When connected to the mains, how do I know if it's running off the mains and not the battery?

Jun 24, 2024
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Hi, first time caravan and wondered if someone could clear something up for me.
I've been told to turn on power I use the master switch then lights switch etc. that was on battery. I've connected the mains and wondering how I can tell if it's running on mains or on battery?

Is the master switch for battery only or do I use that for mains too?
 

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Jan 19, 2002
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Depending a bit on the age of the van you may have some lights that are mains and some 12v. However your water heater will be mains or gas, as will your fridge (although your fridge usually will run on 12v during towing). When using EHU these and electric sockets will operate and the battery will be charged as needed to continue to power 12v items like radio, lights and water pump and maybe a powered loo flush if you have it.
 
Nov 11, 2009
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Hi, first time caravan and wondered if someone could clear something up for me.
I've been told to turn on power I use the master switch then lights switch etc. that was on battery. I've connected the mains and wondering how I can tell if it's running on mains or on battery?

Is the master switch for battery only or do I use that for mains too?
Do you have a voltmeter in the caravan instruments. When on mains it will show a higher voltage than on battery.
 
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Mel

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Mar 17, 2007
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If it is running on mains and not just 12volt, the 3 pin plug sockets will work. The fridge will also work on hook up, and the microwave, if you have one) will work. This may be a bit oversimplified, but tbh that’s how I know.
Mel
 
Jul 23, 2021
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We had a 2009 pageant with the same panel. The master switch is not for the battery, but for the 12V equipment. The 240v to 12v charger is on the battery side of that switch. I.e. if you have the switch on, your 12V systems will work. If you have it off, they will not.
If you are plugged into mains, the charger will keep you battery topped up. If you you are not, the battery will slowly drain.
You will be able to see if you are on mains or not by the difference in voltage level shown on the meter. 13.5 (ish) volts or higher - mains. 13.2 or lower, battery only.
 
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Jun 24, 2024
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@Tobes my DC voltage is sitting around twelve and the 3 pin sockets are working as ,@Mel mentioned . If 13.2 or lower is battery why would the 3 pin sockets work? Would there be an issue with the mains power at the house which isn't bringing it above 13.5?
 
Mar 14, 2005
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We have to make an assumption that the meter is reasonably accurate, in which case your battery voltage is only showing about 11.75V. This means the 12V battery is essentially discharged, and requires charging. By plugging the caravan into the 230V ac mains supply with the Electric Hook Up (EHU) cable, the caravans onboard charger should begin to lift the battery voltage to about 13.8V and charge it.

It unlikely you have a 12V dc to 230Vac inverter fitted in the caravan as standard, so the 13A sockets and other mains only lights will not work if the EHU is not connected.

Somewhere there will be a mains 230Vac consumer unit with an RCD and two or three MCB's for controlling the mains wiring in the caravan, one of the MCB's will likely to have "charger" indicated on it. Make sure all of these switches are turned on (lifted up) there will be a mains power distribution when the EHU is connected

Some built in chargers have a separate mains switch on them. If the charger is working it should lift the battery voltage on the display.
 
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Jun 24, 2024
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Thanks everyone for your advice, I'll have a look for that unit you mentioned @ProfJohnL.

One last question, will the battery charge when the master switch is off and connected to the mains?
 
Jan 19, 2002
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The master switch is for the 12v systems and the battery should continue to be charged on or off. i usually switch off when away from the van - and during the night ‘killing’ radio, lights and importantly the pump - so no clicking in and out of the water pressure switch beneath my head when I am trying to sleep!
 
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Jun 20, 2005
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Thanks everyone for your advice, I'll have a look for that unit you mentioned @ProfJohnL.

One last question, will the battery charge when the master switch is off and connected to the mains?
Like Tobes our 2005 Pageant had the same panel. Yes the battery will charge even if the master switch is off.
The panel voltmeter is not accurate. Only a good multi meter will give an accurate reading.
 
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Jul 23, 2021
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Thanks everyone for your advice, I'll have a look for that unit you mentioned @ProfJohnL.

