PSU/Charger

Oct 13, 2005
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I need to replace a faulty PSU/Charger unit on a 12 year old Super Sprite. The old unit has two +ve output terminals,one for the battery and one for the 12volt supply. It seems that the modern PSU/charger units have only one +ve output terminal, I guess that some rewiring is required. I could use the singe output to connect to and charge a battery and then rewire the 12volt supply directly to the battery but I would then be committed to carrying a battery ( I'm told that the new units can be used as a dedicated power supply and a battery is not necessary). Any advice would be greatly appreciated.
 
Mar 14, 2005
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Hello Brian,

Yes it is technically possible to run the 12V equipment in a caravan with a suitable Power Supply Unit (PSU) and no battery.

You would need to add up all the current demands for the equipment you might use at the same time, and select a PSU to match. The down side is that large capacity PSU's tend to be quite expensive, and of course if you do not have mains power then nothing works.

To keep costs down, a battery and a smaller PSU might be a better solution and of course you will have some power when mains is not available. Depending on the make and model of PSU some rewiring may be necessary.

Please don't be fooled into thinking that 12Vdc is safe, the rewiring needs to be done to a high standard with proper regard for circuit breakers, wire sizes and quality of connections etc. If you are in any doubt consult and use a qualified electrician.
 
Oct 1, 2005
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if the new unit only has 1 live output terminal both your existing wires can be joined at the output terminal. u can get a piggy back female connector which has a male connector on it as well as being a female.

All u have to do is cut off the connector on the battery lead, crimp on the piggy back & push on the lights terminal, as it is an uninsulated terminal wrap it up with insulating tape or get a piece of heat shrink tubing and cover with that, job done for minimal disturbance/effort/time/etc.(i am assuming there are fuses already in these lines.)

I just fitted a new one to a van this week, it was one i'd not seen before, it was either a powerpack or powerpoint, 13.9 volt 10amp nominal output 12 amp max, seemed a decent unit.

As for running mains without a battery, now thats a sore point with fitters, me included.

If u have a battery on its like a reservoir it smooths out flow & keeps things nice and gentle, if u havent got one on, when u put 240 into the cvan its initial surge can and does send a spike throughout the system, which on occasion fouls up sensetive equipment, like trackers, or alarms & it wouldnt be the first time we've had to replace a power relay on a swift 645 that uses a key fob remote to switch the power on, simply because the handover lads are too lazy to connect a battery to it first.

Had to do one 2 weeks ago for that reason.
 
Mar 14, 2005
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Hello Keith,

If what you imply is correct, then the units fitted to the caravans you deal with are not upto relevant standards for low voltage power supplies. They should not "surge" when mains power is switched on.

Perhaps the units you use are designed to be used with a battery, in which case they are not technically power supplies but chargersand thier output may not be as well controlled as a bonefide power supply.
 
Mar 14, 2005
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John's right the 240volt input is always controlled, (or should be Iv'e never seen one without?), to stop a heavy output loads damaging modern PSU's electronics when switched on, by modern I mean from around 1995. I test them under full load and you can watch the output voltage increase as the full input voltage is fed in over a second or two.

However if you switched off and straight back on again?...that could do it!
 

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