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Battery charging

Discussion in 'Photovoltaics' started by George Ghio, Jun 12, 2006.

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  1. George Ghio

    George Ghio Guest

    What do I do about charging? Well not a lot really. You see, when you
    correctly size a system for your load, being honest about the numbers,
    you end up with a system that works as planned. I seldom need to run the
    battery charger.

    My philosophy on battery charging.

    Yes it is important that you not let them remain at a low state of
    charge for long periods, on the other hand they do not need to reach
    100% charge every single day either. I will run the little generator to
    charge my batteries if they drop to around 12 Volts (but like the fine
    print says "Conditions Apply")

    1) Condition: Batteries read 12 volts (or less) at four o'clock in the

    2) Condition: I know the sun won't be out tomorrow.

    3) Condition: I need to use the computer for several hours that night.

    4) Condition: There will be three hours of Red Dwarf on TV that night.

    It takes at least two of these conditions to warrant the running of the
    generator. And even then it comes down to gut feeling.

    And when it comes to charging the batteries I am not trying to bring
    them up to 100%. I am doing what I call ''Maintenance Charging'' which
    is to say that I only require that they be in the top twenty per cent of
    their capacity.

    Yes I know it sounds like it's too easy, but the thing is that when
    I started with solar power there was almost no information other than
    guess work and trial and error. My life with solar power is pretty easy
    these days because of what I learned from two or three disastrous years
    in the beginning.

    So let's say it's 4:00pm and I check the battery voltage on the reg. The
    voltage reads 12V. The weather forecast is for rain for the next two
    days and I have a rather lengthy paper due and expect to be on the
    computer for 5 or 6 hours.

    So I make a decision. I will run the battery charger. The charger is a
    35Amp alternator on a petrol motor. The regulator for this rig is a
    large ceramic rheostat salvaged from a very old spot welder.

    The battery charger actually puts out 30 Amps and 16-17 volts at max
    engine rpm. The tank holds enough fuel to run for approx. 3.5 hours when
    filled to the top.

    Usually around three hours of runtime will bring my batteries up to 15
    volts. On some occasions I will turn the rheo down and wait for the
    batteries to come back up to 15V. I may do this a couple of times, this
    is of course dependent on what the voltage was at 4:00pm and what I know
    about the voltage and the temp. for the last several days.

    The numbers? Well, they mostly look after themselves. After nearly
    twenty years of doing this sort of thing I really don't look at the
    numbers any more. The reg likes to tell me that the batteries are at
    100% charge. I sometimes think that it is not very honest for a little
    black box.

    Probably the most important thing to remember is that all the readings
    are taken from a running system. As such the readings are not a true and
    correct voltage reading. I do not rest the batteries, nor do I take into
    account any voltage drop associated with what may be running at the time.

    When the batteries read fifteen volts and I shut off the charger, I know
    that if there is no load from this point on, the batteries will read
    12.7 volts in the morning. What a surprise 12.7 volts is just what a
    fully charged 12 volt battery should be.

    Do I recommend this for everyone with a solar power system? NO!
    Absolutely not.

    Unless you are prepared to watch the voltage while charging you would be
    best advised to use an automatic charger.

    When I next run the charger I will make note of what the regulator is
    telling me and relate it in this group. Don't hold your breath. I have
    no control of the weather. At the moment we are in a cycle of cold
    frosty mornings and cool to cold sunny days. Ideal weather for

    Wayne says that I don't run my charger enough.

    "Truth is the inquiring minds food, but is often bitter to the taste.
    Most people prefer the savoury lie"

    An example

    Sunday, June 11, 2006. Voltage readings from my regulator. Overcast day
    with periods of sun. Note voltage readings for 11 and 12AM as sun breaks

    10AM - 12.3V
    11AM - 13 - 13.5V
    12AM - 13.7 - 13.9V
    1PM - 12.9V
    2PM - 14V
    3PM - 12.9V
    4PM - 12.7V

    This is the truth of my system. Wayne finds it bitter so he creates a
    savoury lie that makes him feel good.

    But as can be seen, 4:00PM and the batteries are at 12.7V. Yes, this
    reading is not the true and correct voltage of the batteries. But, after
    nearly twenty years of life with batteries I know that this is high
    enough not to place my batteries in stress.

    By far, most of the people who post here prefer the savoury lie and
    there are many who are willing to support the lies because they also
    want to feel good about what they are doing. Irregardless of the fact
    that they only want to hear what makes them feel good, even if it is not
    the truth.

    Merlin keeps posting about his dead battery in the hopes that people
    will tell him what he wants to hear, i.e. "You poor thing, don't worry
    if you keep charging the battery it will magically revive." It may, but
    I sure wouldn't hold my breath.

    The truth is, Merlin has been flogging that battery for around two
    months now and there has been no miraculous resurrection.

    Parallel batteries are not a good choice.