One last question, will the battery charge when the master switch is off and connected to the mains?
On the Pageant the unit was behind the consumer unit with the 240v breakers. Ours died, and we had to replace - it was a very easy job, but cost about £60 in 2014.

The ceiling lights are all G4 halogen capsules (easily replaced with LEDs now) with them all on, there should be sufficient battery drain to see a change in brightness with the charger on or off. You should be able to do that from the consumer unit - the charger will have its own breaker.
 
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I installed a 12V USB socket with voltmeter, they are more accurate.

I placed it under overhead locker next to reading light and connected it 12V feeding the light.
If you have cigarette lighter type 12v sockets it's easier to buy one of these, plug it in (no wiring required) and you're good to go.
 
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I installed a 12V USB socket with voltmeter, they are more accurate.
Unfortunately I have tried several similar meters from cheap sources and I have to say the accuracy of some were about out by nearly a whole volt! referenced to my calibrated Fluke 289. Just becasue they're digital does not always mean they are accurate. They can be quite precisely wrong. Ideally these devices should be connected directly to the battery, otherwise they will also indicate the error caused by voltage drop along cables caused by the current appliances/ lights use.
 
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Ideally these devices should be connected directly to the battery, otherwise they will also indicate the error caused by voltage drop along cables caused by the current appliances/ lights use.
Somewhat irrelevant as testing at the battery terminals won't give a true indication of the charge state if the battery is under load.
 
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the charger fitted to this era bailey are notoriously bad and fail for fun if your caravan battery is not charging this may be the issue. I know that these gauges are not accurate, but with a mains hook up I would expect it to show around the 13 volt mark, at least that's what ours did
My last Bailey , a Pageant S6 failed so badly it tripped half a caravan club site as the transformer had snapped in half shorting out everything.
Replacements aren't cheap but an improved version is available which is even less cheap!
 
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Somewhat irrelevant as testing at the battery terminals won't give a true indication of the charge state if the battery is under load.
In most cases caravanners would welcome an indicator that could show the batteries state of charge (SOC). Generally lead acid batteries exhibit a drop in terminal voltage as their SOC decreases, and for a standard 12V Lead Acid battery a standing (i.e. not being charged or used ) should be 12.8Vdc. Most pundits consider a standing voltage of 11.5Vdc to indicate the battery is discharged. and needs to be recharged.

This is only a 1.3V variation, so if an indicator has an inaccuracy of as little as 0.5V either way it will give an erroneous indication and imply an incorrect SOC.

However , if you can verify the indicators inaccuracy, by comparing it to a meter with a known accuracy, you can fairly easily produce a chart with the corrections you need to apply to the indicators readings.
 
Aug 12, 2023
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Unfortunately I have tried several similar meters from cheap sources and I have to say the accuracy of some were about out by nearly a whole volt! referenced to my calibrated Fluke 289. Just becasue they're digital does not always mean they are accurate. They can be quite precisely wrong. Ideally these devices should be connected directly to the battery, otherwise they will also indicate the error caused by voltage drop along cables caused by the current appliances/ lights use.
Mine was within 0.1V compared to fluke MM. Must of got good one. If you turn most things off including lights its attached to the battery voltage reading is quite accurate.
 
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In most cases caravanners would welcome an indicator that could show the batteries state of charge (SOC). Generally lead acid batteries exhibit a drop in terminal voltage as their SOC decreases, and for a standard 12V Lead Acid battery a standing (i.e. not being charged or used ) should be 12.8Vdc. Most pundits consider a standing voltage of 11.5Vdc to indicate the battery is discharged. and needs to be recharged.

This is only a 1.3V variation, so if an indicator has an inaccuracy of as little as 0.5V either way it will give an erroneous indication and imply an incorrect SOC.

However , if you can verify the indicators inaccuracy, by comparing it to a meter with a known accuracy, you can fairly easily produce a chart with the corrections you need to apply to the indicators readings.
All of which won't change the fact that you have to take the battery 'off load' to get a true indication of the charge state so it doesn't matter whether your measuring the voltage at the battery or any other point on your caravan.
 

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