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Can you keep a relay permanently charged ?

Nakiman

New Member
I am using a standard auto 5 pin 12v relay in my campervan as part of a battery disconnect feature in my campervan. The "normally open" relay switches power to my 12v freezer direct from my house battery. Power for switching is supplied from the solar controller which has a low voltage cutout feature. The relay works well, but it is charged 24/7. It seems to be running at a temp of 40 degrees Celsius (104F). It does not state "continuous duty" but just wondering if it is okay to have a relay permanently charged ?

 

Pommie

Well-Known Member
Most Helpful Member
By permanently charged I assume you mean permanently on. I don't see why not. 40°C is not too high. It would be much better if it was not continuously powered. Can you post a schematic?

Mike.
 

Nakiman

New Member
Mike, thanks for the reply - yes I do mean permanently on. Attached is an amateur schematic. The fridge is a 12v compressor fridge and I have been recommended to not run it from my Victron solar power controller, but from the battery direct. My controller has a low voltage disconnect to protect draining the battery. This defeats the purpose as my fridge would still keep running. Hence the idea of a relay that will disconnect power to fridge when power controller disconnects fridge. I am reading that the Bosch relays are "continuous duty" rated ?
Pommie
 

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alec_t

Well-Known Member
Most Helpful Member
Latching relays exist. They need a current pulse to switch them 'on' and another current pulse to switch them 'off'; so no continuous coil current. Don't know if they're available with sufficient load handling ability for your purpose though.
 

crutschow

Well-Known Member
Most Helpful Member
If the power drain of having the coil continuously on is not a problem, then I see no need to go to a latching relay.

You might be able to configure the relay control circuitry so it is on when the voltage is high, not low, if that would be better.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
I's agree, 40'C is not excessive and should not be a problem.

However; relays take somewhat more power to initially energise than to hold on afterwards.

If you connect an appropriate resistor and capacitor in parallel, then connect that in series with the relay coil, you can reduce the power consumption.

Try a resistor around 20% of the relay coil resistance, in parallel with eg. 100uF??
 

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