need help troubleshooting simple offgrid system

notsobright
notsobright Solar Expert Posts: 247 ✭✭
in Solar Beginners Corner #1
hi everyone,

three months ago I installed a small system on a cargo trailer and its been fine until last week when I noticed the battery was low.

system: 1 Kyocera KC40T 43w panel, 1 Morningstar sunguard 4.5a controller, 1 Everstart deep cycle 12v battery, and 1 voltminder meter.

the first thing I checked was the voltage in and out of the controller, I was getting 19.5v in and 0 out so I assumed the controller was bad and called MS about it and they send another one out right away and a call tag to return the old one. (Great customer service!)

so now I have just installed the new controller and the first thing I noticed is that the battery voltage is only just creeping up very slowly in full sun and it still hasnt reached 13v yet after 30 minutes and before with the orginal controller I could switch it on and the voltage went up to 14v almost imediately.

I decided to measure voltage in and out of the replacment controller, whith full sun Im getting 19.5v in and 13.9v out but on the output when I connect (switch here) to the battery the output drops down to the battery voltage.

Im not sure what is going on here.. so now I want to check the panel output voltage and amps and verify that is OK first so I need to know how.

checking voltage is no problem for me but Im not certain if Im checking the amperage correctly. Im using a cheap Digital multimeter but it can measure amps too but I dont know if I can just probe the wires for this or if I must disconnect and test them directly? then after getting both readings (volts and amps) how do I determine how many amps is good compared to the voltage?

I kinda doubt the new controller is not up to snuff so thats why Im wanting to check elswhere but Im not rulling out that possibility either but I certainly dont know how to test it other than output voltage.

Thanks!
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
    Re: need help troubleshooting simple offgrid system

    It sounds like all is operating correctly (at least with the second controller)...

    Basically, for a battery that is less than 80% charged, the battery voltage will be below the "absorb" voltage of 14.4 volts (battery sets the system voltage)--This is "Bulk Stage" charging. I would expect the solar panel input voltage to be around 15-16 volts at this time (1-2 volt drop across the controller).

    Once the battery reaches 80-90% state of charge, the battery voltage will rise slowly to the set point voltage of 13.8-14.4 volts or so (depending on controller setting). At this point, the charge controller is going to limit the charging current into the battery to maintain the 14.x volt set-point voltage (absorb stage). As the controller uses less and less current, the Vpanel input voltage will rise--eventually hitting 20 volts or so (Voc) of the solar panel.

    If this is a 3 or more stage controller, once it figures the battery is fully charged, it will will drop back to 13.6 volts or so for Float Stage charging (maintenance charge).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #3
    Re: need help troubleshooting simple offgrid system

    I dunno.. its not behaving anything like the first controller was and I havnt seen it above 12.77v yet but it was 4pm when I replaced it and started checking things.


    mabey tomorro will be sunny again and I will be able to determin if there is a problem by the end of the day.


    Id still like to learn how to check amperage correctly and troubleshoot though.

    does a battery being connected or disconnected have any affect on the charge controller output? in other words if a charge controller does not have anything connected to the output will there still be an output voltage?

    also, I wired a switch so that I could turn off the charging and its on the output side of the controller, should I change that to be between the solar panel and controller or does it mater?

    thanks.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: need help troubleshooting simple offgrid system

    What is the "at rest voltage of the battery? My guess is the battery was significantly discharged and it will long time to recharge. 43 watts might only put ~2 amps into the battery, just barely enough to keep a 100 ah battery in float. Check the SG of the battery, and then fully charge it from another source.

    Sounds like everything is other wise good,'


    Tony
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #5
    Re: need help troubleshooting simple offgrid system

    hi Icarus, I edited (added a couple of questions) the post then noticed you replied. just so everyone doesnt think you skipped the questions.

    it was resting at 12.67v before I replaced the controller now its at 12.77 so its probably fine but I wasnt seeing as much voltage as I expected.

    I charged it right away with my B&D after I first noticed it. it got down to 12.30 with only a 4" vent fan running so the controller must have quit atleast a week before I noticed.

    this set up will easily float this battery as Ive ran it down below 12.40v and it was back to full charge before sunset the next day.

    the system is mainly for an alarm system, we've had a rash of trailor thefts in the area lately. I also have some lights, the small vent fan and a couple of output jacks too.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #6
    Re: need help troubleshooting simple offgrid system

    You can't measure amps with a simple DVM unless you use a shunt. Most small meters will only read Milli amps, and will go poof if you connect them and push amps through them. To read amps (current) you have to essentially "cut the line" and wire the meter "in line", sending the full current through the meter. A shunt effectively "cuts the line" and reads the current in the wire.

