Question on the Orion DC-DC Converters.
I am looking at a 24V IN-12V Out Converter for fairly small current output, but one thing that I need to check is one of the devices is a 12V Compressor Fridge. These Fridges have a pretty substaintial inrush current - what kind of peak/overload current can these Converters handle?
I use the Phoenix Inverters for 240V fridges and they are fine at handling big momentary surges. Can the DC-DC Converters do similar?
Hi W. The Orion-Tr's seem to be a fairly common model, so I've picked out this link just as an example: https://www.victronenergy.com/upload/documents/Datasheet-Orion-Tr-DC-DC-converters-isolated-100-250-400W-EN.pdf
There's some specs in there that might help you decide, also the V-sag cutouts and short-circuit A.
The nature of dc loads is that the V may sag if A is limited, but may well 'catch up'. Might depend on your load's protection too (if any).
I grabbed a 48/12-20 (240W) for my dc loads, and totally forgot about a 12V intermittent pressure pump I had, the start load of which was likely quite high. Never experienced any issues.
Thanks for the reply, John.
I've decided to go for the Orion DC/DC rather than the Orion-Tr as the current limit of 20A on the Trs seem a bit low.
This is going in a Live-in Van, with primarily DC loads, which could also increase and so 12V demand could increase. 70A will be more than enough for expansion and I am sure will also cope with the compressor in-rush (which can be surprisingly high. my 34W Fridge has an inrush of nearly 900W!)
And between the 40A and 70A units, I have now decided on the top-power 24/12-70A model now for a couple of reasons.
Make 100% to connect ground FIRST, or you WILL let out the factory installed smoke. Ask me how I know :(
I had a “helper” when I was doing some wiring, and he connected the positive cable first. Less than ideal results to say the least. Replacement unit functions flawlessly.
Make sure you breaker or fuse the input to the max power.
You could always add a 12V battery after the converter and it will buffer the inrush current. Plus, it gives some extended 12V backup in case the 24V battery shuts off.
Interesting point of the ground cable. I see it does make mention of this in the very small user guide but I shall remember this and also attach a label to it saying something like "fit first; remove last" as a reminder to the owner!
Interesting idea with adding a 12V battery :)
Ref Fuse - I do tend to go "fuse-crazy" as I do like to protect circuits. This is another one that needs a note for the owner - as a 24/12V DC-DC Converter will need a smaller input fuse than the output rating of the device of course, so it is important they don't think "70A output; 70A fuse". The documentation does not state a recommended rating. For a 24/12-70 with a max current of 85A and an efficiency of 92% I am thinking a 50A fuse would be the job.
I think I'm hitting a similar problem, and could use some guidance.
I have an Orion IP67 24/12-20 which did fine (apparently) powering a nominal 5.49A@12V portable fridge for a while, from the 24V house battery.
We upgraded to a new (larger) fridge, rated 11A@12V. I got a couple of "compressor won't start" warnings, and I think I'm seeing some indications of false starts in the current traces from the related SmartShunt--instead of the current going to a nice stable ~2A and there being a regular set of running/idle current plateaus and more or less regular duty cycle, I'm seeing more variation in the duty cycle and what look like some start attempts. I suspect that the overload protection is getting a work-out. The wiring is 10AWG and only about 4 feet from the converter to the 12V outlet, then whatever cord came with the fridge. The drop when running is only about 0.3V per the telemetry from the fridge; 12.4V when idle, 12.1V when running.
The 24/12-20 was, let's be honest, very inexpensive, and small enough to fit the space available. Can two of them be paralleled to the same load, possibly through a Schottky diode-OR? Or I could put a nice big cap, maybe 2mF-10mF, 25V, at the load end, but that has its own perils.
