Danfoss BD35 portable refrigerator runs on 12V battery only and not on power supply

Thread Starter

Cratar

Joined Jan 11, 2021
3
Hi All

So I have this portable refrigerator. It has a Danfoss BD35F compressor with 101N0210 control unit. The fridge has a 12/24V switch and I have only used it with 12V. When connecting it to a 12V car battery it runs perfect, never any problem. But when using it with the 230VAC power supply shipped with the fridge it doesn't run. That is 12V 4A unit.
So I have tried with three other different power supplys, providing 5A, 5A and 6.5A, it doesn't work with any of them. The compressor starts but you can immediately hear it is loosing revs and then it stops after a few seconds. I have cranked one of the power supplies up to 14V but it doesn't help, measuring the voltage when it tries to start, it drops to about 6-7V.
When connecting it to a 12V car battery it runs perfect, I have measured the current and it takes about 3.3-3.4A when running. Just when it starts I can see it take about 4.1A, but I have only used a digital multimeter without logging functionality.
In the Control Unit (101N0210) I have removed and measured all large capacitors (four of them), none of them faulty. One of the small ones slightly low so both small where replaced, but it didn't make any difference.
What is the problem here? Why does my fridge not run on a power supply?

Thanks for your help!
 

dendad

Joined Feb 20, 2016
3,913
It sounds to me like the power supply needs to be a higher current one.
Just out of interest, do you have any large value capacitors, like 40000uF that can be connected across the supply to see if that helps?
 
Last edited:

Thread Starter

Cratar

Joined Jan 11, 2021
3
A supply that can give more amps might work. The strange thing though is that the one shipped with the refrigerator is rated at 4A and it has been working for many years. The fridge is used on weekends a dozen times a year or so, and just stopped working on supply.
I'm thinking that something in the Control Unit suddenly has started to use a lot of amps.

I haven't tried with a capacitor across the supply, I'll check if I have a large one.
 

debe

Joined Sep 21, 2010
1,251
A 12V supply at 4Amps is on the minimum limits, a 6Amps 12v is what i would be using. It sounds like your powersupply is probably faulty, if the fridge runs of a battery ok. SMPS dont last for ever.
 

Thread Starter

Cratar

Joined Jan 11, 2021
3
Hi all!
Thanks for everyones input, sorry I haven't followed up earlier.
First regarding the power supplies I have used with this refrigerator, two of them are SMPS, the one shipped with the fridge is of course one of them. But I have also used two different linear power supplies. I am confident that at least three of the ones I have used are in great shape and provide the rated current at 12-13VDC with insignificant AC.
I tried dendad's suggestion and connected a 32000uF capacitor across the supply. With this solution the fridge runs perfect, with any of the power supplies. So it can be used as a workaround.

In my opinion there is some problem with the control unit (101N0210). Sure it can be exchanged, but it is quite costly, a new unit is about the third of a new refrigerator.
Does anyone have a schematic drawing of the 101N0210 control unit? I would by happy to receive a copy.

Thanks
/Cratar
 

debe

Joined Sep 21, 2010
1,251
The only way you will get a schematic is reverse engineer it, & it gets rather difficult with surface mount components. Ive done acouple of early Waecos that had through hole components on the control boards. But not the compressor control.
 
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