Battery charging via ehu

[kerbdog]

I left our caravan hooked up to the mains electric for the past two days and disconnected tonight, i checked the readout on the led screen and it said the caravan battery was at 12.10v which doesn't sound right o me.
I left the caravan hooked up without the panel above the door switched on (panel allows lights to be turned on,water pump, heating and readouts on temp and voltage etc)
Does the caravan charge the battery regardless of this panel being switched on? I cant seem to find anything in the Swift owners manual.

 

[ProfJohnL]

You don't give us enough information about your caravan year or model, so we can't be specific about your switch and power arrangements, but in general there should be a switch that controls whether the charger is turned on or not.

You are right 12.10v is low, but aS you have a meter showing the voltage of your 12v system it would be worth trying different switches until you find the one that raises the displayed voltage. Typically with the charger working you should see about 13.8v.

As you have a Swift caravan, have you tried the swift owners forum?

 

[BML]

I had the same trouble and it was not until my wife stuck her head into the cupboard where the electrical switches are that she found that a switch marked, Charging" had inadvertently been switched off.

 

[otherclive]

I had the same trouble and it was not until my wife stuck her head into the cupboard where the electrical switches are that she found that a switch marked, Charging" had inadvertently been switched off.

My Sprite has the same charging system which requires the switch to be pushed in. Its a three stage charger so in theory can be kept connected when at home, but I always remove then charge before I need to use the van.

 

[kerbdog]

Sorry i should have supplied more detail. My Caravan is a 2008 Swift Conqueror 540. Its has an lcd screen above the doorway for the electrics and there is a separate switch for the charger on the consumer panel in the wardrobe. I've checked that this is switched to the on position.
the control panel is the same as the one in this youtube video.
[video]https://www.youtube.com/watch?v=Npebgt8hVp4[/video]

 

[VicMallows]

I had the same trouble and it was not until my wife stuck her head into the cupboard where the electrical switches are that she found that a switch marked, Charging" had inadvertently been switched off.

That doesn't surprise me at all!. My Elddis has a switched spur for the Truma heater located at the bottom of the wardrobe. It has a very light-action rocker switch and it quite often knocked into the off position by the (wifes!) long dresses.

 

[Dustydog]

Having recently flattened my battery I know the on board charger is a very crude piece of kit.
My smart charger finally brought life back and read 13.4v. Once back on the caravan the Bailey volt meter reads 12v. My old multimeter read 13.2v.
Don't be misled by the on board gauge!

 

[BryanTheSnail]

The voltmeters are quite often a long way (cable length) from the battery and any load on the battery when you test will cause voltage drop and affect the reading. A multimeter reading at the battery terminals would be a more accurate guide The van voltmeter should perhaps be considered as a guide to what the voltage is compared with the last reading.

 

[Woodentop]

The voltmeters are quite often a long way (cable length) from the battery and any load on the battery when you test will cause voltage drop and affect the reading. A multimeter reading at the battery terminals would be a more accurate guide The van voltmeter should perhaps be considered as a guide to what the voltage is compared with the last reading.

I'm sorry but that is *******. Any form of voltmeter has an input resistance in hundreds of thousands of Ohms or even higher so it will draw (typically) 50uA or much less. It does not matter how long the cable is it will not be sufficient current to cause ANY voltage drop that will register.

It is not to say however that the meter is accurate. Try reading the battery volts with two or three different DVMs and I guarantee you will get two or three different readings. Most cheap DVMs are only accurate to about 5% at best - even an expensive ones such as a Fluke or Avo are usually only rated to about 2% accuracy!

 

[ProfJohnL]

The voltmeters are quite often a long way (cable length) from the battery and any load on the battery when you test will cause voltage drop and affect the reading. A multimeter reading at the battery terminals would be a more accurate guide The van voltmeter should perhaps be considered as a guide to what the voltage is compared with the last reading.

I'm sorry but that is *******. Any form of voltmeter has an input resistance in hundreds of thousands of Ohms or even higher so it will draw (typically) 50uA or much less. It does not matter how long the cable is it will not be sufficient current to cause ANY voltage drop that will register.

It is not to say however that the meter is accurate. Try reading the battery volts with two or three different DVMs and I guarantee you will get two or three different readings. Most cheap DVMs are only accurate to about 5% at best - even an expensive ones such as a Fluke or Avo are usually only rated to about 2% accuracy!

Perhaps Brian did not express himself well enough on this one.
I totally agree there are absolute inaccuracies between voltmeters, and the traditional moving iron meters that were typically fitted to caravans were hopelessly inaccurate. There is a common misconception that a digital meter must be accurate becasue its digital! Hmm how wrong that can be! as you point out there are wide variations in the accuracy of all types of meters, and the only ones you can trust are those that are Calibrated and have a known degree of uncertainty.

How calibrated is the meter in the caravan? who knows, so it could be well out, but I think that what Brian was assuming is that the volt meter in the command unit does not have a pair of dedicated measurement wires to the battery terminals, but its most likely to take a reading of the voltage as power enters the command unit from its supply wires. So you have what ever the length of the wires between the battery and the command unit which when they are carrying current will produce a voltage drop along them, so the command unit will not be at the same potential difference as the terminals of the battery. And becasue there will be both + and - wires carrying the same current, the reduction in voltage at the command unit may be bigger than you expect.

 

[BryanTheSnail]

There is little chance that the manufacturer will run a separate feed to the meter because it is a long run with panels often being by the door these days. The point I was making is that any load on the battery will drop the voltage, and especially if that feed is also the one that supplies the connection to the meter. But I will happily concede that my comments could have been interpreted otherwise.