VOLTAGE DROP DANFOSS BDF50 COMPRESSOR 12V FRIDGE

Baz421 · Guru

VOLTAGE DROP DANFOSS BDF50 COMPRESSOR 12V FRIDGE

Peter_n_Margaret · Guru

Maybe?
The BD35 compressor will run down to about 10V though. Don't know anything about the Mobitronics. Why not run it from the 12V house battery?
Measure the voltage at the fridge as it tries to start.
Cheers,
Peter

Baz421 · Guru

Yes drops to 10v,,,,,at fridge. Battery 12.5v before fridge tries to start

Whenarewethere · Guru

The Waeco 28L fridge I have has a compressor actually not much smaller than the larger fridges. Voltage drops about 0.5 volts when running off 78AH of 12 volt batteries only.

Dropping 2.5 volts I think you have a battery problem.

When my battery is fully charged the current is about 3.8 amps (about half the rated current in the manual). The fridge draws less current when the battery is low, about 2.5 amps.

Your 50L fridge is only drawing about 4amps when running, not the, about 6.5 to 7amps rated current in the manual.

I've done endless testing with a clamp meter & also have an inline amp meter so have a pretty good feel for what the fridge uses.

What gauge wire are you using, & how many metres, there & back, ie + & - !

Baz421 · Guru

Whenarewethere wrote:
The Waeco 28L fridge I have has a compressor actually not much smaller than the larger fridges. Voltage drops about 0.5 volts when running off 78AH of 12 volt batteries only.
Dropping 2.5 volts I think you have a battery problem.
When my battery is fully charged the current is about 3.8 amps (about half the rated current in the manual). The fridge draws less current when the battery is low, about 2.5 amps.
Your 50L fridge is only drawing about 4amps when running, not the, about 6.5 to 7amps rated current in the manual.
I've done endless testing with a clamp meter & also have an inline amp meter so have a pretty good feel for what the fridge uses.
What gauge wire are you using, & how many metres, there & back, ie + & - !

Thanks for post. problem is not battery,,, as solar and 240v charger provide constant voltage at fridge. Turn on more load and no voltage drop,,,just damn fridge.

Companies useless here in Western Melb , all too hard ,,, going to Shepparton tomorrow,,, found a fridgie who is experienced with 12v(after 3 attempts - at least they were honest enough and said they were 240v guys not enough experience with 12v controllers). Cheers

Peter_n_Margaret · Guru

Baz421 wrote:
Yes drops to 10v,,,,,at fridge. Battery 12.5v before fridge tries to start

If the battery stays at 12.5V at this time, it is almost certain that your cables are too small.

Cheers,

Peter

DeBe · Guru

Yes drops to 10v,,,,,at fridge. Battery 12.5v before fridge tries to start . If the voltage at the fridge is 12.5V then drops when fridge trys to start, then the wiring is too small.

-- Edited by DeBe on Monday 6th of May 2019 07:26:30 PM

Whenarewethere · Guru

I'm using 6awg & only have a short run loosing about 0.2 volts. I upgraded the wiring within the fridge from 16awg to 12awg saving about 0.17 volts. You will loose about 0.2 volts from the standard Waeco 1.5 metre lead, so cut it as short as possible as in the photo. I put a circuit breaker in the fridge, not shown in this photo.

Aus-Kiwi · Guru

Did similar to above . Used longer cable with Anderson plugs, twice the wire size that came with fridge as the cable was 4m long . We move it around in various locations . Originally I had extension on original lead . Too much voltage drop., Intersting the V difference at board & fridge . In one case recently it was defective fuse !! One has to be observant!! Jack or Jill of all trades !

Brody · Newbie

Hi guys slightly off topic, but in regard to the danfoss control unit- ive recently replaced the thermistor in my waeco cf-35. Im now getting three flashes error code so im thinking the control unit could be gone. Has anyone got a good photo showing all of the wires connecting to the danfoss unit (pref cf-35) i forgot to take one before! and want to be sure ive reconnected correctly before more troubleshooting. Many Thanks Brody

Baz421 · Guru

Peter_n_Margaret wrote:
Baz421 wrote:
Yes drops to 10v,,,,,at fridge. Battery 12.5v before fridge tries to start
If the battery stays at 12.5V at this time, it is almost certain that your cables are too small.
Cheers,
Peter

Same wire for 12 years now,,, never had this problem. Just had fridgie put new controller in and test,,, not controller. He said wiring good for the job.

-- Edited by Baz421 on Tuesday 7th of May 2019 06:02:33 PM

Baz421 · Guru

Aus-Kiwi wrote:
Did similar to above . Used longer cable with Anderson plugs, twice the wire size that came with fridge as the cable was 4m long . We move it around in various locations . Originally I had extension on original lead . Too much voltage drop., Intersting the V difference at board & fridge . In one case recently it was defective fuse !! One has to be observant!! Jack or Jill of all trades !

Yeh I took the fuse out of the equation too no different. Still scratching my head, why OK for 12 years and now a problem.

Cleaned terminals on fridge controller traced wiring all looks good, clean tight connections

Thinking the earth may be a problem,, as I've concentrated on + wire so far.

Fridgie couldn't find a problem so I go backwards from fridge with earth wiring.