    Tony
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #7
    Re: need help troubleshooting simple offgrid system
    icarus wrote: »
    You can't measure amps with a simple DVM unless you use a shunt. Most small meters will only read Milli amps, and will go poof if you connect them and push amps through them. To read amps (current) you have to essentially "cut the line" and wire the meter "in line", sending the full current through the meter. A shunt effectively "cuts the line" and reads the current in the wire.

    Tony

    my noname DVM must not be too bad then.. it has an extra jack that you plug the red lead for amp measurments above 200ma upto 10a. must have a built in shunt.

    I was getting some amperage readings by just probing wires but I wasnt sure if that was an accurate way to do it.

    I'd still like to get some input on these questions:
    notsobright wrote: »

    does a battery being connected or disconnected have any affect on the charge controller output? in other words if a charge controller does not have anything connected to the output will there still be an output voltage?

    also, I wired a switch so that I could turn off the charging and its on the output side of the controller, should I change that to be between the solar panel and controller or does it mater?

    thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #8
    Re: need help troubleshooting simple offgrid system

    You have to be very careful when probing and having your DMM set to Amp scale... The meter is basically a dead short--and if plugged into the 10 amp shunt, may not be any fuse.

    If you go across the +/- terminals on your battery bank, you are looking at 100's - 1,000's of amps potential. Plus the sparks, glowing red wires can start fires (and light off a hydrogen explosion).

    Multimeter Tutorial

    You want to make sure you understand what current you want to measure before you connect your leads--or you may be in for some nasty surprises.

    If you will be measuring lots of current, a good entry level DC clamp meter ($100 USD or so) is a nice tool to have.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: need help troubleshooting simple offgrid system

    "whith full sun Im getting 19.5v in and 13.9v out"

    this could be a problem as that is insufficient voltage to even properly charge an agm battery let alone the requirements of an fla which should be at least 14.4v. the specs for the controller state 14.1v and even at that it may be too low to properly charge your battery. also, if that's the same battery i'm thinking of with 115ah of capacity then the 43w pv will not supply sufficient amps being it's around 2.3a tops from your pv. this is a 2% charge rate at best.

    a possible temporary solution until you can figure out the direction you'd like to go with this may be to put jumper cables from your car to the battery just to bring the bulk charge up on it and let it finish with a few days on the 43w pv to finish off the charge with a sort of absorb charge.
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #10
    Re: need help troubleshooting simple offgrid system
    BB. wrote: »
    You have to be very careful when probing and having your DMM set to Amp scale... The meter is basically a dead short--and if plugged into the 10 amp shunt, may not be any fuse.

    that explains alot HAhaha! indeed, the manual for it says it is not fused. but very helpful as allways BB.
    niel wrote: »
    "whith full sun Im getting 19.5v in and 13.9v out"

    this could be a problem as that is insufficient voltage to even properly charge an agm battery let alone the requirements of an fla which should be at least 14.4v. the specs for the controller state 14.1v and even at that it may be too low to properly charge your battery. also, if that's the same battery i'm thinking of with 115ah of capacity then the 43w pv will not supply sufficient amps being it's around 2.3a tops from your pv. this is a 2% charge rate at best.

    a possible temporary solution until you can figure out the direction you'd like to go with this may be to put jumper cables from your car to the battery just to bring the bulk charge up on it and let it finish with a few days on the 43w pv to finish off the charge with a sort of absorb charge.

    I doubt the DVM I have is that accurate and before this system seemed to charge really well but I wonder if that might be why the controller quit on me?

    so what size battery would be optimal for this panel and controller then?

    my other questions keep getting overlooked but I'd really like to know the answers.

    thanks
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: need help troubleshooting simple offgrid system

    What is the Amp/hr capacity of the battery?

    I think Tony's on the right track here; habitual under-charging leading to ruined battery (even though the Voltage is up it may have lost significant capacity).

    Simply calculations: 43 W @ 80% efficiency = 34.4 / 14.2 V charging = maybe 2.5 Amps on a good day. Enough for 50 Amp/hr battery at most.

