Battery reserve capacity test

System
System Posts: 2,511 admin
in General Solar Power Topics #1
I have a pair of Concorde PVX-2240T AGM 6 volt 220ah batteries. They were manufacured in 2002. I asked Concorde for a method of testing the batteries and they sent be the following:

"The battery should be stabilized at 68 degrees F and then you need to charge it at 2.08 VPC (the 6-volt battery has 3 cells) using constant voltage. You charge the battery until the charger reaches 2.37 to 2.4 VPC and then leave the battery on charge for an addition 4 to 6 hours before removing it from the charger.

With the battery temperature above 60 degrees F, discharge the battery at 25 amps to 1.75 VPC (which is 5.25 for a 6-volt battery). You have to be able to set the analyzer you are using for 25 amps. I'm sure a local battery shop could help you if you do not have one.

Record the amount of time in minutes of full discharge. If the battery fails to deliver 80% of its rated discharge time, it should be replaced. The rated discharge time for the AGM-6220T is 492. So 80% is 394.":confused:

My charging methods are either hook up to ac and use the converter or use the solar controller.I don't have an analyzer and the Interstate battery shop here didn't want to be bothered. Is there a easier method to determine the condition of the batteries.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Battery reserve capacity test

    25 amps * 12 volts = 550 watts...

    Get a 1 kW inverter or so, plug in a pair of 250 watt shop lamps (or 4-5 100 watt bulbs) and start your timer. Checking every so often to make sure that your current is some were near 25 amps.

    If you need to do the testing... I would:

    1) buy this Doc Wattson meter (assuming it can do ~25 amps continuous--don't know anything about the vendor or about the meter--other than what I have read).
    2) setup six lamps sockets as a load bank behind a 500+ watt inverter, and buy some 100 watt, 50 watt, 20 watt lamps and screw them in or out as needed to get the current you need (probably if you keep the current within +/- 20%, you are accurate enough).
    3) Use the Doc Wattson meter to monitor current and totalize amp*hours.

    Whole thing would probably cost you less than $100 (excluding the inverter).

    If you already have a battery monitor, you don't need the Doc Wattson meter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #3
    Re: Battery reserve capacity test

    You will need to check the voltage of BOTH batteries, as one could drop faster than the other. But then again if one is bad/weak they both should be replaced as a set.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Battery reserve capacity test

    concorde's testing involves draining a battery all of the way at a prescribed rate (amps) to see if it can do this in an amount of time consistent with a good battery, but this also stresses a battery whether it's good or not. one can get a rough idea of its state of charge after it rests for 2 or more hours after draining a known amount of current that should give a certain % of charge. wish i had the voltages handy, but without being able to drain off a specific current for a prescribed timeperiod known to equal a certain % of charge then i wouldn't do it. i don't think i'd do their method either, but that's the only official way they prescribe of doing it. i would think any load that draws 25a will allow the test to be done. you could also write back to them and ask them if this is to be a constant current or a graduated drain that starts at 25a and drops as the battery voltage drops. my money is on the latter and the question may irk them as the one answering may not know and have to dig for the answer. you could also ask them how you may construct an acceptable load to test your batteries and/or where to get it. still may be easier locating a mechanic that has a tester even if many miles away. let me know what they say if you ask those questions.
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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Battery reserve capacity test
    BB. wrote: »
    25 amps * 12 volts = 550 watts...
    Get a 1 kW inverter or so, plug in a pair of 250 watt shop lamps (or 4-5 100 watt bulbs) and start your timer. Checking every so often to make sure that your current is some were near 25 amps.
    -Bill

    I have a 1750 ProWatt inverter. To see if my Morningstar ProStar-30 controller's meter would work to measure the load I took 3 house lamps with 100 watt bulbs to the trailer. I plugged two of them in and the load only showed 6 amps, I added the third and it still showed 6 amps. What was disturbing, after about 30 minutes of trying this the battery tested 12.1 volts. I wasn't sure of the battery condition when I started so I charged the rv overnight and turned off solar charging and allowed batteries to rest for 4 hours. I plugged in the three 100 watt lamps and checked them periodically, after 4 hrs they tested at 11.9 or 40%. I decided to let the test run longer to see if it would get to 0% with only the 300 watt load so I charged the rv again overnight and ran the test again. This time after 4 hrs the alarm went off on the inverter and battery tested at 10.16. I am looking at new batteries.

