i have got a few things at home that plug into the mains and then are reduced via a transformer to 12vdc. can these items be plugged straight into the vans 12v system? one item says"12v dc 700mA". what is the caravan mA, or is that not important? many thanks for viewing this and any help that might be forthcomming. geoff
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12 v items
- Thread starter geoff_5040010
- Start date
Hello Geoff,
Lets deal with the simple bit first. All electrical appliances will use current. Current is measured in A (Amps). Some appliances will use much less than an Amp and so their consumption will be measured in mA (MilliAmps) 1000mA = 1A. In general caravan supplies will be able to deliver 8 to 10 Amps without too much trouble.
The slightly more complicated bit is whether your 12V appliances will work in your caravan. When you see that a caravan has a 12V supply, in fact it is usually anything but 12V. When your battery is being charged, its voltage can be as high as 14.5V, and when it is nearing exhaustion (Flat battery) it can produce as little as 10V. That is quite a wide range.
Some appliances (like electronic items such as televisions, computers etc) need a well controlled supply (11.5 to 12.5Vdc) to operate correctly. Other items (lights and motor driven items)may be far more tolerant of big changes in the supply voltage.
If the appliance is sold for use in cars, then it should be ok in the caravan, if not then it may malfunction or at worst it may be damaged by the charging voltages.
Lets deal with the simple bit first. All electrical appliances will use current. Current is measured in A (Amps). Some appliances will use much less than an Amp and so their consumption will be measured in mA (MilliAmps) 1000mA = 1A. In general caravan supplies will be able to deliver 8 to 10 Amps without too much trouble.
The slightly more complicated bit is whether your 12V appliances will work in your caravan. When you see that a caravan has a 12V supply, in fact it is usually anything but 12V. When your battery is being charged, its voltage can be as high as 14.5V, and when it is nearing exhaustion (Flat battery) it can produce as little as 10V. That is quite a wide range.
Some appliances (like electronic items such as televisions, computers etc) need a well controlled supply (11.5 to 12.5Vdc) to operate correctly. Other items (lights and motor driven items)may be far more tolerant of big changes in the supply voltage.
If the appliance is sold for use in cars, then it should be ok in the caravan, if not then it may malfunction or at worst it may be damaged by the charging voltages.
many thanks for yourhelp john. the item in question is a freeview box so i guess i will have to use the mains adapter supplied with it. i just wanted to have less wires around. i am surprised that the caravan 12v system is not regulated at closer to 12v. thanks again. geoff
Geoff, DC to DC convertors are available which will give a regulated 12v output with a varying input. I use one regularly in my car to power a laptop which requires 14v. It appears to work ok whether the engine is running or not, so I guess it is giving the regulated output whether the input voltage is above or below the output voltage.
Hello again Gary,
For the reasons I have already alluded, caravan 12V is anything but! However all is not lost. As Ray points out there are a variety of adaptors that will produce a range of different stable dc voltages designed for cars that will work equally well in your situation.
Maplin electronics offer a wide range of devices. See:
http://maplin.co.uk/
Alternatively you can use an inverter. These take 12Vdc and produce 230V ac. Again Maplin carry a range of these devices. If you are considering an Inverter, then the ones that offer a "full or pure Sine" wave are the best, but "quasi or modified Sine wave" will operate all but the most sensitive appliances.
Do be aware that as a rough guide, for every 100Watts needed to power a 230V appliance the Inverter will draw about 8Amps from the 12V supply to power it. You must choose your inverter to meet the maximum watts of the appliances you intend run, but for practical reasons don't go above about 300W.
For the reasons I have already alluded, caravan 12V is anything but! However all is not lost. As Ray points out there are a variety of adaptors that will produce a range of different stable dc voltages designed for cars that will work equally well in your situation.
Maplin electronics offer a wide range of devices. See:
http://maplin.co.uk/
Alternatively you can use an inverter. These take 12Vdc and produce 230V ac. Again Maplin carry a range of these devices. If you are considering an Inverter, then the ones that offer a "full or pure Sine" wave are the best, but "quasi or modified Sine wave" will operate all but the most sensitive appliances.
Do be aware that as a rough guide, for every 100Watts needed to power a 230V appliance the Inverter will draw about 8Amps from the 12V supply to power it. You must choose your inverter to meet the maximum watts of the appliances you intend run, but for practical reasons don't go above about 300W.
Geoff, caravan systems are regulated very closely to 13.8v when the mains power supply is connected to the battery but can vary considerably when reliant solely on battery.
Although a volt is a very precise scientific unit of measure, battery systems are only nominal voltages.
This is no different in concept to a car where the "12v" system runs at 14.4v when the engine / alternator are running and anywhere between 9 and 13 volts otherwise.
Although a volt is a very precise scientific unit of measure, battery systems are only nominal voltages.
This is no different in concept to a car where the "12v" system runs at 14.4v when the engine / alternator are running and anywhere between 9 and 13 volts otherwise.
