Leisure Battery Conundrum

Discussion in 'Motorhome Chat' started by PhilandMena, May 23, 2015.

  1. PhilandMena

    PhilandMena Funster

    Joined:
    Feb 9, 2008
    Messages:
    2,621
    Likes Received:
    3,624
    Location:
    Corby, Northants
    I would like to improve my understanding of what is going on with my leisure batteries and Sargent system and would appreciate input from informed members.

    I have been undertaking a load test on my leisure batteries, 2 x 110 AH. They have been fully charged and left to settle with no incoming source. Voltmeter reading at start of test 12.7

    I then put a load of 6 Amps on the batteries and after 1 hour measured again with VM, reading 12.52 V. The Sargent Control panel stated 11.9 V. good.
    The reading was the same for the next 2 hourly visits. i.e. 6 Amp draw and VM reading 12.5. (did not check control panel).
    On 4th visit (4 hrs on load test) one of my TV's had shut down due to a low voltage warning and my control panel was stating 9.8 V poor. Yet when I measured with my VM directly from the battery terminal I was getting 12.5 V.
    I have shut down the system completely now and will see how far the batteries recover tomorrow morning.
    Can anyone make sense of this ! I know both the sargent system and my VM are not faulty but clearly there is a conflict.
    It's possible my batteries are on there way out, 4 years old and hammered last winter in Morocco but still reading 12.7 when fully charged.
     
  2. jonandshell

    jonandshell Funster

    Joined:
    Dec 12, 2010
    Messages:
    5,258
    Likes Received:
    7,875
    Location:
    West Norfolk
    It is because Sargent use cable which is way too thin for the load.
    As a result you get a massive voltage drop between the battery and PSU. This also adversly affects the efficiency of the split charge system.
    Rewiring with a cable which is fit for purpose is the only way.
     
    • Like Like x 6
  3. karl c

    karl c Funster

    Joined:
    Mar 25, 2014
    Messages:
    150
    Likes Received:
    203
    Location:
    nottingham
    how have you linked the two batteries up
    and where have you fitted the out put to psu
     
  4. DavidG58

    DavidG58 Funster

    Joined:
    Feb 24, 2013
    Messages:
    6,280
    Likes Received:
    12,109
    Location:
    Bolsover, Derbyshire
    I have such little knowledge I really should not be contributing, but your meter readings sound too good to be true, if you are taking 6A out I am amazed they have held 12.5 V for 2 hours

    Or have I read it all wrong :)
     
    • Like Like x 1
  5. jonandshell

    jonandshell Funster

    Joined:
    Dec 12, 2010
    Messages:
    5,258
    Likes Received:
    7,875
    Location:
    West Norfolk
    Why not? It's only 12Ah drawn from the battery out of 220 available Ah at 100% DOD.
    In fact a draw of 6 amps is about what the batteries should be able to supply for a 20 hr rating.
     
    • Like Like x 1
  6. jonandshell

    jonandshell Funster

    Joined:
    Dec 12, 2010
    Messages:
    5,258
    Likes Received:
    7,875
    Location:
    West Norfolk
    Of course, not all batteries are what they say on their labels though.......:)
     
    • Like Like x 1
  7. DavidG58

    DavidG58 Funster

    Joined:
    Feb 24, 2013
    Messages:
    6,280
    Likes Received:
    12,109
    Location:
    Bolsover, Derbyshire
    When I plug my 300W inverter in it shows a draw of about 5A when in use, my controller then shows at least a 0.1 V drop every half hour, drawing from 2 x 110A new batteries.

    As those that have read of my mishaps will know I completely flattened by cab battery twice in 6 months :D (using wrong socket) hence my surprise that the 12.5 is held for so long
     
  8. Stealaway

    Stealaway Funster

    Joined:
    Jan 8, 2013
    Messages:
    949
    Likes Received:
    1,092
    Location:
    Dronfield - Derbyshire
    I don't trust my Burstner Micky Mouse gauge, I only treat it as a gauge (if that makes sense).
    Your volt meter will be a truer reading.
    My fully charged 2 x 100a Varta battery's will drop from 12.8 to 12.2V after 3 hours of TV use (about 5A)
    I think that's perfectly acceptable, we watch TV from 9.00 to 12.00 and then turn it off.
    Battery's will fully recharge after 3 hours of travelling
    Four year old well used battery's will be getting a bit tired but they should see you OK for another year.
     
  9. PhilandMena

    PhilandMena Funster

    Joined:
    Feb 9, 2008
    Messages:
    2,621
    Likes Received:
    3,624
    Location:
    Corby, Northants
    I think not! I did the same test 3 years ago with a 6 Amp draw over 4 hours and no warning on the control panel and no TV cut out due to low power.
    The wiring is the original wiring and installation from new in 2011. So, I think it must be something other than that. Although I do find your comment interesting and am aware cable thickness is important.
     
  10. PhilandMena

    PhilandMena Funster

    Joined:
    Feb 9, 2008
    Messages:
    2,621
    Likes Received:
    3,624
    Location:
    Corby, Northants
    By my reckoning, I should get at least 12 hrs of safe usage if a 6 Amp draw is taken from 220 AH battery bank. I will see how well the batteries have recovered in the morning and take it from there.
     
  11. irnbru

    irnbru Funster Life Member

    Joined:
    Jun 27, 2013
    Messages:
    5,329
    Likes Received:
    9,686
    Location:
    Glasgow
    I would like to learn too.
    So he starts off at 12.7
    1hr and 6amps later drops to 12.52
    2hr and another 6amp=12.5
    3hr and another 6 amp =12.5
    4hr and another 6 amp and its srill at 12.5
    So why did it drop almost 2 for the first 6 amps and hardly anything for the next 18 ?
    A wokshop at the fixit meet or such would be great on this topic.
     
