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    Battery isolator

    I've just had a split-charging regulator (not diode) fitted to our Fiat Doblo and it's been connected to the leisure battery without the battery isolator which I provided being included in the circuit.

    The installer (lovely chap with a lifetime's experience in the trade) ignored the 100 amp isolator "because it isn't necessary".

    Do most motorhomes have battery isolator switches? Am I being over-fussy?

    I can easily change his wiring round to include the isolator (or he's happy to do it) but am I being over-fussy?

    Paul.
    Seek to make a virtue of necessity.

    #2
    Originally posted by Doblo7 View Post
    I've just had a split-charging regulator (not diode) fitted to our Fiat Doblo and it's been connected to the leisure battery without the battery isolator which I provided being included in the circuit.

    The installer (lovely chap with a lifetime's experience in the trade) ignored the 100 amp isolator "because it isn't necessary".

    Do most motorhomes have battery isolator switches? Am I being over-fussy?

    I can easily change his wiring round to include the isolator (or he's happy to do it) but am I being over-fussy?

    Paul.
    Paul A short answer is to fit 50A fuse in thr Split charger links and fuse each take of with the correct size fuse

    Alf

    Comment


      #3
      By no means a definative answer but we have owned a romahome demountable, a Japanese imported coachbuilt Motorhome and a pilote Motorhome and none had an isolator switch.
      Why not have a look at my latest wildlife photos, habitat projects and general natural world related shenanigans? https://facebook.com/Watsonswildlife

      Comment


        #4
        Thanks to Alf (on and off list) and Glen W.

        As it stands, our wiring has a 40 -amp fuse each side of the split charging relay. The cable is "66", whatever that means. It's 5mm outside the sheathing. If it's 66 x .25mm2, that gives a rating of 40 amps by comparison with Maplin products. The electrician who put it in thinks it's adequate. I plan to investigate further.

        To answer another point, the 12 volt distribution is via three sockets, each fused at 5 amps (slow-break type). But this can be varied, of course.

        We have no 240 volt system. I'm adding a socket inlet to the switch panel so that we can easily use a battery charger from the mains, as a loose item.

        The aim of the leisure battery isolator is to be able to isolate this battery if, for instance, it is very low and overtaxes the alternator, or under-supplies the starter motor when starting. Also, in bad weather in Winter, I would prefer to allocate car demands only to the alternator and not expect it to supply the leisure battery too. This may be an extreme case scenario, but if we are on site using the diesel heater for long evenings and perhaps mornings in Winter - especially if for several days - and then we have to drive home through foul weather, I think the scenario is realistic. So, then, the leisure battery isolator goes "off" and we wait until we get home to top up the battery, from the mains, or while driving about in more clement conditions, in daylight.

        Is there anyone out there who is interested enough to read this treatise and get this, far who DOES have a leisure battery isolator fitted in his or her van? Do any Romas have one, for instance? And any comments on why?

        Paul.
        Seek to make a virtue of necessity.

        Comment


          #5
          Barrtey Isolation

          Paul .... I note you come from a boat building background in boats a battery isolator is of paramount importance but not so in a motor caravan theoretically it would be better to have one but fuse isolation is far better.
          In a small unit such as yours I doubt you are going to overtax the alternator

          Comment


            #6
            If the leisure battery is fed via a split-charge relay, there is no reason to isolate the leisure battery to prevent alternator overload. The relay will not pass charging current to the leisure battery until the vehicle battery is "up to scratch". Nor will it allow a reverse flow from the leisure battery to the vehicle battery.
            If an isolator is fitted, it needs only to be a precautionary measure in case of a discharge from the leisure battery from drain to such items as electric clocks, or a short circuit, which could perhaps start a fire. Though strategically placed fuses should minimize that risk. If a control panel is fitted it should, in the "off" position, isolate the battery from the domestic appliances anyway. With no further action necessary.
            If you insist on an isolator it would make more sense fitted in the feed cicuit to the domestic appliances (where a control panel would be anyway).
            Jim.
            Last edited by Twolitre; 19-11-2011, 09:54.
            Keeping people waiting is stealing a part of their lives.

            Comment


              #7
              I always find that when i have decided something should be done a certain way and its dosent, even if its perfectly safe and up to the job i always wish that i had done it anyway, just for my own piece of mind. ( a bit of OCD perhaps )

              If you feel that this is what you want, add one anyway, for as my mum used to say "it wont eat anything" (meaning you don't have to do anything of it will cost money to run !)

              Comment


                #8
                Battery Isolation

                Originally posted by Twolitre View Post
                If the leisure battery is fed via a split-charge relay, there is no reason to isolate the leisure battery to prevent alternator overload. The relay will not pass charging current to the leisure battery until the vehicle battery is "up to scratch". Nor will it allow a reverse flow from the leisure battery to the vehicle battery.
                If an isolator is fitted, it needs only to be a precautionary measure in case of a discharge from the leisure battery from drain to such items as electric clocks, or a short circuit, which could perhaps start a fire. Though strategically placed fuses should minimize that risk. If a control panel is fitted it should, in the "off" position, isolate the battery from the domestic appliances anyway. With no further action necessary.
                If you insist on an isolator it would make more sense fitted in the feed cicuit to the domestic appliances (where a control panel would be anyway).
                Jim.
                Jim ..... The OP stated this was a non diode relay so it should allow a reverse flow between the battery's whether it does this before or after the engine starts depends on how the control circuit is wired. I don't think Doblo7 the OP is to fit a dedicated control unit such as a Zig unit and if he is to wire each 12volt circuit back to the leisure battery so a Isolation switch may be a good idea but individual fusing would be a better thing to do.


