How long will it take to fill up my battery bank at 3A?

quique
quique Solar Expert Posts: 259 ✭✭
My wind turbine seems to be operating just fine. Ive connected the 4-12V batteries to it and it originally read 51V. After a couple of days its down to 48V so I decided to unlock the brake on the turbine and have it charge my battery bank.

The display on the CC/Inverter reads that the battery bank is at 48V and that the charging current oscillates from 0.0A to 3.0A at times.

How would I calculate how long it would take to charge back up to 51V?

If the batteries are rated at 75Ah (c/20)...does this mean that at full charge (IF thats what 51V was...):

51V x 75Ah = 3,825Wh

And it is currently at:

48V x 75Ah = 3,600Wh

Wait that cant be right because Ah are depleted...

Comments

  • Joe_B
    Joe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    Re: How long will it take to fill up my battery bank at 3A?

    You have not supplied enough information to answer the question. What is your wind turbine output? The more poignant question is why your batteries are not charging. You have to set the output of your charge controller to a voltage that will supply current to the bank. If your bank is at 48 volts and your charge controller is not supplying current to the bank, it might not be set correctly.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: How long will it take to fill up my battery bank at 3A?

    Oh if only it was that easy!

    You have four 75 Amp hour batteries in series for 75 Amp hours @ 48 Volts. You're putting 3 Amps to them, which is 4% peak charge rate.

    The proper charging Voltage for a 48 Volt system is around 58 Volts, not 51.

    Good luck ever getting them charged.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: How long will it take to fill up my battery bank at 3A?

    No, perhaps I didnt explain myself. I have everything connected. I just had the brake on. So the inverter/cc read 48V from the battery bank and 0.0A of charging current.

    When I took the brake off, it started charging between 2-4A of current as displayed by the inverter/cc. It did already move up from 48 to 49V. Im just wondering how much it would take.

    its a 1000kW@48V wind turbine.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: How long will it take to fill up my battery bank at 3A?

    Caribocoot...

    Again I guess I didnt explain myself. I didnt say the voltage the turbine was putting out was 48V. I said my battery bank is being diagnosed as being at 48V. I remember when I had the thing connected to a voltmeter, it ranged from 0 (when still) up to 90V at times. I dont know what the charging voltage is, I only know the amperage because it is displayed onscreen at the inverter/cc but im sure its well above 50V.

    So what I guess must happen is that I would need to know the voltage at which those average 3 amps are coming in which if they were 60V, it would mean i would have 60V @ 3A = 180W?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: How long will it take to fill up my battery bank at 3A?

    Batteries at 48 Volts resting = half charged (more or less).
    3 Amps of current (regardless of Voltage) from turbine = 4% charge rate, which isn't going to be very effective at charging.

    If your batteries are "down 37.5 Amp hours " (50% SOC) it is not simply a matter of 3 Amps * 12.5 hours = full battery, even with the usual 20% extra factor added in (15 hours charging).

    In essence your turbine would have to be able to maintain > Absorb Voltage into the charge controller for 15 hours or more at 3 Amps to get the job done. If the current and Voltage both are fluctuating it may never happen. It would be even worse if power is being drawn while charging takes place as that would reduce or even negate any charging activity.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: How long will it take to fill up my battery bank at 3A?

    Ok, it actually ranges from 3-7Amps.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: How long will it take to fill up my battery bank at 3A?
    quique wrote: »
    Ok, it actually ranges from 3-7Amps.

    7 Amps is much better.
    Still you have the fluctuation which makes predicting charge time impossible.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: How long will it take to fill up my battery bank at 3A?

    You have got to get those batteries up to fully charges as soon as possible, otherwise, if it hasn't already happened, your batteries will be damaged, or ruined. Not kidding.