RE: OT : Regulating 12Volts

["Keith Doxey" <ukha@xxxxxxx>]

Hi Paul,

 

Can the pump run off less than 12V ...ie about 9V ?

 

If so a 9V regulator will do the trick.

 

The problem is that ALL regulators need to drop about 3 volts to work. If you did something that just dropped 2 volts rather than giving a definate output, you would only have 10V when running on batteries

 

You could try 3 heavy duty diodes in series, that would give about 1.8V - 2.1V drop so that the 13.8 would be about 12. You would then need a switch to bypass the diodes when running off batteries only. (You could use a relay powered by the mains that was open when the mains was on, thereby putting the diodes in series with the pump power supply, but closed in the absence of mains thereby feeding the full battery voltage to the pump. That gives you an AUTOMATED solution so this is no longer [OT] )

 

The design of the pump seems to be flawed if a small voltage variation affects it correct operation. What happens if the batteries get low dropping to say 11V, does the same problem occur ?

 

KEith

-----Original Message-----
From: Paul Smith [mailto:wheelbarrowhandle@xxxxxxx]
Sent: 01 September 2001 19:05
To: 'UKHA'
Subject: [ukha_d] OT : Regulating 12Volts

Guys,

 

            I bit OT but I hope someone can help. My dad has had a caravan for years, and has now invested in a 240v generator. The problem is as follows and I could do with a neat cheap solution.

 

            Generator provides 240V into the caravan as though it was plugged into the mains. Inside there is a battery charger which puts 13.8volts across the battery. This is where the problem is. Because of the greater voltage the pumps pressure switch clicks on and off too quick. If he adjusts it so that it works correctly then it never turns off when only running on 12Volts.

 

            What he needs is a way to regulate the 12volt feed so that it is always 12votls and not 13.8. Any ideas ? the only other issue is that it needs around 3 to 4 Amps DC.

 

Any Pointers ?

 

TIA

 

Paul

 

 

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