                On our Romahome Dimension the battery's were connected together via the relay as soon as the ignition was turned on this is Standard practice on the Dimension. I have altered mine so it only happens when the engine is running.

                On the Dimension all the 12v appliances have a Isolation switch as have all the 240v appliances.There was only a 10a fuse for the pump,lights and auxillliary supply these I have given individual fuses

                Alf

                Comment


                  #9
                  I cannot comment on the Dimension, But in general. On boats and trailer caravan systems reverse flow of current from the leisure (or domestic) battery is not possible. Otherwise the starter motor would be seeking current from both batteries, which after standing for a period would have balanced charge status.
                  The Zig unit in my Romini isolates ALL circuits in the caravan whether any individual unit is switched on or not. The SPLIT charge relay between car and 'van is intended to ignore the 'van battery until the vehicle battery is up to charge and will not allow reverse current flow from ,van battery to vehicle battery.
                  My apologies, but I was pretty sure all systems would be the same from a common sense viewpoint. My Romini is undoubtedl older than your Dimension, but it seem things have progressed backwards.
                  By the way, the fuse between batteries is only 20 Amp and it has never blown yet.
                  Keeping people waiting is stealing a part of their lives.

                  Comment


                    #10
                    Split Charge

                    Jim in general most converters feed the relay connection from the alternator this means the relay only equalises the battery's on the engine running whilst I cannot comment on any other Romahome the Dimension has the relay feed for both the charging relay and the fridge fed via the drivers side fusebox indeed it is a Heath Robinson connection being a male spade terminal shoved into a unused relay connection touch it and it falls out,
                    I found this by accident when the fridge flattened the battery whilst working on the van. Checking both with Romahome and Ant I found this was the standard practice I have rewired mine to the Alternator.

                    The charge relay is just a connection between the van and leisure battery as it was a current will flow from the better battery to the poorer one.
                    I know of 2 Dimensions that have been on mains Hook up when started and the Mains unit burnt out by engine current draw before tripping out.

                    Alf

                    Comment


                      #11
                      I can't find a suitable smiley, so you will just have to imagine I am waving a white flag!
                      jim.
                      Keeping people waiting is stealing a part of their lives.

                      Comment


                        #12
                        There seems to be a battle here, albeit resulting in a truce. Having started this discussion, I think I need to come to a conclusion. I will follow my original plan and include the isolator (already fitted) into the circuitry.

                        Billy who installed the relay and wiring says an isolator isn't necessary, but he says he'll happily alter the wiring to include it. In the event it's easier for me to do it myself.

                        I've convinced myself of the advantages of being able to isolate the leisure battery with the turn of a switch: if the battery is badly run down (quite likely after a few days camping in the Winter); and/or if the weather for driving home or anywhere else is awful, requiring headlights, fog lights etc etc in which case the addition load of charging two batteries is more than I wish to impose on the alternator. There are circumstances when it could help start the car too. After all, the alternator has plenty of its own loads to support and presumably wasn't designed for additional loads, as a truck alternator for instance might be.

                        Being able to switch off if there is a malfunction is an advantage too, enabling me to sort out the problem "at leisure" .

                        Many thanks to all contributors especially Alf and Jim.

                        Paul.

                        PS: In the absence of anyone saying he or she has one, I assume that battery isolators are NOT to be found on vehicles owned by contributors to this Forum.

                        PPS Alf writes that the arguments in the marine field are different. We used to fit isolators to minimise the corrosion effects of electricity leaks both in wooden and steel boats. On one occasion I was accused of causing major corrosion to the fastenings of a wooden boat moored adjacent to a steel boat I designed, but I was able to establish that the corrosion was caused by the earth (or lack of it) to the chap's own powerful two-way radio.
                        Seek to make a virtue of necessity.

                        Comment


                          #13
                          The downside of fitting a battery isolator is that in most cases it leads to faulty battery's ( due to leaving turned off and forgetting to turn on or recharge )a battery allowed to discharge below 10volts or so soon goes faulty trying to recharge via a alternator would properly be worse for the alternator.
                          Alternators are designed to recharge and supply varied loads all the time I think my advice would be leave well alone and do not fit the isolator

                          Alf

                          PS your Billy being ex LUCAS employee should be well suited to give advice I would agree with him NO isolator

                          Comment


                            #14
                            So I'll have to use the isolator responsibly - I think I can do that. Paul.
                            Seek to make a virtue of necessity.

                            Comment


                              #15
                              Originally posted by Doblo7 View Post
                              So I'll have to use the isolator responsibly - I think I can do that. Paul.
                              Doblo7 A Short answer to your query on isolators on boats

                              ...The main reason for a battery Isolator on boats is because unlike a motor caravan a boat is a unventilated enclosure that is liable to hold explosive vapours from leakes etc i.e. gas and fuel for this reason it is required to be able to turn of the 12 volt electrical supply quickly and safely.
                              There can be no gas drops etc on a boat


                              Alf

                              Comment

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