Electrical boffins please

Discussion in 'Motorhome Chat' started by knokinonabit, Sep 10, 2012.

  1. knokinonabit

    knokinonabit Funster

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    I know there are lots of threads re charging batteries etc, so I apologise in advance. :Blush:

    1/ Could someone tell me how long two new leisure batteries should take to reach full (100%) amp hours when on EHU and when charging from the engine.

    My problem is that they reach full volts (ie 13.7 at rest, 14.2 when charging) fairly quickly, but the AH takes days to get back to full.
    I have re-calibrated the control panel to the PSU and reset the AH start at 100% for fully charged batteries, as per the instructions sent to me by Autotrail, but it still takes an eternity to reach full AHs

    2/ Because I am sometimes not close enough to a tap to use my hosepipe to fill the onboard fresh water tank, I use an aqua roll and a Whale pump with hose connected to empty the roll into the tank. This is powered by connecting to the leisure batteries directly (crocodile clips). Sometimes I am on EHU and sometimes not. Is this going to nadger up the batteries ? Is this the cause of the long time to reach full AHs ?

    I have e-mailed Autotrail but haven't had a reply yet. The MH has only been on the road for a couple of months.

    I know some of you will have more questions, and some answers as well, so fire away and thank you in advance. :thumb:
     
  2. Pikey Pete

    Pikey Pete Read Only Funster

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    I thought that Current was equal to the volts divided by the resistance. In which case once the voltage is realised then the current is also realised, providing the resistance is constant.

    Or have I been out the game for too long and lost the plot.


    Pete:Cool:
     
    Last edited: Sep 10, 2012
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  3. Wildman

    Wildman Read Only Funster

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    a fully charged battery is fully charged the amp/hrs available are dependant on the condition of the battery plates. You do not add amps seperate to volts. Amps are the rate of charge or discharge. Displayed amp/hrs left in a battery are a bit of electrical bullshit when shown on a meter as they cannot be correctly calculated other than by use. Stop worrying and just enjoy the van.
     
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  4. knokinonabit

    knokinonabit Funster

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    A thought has occured to me that it could be the control panel that is at fault.
    One of the light switches on the panel, which has a built in dimmer, sometimes only works when it feels like it.
     
  5. wiljoy

    wiljoy Funster

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    All the help I can give is ibased on past experience. The pump drinks the power from your batteries and coupled direct will certainly pump in fast but so will the power loss.
    I have had issues like this before and it was traced to a faulty battery. I had two fitted but one was dodgy causing the readings to be very suspect and charging time to go on for ever. Best to check the strength of both batteries first to eliminate this as a cause, even if they aren't very old.
     
  6. knokinonabit

    knokinonabit Funster

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    You are most probably right as I have never run out of power yet.
    On our previous MH I never had an AH gauge, just volts, and I never worried.
    Ignorance is bliss eh.
     
    Last edited: Sep 10, 2012
  7. Pikey Pete

    Pikey Pete Read Only Funster

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    Thanks Roger that is what I was trying to say.


    Pete:Cool:
     
  8. Pigwam

    Pigwam Read Only Funster

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    Right where do I start, have read all the replies and everyone has vailid points, although i think you may be worrying over nothing.

    I will try to answer your questions the best i can.

    1. - if your HM has a 15A charger and only one battery, by fitting another battery the same size and not increasing the charger to suit it will take twice as long to charge the batteries up, the voltages seem about right without seeing the battery charging spec and not knowing the construction type of battery. as for charging while driving i don't have enough info to answer that one.

    I've not seen the the AH meter you talk about but assume its what is commonly called a 'battery fuel gauge' which i have seen many types over the years and most tend not to be that accurate unless your dealing with battery capacities over 200AH, how ever a company called Curtis make possibly the best on the market and they do a 12v one with a simply bar gauge which works quite well.

    Depending on how good the good fuel gauge is and how they self calibrate it make take some time / cycles before they are that accurate.

    Of course as someone has already said are you batteries ok, if not then its a none starter as they need to be checked first, most batteries will fail within the first 3 months of use.

    2. - The external pump, well it shouldn't make any difference as it proberly wont draw that much compared to your internal pump

    I hope that has given a little bit of an insight, always remember to put your MH on charge when you get home and if your batteries are the type that needs to have the electrolyte topped up always check them and make sure that the electrolyte id 6mm above the plates

    Stephen:Smile:
     
  9. knokinonabit

    knokinonabit Funster

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    Thanks for your observations.

    The control panel is a Sargent with bar and number readouts combined.

    The batteries are both new (although that is no guarantee) and total 220 AHs (110 each)

    This problem has occured from new, which is now approaching 2 months, and the batteries have been exchanged by the dealer.