Cheers

Baz421 · Guru

Brody wrote:
Hi guys slightly off topic, but in regard to the danfoss control unit- ive recently replaced the thermistor in my waeco cf-35. Im now getting three flashes error code so im thinking the control unit could be gone. Has anyone got a good photo showing all of the wires connecting to the danfoss unit (pref cf-35) i forgot to take one before! and want to be sure ive reconnected correctly before more troubleshooting. Many Thanks Brody

Danfoss manuals are online, easy to find

.

Peter_n_Margaret · Guru

Look for some other high resistance in the lines. Is there anything warm?
Cheers,
Peter

Baz421 · Guru

Peter_n_Margaret wrote:
Look for some other high resistance in the lines. Is there anything warm?
Cheers,
Peter

Thanks peter am doing that,,, maybe do again I guess. What do you think chances of an earth problem.

Peter_n_Margaret · Guru

Baz421 wrote:

Thanks peter am doing that,,, maybe do again I guess. What do you think chances of an earth problem.

A resistance in the earth has the same effect as a resistance in the active cable.

You could experiment by running new heavy temporary cables, both +ve and -ve (one at a time, then both together) to check what the effect is.

Cheers,

Peter

Baz421 · Guru

Peter_n_Margaret wrote:
Baz421 wrote:

Thanks peter am doing that,,, maybe do again I guess. What do you think chances of an earth problem.
A resistance in the earth has the same effect as a resistance in the active cable.
You could experiment by running new heavy temporary cables, both +ve and -ve (one at a time, then both together) to check what the effect is.
Cheers,
Peter

Yes been doing that,, I was alluding to a earth problem between batteries - solar controller - and fridge.

Anyway direct wired fridge to existing solar + and - load connections AT VAN ie the common connections,, same result.

I'm not sure if I have the right compressor controller as the pdf download says the 600 is not for my compressor BUT I can't fully understand the tech stuff.

Thanks for assistance Peter

Aus-Kiwi · Guru

Run a temp lead back to neg battery terminal ? Jumper leads etc ?? I found with my spot lights .. The earth or - was restrictive . I just earthed at last light . Fixed ., In this case with HID the start up current- voltage drop the HID light at the end of circuit wouldnt start !! Is the frame or chassis the earth ? This is possibly the issue here IF theres other load on circuit ?

Baz421 · Guru

Mysteriously,,, solar controller load on/off switch seems to be working now, don't know why but voltage drop today was 0.2v.

Previous unit that failed at Easter wouldn't charge at all load or battery.

Maybe there is a problem with load on/off function at the controller.

Thanks for all ideas,,,, see if it's working OK in the morning xxxxx fingers.

Cheers baz

DeBe · Guru

I personaly would not be using an internal load switch on a Solar regulator to run a fridge.

T1 Terry · Guru

If you use the load terminals to drive a relay rather than trying to power the fridge through the controllers transistor you will have more luck. The stall current required to start up the 12v compressor can be quite high, only short term load but transistors don't understand short term, only peak load and after that the fail. I've seen a Plasmatronics 20/20 burn out the 20 amp load transistor running a 225ltr Waeco fridge, the numbers don't add up but the transistor and circuit board said it couldn't handle it.

T1 Terry

Baz421 · Guru

Thanks guys I'll look to change fridge off load. Cheers

Peter_n_Margaret · Guru

DeBe wrote:
I personaly would not be using an internal load switch on a Solar regulator to run a fridge.

Depends on the regulator.

I have two Danfoss BD35 compressor fridge units (one fridge and one freezer) that have been running directly from the PL60 load terminals successfully for 14 years.

Cheers,

Peter

T1 Terry · Guru

Peter_n_Margaret wrote:
DeBe wrote:
I personaly would not be using an internal load switch on a Solar regulator to run a fridge.
Depends on the regulator.
I have two Danfoss BD35 compressor fridge units (one fridge and one freezer) that have been running directly from the PL60 load terminals successfully for 14 years.
Cheers,
Peter

PL60 has a load current rating of 30 amps, the newer Pl80 load rating is 40 amps. The PL20 has a load rating of 20 amps, yet the PL40 is only rated at 7 amps, so the actual rating of the load circuit is very important. The stalled rotor current for a BD35 would be a lot smaller than the stalled rotor current for the BD50. Much easier to shift the load to a relay, cheap and easy to replace, not like the circuit board and transistor in the solar controller ....

T1 Terry

KevKim37 · Senior Member

Hi Baz421,

Did you find the voltage drop problem.

If not, my advice is too Turf the useless, overpriced Mobitronic auto changeover unit.

These have too much internal voltage drop/resistance problems to run the 12 volt side.

Test your input and output volts at the unit terminals.

I fitted heavier gauge wire to our 220 litre Waeco Coolmatic compressor fridge 7 years ago and it still didn't correct the problem.

On further testing found approx 2 volt drop at the Mobitronic output terminals.

I bypassed it and no more problems.

I then purchased a Jaycar Powertech 12 volt/12.5 amp Power Supply unit for $119 and it has worked great ever since on 240 volt mains.

The only problem with this unit is that it isn't an Auto Changeover unit.

I've had 3 of the Mobitronic fail in the early years.

Cheers Kev. (2K's from Home).

-- Edited by KevKim37 on Saturday 18th of May 2019 02:38:10 PM

-- Edited by KevKim37 on Saturday 18th of May 2019 02:39:03 PM

Baz421 · Guru

Thanks Kev,,,, voltage drop is still 0.2v,,,,, the load switch seemed to be the problem on the Powertech solar controller,,, stays on load ok now. No voltage drop across Mobitronics.