    A side note, I talked to my rv mechanic who installed my solar system and he checks the batteries by "short circuiting" them and then check to see how they rebound. Comments?
    niel wrote: »
    you could also write back to them and ask them if this is to be a constant current or a graduated drain that starts at 25a and drops as the battery voltage drops. my money is on the latter and the question may irk them as the one answering may not know and have to dig for the answer. you could also ask them how you may construct an acceptable load to test your batteries and/or where to get it. still may be easier locating a mechanic that has a tester even if many miles away. let me know what they say if you ask those questions.


    This is the answer I got back from Concorde:

    It should be done at a constant current of 25A. Many dischargers can do this. You can find a couple on our website, but you may want to check with a distributor for us that may have something more reasonably priced for an individual.

    That method is way too expensive. I could just as well and go buy the replacement batteries.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Battery reserve capacity test

    you actually had a bigger drain than 25a, but only because of the efficiency of running the inverter. the inverter draws some power to run itself, but it doesn't matter as i believe you have sufficiently proven your batteries are below that 80% mark. out of curiosity, in just what capacity did you use your batteries?
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #7
    Re: Battery reserve capacity test

    Your prostar only shows the amps from the solar to the battery's, not the battery to inverter load.

    You need a battery monitor or a shunt with a DVM to measure the inverter current draw
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
    Re: Battery reserve capacity test

    good catch sg, as that is only what is passing into the batteries from the pvs and as you said the loads are a different animal that need their own metering from another piece of equipment.
    herefishy,
    the loads (3-100w lights) you indicated over the time you said is how i agreed with your decision to replace them.
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  • System2
    System2 Posts: 6,290 admin
    #9
    Re: Battery reserve capacity test
    niel wrote: »
    i believe you have sufficiently proven your batteries are below that 80% mark. out of curiosity, in just what capacity did you use your batteries?

    From '02 to '05 we has them in our old 5th wheel with an inefficient controller(Magnetek Model 6345) that "cooked" our batteries at times. The solar regulator was an ASC Specialty Concepts that has a red light to show when charging, 4 wires, 2 for the battery and 2 for the array. When I called the company they said it was a old discontinued model. The batteries had white powder around them when we transferred them to our new 5th wheel in '05.

    We replaced the original equipment with an Intellipower PD9145A converter along with a Charge Wizard, a Morningstar Pro Star-30 controller along with a Xantrex Prowatt 1750 inverter. We have 2 solar panels(Kyocera 75 and 80 watt). After all that, the wife found out she needed an oxygen concentrator so there was no dry camping until this last year when she switched to a C-pap. By the way, the controller, converter and inverter was acquired with the coaching of you, crewzer, and a couple others from this forum in early '05 Thank you.
    Solar Guppy wrote: »
    Your prostar only shows the amps from the solar to the battery's, not the battery to inverter load.

    You need a battery monitor or a shunt with a DVM to measure the inverter current draw

    I've always wondered about the load light on the controller; the meter flashes battery power, solar power, and load. The solar power and load always seem to be identical or very close. Could you explain what the load light represents?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #10
    Re: Battery reserve capacity test

    From the Prostar manual:
    The 4 LEDs in the lower label indicate system status and various faults. These functions are described below.

    CHARGING (LED 1 – green)
    • ON: battery charging during sunlight (always on during sunlight)
    • OFF: normal during night (off during sunlight indicates solar reverse polarity or over current)
    BATTERY STATUS (LEDs 2 – 4)
    • GREEN: ON indicates battery is near full charge
    • BLINKING indicates PWM charging (regulation)
    • YELLOW:ON indicates battery at middle capacity
    • RED:
      • BLINKING indicates a low charge state and a low voltage load disconnect (LVD) warning
      • ON indicates the load has been disconnected (LVD)
    FAULT INDICATIONS (G = green; Y = yellow; R = red)
    • G/Y/R blinking together – battery select fault
    • R – Y sequencing – high temperature disconnect
    • R – G sequencing – high voltage disconnect
    • R/G – Y sequencing – load short circuit or overload

    If the RED Load LED is blinking--or on--indicates you are not getting enough charge (battery voltage is low). Or, you have other issues (like too small of wire between the battery and the controller).

