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What is the power supply capacity of the Blue Smart IP65 12/15? Can it be used as a power supply for a 12V Dometic CF18 portable fridge / freezer? Dometic's Mobitronic MPS-50 mains rectifier has a 6 amp output @ 24V. Since the fridge is rated 7A, I suppose the additional MPS-50 capacity (150 watts) is needed for compressor surge.
The CF18 requires 7A @ 12v according to its spec sheet. The blue smart 12/15 can go up to 15A @ 12v. So on paper, without looking at surge, it looks ok as is. I don't know if the CF18 has a ramp up feature for the compressor, but if I had to guess surge is unlikely to be significant issue with a small DC compressor.
EDIT: was a little cavalier with surge assumption. A more conservative approach would be as Justin suggested in the thread to not run compressors off a power supply directly. If you do want to do so, you would have to consider/assess the surge required by the controller unit that drives the compressor (e.g. the 101N0xxx unit for the Danfoss BD series), and the actual short term response of the power supply. Need to have a DSO or similar to catch the inrush for that.
I have an issue with this. I tried to use my 12v10A charger as a DC supply for a waeco fridge with BD35 compressor. The fridge would not start, instead flashed the error light twice which indicated overload on the fan circuit. Disconnecting the fan made no difference, leading me to believe that the compressor controller had a fault. Of course I tested the voltage being supplied by the charger at the fridge terminals - 13.5v so I didn't give the power supply a second thought in my quest to "fix" the fridge. $200 later for a new compressor control module, same fault. It took me days of tinkering to come back to the supply source. Connected a battery between the charger and the fridge and viola, it works. Checked to power supply on a different fridge, an everkool with the same compressor, and got the same two-flash error.
So even though the charger can supply 10A, there's something about the way it supplies this that makes the fridge go into error mode.
Bit disappointed as that was one of my preferred features of a smart charger, that I could run this fridge on the back verandah as a drinks fridge without needing a battery.
You're right if the system can run off a battery then its indicating the charger is not supplying the required power (whether its a momentary startup surge or ongoing). That being said, 10A is 10A so if you can confirm your power supply can hold 12v at 10A output then there's something really odd going on.
There's more than a few threads on BD35 on boat forums because its a staple for lots of onboard fridges, e.g.
http://www.ybw.com/forums/archive/index.php/t-502988.html
I'm not sure whether you want to try to get your smart 12/10 to work or is "ok" with a battery solution. Suggest creating a new thread with as much info as you can provide if you want to ask the hive mind.
@jfeiman @Andrew1964, it's very relevant here that although the chargers can put out a sustained "x" amperage, using them as a power supply for a motor/compressor/etc is inadvisable because the momentary startup current requirement of any motor will easily be 3-6x the rated draw. This is why when @Andrew1964 connected a battery in between the fridge and charger it worked fine, because the battery acts as a cushion for the momentary inrush current of the fridge compressor starting up.
An example of this is, say, the starter on my truck pulls 160A... but the inrush current is 516A for about 50ms. If you purchase a DMM capable of measuring inrush current, you'll find the same thing with your various motors including fans, compressors, and etc... the motor may only need 6A of current to run, but the inrush current to start it from a dead stop will easily be 20-30A, which of course exceeds the output capacity of your charger, and as such -as a general rule- it will not work as a power supply for this particular type of DC load.
OK, thanks @Justin Cook, that makes sense. I used to have a 10A Ctek charger and it would handle it no problems, so I'm now wondering why the victron can't or won't do it, and whether there's any software update that would enable it to overclock the current momentarily. Or am I stuck with using a battery now? Maybe some input from victron tech support? I can't be the only person to be caught out like this!
@Andrew1964, the thing is, what you're viewing as a fault in behavior when using it as a power supply is actually a statement of its proper engineering as a battery charger, which is of course its sole design purpose - the ability to use it as a power supply for small loads is entirely incidental to its primary design.
The thing is, if the charger has the ability to produce a surge to power a load, then it also has the ability to produce a surge into a battery, which -depending on the size and chemistry of the battery to which it's connected- could have disastrous results. That's why I say that the fact that this charger won't do that is a testament to its proper engineering; the current is held to its rating, which is exactly what it's supposed to do.
I'm curious as to why you didn't just buy a power supply, if that's what you were intending to use it for?
"I'm curious as to why you didn't just buy a power supply, if that's what you were intending to use it for?"
Well, I used to have a power supply for it but it died and Waeco wanted an insane amount of money for a new one. The 10A Ctek charger I had also had a power supply mode which worked with the fridge so I just used that on the small number of occasions I needed to without any problems. When it also died and I ended up with a Victron instead, I naturally thought it would also do the job of two separate devices ie charge and power supply. So no, I didn't buy it just to be a power supply, the victron is primarily my battery charger but I was under the much mistaken belief that it could do both.
Ah, I see... well as I commented to the OP on this thread, if you run your fridge off the battery and just leave the charger plugged in charging the battery, you're effectively doing the same thing... just still using the battery as the surge cushion.
I got the Victron IP65 charger for the task of charging a battery off AC. I got the Dometic fridge to keep food cool using 12V DC. Then I thought it might be convenient to be able to use 120 AC occasionally for that task. So the idea of using the charger came after the facts. I knew a fridge compressor would pull more than steady state amps when starting, but did not expect the 3x-6x magnitude mentioned by @Justin Cook. Specs for the IP65 do not call out a maximum current, only a charging current (15 amps). I'm not going to risk blowing the charger electronics, or worse yet, somehow damaging the fridge electronics. There might be a reason Victron doesn't sell a female 12V adapter to go with the charger (I had to build my own). I don't need to run the fridge with AC - it might be convenient, but I can let it go. Or save up the $80 to get the rectifier Dometic sells to do the job.
Thanks all for the discussion!
@jfeiman, yes, the 15A is the maximum current; technically you don't ever want a battery charger to be capable of putting out a surge (except for those ones you can use to jump-start your car) because a charger capable of putting out a surge is also capable of putting that surge into your battery, which depending on the type of battery could have disastrous results.
Best bet is to run the fridge off the battery while you're charging the battery with the charger, and you're effectively running the fridge off of AC then... not exactly, but effectively.