    Parallel batteries of different types, capacities and age are a dead loss.

    More than two parallel strings of batteries are such a dead loss that
    you can smell the rot from several hundred metres away.

    Now we come to today, 12 June 2006.

    It is now 4:00PM and the reg reads 12V. I'm not surprised as it has been
    a fairly overcast day. Tomorrow looks to be the same forecast so tonight
    I will run the battery charger generator.

    5:30PM - Reg reads 12V so I start the gen set.
    5:31PM - 12.5V
    6:00PM - 13.4V
    6:30PM - 13.5V
    7:00PM - 13.6V
    7:30PM - 14V
    8:00PM - 14.5V
    8:30PM - 15.1V

    Generator out put;

    30 Amps @ 16Volts

    Works for me. On very rare occasions my battery set might reach 70% max
    DOD. But not often. My daily DoD is around 12% (1.2kWh/day).

    My system was designed for the Peak Sun Hours of the 22 June. I like to
    keep my batteries charged. But, if required, my system will run with no
    input at all for an honest five days of autonomy, without some mystical
    reduced load.

    Bitter truth or savoury lies. If you only want answers that make you
    feel good - say so up front. But remember, "There is no substitute for a
    properly sized and designed system. Whether you like it or not."
  2. wmbjk

    wmbjk Guest

    Good. When will you *begin* being honest about your battery charging
    stories George?
    You're talking about *system* voltage. Repeatedly referring to
    "battery" voltage is very unprofessional. Something closer to proper
    terminology would make your "lessons" less silly.
    Without knowing the loads, your system voltage doesn't help readers
    estimate your SOC But we shouldn't have to estimate. Simply *tell* us
    the SOC. Surely you agree that you should know it. Given your
    experience it's something you ought to know by instinct within 20%.
    You should be able to get within 10% using experience combined with a
    voltmeter. With a hydrometer you could tell us exactly. You do own a
    hydrometer right? Then why beat around the bush with an irrelevant
    system voltage?
    Then you should be able to relate.... If you charge at 30A for 3
    hours, then the most you can replace is 90Ah, which is 10.7% of an
    840Ah battery's capacity. Less if you're tapering the charge by
    diddling with the rheostat. Your "conditions" indicate a somewhat low
    battery SOC, and you state that you're happy to get to 80% full. If
    you add 10%, and end up at 80, then you started at 70. Unfortunately
    you repeat your old claim (below) that the batteries are full when you
    finish. Which means that you'd have to start at ~90%. Why would you
    start at 90 if your target is 80?
    Not much of a surprise, it's exactly what you said seven months ago,
    and it still sinks your story. If the rested voltage is 12.7, then the
    charging *must* have started at ~90%.

    Which begs the obvious question - why would you be running a charger
    when you haven't even exhausted a single day's portion of your 5 day's
    Whether a charger is automatic or manual, the operator ought to be
    able to explain the purpose and results of his charging in plain
    English. Which doesn't include writing in circles for months.
    Above you say that the weather "at the moment" is ideal for PV, yet
    below you write that on June 12 you ran the generator. One would
    expect perhaps three days between ideal conditions and needing a
    backup charge right? Don't tell me you started writing that tripe on
    the ninth!
    No quote? I'm shocked.
    Not most people, but you obviously. Such as repeatedly claiming that a
    30A charger can take an 840Ah battery from a somewhat low SOC to
    fully-charged in three hours. And writing long-winded explanations
    which only prove that you're both ignorant and transparently
    There isn't anything savory about your BS George. Better terms might
    be pathetic, pointless, self-destructive, and at times entertaining
    (in a train wreck kind of way).
    No, most people here write in plain English. You're the only poster
    for whom readers usually need Weasel to English translations.
    Sounds like a conspiracy... have you tried tinfoil preventative
    I must have missed that. Please supply the quotes where anyone told
    him that his battery *will* revive.
    Can we get you to change your mind on that breath-holding?
    IIRC, he commenced his "nothing to lose" charging experiment a few
    days ago.
    Have you tried using your sense of smell to determine battery SOC?
    Rare huh? OK then, let's say that you sometimes get down to 60% DOD, a
    reasonable point to run a backup generator. Your typical charging run
    as described replaces ~10%, bringing you up to 50% DOD. So far so
    good. But what is the likelihood that after half charging your
    batteries, that they'd somehow have a rested voltage of 12.7 the
    following (overcast) morning? Do your fairies bring Ahrs instead of
    fetching teeth?
    Most off-gridders use an engine-driven generator to either catch up
    their batteries when other sources aren't sufficient, or to equalize.
    There are clues in your posts that you're trying to do some of both at
    the same time, which isn't possible. It appears you've decided to join
    two completely separate stories, yet pigheadedly refuse to believe
    that no amount of irrelevant elaboration can hide the stitches. No
    matter. You've had seven months to withdraw your claim that your
    charging routine results in fully-charged batteries. Instead you've
    repeated the absurdity. Therefore we should conclude that your
    charging *must* begin at about 90% SOC. Do you think anyone will
    believe that you stayed above 90% for seven months between generator
    runs? Or that a "power consultant" could somehow be sincere while
    writing dozens of irreconcilable posts without ever coming close to
    simply stating the battery SOC? The mind boggles.

