Autofridge works on 12V but not 24V
Submitted: Monday, Nov 24, 2014 at 07:15
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balachai
Hi everyone!
I bought a 75 litre Autofridge about 6 years ago. It’s been working great on 12 volts. :-)
Now I’ve upgraded my power supply to 24 volts, but when I plug in the fridge its red light just does the “single flash” thing. :-(
I’ve checked the input voltage – it’s 24.4 volts steady. The fuse is an auto blade fuse, 10 amps. The power supply is rated at 12.5 amps.
Is there anything I need to do to tell the fridge to use 24 volts not 12?
I did try emailing Autofridge, but they didn't reply.
Reply By: balachai - Monday, Nov 24, 2014 at 20:55
Monday, Nov 24, 2014 at 20:55
Thanks for the advice everyone.
The fridge lives in my garage running off 240V mains power via a DC power supply. I can run it fine with one of these:
http://www.jaycar.com.au/productView.asp?ID=MP3573&w=12v+power+supply&form=KEYWORD
But I'm upgrading to 24V because I'm also running a 24V water pump. And I want to future-proof for a small off-
grid solar setup with a 24V battery.
The 240V plug on the power supply has no earth pin - its output DC voltage is "floating". So I got a second identical power supply and linked them in series to boost the voltage to 24V. The 24V water pump runs perfectly off this setup.
I opened up the Autofridge case and yes it's got the Danfoss BD35F compressor, which should automatically accept either 12V or 24V. And yes the single flashing light indicates the input voltage is too low, and the fridge is shutting off to protect the battery (which is not present in my setup).
OK I've got a theory now! Perhaps the Danfoss low voltage protection is jumping in too quickly. When I turn on the pump, it starts to draw current. It takes a millisecond for the second "boost" power supply to start, during which time the voltage sags below 12V. The second power supply then kicks in and the pump runs fine.
However when running the fridge, its voltage protection cutoff jumps in during that brief voltage sag, turning off the fridge.
To avoid this voltage sag, I'm considering getting a maximiser:
http://
shop.ata.org.au/shop/maximiser-20-amp
Apparently they are available for 24V instead of 12V.
What do you think?
AnswerID:
542161