    Assuming you have a 100 Amp/hr battery even the controller's 4.5 Amps would be low. To reach the controller's maximum current you'd need approximately 80 Watts of panel (rough estimate).

    Now, which question has still been missed? :blush:
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #12
    Re: need help troubleshooting simple offgrid system

    you are getting your questions answered believe it or not as we are addressing why your system may not be right. the current verification is good to do too, but it may not be necessary. your battery voltage is coming up slowly because there is insufficient charge going to the battery noting that the battery has slowly been depleted over an appreciable time period. we have said numerous times how the charge rate should be between 5 and 13%. now i did not look up that kc pv's specs until now and it is rated for 2.48a which you will rarely see anyway. i did mean to put 2.5a there before, but i saw the wrong number due to my poor eyesight and entered the 3 instead of the 5. no matter.
    taking the pv at its best at 2.48a and for a minimal battery charge rate of 5% that would be a battery capacity of 50ah and at 13% it would be about 19ah. you have the battery already so just get more pv to it and either add another controller or replace with a single larger controller. you could regress the other way as you indicated you wanted to do and just get a battery between 19 and 50ah and only use the present pv and controller.
    now you did not state if i was correct on the ah capacity of your everstart, but assuming it is 115ah then the 5% charge rate would be 5.75a.
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #13
    Re: need help troubleshooting simple offgrid system

    its the 24DC6 but I dont know the ah, I'll see if its printed on the label.
    Cariboocoot wrote: »

    Now, which question has still been missed? :blush:

    the only ones Ive posted twice allready;-) heres a third repost for good measure:
    notsobright wrote: »

    does a battery being connected or disconnected have any affect on the charge controller output? in other words if a charge controller does not have anything connected to the output will there still be an output voltage?

    also, I wired a switch so that I could turn off the charging and its on the output side of the controller, should I change that to be between the solar panel and controller or does it mater?
    niel wrote: »
    you are getting your questions answered believe it or not as we are addressing why your system may not be right.

    OooKayee...


    anyway, if need be I can use this battery elswhere and Im sure I have a 50ah or less one arround here allready. I'll see how it does today if its sunny and then run it down to 12.5 or so and see how well comes back up and go from there.

    I cant justify another panel just to keep the alarm power source alive.

    one question at a time here from now on.

    thanks
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #14
    Re: need help troubleshooting simple offgrid system

    ok so we missed some.
    1> "does a battery being connected or disconnected have any affect on the charge controller output? in other words if a charge controller does not have anything connected to the output will there still be an output voltage?"

    2> "also, I wired a switch so that I could turn off the charging and its on the output side of the controller, should I change that to be between the solar panel and controller or does it mater?"

    1> you kind of answered that one for yourself. did you get any on the bad cc/good cc?

    2> it will stop the charging either way, but where you did it between the battery and controller is best as sometimes there's a small drain (phantom load) off of the battery running the controller.

    oooo kayee?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #15
    Re: need help troubleshooting simple offgrid system
    niel wrote: »
    1> "does a battery being connected or disconnected have any affect on the charge controller output? in other words if a charge controller does not have anything connected to the output will there still be an output voltage?"
    Many controllers will not even operate if there is no DC battery power (i.e., the battery needs to be 6-10 volts or so before the controller will configure itself and turn on the output.

    Solar charge controllers, for the most part, assume there is always a battery connected. They do not usually control their output very well if there is no battery there (output will swing between zero and Voc and may even over-voltage/fault). They are not designed to regulate (i.e., output 14.4 volts) without the battery connected.
    2> "also, I wired a switch so that I could turn off the charging and its on the output side of the controller, should I change that to be between the solar panel and controller or does it mater?"

    I don't quite understand why you would want to turn off the solar charge controller during normal operation... You can parallel multiple charge controllers (solar, AC power, generator, etc.) to one battery.

    If you want to cut parasitic loads (say the RV is parked under trees or in a garage for storage)--then you would want to cut the Battery Side of the controller to lessen drain on the battery bank.

