Amp hours

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banjorene
banjorene Solar Expert Posts: 36 ✭
in Solar Beginners Corner #1
The charging amp hours on my cc read 4 amp hours more every day and my batteries are fully charged 12.6 to 12.8 volts every morning and I am using this system just for power outages does this reading represent what my panels are putting out or what the cc will allow to go to batteries because they are fully charged? I do run one small 12 volt light for around 5 hours drawing around .5 to .75 amps at night
The cc is set to shut down at 13.7 volts (over charge protection )and goes into a float trickle charge at 13.4 volts.
Thanks
Rene
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
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    Re: Amp hours

    A bit more info please.

    What do you have for panel, cc, batteries etc.

    I would guess that the amperage reading is what is going into the batteries. (BTW, just because the battery "reads" 12.6-12.8vdc on a volt meter doesn't mean it is charged. Determining if the state of charge of a battery has to take into account many things, but most especially the specific gravity of the cells.
    I suggest you read the following: http://www.batteryfaq.org/ http://www.rpc.com.au/products/batteries/car-deepcycle/carfaq4.htm#charge
    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

    Tony
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  • banjorene
    banjorene Solar Expert Posts: 36 ✭
    #3
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    Re: Amp hours

    2 kyrocera 50 watt panels....4...12 volt batteries 450amp hours,,,,CMP24 JUTA cc

    The volt meter on the cc reaches float mode everyday and with using the one light for around 5 hours every night battery voltage reads between 12.6 to 12.8 every morning when I roll out of bed.
    Thanks
    Rene
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
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    Re: Amp hours

    I'm still a bit confused. You say that the cc shows "4 amp hours more every day" I don't know what that means.

    The 100 watts of panel might put out a Max of ~ 8 amps under ideal conditions,, more like in the real world, average.

    Your load would be some where in the neighborhood of ~4 amp/hours/day.

    Do you have a battery monitor, or are you just reading the cc. (I have to admit I have no knowledge of your cc.) ( I looked on line and it seems the controller meter will give you a "soc" reading. I'm not sure how it does that considering charging/loading)

    In any case, it would seem like you are keeping the batteries virtually fully charged each day with limited loads. (less than 1% of the battery capacity).

    Don't know if this helps any.

    Tony
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  • wxh3
    wxh3 Solar Expert Posts: 70 ✭✭✭✭
    #5
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    Re: Amp hours
    icarus wrote: »
    I'm still a bit confused. You say that the cc shows "4 amp hours more every day" I don't know what that means.

    ....

    Your load would be some where in the neighborhood of ~4 amp/hours/day.

    I think the poster is saying the total (not daily) amp-hour battery charging reported by the controller is increasing by 4 amp-hours a day, which matches exactly with your load estimate.
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  • banjorene
    banjorene Solar Expert Posts: 36 ✭
    #6
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    Re: Amp hours

    The cc reads,volts,amps of charging(this depends on amount of sun clouds etc and changes all the time one second it may read 5 amps then a cloud and it reads .2 amps,
    it also gives me battery % state of charge,load,and Amp Hours
    The load never changes because I do not have the light wired into the cc I am going fused to the battery so I would guess the cc has no idea what I'm drawing,the CHARGING AMP HOURS change everyday and the last 3 days increase 4 amp hours a day ( I just hooked this cc up ) I THINK I MAY HAVE ANSWERED MY OWN QUESTION SEEING that the cc regulates charging rate and seeing that the battery is close to fully charged the panels may be sending the cc 3, 4,or 5 amps but the cc will only allow enough to fully charge battery and that is probably the 4 amp hour total
    per day I'm getting.
    Does this sound correct ???
    I guess to try to prove this out I would have to draw down the battery bank and then see if the AMP HOURS per day increases after a day of good sun
    I keep thinking that 4 amp hours is low but if thats all that is needed........
    Thanks
    Does this sound logical ????
    Rene
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  • banjorene
    banjorene Solar Expert Posts: 36 ✭
    #7
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    Re: Amp hours

    That is exactly right the amp hour total increases 4 every day
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
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    Re: Amp hours

    It seems a bit odd to record a cumulative charge amp/hours. I know that the Bogart Trimetric record net amphours out of the battery. (a useful tool to estimate how many cycles your batteries have been drawn).

    Perhaps it you wire the cc to control the loads you would get a net, charge in, load out.

    I assume this is what is going on.

    Do this test. Put a know load on for a known time to draw the batteries down a know amount, say 10%. Measure the specific gravity if you can to confirm the draw down, Record what the meter is telling you. Then fully charge the batteries, recording how many ahrs it takes to recharge. (should be ~ 120% of the drawdown).