  3. Landline

    Landline Guest

    George would it not make sense where you live to have a wind generator as a
    backup instead of a noisy smelly expensive to run engine generator? The
    wind figures for your area appear to support a wind generator.
    Considering now wind generators are so ridiculously cheap this would surely
    be the choice of smart operators.
    I have a wind generator.


    <major snip to save strange electrons>
  4. Landline

    Landline Guest

    George would it not make sense where you live to have a wind generator as a
    backup instead of a noisy smelly expensive to run engine generator? The
    wind figures for your area appear to support a wind generator.
    Considering now wind generators are so ridiculously cheap this would surely
    be the choice of smart operators.
    I have a wind generator.
  5. George Ghio

    George Ghio Guest

    Actually my batteries are in very good condition. This is easy to tell
    as they are clear cases and visual inspection is easy.
  6. George Ghio

    George Ghio Guest

    No. you have been fishing for the answer you want to hear ever since you
    first posted about your battery failure.
    NO. It will work for a time but in the end you will have ruined more
    batteries. Seen it all, far too many times. You will learn, how much you
    pay for the lesson is up to you.
  7. George Ghio

    George Ghio Guest

    Don't I wish. Unfortunately my site does not lend itself to wind. Not
    flat country.

    While wind gen's are quite cheap the 200 foot tower is not.

    On your other point I ran the battery charger for the first time
    yesterday, in something like 10 months. Not exactly breaking the bank is
  8. George Ghio

    George Ghio Guest

    840Ah @ 120 Hour rate.

    One - 6 x 2volt series string.

    Daily load is 1.2kWh
  9. George Ghio

    George Ghio Guest

    So now the savoury lies start.

  10. Landline

    Landline Guest

    George what do you have in the way of solar panels
    Any pictures of your setup?
  11. Guest

    .... 200' of rope is cheap, with an H2 dirigible. I just bought 600'
    of 1/4" yellow polypropylene for $9.99 from Harbor Freight.

  12. George Ghio

    George Ghio Guest

    When are you going to stop yapping and do something?
  13. George Ghio

    George Ghio Guest

    Actually, no I don't have pictures.

    6 x 85watt BP panels

    A point of interest is that when I run the battery charger I replicate
    what the panels do.
  14. Guest

    When will you stop beating your wife? :)

  15. wmbjk

    wmbjk Guest

    George, the only lie here is from you. I believe that you bungled the
    original story, and as usual are too spineless to own up to the
    mistake. One can't take a battery from a somewhat low SOS to fully
    charged by adding only 10%. It just ain't possible, and no amount of
    your strained elaborations can change that. I do hope you keep trying

  16. wmbjk

    wmbjk Guest

    Batteries that haven't been equalized for ten months (and probably
    never) sulphated? Naw, that can't be it, because even George would
    notice the lost capacity. Assuming he'd tell anyone... Now that I
    think about it though, about 2 years ago he announced that he intended
    to replace these batteries. Later he changed his tune and said they
    didn't need replacing. Hmm... Still, they'd have to be in really bad
    shape to account for the contradictions in his charging story. They
    *could* be that bad. But considering his history, I think it's more
    likely that he wrote himself into a hole with senseless hyperbole and
    is now trying to write himself out. Supplying a few simple details
    like the beginning and ending SOC would be a lot easier for him and
    better for his rep. Instead, as usual, he prefers to do things the
    painful way.

  17. wmbjk

    wmbjk Guest

    My site is as rugged as any, with some ~1000' elevation changes in a
    half mile. Yet like so many others in "not flat" country, wind power
    is a major portion of my supply.
    You only *believe* you need a tower that tall. In fact you believe a
    lot of strange stuff. It seems to me that being a renegade has cost
    you more than any tower ever could.
    Then why do you "wish" for wind power Shakespeare?

  18. wmbjk

    wmbjk Guest

    But your panels aren't capable of finishing your battery maker's
    recommended absorption charge (according to you). Neither are they
    capable of equalization. Most owners in that situation would want
    their backup source to cover those two deficiencies. Would you say
    that the battery manufacturer doesn't know as much as a guy on his
    fifth set of batteries? Or is that the company's recommendations on
    absorption and equalization don't apply to self-titled "power

  19. George Ghio

    George Ghio Guest

    I never beat my wife, she's a wicked card player.

    When are you going to stop beating your meat and build one of your fantasys.
  20. George Ghio

    George Ghio Guest

    And the savoury lies continue.
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