dead. Maybe the newer inverters do this?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    Re: Solar problems. Please help!

    The 13 volts when you got there--really depends if the batteries were "resting" for several hours or if that was with sun on the panels and "charging".

    If that was 13 volts "resting" (still dark in the morning), then this is actually "over" 100% charge (12.7 volts at 77F).

    If this was 13 volts at 10am-12noon... Then it is possible that this indicates the batteries are not charging sufficiently (current flowing through the controller).

    If this was 13.02 to 13.20 volts, and you have a 3+ stage controller with a "float" setting, then this could indicate that the solar charge controller thought that the batteries where fully charged.

    For random (maybe a couple times a month), a hydrometer and thermometer would tell you very quickly if the battery bank was fully charged or not--regardless of the load/charge currents and/or time of day. The first time you check your battery bank, you should measure (and log) the specific gravity of all cells/batteries to ensure that they are tracking closely together... If not, then you should check for improper or bad wiring, or possibly, one or more failed cells.

    Personally, I really like the Battery Monitor type devices... They are the closest you will get to a "battery bank fuel gauge" short of using a hydrometer multiple times a day. The older Xantrex XBM was recommended by a few people here--and I like the looks of the Xantrex LinkLite and LinkPro meters (I have not used any of these products). However--not everybody can justify the $200-$400 these things cost.

    Regarding the Inverter Shutdown... Typically, these are set to around 10.5 volts or a bit less... This voltage setting, in my humble opinion, is not set to protect the battery, but instead to protect the inverter itself attached loads)....

    Since Inverters are constant power devices (for a set load, say 100 watts and 80% efficiency=>120 watt load at 12 vdc; at 14.5 volts the inverter will draw 8.3 amps; and at 10.5 volts it would draw 11.4 amps) to prevent it from drawing too much current and burning itself out, and to prevent "brownouts" at the AC appliances that are attached to the inverter (which can damage motors and electronic devices).

    At 10.5 volts--the battery is 100% dead (assuming no load)--well below the 50% discharge that we normally aim for.

    In the end, because during heavy loads/surges you can see the battery voltage / wiring leads drop by several volts (large load relative to the battery bank--such as starting a well pump)--the voltage trip point is usually set pretty low to prevent false triggers (turning off) when trying to start heavy loads.

    But, in reality, it is almost impossible to know the battery's state of charge using a volt meter to estimate the state of charge of a battery when under load or under charge... The only time you can use a volt meter is after the battery has rested for 3 hours or so. And the meter needs to be accurate to 100th of a volt--12.xx--volts at least).

    The meter should be attached directly to the batteries for accurate voltage measurements--placing the meter on the inverter inputs also takes into account the voltage drop of the cable when the inverter is on and under load... Measuring the voltage at the inverter is OK and accurate if done when the inverter is turned off.

    If you need to run the inverter while the cabin is unattended--I would use something like the Xantrex LinkLite which gives you real battery capacity and you can set it to turn off a switch if the battery capacity falls below 50% (or whatever setting you choose).

    Setting up a voltage trigger to turn off your inverter is not going to be very accurate because the battery voltage not only changes with state of charge, but if charging/discharging and with temperature changes too.

    In the end, I am not saying you are deficit charging--but if you have no other explanation (shorts, something left on, etc.), then you are tending towards deficit charging--either because of to much load, to few solar panels, or a charge controller not properly charging the battery (wrong settings, controller hot while batteries cool, bad wiring, bad controller, one or more open/shorted cells in your batteries, etc.)...

    Sorry I can not be more exact in my diagnosis--but it is difficult based on what I know so far.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Solar problems. Please help!

    That is some great info Bill and I really appreciate it. Lots of things for me to test out once I get up there. Hopefully the batts have charged up enough to not be ruined. Like I said earlier, the batts are only 2 months old. I'd hate to throw away $700. Anybody in Flagstaff feel like running out to Elk Park Meadows with a genny for a few hours?
  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    Re: Solar problems. Please help!

    Chance
    Just curious, but are those panels kind of a brownish color, if so they may be the old arco panels that I see alot of down here in Baja. Most of the ones I see down here are pretty much dead. See if you can check the amps output of your panels.
    Larry
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Solar problems. Please help!

