Guest Tracker Posted April 19, 2010 Share Posted April 19, 2010 I fitted a leisure battery isolator switch on the NEGATIVE side of the battery recently to help conserve battery power when the van is not in use. However following problems with the Sargent PSU not 'allowing' the full battery voltage to flow when the isolator is turned on I contacted Sargent for their views. Following several voltage checks at various points it was decided that there is nothing wrong with either the batteries or with the PSU as it is a fairly common 'quirk' of certain Sargent systems to react in this way when the Negative side is disrupted as with an isolator switch. The symptoms are that when switched back on after even a very short time off the control panel shows a very low voltage of around 10.0 to 11.0v which is reflected at the PSU and at the various 12v lights and pump etc. in spite of the batteries showing 12.8v at the terminals. I quote from a recent email from Dave Chapman at Sargent who has been most helpful. "It is not technically incorrect to fit an isolator switch on the negative side of a leisure battery, it is just that removing the negative can cause our system to operate erratically. We have not undertaken a large amount of testing with this scenario, but with no leisure negative a permanently connected item with be connected from leisure positive, to the harness negative which is also connected to the vehicle chassis, which is also connected to the vehicle battery negative, and the vehicle battery positive is connected to the PSU and in turn to the control panel. Overall this can cause incorrect voltage readings as the leisure negative can float above zero. In light of our previous experience, and your findings so far, we would recommend that you do not place an isolator switch in the negative leisure supply. Fitting one in the positive supply should have no effect on the system." I also clarified the correct way to fit an isolating switch to a solar panel and it seems I did at least get this bit right! Question " The solar panel regulated input of about 14.6v on a good sunny day is direct to the battery side of the isolator switch so that the solar panel is always charging the battery but never feeding back into the PSU and 12v system without a battery load connected.This was my own idea as I - rightly or wrongly - figured that the PSU might not appreciate a direct non battery input?" Reply "Yes, you have done what we would recommend, as most regulators do need the battery 'in circuit' to operate correctly." So it looks like my mission for this week, should I choose to accept it, is to alter the leisure battery isolating switch from the Negative side to the POSITIVE side. At least the most 'positive' aspect of this is that I don't need a new PSU! Meanwhile, I live and learn! Link to comment Share on other sites More sharing options...
lennyhb Posted April 19, 2010 Share Posted April 19, 2010 Well that's a first Rich, never heard of anyone fitting an isolator switch on the negative side before except on old positive earth vehicles. Link to comment Share on other sites More sharing options...
spospe Posted April 19, 2010 Share Posted April 19, 2010 Rich It is standard practice to fit switches in the 'live' not the 'ground' lead when only one wire is being switched. This is especially relevent as the voltage being switched rises e.g. mains electricity. Link to comment Share on other sites More sharing options...
Guest Tracker Posted April 19, 2010 Share Posted April 19, 2010 Fitting to the positive was my first thought too but I was advised that fitting to the negative would work just as well - it didn't! Link to comment Share on other sites More sharing options...
Brambles Posted April 20, 2010 Share Posted April 20, 2010 Tracker, the problem is you did not fit in such a away to isolate the battery, you fitted so solar system was still connected to the battery. So in effect not an isolation switch but a liesure equipmentt main battery switch. I guess it was me who said fit in negative, The reasoning is becaue it is safer than trailing the postive lead about, epecially if under the seat with metal chassis parts like the seat frame around. If on the negatve side then anything conductive falling on the battery is less likey to cause a short to ground. As your signature says, there is no right or wrong way, just different. My suggestion was to isoate he battery completely after it is fully charged and laid up. the Vartas will maintain their charge quite happily for 3 to 6 months no problem as they have lowe self discharge. The Calcium Technology ones for even longer. Link to comment Share on other sites More sharing options...
Brambles Posted April 20, 2010 Share Posted April 20, 2010 p.s. tracker, You mentioned elswhere you had not got away yet, I would give your betteries a discharge by leaving lights on or whatever and recharge just to excercise them a bit and condition the plates, mix the acid etc before leaving on solar panel to keep charged up or left isolated. Link to comment Share on other sites More sharing options...
Guest Tracker Posted April 20, 2010 Share Posted April 20, 2010 Thanks Jon - good idea - will discharge and recharge as suggested. But I can't quite see how having the solar panel connected to the leisure battery but not connected to the Sargent PSU would cause the effects experienced in the PSU? The suggestion to isolate via the negative came from more than one source and no 'blame' is attached to you or to anyone else because the disfunctional PSU was not forseeable by anyone - except Sargent and I didn't ask them first! Link to comment Share on other sites More sharing options...
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