Battery charging arrangement on Solar & Mains

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  • peedee
    peedee Club Member Posts: 9,389 ✭✭✭
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    edited December 2018 #32

    Ditto Boff. My 120 watt panel via a MTTP controller keeps both my leisure and engine batteries charged all year round without EHU.  FYI  Geoff I have a 3 stage mains charger installed in the van and have suffered no ill effects from having both the solar panel and EHU charging the batteries.

    peedee

  • young thomas
    young thomas Club Member Posts: 11,357 ✭✭✭✭✭
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    edited December 2018 #33

    my 100w panel with 'only' a PMW ttwin channel regulator keep two 95ah leisure batteries and the vehicle battery fully charged all year, whatever the weather....

    however, R, I agree with CY in that the sun is knly replenishing a small loss from alarm, immobiliser etc..

    yes, we could easily go away for the weekend without EHU, but the batteries would be further charged (if required) from the journey and a full pair of 95s would easily last two days, again whatever the weather.

    a real test (of the panels influence) is using it for a week or more with no driving....

  • GeoffROD
    GeoffROD Forum Participant Posts: 10
    edited January 2019 #34

    Thank you all for your kind inputs. I have been away and could not reply.

    Having thrown out the cheap solar panel controller supplied with our lovely new caravan that resulted in over-voltage alarms, our 80w panel is now feeding our battery correctly 24 hours a day via its new ‘intelligent’ MPPT controller (when the suns out).

    So now to the 230v / 12v PSU, the reason for my post  >>

    Our caravan definitely has a 13.8v ‘’constant voltage’’ PSU.
    It does not vary in voltage.  
    I have had this confirmed by the PSU manufacturer.  

    Obviously a 12v lead-acid leisure battery should not have 13.8 volts supplied to it ‘’constantly’’ when on mains hook-up, but I think I may have found a solution  (??) 

    1.
    I throw out the standard 230v / 13.8v constant voltage PSU as delivered with my new caravan. 

    2.
    I install the ‘’wiring with plug’’ supplied with our new ‘’intelligent’’ CTEK mobile battery charger, wired direct to the caravan’s battery terminals so I can quickly plug in the CTEK charger whenever we go caravaning with mains hook up. Our CTEK mobile charger ( https://www.ctek.com/products/vehicle/mxs-7-0 )   will in effect replace the original PSU I have thrown out and being ‘intelligent’ it will ‘properly’ look after the battery charging when 230v is connected.

    I can easily unplug our CTEK charger at any time and use it elsewhere with its alternative plug-in lead with crocodile clips.   

    HOWEVER Intelligent chargers, (intelligent solar regulator or intelligent PSU) will give a much higher voltage that 12v, as this is needed to charge a PB battery.
    SO …..

    3.
    For a guaranteed 12v supply to the caravan’s systems, to prevent any over-voltage, I would fit a Votronic DC/DC 20A converter ( https://www.votronic.de/index.php/en/products2/dc-voltage-transformers/standard-version/dcdc-1212-20  ) between our battery and our caravans 12v system, to give a properly regulated 12 volts, regardless of the ‘’charging voltage’’ of the battery. Our battery will still provide ‘smoothing’ via this DC/DC converter.  


    Does anyone see any flaws in this proposal (other than cost … and the caravan control panel not showing the correct battery voltage)?  
    THANK you for your thoughts and wishing everyone a very HAPPY NEW YEAR !  

     

  • hitchglitch
    hitchglitch Forum Participant Posts: 3,007
    1000 Comments
    edited January 2019 #35

    I can see a flaw. A new battery will cost you less than £100 so if it ages prematurely it’s no big deal.  Why bother with all the expensive “fixes”; unless, like me, you just like messing around with things.

    By, the way, for those that think this thread has some complexity, try reading some threads on motorhome forums concerning Sargent power supply systems. I am am electrical engineer and still find it all rather complex.

  • GeoffROD
    GeoffROD Forum Participant Posts: 10
    edited January 2019 #36

    Just an update for those, like me, who like 'playing' ...

    BCA has just kindly confirmed that removing their 20A constant voltage 13.8v PSU will only mean no EHU signal displayed on their control panel; so it should be straight forward to extend their kettle plug from the removed PSU to run a new 13A mains wall socket for the 13a fused plug of our new 'intelligent' charger. 

    I am about to install a 100A shunt for a battery condition monitor, which will by default allow me to measure our actual off-grid 12v consumption in amps. This will then allow me to size a suitable dc-dc 12v to 12v converter to ensure in-dependency between the potentially high battery charging voltage and the caravans '' 12v '' consumer circuit. A 100 amp shunt is the right size for our caravan with single axial motor mover.

    The DC-DC converter manufacturer also confirms that I can install a switched by-pass for when the 230v EHU is not connected (as the DCDC converter wont be needed if the 230v battery charger is not supplied with power).  This means when off-grid or storage there will be no power loss from this item. 

    I am also taking the opportunity to put in a +ve bus-bar, so in future we will only have one 25mm2 cable running to each battery terminal.

    I hope this is all sounding sort of correct.        

    This whole system, once installed, should give multiple benefits, but of course comes with a cost.  Fun to design and sort out though (smile) 

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