Autofridge works on 12V but not 24V

Submitted: Monday, Nov 24, 2014 at 07:15
ThreadID: 110239 Views:3297 Replies:5 FollowUps:2
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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.
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Reply By: Members - Bow & Nan - Monday, Nov 24, 2014 at 07:47

Monday, Nov 24, 2014 at 07:47
From memory, I think Autofridges will only work under 18v. They are a 12v fridge only.
AnswerID: 542129

Follow Up By: Ozhumvee - Monday, Nov 24, 2014 at 08:43

Monday, Nov 24, 2014 at 08:43
No not correct the latest versions probably for the last ten years or so were dual voltage 12 or 24 volt. I've been using ours on both voltages for at least that long, in fact it has been working more on 24 than 12v.
They use a BD35 Danfoss compressor, if you unscrew the lid on the refrigeration end you will be able to see the sticker on the compressor.
You may also be able to see it through the slots in the casing with a torch.
FollowupID: 828363

Follow Up By: Members - Bow & Nan - Monday, Nov 24, 2014 at 08:57

Monday, Nov 24, 2014 at 08:57
Peter My autofridge was at least 25 years old, I should keep up with the times.
FollowupID: 828364

Reply By: vk1dx - Monday, Nov 24, 2014 at 10:08

Monday, Nov 24, 2014 at 10:08
If my question if off topic then I am quite happy for this post to be deleted.

Question: Why change to 24V? Is that for the van only or the car as well?
AnswerID: 542135

Reply By: Sigmund - Monday, Nov 24, 2014 at 11:06

Monday, Nov 24, 2014 at 11:06
Maybe ring Autofridge. The flashing light is a code obviously and should tell you what's happening at the fridge.

When the fridge compressor starts up it will draw more current than when it's running and your power supply may not be up to it. The input voltage is only part of the picture. Apart from that unless you prepare the battery, if that's where it's coming from, to avoid the misleading reading of the surface charge it has, the voltmeter reading is useless.
AnswerID: 542136

Reply By: Frank P (NSW) - Monday, Nov 24, 2014 at 17:18

Monday, Nov 24, 2014 at 17:18
The Autofridge has a Danfoss BD35 compressor. The single flash from the LED indicates (from the manual)
Battery protection cut-out
(The voltage is outside the cut-out setting

Here is the documentation I have. Hope it helps.


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AnswerID: 542152

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:

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:

Apparently they are available for 24V instead of 12V.
What do you think?
AnswerID: 542161

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