WARNING Re Autotrail wiring

Discussion in 'Motorhome Chat' started by Jaws, Sep 15, 2016.

  1. Jaws

    Jaws Funster Life Member

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    First off this is not about ANY other model than a 2007 Chieftain SE as I have no way to know what wiring was used on any other van.. Logic suggests all of that era will be the same but I must keep my comments to that of which I absolutely know.

    I fitted 300w of solar panel on the roof when we got the van, and used a fairly up market controller with digital display.
    From day one there was a discrepancy between the voltages displayed on the solar controller and the vans control unit.. I put that down to a not very accurate read out on one or other of the displays.

    Whilst doing the fitting I noticed the feed wires from the Sargent charger to the battery(s) had gone hard and crispy towards the lower ends indicating how hot they had become at times
    I just cut them back to good clean wire and refitted*

    At the Thetford meet this year I bought a very nice battery condition display unit from John ( @Don Quixote ) and that showed again a discrepancy between the solar controller and the actual battery voltages.
    I decided to run a couple of checks and discovered there was indeed a .3 volt** different when the charge or draw was at about 5 amps.
    Given the only thing between the two check points was about 3 metres of wire I was quite concerned.. Initially I thought maybe I had made a mistake and connected the solar controller output to the wrong wires.. That was soon dismissed though

    Yesterday I doubled up the size of the originally fitted wires from the Sargent unit to the batteries ( To which I had connected the solar feed in )

    The difference in voltage read out immediately became 'acceptable' at .01 volts when 5 amps were drawn

    Conclusions:
    1) * Inspection of the original feed wires from the Sargent charger to the battery(s) should have raised my suspicions from the go that the wiring was not 'man' enough for the job,, but in my defense they appeared to be the correct gauge, were original fit, and I just thought that someone at some time had done something daft with an after market charger and cooked the wires a bit :)

    2) Those wires had got hot. Heat is bloody dangerous !

    3) This is the bit that really gets me..
    Apart from the obvious danger of wires getting hot there is also the issue that any type of charging system ( mains, engine or solar ) was being fooled in to thinking the batteries were reaching a higher state of charge than was the case.. So what ?
    Well the charger ( what ever source ) will shut down and reduce the amperage fed to the batteries if said source believes the charge state is good.
    For the past two plus years the solar ( and other ) system has never fully charged the battery(s) as it THOUGHT a fully charged state had been reached

    ** At a 10 amp charge the difference was much worse.. I expected to see a .6 volt drop but it was a logarithmic progression rather than the expected linear one.. And went up to .9v difference

    So folks.. get busy running checks. !
     
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  2. tonyidle

    tonyidle Funster

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    I've never seen adequate wiring on any caravan or MH. Incidentally although in the case of your wiring it would slow down the charge (and affect any smart charge facility) the battery(s) would still achieve full charge. This is because as the current required to charge the battery fell towards full charge the voltage drop would reduce until it was negligible. Much more worrying, as you say, is wiring so dramatically undersized that it over-heated.
     
  3. Jaws

    Jaws Funster Life Member

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    A lot of intelligent chargers have a cut off point of 14.2 v., some are set to 13.8v ( gassing voltage )
    If the Sargent is set to 13.8v then the highest charge they ever got was likely to be 13.5v
    A good healthy charge but not actually up to maximum capacity
     
  4. PhilandMena

    PhilandMena Funster

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    Hi John, we had a chat about solar panels and the Sargent system several days ago on Shell Island and I remember you telling me the Sargent control panel readout would be different to that of the true battery status. So, yesterday as it so happened, while on hook up at home I checked my batteries with a digital volt meter and compared the reading to the control panel and they were both the same. I guess this means the Sargent wiring and control panel/charger is 'as it should be' I have not done this off hook up but as the current is going into the factory fitted Sargent S.P. Controller then down the same wires I'm assuming all will be well.
    You say in your post you had a loss of 0.3 V at a 5 Amp draw ? What I fail to understand is how this loss occur's. I understand the bit about thinner cables getting hotter and becoming a fire risk but cant grasp how a voltage drop occurs in these cables, where does it go ?
     
  5. PhilandMena

    PhilandMena Funster

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    If this is correct won't the on board charger try and put 14.2 volts in at some stage bringing the battery back to a good state ?
     
