Oh' the electrical confusion of it all...

Discussion in 'Tech/Mech General' started by Trikeman, Jan 29, 2014.

  1. Trikeman

    Trikeman Read Only Funster

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    Allll righty then,
    Son bought an 'intelligent' charger for his MoHo cab battery, (yes a split will be fitted when he has time) no probs there... we say.

    He has a permanent live auxiliary plug (cigar lighter) in the dash, so all OK there also.....

    He then reads the battery charging section in the Fiat handbook and it states, 'before charging the battery ensure that it is disconnected - negative lead is removed - as charging a connected battery could damage the ECU'.:Confused:

    If, the battery is disconnected, as in the handbook, then the auxiliary plug is now disconnected - so won't charge.......:Angry:

    What the fox and the pigs can be done about this (other than disconnecting the negative battery cable and wiring the auxilery plug's negative onto the negative pole direct?????

    Does everyone disconnect the cab battery to charge it?

    Regards,

    Trikeman. :Wink:
     
  2. lunarman

    lunarman Funster

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    What is more interesting is if this is correct what do the main converters do to enable the charging of the vehicle battery when on EHU? As most MHs have this facility. Im sure they don't advise owners to disconnect the battery.

    Lunarman
     
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  3. jhorsf

    jhorsf Read Only Funster

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    no
     
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  4. hilldweller

    hilldweller Funster Life Member

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    Of course not. They are covering their backsides. They do not know what a numpty might connect to the battery, like an old welding transformer.

    But they are making it clear, you are taking the risk.

    I don't hesitate to connect an little Aldi charger to the MH or my bike, but if it goes wrong I carry the can.
     
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  5. jhorsf

    jhorsf Read Only Funster

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    I have to ask when your van is running and it is being charged at maybe 70 amps why does it not have to be disconnected then?
     
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  6. Mike B

    Mike B Funster

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    I've got an autotrail scout and when on EHU with the onboard charger switched on the cab battery is still connected whilst charging. When I charge the cab battery using an external charger I don't bother disconnecting it as it causes problems with re-registering the radio. Having said that I was always taught that you should disconnect the battery for safety reasons, it's about on par with leaving the TV switched on at the wall socket. Maybe one in a thousand TVs could catch fire but very unlikely, the problem is if you have that one in a thousand MoHo.
     
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  7. Trikeman

    Trikeman Read Only Funster

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    Aye, sort of thought it could be what Hilldweller 'so eloquently' explained.:Wink:

    I've not disconnected cars, trucks and bikes in the past, but just had a look in my Fiat book and it's in there........ also mentions the alternator.

    I understand the 'backside covering' statements in handbooks just in case some numpty connects it to Hinkley B - just struggling to explain to a wild, enthusiastic youngster.:Laughing:

    Cheers,

    Trikeman. :Wink:
     
  8. ludo

    ludo Funster Life Member

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    If the battery is disconnected while being charged, an additional problem is that the vehicle alarm is disabled. Not good as far as the insurers are concerned.

    I noticed, when we bought our MH new, just over a year ago, that the vehicle battery would drop to about 12.2 v after about a week. We took it to the Fiat main dealer who, after testing the battery, declared it to be in perfect condition.

    I have noticed that when on EHU the Electroblock system shows the hab batteries being charged at a much higher rate than the cab battery.

    I suspect that this might be due to the fact that the hab batteries are Banner AGM ones so the Electroblock switch is set to Gel rather than lead acid, which is of course correct. However, does this mean that the cab battery is being charged as a gel/agm one, thus being perhaps undercharged?

    Every few weeks, I charge the cab battery with a Aldi charger and find that this helps considerably.
     
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  9. daisy mae

    daisy mae Read Only Funster

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    I was told this also by the dealers mechanic I bought it from also, in hand book. the system will set itself within ten minutes, haven`t had to do it as It is in use everyday so is being charged.
     
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  10. hilldweller

    hilldweller Funster Life Member

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    In a word "spikes".

    Attack the battery with some "hot" wires and the arcing may cause spikes that could do damage.

    Attach a modern charger as per instructions and there will be no spikes.
     
  11. eddievanbitz

    eddievanbitz Trader - Funster

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    If any one rang us and asked should they disconnect the battery prior to charging, we would say "yes" of course, then go on to say if you'd asked me do "you" we would say "No"
     
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  12. Allanm

    Allanm Funster

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    Some car handbooks go into great detail about the perils of disconnecting and reconnecting your battery. Mercedes a few years ago used to blow their ECU's when you reconnected the battery. I would have though voltage spikes from incorrect discon / recon would be more of a danger.
    But, it's been common knowledge since I had my first Mini in 1972 that you never charge the battery with it connected:Rofl1::Rofl1::Rofl1:
    Allan
     
  13. TheCaller

    TheCaller Funster

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    Because irrespective of current, an alternator won't usually raise the voltage at the battery above 13.6v.

    Mains chargers will often have a section in their charge phase where the voltage can be in excess of 14.5v. Those that claim to rejuvenate tired batteries will go up to 15.8v, albeit with only a couple of amps of current. That sort of voltage might well damage the electronics in the ECU.

    You should always disconnect a battery before one of these reconditioning charge sessions, but for ordinary top-ups from a decent charger, I'd do the same as everyone else - risk it. But it will always be at your risk.

    In short - wot eddie said. :thumb:
     
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