Alarm to show if fridge circuit looses power?

[jameshowison]

I have a travel trailer and I would like an alarm in my truck if my fridge loses 12v power while driving.

I thought about running a cable from the last junction to the fridge, showing a light if all is good but an audible alarm on power loss would be better.

So perhaps something with a small rechargeable battery in it that fires off if it loses 12v?

The low voltage alarms aren’t relevant because they don’t work if voltage goes from good to zero, right? Like if a fuse blows or some such.

 

[RCinFLA]

You could use a low power 12v relay with SPDT contacts. Hook whatever sound maker you like for unenergized relay normally open contact.

 

[No Idea]

Both my upright fridge freezers have a standby light plugged into same socket so if the circuit they are on trips we know to reset it. It has a 12v 7Ah SLA internal battery but it is loss of AC mains that triggers it. Internally I think the circuit goes AC to 12v DC and the light trigger is DC so might be worth a think and swap the lights for audible alarm.

 

[deeuubee]

Oops, deleted.
Didn't see 12v at first.

 

[chrisski]

I’m not exactly sure what you’re looking for, but my VICTRON BMV 712 can monitor Bluetooth which I can get from my truck to the RV. It can trigger a relay on a voltage which you could use to turn a alternate source. You’d have to rig this alternate source.

https://www.amazon.com/Victron-BMV-712-Battery-Monitor-Temperature/dp/B07F3C7ZV7/

There is cheaper ways, that’s just an easy way to do something like you’re asking.

If you’re worried about one leg, I could even see running two sources in parallel to this fridge.

On a separate note, IMO the fridge would be OK without power for a few hours IF already cold.

 

[cs1234]

This has nothing to do with monitoring the voltage to the fridge, but you could just monitor the temp and sound an alarm it it drops below what you like.

I use these at my house in all my fridgers/freezers to watch for temp fluctuations. They work pretty well, batteries last a long time, and the signal easily penetrates the freezer and goes across my house. The alarms will make you want to kill yourself if you don't silence them, they are hard to ignore.

Wireless fridge/freeze temp monitors