    If you want to just stop charging for some reason (work on system, use AC charger when in storage, etc.)--then it would not matter--Panel side or Battery side. Although, I would probably cut the solar power with a switch. I don't like the idea of running solar panel power into a charge controller without a battery connected (but it really depends on brand/model of controller--some have memory for charging, state of charge, equalization timers, etc.--disconnecting DC power may mess all of those stored states/information up for you--if you need that information, use controller timed equalization).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #16
    Re: need help troubleshooting simple offgrid system

    hi niel, thanks and hopefully no offence to you but I find your post hard to read/understand most of the time esspecially the longer ones but Im sure its just a text thing and I could easily understand your communications in person.

    you do a good job with moderating here though, at least your show some courtesy when moving or editing threads by notifying the posters and thats a rare occurance with most other forums I participate in. it also reflects well for NAWS and I know first hand their customer service is second to none
    niel wrote: »

    1> you kind of answered that one for yourself. did you get any on the bad cc/good cc?

    yes "kind of" but then thats why I asked.


    niel wrote: »

    oooo kayee?
    yeah, kinda like "well allright then" like when youre not sure what to make of something. no enjoyment for me in causing confusion or instigating hard feelings for others but I think thats an abnormality these days and many times it seems to have an opposite effect than intended (even in person) mabey it did that this time, hope not anyway.


    todays not a sunny day for us so I wont be able to make a good determination on what I have here yet.

    have a great weekend!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
    Re: need help troubleshooting simple offgrid system

    Short-term memory is the first to go. Sometimes we forget what we're saying while we're saying it. It's real easy to get lost in a post and not address all the issues the OP brings up. Then get side-tracked and start talking about the weather, price of oil, who will win the Stanley Cup ....

    Did I mention short-term memory is the first to go? Why, when I were a lad we didn't even have solar power! Thomas Edison was still working with incandescent bulbs, the fool! Why didn't he start out with CFL's? Think of the power that could have been saved over a century!

    Er, what were we talking about? :p
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #18
    Re: need help troubleshooting simple offgrid system

    we got a good mostly sunny day today and I was seeing voltages I was acustomed to seeing on this system so I think its good. I also correctly tested the amps from the panel in full sun and was getting 2a. that was at noon and the panel is mounted horizontal.

    now that y'all have indicated that I may have too much battery for the system I will run the battery down some and see if it can recover. Im almost sure it has before but I want to be certain.

    thanks again.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #19
    Re: need help troubleshooting simple offgrid system

    Rather than having "too much battery" I think, in fact you have too little PV, not a semantic difference. There is a reason charging rates of ~5-13% of ah capacity is recommended.

    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
    http://www.batteryfaq.org/

    Tony
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #20
    Re: need help troubleshooting simple offgrid system
    icarus wrote: »
    Rather than having "too much battery" I think, in fact you have too little PV, not a semantic difference. There is a reason charging rates of ~5-13% of ah capacity is recommended.

    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
    http://www.batteryfaq.org/

    Tony

    nope.

    the fact is: Ive got way to much battery for this. as Ive previously posted the main purpose here is to run an autopager security system, everything else is usefull but not required.

    at the time I thought more would be better. (insert you favorite saying) but like I said I can use this battery elsewhere (trolling motor) and I have several smaller ones available that I can fit here if needed. which may be the case but I'll wait and see how this one recovers from 12.5v they way it is first.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    #21
    Re: need help troubleshooting simple offgrid system

    This is a PWM charge controller. It is basically just a MOSFET switch that connects and disconnects the panel to the battery.

    Sometimes a low current, inexpensive charge controller put a blocking diode (instead of a second MOSFET switch) which adds another 0.5 vdc drop across input to output of controller.

    If your battery is in need of charge and you have decent sun on panel, the controller will connect the battery to panel. The panel voltage will drop and the input to output voltage drop through the controller should be no more then 0.5v or 1.2vdc if a blocking diode is used. Make measurement with battery connected. Without battery connected the controller may not have power to run the voltage comparitors within its circuitry.

    The current will depend on panel illumination. When battery is in need of charge (less then 12.5 vdc) the panel output current and battery charge current output should be similar.

    When battery gets close to 14.2 vdc the charge controller starts chopping on and off to regulate the average battery voltage. After the battery has sat at 14.2 vdc charging for several hours the controller will drop the voltage regulation to float level of about 13.2 vdc.

    4.5 amps is enough to charge a 125 A-H lead calcium battery. Once battery is charged the battery should only need less then 0.3 amps to maintain a float voltage of 13.2 vdc. Again, at float condition, the controller will be chopping on and off to maintain the average float voltage on battery.

    You can use the 10 amp capability of a simple DVM but should avoid using the regular, rather small guage test probe lines. Use a larger guage wire to banana plugs directly into the separate 10 amp input on meter and 'com' black input (don't use regular red + jack input you use for volts and mA's).
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