    Good luck,

    Tony
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  • wxh3
    wxh3 Solar Expert Posts: 70 ✭✭✭✭
    #9
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    Re: Amp hours
    icarus wrote: »
    It seems a bit odd to record a cumulative charge amp/hours.

    The MorningStar MPPT controller also reports (via RS232 output) the cumulative charging in both amp/hours and kWh. (However, the kWh is too high by factor of ~10 due to an apparent bug...somebody left off a zero in division I guess.)
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
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    Re: Amp hours

    is that 4 12v batteries at 450ah each or 450ah total? i'd also guess both of the pvs total output at around 7a if you're lucky. 7/450=1.5% charge rate assuming it's not 4x450ah for 1800ah in battery capacity as that'll make it a .39% charge rate. in either case your charge rate is far too low.
    you also state you limit the charge to 13.7v (bulk) and most batteries are required to go at least to 14.1v and some to as high as close to 15v. those batteries are not charging properly.
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  • banjorene
    banjorene Solar Expert Posts: 36 ✭
    #11
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    Re: Amp hours

    Hi Niel
    That would be 450 amp hours total
    I guess my question is IF I am not drawing any current out of my batteries then the cc will regulate what gets put back into the batteries.
    In this case I am only drawing around 4 amps total a day and 4 amps is going back in everyday
    The cc goes into a float mode at 13.4 + or - and shuts down at 13.7 to prevent overcharge the 13.7 I can raise the setting on the cc
    I am using 4 US 2200 xc batteries
    This morning my AMP HOUR reading increased 5 amp hours over yesterday morning.
    I realize that is not much but then again I did not draw much out of the batteries the night before.
    I tried to find specs. on the batteries that would tell me what the bulk charge rate should be but I was not able to find anything.
    I could probably get a better charge if I change my panel angle they are set for 60 degrees ( winter mode ) and they should be around 45 degrees at this time of year but I wanted to set up for winter now so I don't have to worry about getting on the roof when it's cold and miserable later in November ,December( Connecticut can be a fickle place when it comes to weather )
    This is my first season with the panels so I'm toying with different season angles but I'm thinking it may be easier to just set them at (lets say 45 degrees ) and leave them there all year.I'm am looking into getting a site evaluation from a solar co. not far from here
    and see what they have to say has to where my panels should go etc.
    I do have a couple diff. options and I do have tree problems ( not on my land ) so I guess what I want is the best charge rate I can get even if it's not 100% what it should be,
    Thanks to all for the reply's
    Your help and suggestions are a huge help.
    Does all this make any sense ????
    Rene
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  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #12
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    Re: Amp hours

    The way I take this is the cc is putting 4 ah in the battery that day. If that is correct that seems low. I would think a 450 amp 12v bank would need at least that, if not more to be topped off every day even without a load on them. If it drew 4.5 amps that would be 1% to maintain the batteries each day, which wouldn't be far off. BUT if you’re adding a light (load) on top of that it should be even more.

    Again if this is correct you’re not truly topping off the batteries and you should do that. Even a sealed AGM battery wants 14.3v before going in to float stage, so at a minimum I would bump up your absorb voltage to at least 14.1v, I have never seen an absorb voltage below that. This should make that number larger since it will be pushing the batteries all the way full, which is good for them. The worst thing you can do to a lead acid is let it sit not fully charged.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #13
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    Re: Amp hours

    As I suggested in an earlier post, making sure you batteries are fully charged is not just a matter of their voltage but more their specific gravity. Find the proper absorb/float voltage for your particular battery adjust the cc accordingly. Also check the sg to see if they are getting fully charged. I have a hunch that the cc is a rather cheap controller that simply shuts off at a predescribed voltage, with out taper.

    I agree with Neil and Brock about the size of the array relative to the size of the battery. My system is a bit small as well, but I keep it topped up with a generator, with guidance from the trimetric as well as the hydrometer.

    Tony
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  • banjorene
    banjorene Solar Expert Posts: 36 ✭
    #14
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    Re: Amp hours

    I realize my array is small for the batteries but I hope to add a new panel every month as funds allow. I started with a 15 watt and have sense purchased two 50 watt
    If I continue for a year it will give me a nice little system of 600 watts.And who knows maybe I'll keep going.
    Thanks for all the help
    Rene
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #15
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    Re: Amp hours

    If you are really going to go for that many panels, be careful, I suspect that you will run out of cc capacity. (You might think about getting a better Mppt controller, ~10-30% more output with a mppt controller, comes at a cheaper cost than a similar amount of panel capacity, leaving more money for even more panels).

    Consider a controller with enough head room capacity to grow.

    Tony
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  • banjorene
    banjorene Solar Expert Posts: 36 ✭
    #16
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    Re: Amp hours

    Oh I will surely get a diff. charge controller but I'm not there yet.
    Rene
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