Low Voltage Sensing Relay ???? --HELP!!

[R. A. Piziali]

I have need of the following:

A relay that will handle a 15amp load and close at about 13.0-13.4vdc and
open at, say, about 12.7vdc. Is such a device available - if so where? OR what
can I put together to operate in such a manner??

The application: I want to AC power an RV refrigerator with an Inverter from
the vehicle DC charging system but automatically disconnect when RV battery is
not being charged, ie, to prevent powering Inverter from RV battery.

Ray
--\\\//
(o o)
*----------------------ooO-(_)-Ooo------------------------*
---- REMEMBER ----
+++++ Those who IGNORE history are doomed to repeat its mistakes!! +++++

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Government is not reason; it is not eloquence; it is force! Like fire,
it is a dangerous servant and a fearful master." -- George Washington
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
No God, No Peace!
Through Jesus,
Know God, Know Peace!
~~~~~~~~~~~~~~~~~~~~~

 

[william_b_noble]

get a standard relay with 12V contacts that will handle the current you
want. Drive the relay with a 2n3055 (or a more modern equivalent), drive
that with a voltage comparator. On one leg of the comparator, use a 10K
resistor and an 8V zener, on the other leg of the comparator, use a 10K
pot - adjust the pot for the trip point you want

 

[Harry Bloomfield]

| A relay that will handle a 15amp load and close at about 13.0-13.4vdc and
| open at, say, about 12.7vdc. Is such a device available - if so where? OR what
| can I put together to operate in such a manner??
|
|
|

We have these in the UK, so I think they will also be available in the
US.....

We use two types of relay for caravan towing purposes. The older style
one is fed from the ignition warning light system, which means that the
relay is only made when the ignition is on and the alternator is
producing a charge sufficient to turn the ignition warning light off.

The second and more recent type, simply requires a feed from the
battery alone. It senses the voltage across the battery and makes the
relay when the voltage indicates the battery is being charged.

Both are used for supplying fridges and charging the battery in a
caravan and are rated at 20amps or better.

--
Regards,
Harry (M1BYT)...

Remove the 'NOSPAM' in my email address to reply.

Free Amateur Radio Courses:-
http://www.ukradioamateur.org