    • Like Like x 1
  12. funflair

    funflair Funster Life Member

    Joined:
    Dec 11, 2013
    Messages:
    4,458
    Likes Received:
    4,705
    Location:
    Guisborough
    Hi @irnbru I dont think that would be typical, I would expect to see something a bit more linear, I would be pleased to teach you what I know But the trouble is I dont know much;) will be good to meet you at fix it as we have not crossed paths before.

    Martin
     
    • Like Like x 2
  13. funflair

    funflair Funster Life Member

    Joined:
    Dec 11, 2013
    Messages:
    4,458
    Likes Received:
    4,705
    Location:
    Guisborough
    Hi @DavidG58 at 5 amps you are only running about 50 watts from your inverter at 240 volts, If you plug your hairdryer in it will draw a lot more (or go up in smoke):LOL:
     
    • Like Like x 1
  14. andy63

    andy63 Funster

    Joined:
    Jan 19, 2014
    Messages:
    1,847
    Likes Received:
    6,435
    Location:
    south shields
    Any battery will show a drop in voltage as soon as a load is applied..as the current draw continues the batteries ability to hold its voltage is a measure of its condition and how good the battery is and a gradual drop in voltage would be normal..

    I thought Jon's assessment was resonable. . If vm and Sargent are not faulty as you indicate then the Sargent is not seeing the true battery voltage .
    I posted a week or so ago about connecting solar to a van with a Sargent control... 2 X 110ah leisure batteries connected to the Sargent panel individually through longish ie 2.5 m runs wire which I thought looked rather thin. They met at the panel but the batteries were not paralled at source...
    Looking forward to your findings cause I can't think of what else it could be.
    Ta Andy.
     
    • Like Like x 2
  15. PhilandMena

    PhilandMena Funster

    Joined:
    Feb 9, 2008
    Messages:
    2,621
    Likes Received:
    3,624
    Location:
    Corby, Northants
    OK! Firstly, apologies all round, as I have not given you the full picture (unintentional I assure you). My aim was to put as big a draw on the batteries as I reasonable could so in addition to all my internal lights, external Hab door light and two TV's being on the go, I also switched on my Inverter (300W) and attached a mini battery charger loaded with 4 AA batteries.
    The control panel indicated a draw of 6.2 A and now in hind sight I'm sure it was not registering the draw taken by the Inverter as this is wired directly to the leisure batteries and the Sargent system would not know of it's existence.(I believe?)
    The battery charger has an output of 1.8 A and for each AA battery .45 A so by my maths a total draw of 3.6 A. The inverter itself would have a draw of 0.95 A making a total of 4.5A to be added to the 6.2 A draw indicated on the control panel.
    So, by my reckoning I have taken a total of 25 A out of each battery over 4 hours which the batteries should cope with easily.
    When I checked my batteries again this morning, after resting for some 13 hours they had fully recovered and were reading 12 .69 on the VM. This indicates to me that the batteries are still A-O-K.
    I just want to understand why the Sargent system indicated 9.8 V after 4 hours of draw and shut down one of my TV's.
    I'll have a chat with Sargent next week and see what they say.
    Any Idea's what has happened ?
     
  16. andy63

    andy63 Funster

    Joined:
    Jan 19, 2014
    Messages:
    1,847
    Likes Received:
    6,435
    Location:
    south shields
    Can you open the Sargent control panel up and measure the battery voltage at the point the battery wires enter the Sargent ,with the volt meter? See what you get there..
    Ta andy
     
  17. PhilandMena

    PhilandMena Funster

    Joined:
    Feb 9, 2008
    Messages:
    2,621
    Likes Received:
    3,624
    Location:
    Corby, Northants
    I had the control panel off two years ago when I fitted a Solar Panel and fortunately there was already a Sargent regulator installed from new so making the connection was simple. The only problem I would have with your suggestion is knowing which wires were coming from the battery ? However, it's an option and I'll bank it in case no other explanation makes sense. Thanks.
     
    • Like Like x 1
  18. Emmenay

    Emmenay Read Only Funster

    Joined:
    Dec 11, 2011
    Messages:
    364
    Likes Received:
    274
    Location:
    Anywhere
    I have the same problem with the Sargent control panel, or should I say the inadequate wiring to and from it.
    My panel reads 12.2 volts with the TV on but my v/Meter reads 12.5.
    I have made my own panel now with digital v/meters wired directly from the leisure batteries and the cab battery. No more confusion :D
     
  19. andy63

    andy63 Funster

    Joined:
    Jan 19, 2014
    Messages:
    1,847
    Likes Received:
    6,435
    Location:
    south shields
    Hi your Sargent is a later one than the one I'm on about as mine didn't have the built in solar regulator...
    The Sargent harness from the batteries was colour coded (orange/white. And brown /blue ) from memory... It was easy enough to pick them up inside the panel...
    Just thought if you could do that it would answer the question about the voltage the Sargent was seeing.
    Hope you solve it.
    Ta Andy.
     
    • Like Like x 1
  20. PhilandMena

    PhilandMena Funster

    Joined:
    Feb 9, 2008
    Messages:
    2,621
    Likes Received:
    3,624
    Location:
    Corby, Northants
    I find your comment interesting. Does that mean when your TV is on, the panel is indicating a true voltage state at the point of measurement because of the wiring (? and if so, this could indicate why the system shut down the TV when there was still plenty of juice in the batteries) and, if fitting an alternative measuring point would this prevent the system shutting down ?.
     
Loading...

Share This Page