Battery state

Discussion in 'Tech/Mech General' started by PhilandMena, Oct 20, 2009.

  1. PhilandMena

    PhilandMena Funster

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    Advice please!
    I have fully charged my leisure batteries (New) and disconnected them. I intend to moeasure them with a multi - meter (Digital) once a month through the winter months.

    How low (12.3?) should i let then go before i recharge them and can you estimate how long it would take to discharge to the level it needs recharging.
    Thanks in advance,
    Philip.
     
  2. Douglas

    Douglas Read Only Funster

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    A Battery at rest will be fully charged at 12.8v and fully discharged at 11.8. If you only have a bog standard charger leave it on untill the charging voltage reaches 14,2, if the battery is a good one the excess voltage i.e. above 12.8 will hold for many days.

    If you have a small charger; think about leaving the connected to the charger via a timer switch set to 15 mins a day, the will stay topped up forever...

    Doug...
     
  3. Losos

    Losos Read Only Funster

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    Sorry Philip, that's a bit like asking how long is a piece of string :BigGrin:

    You'll need to say what load you are drawing and for how long, to keep it simple take the watts of all the kit you have and how long each is on per day.

    Then someone will likely come back to you.
     
    Last edited: Oct 20, 2009
  4. Losos

    Losos Read Only Funster

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    Doug, I know there has been a discussion on another thread about 'ball park' figures and not confusing people but I'm bound to say IMO the battery will only last for many days if it is large (Amp hr wise) in relation to the load (Watts)

    So with greatest respect aren't we in danger of making it all seem to simple for Philip especially if he has only an 85A/Hr. battery and he likes to run something pretty heavy all night ???
     
  5. Snowbird

    Snowbird Funster Life Member

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    The guy says he has DISCONECTED them, so he won`t be drawing anything from them.
    Keep it simple.
     
  6. Douglas

    Douglas Read Only Funster

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    Re-read the original message by the author. he is disconnecting the batteries after charging and not putting them on discharge...

    Doug...
     
    Last edited: Oct 20, 2009
  7. Douglas

    Douglas Read Only Funster

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    Re-read the original message by the author. he is disconnecting the batteries after charging and not putting them on discharge...

    Doug...
     
  8. pappajohn

    pappajohn Funster Life Member

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    every battery has an internal (self) discharge rate and evey battery will be different....even new ones.

    look at the chart and dont let the battery go below 60% full.
     
  9. hilldweller

    hilldweller Funster Life Member

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    I've just bought a Sterling inverter and it's low voltage warning is set at 10V and low voltage cut off at 9.5V.

    That is at odds with your table yet I thought Sterling were a reputable firm.

    Though that is obviously on load voltage.
     
    Last edited: Oct 20, 2009
  10. pappajohn

    pappajohn Funster Life Member

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    no it isnt Brian.....

    the invertor will pull the battery down to 9.5v pretty quick but as soon as the (heavy) load is removed the battery will show the true state of charge which will probably still be 12v+.

    drain it quick and it recovers...drain it slow and it doent recover.


    your fully charged starter battery may show less than 9v when cranking but straight back to full charge if you stop cranking.

    (unless its an old ford then you'll flatten it anyway....Ruh Ruh Ruh RuhRuhRUh Ruh Ruh !!!!)
     
  11. Wildman

    Wildman Read Only Funster

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    The batteries in my land rover remain charged for many months if disconnected, however why not just put a small solar panel on them a 10W panel would be ample to keep them in good order
     
  12. Tony Lee

    Tony Lee Read Only Funster

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    I don't think you specified exactly what type of battery you have. Three main general types - normal lead-acid flooded cell, AGM and Gel.

    The first has the highest rate of self-discharge and in hot weather may lose up to 30% of its charge in one month. Winter will be a lot less but you also run more risk of the battery freezing so it is best to err on the right side and re-charge the battery when it has dropped say 0.25V below what it was on the day after you disconnected it.
    AGM and Gel can be left for at least 6 months before worrying about recharge.

    This assumes that you did actually charge them up fully to start with and that means at least a three-stage charger going through a fully cycle of bulk charge, equalisation charge before dropping to float for at least a few hours.
    100% charge is indicated by a voltage of at least 12.6V (but it depends on the battery type and could be 12.8V) measured the day after you disconnected. If it was 12.5 or less, then the battery charger is not doing a proper job and you would need to recharge more often.
     
  13. hilldweller

    hilldweller Funster Life Member

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    My fingers working quicker than my brain.
     
  14. pappajohn

    pappajohn Funster Life Member

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    wear gloves Brian....that'll slow you down.
     
  15. Johno

    Johno Read Only Funster

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    I have been using an "Airflow" battery conditioner to keep batteries fully charged for some years and have found it to be ideal,I believe they are very popular among the classic car fraternity. It's a neat little job measuring about 100 x 50 x 50 mm and made in Switzerland therefore not particularly cheap at just under £40 but it does the job for me.
    John.
     
  16. beemerboy

    beemerboy Read Only Funster

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    batteries

    I was told by an electriction friend that if you let your batteries discharge over winter months(in this case a boat) then the plates inside can warp and the battery will be incapable of taking a charge later to this end i keep my batteries charged when not in use.on the van I have a present i got stuck with the step extended because the battery was flat-not long after I bought it , on looking into the battery top up holes the plates were twisted- new battery not a spark but bright enough to know the cost of a leisure battery to keeping it charged
     
  17. Ruddy

    Ruddy Read Only Funster

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  18. pappajohn

    pappajohn Funster Life Member

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    i dont think the plates warp but they appear to look that way.

    it will be an uneven build up of lead oxide on the plates and its this lead oxide that prevents the battery from accepting and holding charge.

    keeping a battery well charged breaks down and prevents further lead oxide forming.

    if the battery hasnt been dead flat for too long it may recover by charging at a relatively high charge rate....14.8v or slightly higher.
    this breaks down the oxide and exposes the plates to the electrolite and starts to accept a charge.

    but, as you keep it charged, you wont have this problem.:thumb:
     
  19. lebesset

    lebesset Read Only Funster

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    a big thank you to philip !

    normally my landie gets used during the summer period , then sits in the barn for the winter with the other vehicles while we go off in the motorhome ; this is more than sufficent to keep the battery going so that in the spring I can turn the key and away she goes ...if anyone knows the old landie series 3 diesel they will know that is no mean feat
    but this summer , instead of staying home in the garden we decided to make a special trip , so landie didn't get used at all , rather it got forgotten ...until I read philips post today

    so up to the barn , out with the meter and , after 11months ....12.0 volts instead of the fully charged 12.7 [ battery is [still ? ]good but not new

    so does that answer your question philip ? how low does it go ? tomorrow will take the charger off [ 8 amp but battery only taking 6 amp when I switched on , not a lot for a 90Ah ]; then will leave for a day and see what we have

    where did I go in the summer ? after the le mans 24hour we went to an island we hadn't visited in the summer for 20 years . don't know if you have been there , it's called great britain , people are a bit odd but other than that a great place to visit
     
  20. PhilandMena

    PhilandMena Funster

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    Pappajon,
    Many kind thanks, this is exactly what i need. the batteries are both new & 115 amp. both located under the front seats of my motorhome. Hence, disconnected and left in situ. My plan is to let them discharge to 80% (the advice i received from the caravan club was never let batteries drop below 80% of total capacity and when fully charged they should provide 12.7 volts) . Your chart seems to be spot on and when the batteries drop to 12.5 v. I'll reconnect them bring the Motorhome - home and charge them upagain over the weekend.
    I've currently got the Cab battery on long term charge with a modern charger, in my conservatory. I hope it will take several weeks to for the leisure batteries to drop 20%.

    Thanks again for your kind help.
    Philip.
     
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