    I am sure that you are correct and that I am worrying over nothing.
    When I didn't have the gauges, in our previous MH, I was none the wiser.
    Possibly a case of too many toys. :BigGrin:
     
  10. pappajohn

    pappajohn Funster Life Member

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    as Roger said...you cant get a reading of amps remaining in a battery...only whats going in or coming out..

    the control panel electronics simply calculate the amps from the voltage.

    if your battery is showing 13.7amps at rest, presumably just after turning off the charger, then your battery will be fully charged.

    turn off the charger and run the water pump for 15 seconds to take the 'float' voltage off then take a voltage reading using a multimeter....not the onboard meter.

    12.7volts is classed as a fully charged battery.

     

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  11. Pigwam

    Pigwam Read Only Funster

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    Hi

    Try this link to Sargents they have just introduced a help section http://sargentshop.co.uk

    they also have quite a detailed section on their various control systems.

    one thing i noticed while reading the spec it does say that their system must never be disconnected from the battery or it wont read correctly.
     
    Last edited: Sep 10, 2012
  12. pappajohn

    pappajohn Funster Life Member

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    charging via the engine alternator through a split charge relay is a bit of a waste of time unless you have a proper battery to battery charger fitted.

    the alternator senses the voltage in the engine battery only...once that is fully charged it just about shuts down, only keeping the battery topped up.

    this means the alternator is basically doing nothing to charge the leisure battery...maybe a couple of amps which will take many, many hours to charge a discharged leisure battery but is enough to keep a charged battery topped up.
     
  13. Wildman

    Wildman Read Only Funster

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    not sure how you arrive at that notion John. a standard split charge relay effectively connects the engine and the leisure battery in parallel the alternator regulation system would only see one big battery both of which would be equally charged, or am I missing something.
     
  14. pappajohn

    pappajohn Funster Life Member

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    So the Sterling b2b charger is a waste of money.....

    This system enables one to simply attach the unit to a standard engine battery and it will fool the alternator into working at its maximum ability, this will ensure all its surplus power is used to charger the auxiliary battery bank to its maximum.

    In a nutshell it charges your extra battery system about 5 times faster than it would otherwise charger and puts about 100% extra use full power into them
     
  15. Dubiousp

    Dubiousp Read Only Funster

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    I've had an issue on my Autoquest in that my calculations gave the impression I would have enough battery power a good three days in a static location. What appears to be giving me a problem is the solenoid on the water system which is energised all the time you are on aux power. The only way to preserve power is to switch aux off during the day at the mo for me
     
  16. hilldweller

    hilldweller Funster Life Member

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    The resistance of the leisure battery circuit.

    Wildly varying depending on where the leisure battery is sited.
     
  17. Wildman

    Wildman Read Only Funster

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    That resistance is seen as the whole battery, i.e. both of them so are you suggesting neither battery is charged properly, if so then it must vary a hell of a lot between installations as I have never actually had a problem. The sterling B2B ensures the engine battery if fully charged before transfering power to the leisure battery which means if you only do short runs then the engine battery is maintained rather than charging both batteries to a lower level and the leisure battery does not receive a full charge. However if you tend to do long runs then as far as I can see there is no advantage. If you have solar charging the leisure batteries then the B2B ensures the engine battery is fully charged at all times because the bulk of leisure battery charge comes from the solar array. I have no experience of the sterling B2B charger other than to know people speak highly of it. so maybe it does more than I realise. I am always ready to learn something new.
     
    Last edited: Sep 11, 2012
  18. hilldweller

    hilldweller Funster Life Member

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    ASCII art is a nightmare but here goes......


    +...................rrrr........RLY....+...r...ALTERNATOR
    LEISURE BAT __________ START
    -....................rrrr..................-....r..ALTERNATOR

    As I see it the alternator is very close coupled to the STARTer battery, negligible volt drop.

    But the leisure battery has all those rrrrrrs and a relay so there will be a small V drop, it needs only 0.3V to make the leisure battery charge to only 75%.

    So, the alternator sees a charged starter battery and backs off leaving a poorly charged leisure battery. It all depends on individual layouts.

    Again as I see it, b2b overcomes this by boosting the output voltage as needed to fully charger the leisure battery and of course sensing the leisure battery accurately. In other words, it can take in 13V from the starter and boost it to 14.6V to fully charger the leisure battery. Whether anyone needs that degree of control depends on how long the engine is running. When touring they probably do not.
     
  19. knokinonabit

    knokinonabit Funster

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    I have had a reply from Autotrail and thought that you may be interested in the answers to my questions.

    It would appear that if you connect a second battery you have to alter the settings on the control panel. The default setting is 110ah, one battery, and this requires resetting to 220ah with the two batteries (110ah each). This is so the software knows what capacity it is calculating.
    There is an update for the software that can be downloaded by the dealer (if he has the capability) or the factory to bring the control panel up to date.

    Also the "start" setting for the ah percentage for a fully charged battery is 100%, which I had previously set, but for some reason mine had reset itself to 390%.

    Everything is now set as it should be and the control panel is re-calibrated to the PSU, as per factory instructions. I will be monitoring everything closely over the coming week as we are going to a steam fair this weekend and will be without EHU. Should be a reasonabley good test.

    Time will tell.
     
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