  6. Jaws

    Jaws Funster Life Member

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    Not if the on board charger is not seeing the correct voltage ( as in the case in question ) as the on board charger is seeing a higher voltage than actually exists at the battery terminals.
    It 'believes' an optimal voltage has been reached.
    As soon as the charger drops out and it sees the true voltage at the batteries then yes, the charger will kick in but for only a couple of seconds because it will immediately think the batteries are fully charged
     
  7. Jaws

    Jaws Funster Life Member

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    It is converted to heat !
    Glad your readout checked out ok (y)
     
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  8. tonyidle

    tonyidle Funster

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    That was my point about intelligent charging being affected. The charger times the boost stage which may be so extended by the reduced current available that it runs out of time. However most of the boost will occur and once back to float 13.8 will be achieved because, as I said, volt drop is proportional to current draw. As the battery terminal voltage will be at (or briefly above after boost) 13.8 current draw will be minimal to zero. And therefore so will volt drop.
     
  9. andy63

    andy63 Funster

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    I remember fitting @irnbru solar on an auto trail apache 700se I think.... I only had experience of my own self build and knew nothing of coach built mh''s. .
    I couldn't believe the wire that was used between the batteries and the sergeant unit..
    I'm sure you replied to that post at the time @Jaws saying it was a bit flimsy lol..
    Andy.
     
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  10. jonandshell

    jonandshell Funster

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    I haven't been impressed with Autotrail wiring. On all Autotrails I have played with, the voltage drops have been horrendous.

    Fine if you like sulphated batteries and fires!
     
  11. Raybreck

    Raybreck Funster

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    Hi, just sitting here in gran caneria nice and hot and bloody glad I picked up on this. Now, as I about as useless as the poor old cockroach stuck on his poor back we saw yesterday about anything electric, can someone enlighten us dimwits what spec wire we should have so we can at least ask the manufacturing company if we have the correct wire fitted.
    Ray
     
  12. Jaws

    Jaws Funster Life Member

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    From memory so do not rely on me.. 8 or 10 AWG multi strand should be good for about 4 metres with a max current of 15 amps
     
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  13. Cliffdale

    Cliffdale Funster

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  14. John Laidler

    John Laidler Funster

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    Where it goes is into the air as heat. 5 amps running through a voltage drop of 0.3 volts means 1.5 watts of heat. Not a lot and to be honest not enough to melt insulation so I can only assume there is something else going on to explain that. Possibly a momentary short circuit at some time and for reasons unknown or perhaps a poor connection at the terminal.
     
  15. hilldweller

    hilldweller Funster Life Member

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    Many times on here I've seen pictures of Sargent battery cables that looked woefully inadequate.

    Many times on here I've seen posts of Sargent inadequacies, esp for a gut called Jaws who is oh so impressed with there step controls and many others who have had to learn how to strip a control panel to unplug an internal connector to reset it.

    And also many cases of what good service they give when their systems go tits up.
     
  16. PhilandMena

    PhilandMena Funster

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    Thank You. More or less what John said a few posts back. Always nice to get confirmation from an informed ketchup though.
     
  17. PhilandMena

    PhilandMena Funster

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    Now I'm wandering how hot is 1 .5 watts in deg C ?
     
  18. Adbt

    Adbt Funster

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    HOT WIRES CAUSE FIRES !
     
  19. John Laidler

    John Laidler Funster

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    There is no direct relationship but 1.5 watts spread over three metres of wire might raise the temperature a few hundredths of a degree C in normal ambient temperatures. Which was the point I was trying to make. Whatever melted the insulation on these wires it wasn't a 0.3 voltage drop with 5 amps running, something more like 50 amps or more would be needed but impossible to say exactly because I don't know how thick these wires are but unless they were ridiculously thin they shouldn't get hot enough to melt the insulation in normal use. They may be inefficient and causing an unnecessary voltage drop but it needs a lot more power to heat them up to the melting point of the insulation.
     
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  20. Gorse Hill

    Gorse Hill Funster

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    If the cable is insufficient and causing overheating how come the MCB/Fuse didn't trip (it would if correctly sized by design engineer) is it possible there was a loose connection poor connections can be very efficient at overheating, because they can generate a high over a small area over long periods
     
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