    Chance, perhaps you could change "arrived Friday night" to a time. The sun is still up till after 8 in our neck of the woods and when we arrive at ' night ' ( 21:00) the PVs are still putting out > 13 volts BUT only .1 amps.
    HTH
    Eric
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
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  • System2
    System2 Posts: 6,290 admin
    Re: Solar problems. Please help!
    rplarry wrote: »
    Chance
    Just curious, but are those panels kind of a brownish color, if so they may be the old arco panels that I see alot of down here in Baja. Most of the ones I see down here are pretty much dead. See if you can check the amps output of your panels.
    Larry

    No, they're not brown ones. I don't think they're dead because when they're disconnected from the CC the panels are reading 20 volts.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar problems. Please help!
    westbranch wrote: »
    Chance, perhaps you could change "arrived Friday night" to a time. The sun is still up till after 8 in our neck of the woods and when we arrive at ' night ' ( 21:00) the PVs are still putting out > 13 volts BUT only .1 amps.
    HTH
    Eric

    We arrived at about 6pm. Yes, the sun was still up but it was super cloudy and getting ready to rain.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    Re: Solar problems. Please help!

    The batteries really need to sit (no load/no charging currents) for 3 or more hours before you can accurately measure their charge using a volt meter...

    Given it was cloudy--probably did not get much charging that afternoon.

    Lastly, you really need to measure the current from the panels when they are (or should be) charging your batteries.

    Many solar panel faults are "high resistance" types (corrosion, burned spots, etc.) and with a modern DVM--the meter does not supply enough load for the high resistance to show voltage depression.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Solar problems. Please help!
    BB. wrote: »
    The batteries really need to sit (no load/no charging currents) for 3 or more hours before you can accurately measure their charge using a volt meter...

    Given it was cloudy--probably did not get much charging that afternoon.

    Lastly, you really need to measure the current from the panels when they are (or should be) charging your batteries.
    Many solar panel faults are "high resistance" types (corrosion, burned spots, etc.) and with a modern DVM--the meter does not supply enough load for the high resistance to show voltage depression.

    -Bill

    How do I do that? When the panels were hooked up to the CC, everything was reading 9 volts (the terminals on the panels, the terminals on the CC, the batts, and the inverter). But when I disconnect the panel from the CC the panel was reading 20 volts. When you say "current", does that mean amps? Obviously, I'm a total newb at this stuff so bare with me guys. Thanks for all the info so far.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar problems. Please help!

    Got any old car headlights where one beam is burned out, but the other beam is OK - that can be your load, they are often a good 40 watts or so. If it was my system, I'd disconnect the controller, and attach the PV array to the headlight, if it comes on full bright, and then burns out, the array is pretty good ! If it just glows, then the PV's are sick.

    If it was good and bright, I'd connect the PV to the battery, and see if that gets the battery to start charging. But I gotta tell you, if your battery is really 9 v at this point, it's so deeply discharged, it may not recover. You will be able to charge it, but it will go flat very quickly after you stop charging. Check the battery voltage every half hour, it should slowly start to charge up, if the sun is out. It may take several days of sun to recharge this dead battery, if you have another way to charge it, use it. I would NOT use jumper cables to a car battery, until the sick one is over 12V while charging, as it would be a terrific load, and if the battery was really bad, the high current could make it explode. just being cautious.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    Re: Solar problems. Please help!
    Chance wrote: »
    How do I do that? When the panels were hooked up to the CC, everything was reading 9 volts (the terminals on the panels, the terminals on the CC, the batts, and the inverter). But when I disconnect the panel from the CC the panel was reading 20 volts. When you say "current", does that mean amps? Obviously, I'm a total newb at this stuff so bare with me guys. Thanks for all the info so far.

    You need a "multi-Meter" that has a 10 amp scale on it (or a dedicated Amp/Current meter that you can install into your solar panel wiring).

    Depending on how many panels you have and how they are wired--you will need to lift one panel (or string) at a time and put your amp meter (set on max or 10 amp scale) in series and check the reading. Your system (when running correctly) probably outputs more than 10 amps in full sun--so you cannot measure the total current with a 10 amp multi-meter without blowing a fuse or damaging the meter.

    Without knowing both the current from the panels and the system voltage--you are sort of flying blind here.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset