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A few questions on small dual battery solar

Discussion in 'Power Electronics' started by Ian Wallis, Sep 20, 2018.

  1. Ian Wallis

    Ian Wallis

    12
    0
    Nov 13, 2017
    Hi all, I have a 100watt 18volt 5.55amp solar panel, to which I've fitted a 10 amp dual output battery solar charge controller, and two car batteries a 95ah & a 45ah.

    1st question: if the panel is 5.55amp is this what the charge rate will be, or will there be more in the conversion?


    I was using about 3 to 4 amps max from each battery (12volt sat tv & lights) and I was shocked at how fast they lost power; within a minute they were 10.5 to 11 volts.

    2nd question: 12 volt, 3 or 4 amps should be nothing out of either of those batteries, right? or are the batteries duffers?

    The batteries started to fizz like mad while being re charged and the 45ah which I always thought was good, now works at 10.5 volt. Grrrrrr...

    3rd question: Even if the controller was on the fritz, how could it charge that badly if the panel was only 18volt 5.55amp 100watt?

    Link to the controller:
    https://www.ebay.co.uk/itm/10A-20A-...hash=item466bc9ff4b:m:mmdWKT4xEKteDljfMJEHG-g

    Thank you in advance.
     
  2. Audioguru

    Audioguru

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    591
    Sep 24, 2016
    Your charge controller or your batteries is/are defective.
     
  3. debe

    debe

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    63
    Oct 15, 2011
    If the voltage drops that quick then they are either faulty or flat. Automotive batterys are no good for cyclic use on a solar system. Use deep cycle batterys
     
  4. Ian Wallis

    Ian Wallis

    12
    0
    Nov 13, 2017
    Defiantly not flat, they held their charge for months.
    I'd love to use deep cycle but they are so expensive.

    Do you think that the 10amp charger could physically damage the batteries, given the low amps (5.55) of the solar panel?
     
  5. debe

    debe

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    63
    Oct 15, 2011
    Was there any instructions with the regulator? Those types of regulator need to be connected to the battery first so it can recognise the battery voltage, then connect solar panel. If not done in that order the regulator can be damaged, & either not work or over charge the battery. What is the voltage at the battery terminals when its fizzing? 15V & above will cause that as its boiling the electrolyte. How do you know the battery is fully charged?? In 24 hours how long are you drawing current from the battery & for how many amps?
     
  6. Ian Wallis

    Ian Wallis

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    0
    Nov 13, 2017
    Yes I have the usual Chinese to English bit of paper.
    I did connect the batteries first: as always.
    I'm not sure of the charging voltage when it was fizzing, I quickly switched the panel off at the circuit breaker / switch, and unfortunately had to go out. The intentions were to check it out later but we have had nothing but awful weather since then.
    Instructions state: Equalizing 14.6 - Boost 14.6 - Float 13.7.
    I charged the batteries fully with an Optimate charger a few months back and they seem to have kept their charge at around 12.5 volts.
    I tried to use 12 volts 3 to 4 amps and watched the voltage nose dive in about a minute.

    I have just now tried another car battery and 12.8 volts down to 11.3 volts in about 45 seconds. So that answers my own question that 3 to 4 amps is way to much for a medium sized car battery to handle.

    Thanks for your help.
     
  7. Audioguru

    Audioguru

    2,616
    591
    Sep 24, 2016
    In winter, the car oil is thick then cranking the engine takes 200A to 300A. The engine might not start immediately so you crank it at hundreds of Amps for many seconds. Lookup the hundreds of "cold cranking Amps" of a car battery.
    3A or 4A is nothing to a half-decent car battery. Yours are old or dead.
     
  8. debe

    debe

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    63
    Oct 15, 2011
    Just to prove a point to you this is a 4year old car battery. Showing its state of health & state of charge & voltage before running a 4Amp aprox load for a total of 10 minutes. On this test I would expect at least quite a few hours continuous use. Your batterys are either not charged properly or past there use by date. 1.JPG 2.JPG START.1.JPG 5 MINUTES.JPG 10 MINUTES..JPG
     
  9. Ian Wallis

    Ian Wallis

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    0
    Nov 13, 2017
    Five batteries with various states of no goodness, ho hum.
    Time to buy some deep cycle.

    Thanks for the info and for taking the time to take photos.
     
  10. Bluejets

    Bluejets

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    713
    Oct 5, 2014
  11. twister

    twister

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    Feb 12, 2012
    I use car batteries for solar power. They work fine but don't last as long as deep cycle batteries. If your batteries were boiling, something is wrong with your voltage regulator.
     
  12. Bluejets

    Bluejets

    3,517
    713
    Oct 5, 2014
    It depends on what is conceived as " boiling".
    It is quite normal to have hich gas discharge at high rates of charge.
     
  13. Ian Wallis

    Ian Wallis

    12
    0
    Nov 13, 2017
    Thank you all for you help.

    When you say deep cycle, I take it you mean below 12 volts?
    Now this is a real pain, I have a brand new 45ah deep cycle battery, and it only ever charges to around 12.5 volts. If we are only supposed to use the volts over 12 volts then that doesn't leave me very much arm room.

    Oh, thanks for posting photos of the battery checker, I now have one, and I can now see what the state of play is. Cheers.
     
  14. kellys_eye

    kellys_eye

    4,281
    1,144
    Jun 25, 2010
    A standard lead-acid battery requires 14.4V to charge, shows 13.8V off charge and can drop to around 10.8V before requiring recharge. Systems that operate from "12V" should be designed to work from 10 to 14V without modification thus using the available supply voltages to their full extent.

    A 45Ahr battery is really 'small' in the scheme of things but depends on your consumption. It is always wise to fit 200% of your expected requirement in order to safe guard the system and battery.
     
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