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  1. #31
    Join Date
    Apr 2002
    Location
    Cornwall
    Posts
    9,053

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by Chanquete View Post
    Hello Rainbow
    Here are the answers again:
    Before operating the glow plugs 12.64V
    Whilst operating the plugs 10.3V
    10 minutes later without starting the engine 12.85V
    l
    Couple of passing questions

    10.3V ... at the start of running the heater, part way, or at the end ? what run time estimate.

    12.85V ... was engine run after the heater operation ?

    Brian
    Kddpowercentre VASR charge

  2. #32
    Join Date
    Jan 2013
    Location
    Buenos Aires, Argentina
    Posts
    131

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by halcyon View Post
    Couple of passing questions

    10.3V ... at the start of running the heater, part way, or at the end ? what run time estimate.

    12.85V ... was engine run after the heater operation ?

    Brian
    Constant 10.3 V during the 13 seconds of the heater operation
    The engine was run one hour after the heater operation

  3. #33
    Join Date
    May 2018
    Posts
    249

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by Chanquete View Post
    Before operating the glow plugs 12.64V
    Whilst operating the plugs 10.3V
    10 minutes later without starting the engine 12.85V
    It doesn't make sense to me that the engine voltage is higher 10 minutes after. Where has that come from?

  4. #34
    Join Date
    May 2007
    Posts
    38,227

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by KompetentKrew View Post
    It doesn't make sense to me that the engine voltage is higher 10 minutes after. Where has that come from?
    Heating and agitating the battery. Seen this happen!

  5. #35
    Join Date
    Jan 2013
    Location
    Buenos Aires, Argentina
    Posts
    131

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by KompetentKrew View Post
    It doesn't make sense to me that the engine voltage is higher 10 minutes after. Where has that come from?
    The voltage was lower because the plugs consumed more than 30 Amperes. As soon as the plugs were disconnected without startin the engine the voltage increases to values without current consumption. As the engine was running and charging the battery one hour before I performed this test the voltage without consumption increased from 12,64 when I just arrived at the boat to 12.85

  6. #36
    Join Date
    May 2018
    Posts
    249

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Yes, the fall from 12.64v to 10.3v seemed obvious.

    It's the rise from 12.64v to 12.85v for no apparent reason that I don't understand.

  7. #37
    Join Date
    Jan 2013
    Location
    Buenos Aires, Argentina
    Posts
    131

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    After a week of inactivity I went to the ship. At that time measured a battery voltage of 12.64V
    Then I activated the glow plugs and measured 10.3V during warming.
    I started the engine and let it running and battery charging for an hour.
    Then I stopped the engine , disconnected everything and measured a battery voltage of 12.85V.
    This increase seems obvious due to the recent charging.

  8. #38
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    8,013

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by Chanquete View Post
    Hello Rainbow
    Here are the answers again:
    Before operating the glow plugs 12.64V
    Whilst operating the plugs 10.3V
    10 minutes later without starting the engine 12.85V
    Quote Originally Posted by Chanquete View Post
    After a week of inactivity I went to the ship. At that time measured a battery voltage of 12.64V
    Then I activated the glow plugs and measured 10.3V during warming.
    I started the engine and let it running and battery charging for an hour.
    Then I stopped the engine , disconnected everything and measured a battery voltage of 12.85V
    .
    This increase seems obvious due to the recent charging.
    You need to be very clear about the 12.85v reading.

    You first said you took that reading without running the engine.12.64v is about 95% charged, 12.85v is fully charged.

    Getting from 95% to 100% by just using the glow plugs is not possible, if it is i'll be energising my glow plugs for 13 minutes each hour and i'll never need to charge my batteries.

    If, on the other hand, you ran the engine for an hour, stopped it and immediately too a voltage reading, that reading is meaningless. To take a reading after charging you need to leave the battery at rest, no load or charge, for quite some time.

    Back in post #4 i suggested you take some readings and said exactly how they should be taken. They needed to be taken at the battery, with a reliable voltmeter (multi-meter is ok), not the boats panel meter, these are not generally accurate, as you found. They also needed to be taken at specific times, as i said. Taking them at different times, or running the engine makes the readings meaningless.

    Taking the final reading after running the engine only tell you that the alternator is charging, you could have done that test without using the glow plugs. Taking it 10 minutes after using the glow plugs gives an indication of how much the battery was affected by using the glow plugs.

    That said, i suspect your battery is OK, but would benefit from being on charge to get it to a genuine 100% SOC on a regular basis.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  9. #39
    Join Date
    May 2018
    Posts
    249

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by Chanquete View Post
    After a week of inactivity I went to the ship. At that time measured a battery voltage of 12.64V
    Then I activated the glow plugs and measured 10.3V during warming.
    I started the engine and let it running and battery charging for an hour.
    Then I stopped the engine , disconnected everything and measured a battery voltage of 12.85V.
    This increase seems obvious due to the recent charging.
    Right, but I thought the point was to measure the battery voltage before and after putting the load of the glow plugs on the battery, but WITHOUT running the engine.

    Perhaps the post which asked you to do this was not explicit about the without-running-the-engine part, but running the engine charges the batteries again. As you say, this is obvious.

    But you don't want to know the batteries' state of charge after being recharged again by the alternator - to learn the condition of the batteries you want to test them being loaded and discharged. You measure their voltage, put the load on, take the load off and see if the voltage returns to (nearly*) where it was before. If it does then they're good.

    If loading the batteries for a short period lowers the battery voltage significantly* then that means that the load is flattening the battery and it may be knackered.




    * I don't know the correct values for "nearly" and "significantly" here, but others on this thread do and can diagnose if you give them the measured values.

  10. #40
    Join Date
    Jan 2013
    Location
    Buenos Aires, Argentina
    Posts
    131

    Default Re: Voltage drop curve of lead acid batterry with increasing discharge

    Quote Originally Posted by KompetentKrew View Post
    Right, but I thought the point was to measure the battery voltage before and after putting the load of the glow plugs on the battery, but WITHOUT running the engine.

    Perhaps the post which asked you to do this was not explicit about the without-running-the-engine part, but running the engine charges the batteries again. As you say, this is obvious.

    But you don't want to know the batteries' state of charge after being recharged again by the alternator - to learn the condition of the batteries you want to test them being loaded and discharged. You measure their voltage, put the load on, take the load off and see if the voltage returns to (nearly*) where it was before. If it does then they're good.

    If loading the batteries for a short period lowers the battery voltage significantly* then that means that the load is flattening the battery and it may be knackered.




    * I don't know the correct values for "nearly" and "significantly" here, but others on this thread do and can diagnose if you give them the measured values.
    I checked the voltage of the battery , before and after putting the load on, and after taking the load off I found the same voltage as before.

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