    Are you using the LVD connection to power any loads? In general, the LVD should only be used for smaller loads. Larger loads, such as inverter, will probably trip the over current protection and/or might damage the controller.

    If you don't have one yet, take a look at installing a battery monitor. The Trimetric is good for the price. The Xantrex is a higher end product and has a programmable alarm output--really nice for the non-technical spouse to know when to turn off the lights or start the genset. The battery monitor will tell you a lot more about your loads and the state of your battery.

    Also, do you have a remote battery temperature sensor for your ProStar controller? Can really help ensure your battery bank is properly charged. Highly recommended option for any charge controller (including your shore power based charger).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #11
    Re: Battery reserve capacity test

    Hi BB,

    I am talking about the Digital Meter that displays battery voltage, solar current and load current. The values in the latter two are always the same or close.

    The only direct connect to the battery is the rv sensors(CO2 etc) and the c-pap which draws 1 amp normally, max 3 amp.

    The controller is in a compartment right next to the batteries so we did not get a remote temperature sensor.

    I just ran a self diagnostic test and in the display after the system voltage(12v), prostar current rating(30a), software version( 1.8 ), E07 is the next field??

    I will look at getting a battery monitor.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Re: Battery reserve capacity test

    HereFishy,

    First, the disclaimer--I do not have any of the off-grid solar products here--so my information is just from the manuals and faceplate information...

    If, your solar panel current and Load current is always the same--I would suspect that you are reading the meter when the sun is up and the battery bank is near 100% charged... So, all is OK.

    Feel free to skip the following if I am just confusing you:

    You should be able to look at the PS-30m at night--and anytime you turn a load on or off, the Solar PV Panel current should remain zero... And the Load current should go up and down with the changes in load (and should be very close to what you expect the loads to be).

    When the Sun is up, the PV Current should only respond to the the sun and state of battery charge (assuming the battery is less than 85% State of Charge--15% state of discharge).

    Now--here is where it gets tricky... If, your battery is near 100% charged and there are no loads, you will see very little current coming out of the panel (probably well less than 1 amp) because the Charge Controller has determined the battery is full and needs no more current. The amount going into the battery should be:

    Solar PV Current - Load Current = Battery charge/discharge current (+ is charging, - is discharging).

    You have a little bit of "error" in battery charging current because of the CO detector and C-Pap machine connections/loads you have directly connected to the battery bank (not a problem--just a source of "difference").

    If your battery is near 100% charged--the PS-30M is in "float" mode. Meaning it is just trying to keep ~13.8 volts (or whatever your setting is) on the battery.

    When you turn on a 2 amp load, the PS-30M will now draw 2 amps from the solar array to match the 2 amp load from applied to the LOAD terminal to keep the battery at ~13.8 volts (float/trickle charging).

    So, in the case with a battery fully charged, the current flow out of the solar panel will just about equal the current flow out to the load (assuming a) the sun is up and b) the panel has enough power to supply 100% of the load). If the sun is down or the power drawn by the load exceeds that available from the panel, then the battery will make up the difference (and the solar PV current will not equal the load current).

    -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 ✭✭✭✭
    #13
    Re: Battery reserve capacity test

    herefishy,
    i am glad we helped you, but i don't think i'd have recommended that original magnetek or asc charge controller. anyway, you might want to re-evaluate your pv and battery needs as your load requirements seem to have gone up.
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  • System2
    System2 Posts: 6,290 admin
    #14
    Re: Battery reserve capacity test
    niel wrote: »
    herefishy,
    i am glad we helped you, but i don't think i'd have recommended that original magnetek or asc charge controller. anyway, you might want to re-evaluate your pv and battery needs as your load requirements seem to have gone up.

    I edited my post to make it more readable. What I was trying to say is that this group helped be in acquiring my current converter, controller and inverter. Sorry for the confusion

    Bob
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