Waeco CF35 - Voltage Drop Problem

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onewheeltoofew
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Waeco CF35 - Voltage Drop Problem

Post by onewheeltoofew » Tue Jun 25, 2013 10:59 am

Hi,

Just a quick question to try and sort out what is going wrong with my waeco CF35fridge. I had quite a big voltage drop running to my fridge making it cut out quickly if running from the leisure battery alone. So after checking with an online voltage drop calculator, I rewired the connection with 6mm square cable. The run is about 4 meters from battery (it's actually the load output from a solar charge controller-which is only a matter of feet from the battery) to connection, but I'm still seeing a large voltage drop! The battery is in good condition but the output at the DIN connector, that the fridge plugs into, drops to around 11.6v when the compressor kicks in with it's initial load. Obviously, it won't run for long before the low voltage protection cuts in and turns the fridge off. What size cable do others use to run their fridges off the battery? Anyone got any other ideas for me to try, it's drying me potty!

TIA

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Re: Waeco CF35 - Voltage Drop Problem

Post by roosmith » Tue Jun 25, 2013 12:08 pm

I'm afraid I don't have answers however I do have the same fridge. I initially had similar issues when using the fridge through a 3 way adaptor, from the back socket. I also have solar panels but connected to leisure battery, then the original cabling to the rear socket. The adaptor was too clever for its own good and it was cutting out when the compressor cut in, as it saw the voltage drop. For me, I took that out and plug in directly it works just fine.

I haven't measured mine but I don't think the voltage drop you're seeing would be unusual when the compressor cuts in, momentarily at least. Does it not pick up again after starting up, or does it cut out immediately? Also which setting do you have the fridge on (high or low battery protection)?

Hope you get it resolved. Our first trip away before I discovered what was wrong with mine was very frustrating. On the drive there I had the setting too low and everything froze, then everything defrosted again with the 3 way adaptor issue! I know how frustrating it is to pay for panels, then a fridge, then for it not to work!!
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onewheeltoofew
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Re: Waeco CF35 - Voltage Drop Problem

Post by onewheeltoofew » Tue Jun 25, 2013 4:22 pm

Thanks for the help and its given me something to check, perhaps it's the solar charge controller cutting off the juice when it detects the drop...?

I've set the fridge to cut of at the low position but due to the drop it's not low enough! and the drop seems to be pretty constant after the compressor starts up...well until it cuts out again! It's very odd as the cable is pretty hefty now, certainly bigger than the original stuff that you've got your's working off.
I've never tried it from the rear socket either though (mine's connected to a socket I put in the side conversion) so I'll give that a go too.
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Re: Waeco CF35 - Voltage Drop Problem

Post by mikexgough » Tue Jun 25, 2013 5:08 pm

I run my Waeco CF-18.... similar "kick" on start up to the 25/35 models as they use the same compressor.
Mine is wired direct to the Leisure Battery via a 10 amp fuse....and I used 30 amp cable... The socket I use is built into my rear kitchen and I guess 3 metres ish run
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Re: Waeco CF35 - Voltage Drop Problem

Post by windywatson » Tue Jun 25, 2013 6:20 pm

Hi,

The voltage drop your measuring at the battery I take it?
It's not the cable your using causing the voltage to drop to 11.6 volts, but the load of the fridge ie the current being drawn that is doing it.
It is the internal resistance of the battery when placed under load that causes the voltage at the battery terminals to go low. This happens with all batteries to some degree, dependent on type etc.
The voltage your seeing is not unusual, I would wire the fridge via fuse and any switch you may want to use directly to the LB & this will be fine.
Where your getting confused is that if your using to small diameter cable & pulling large currents throgh it, the cable can then cause a volts drop (as its own resistance will be high) that would give you a low volts reading at the load end compaired to the reading at the source. Hence the term Volts Drop.

Hope this helps.
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onewheeltoofew
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Re: Waeco CF35 - Voltage Drop Problem

Post by onewheeltoofew » Tue Jun 25, 2013 10:14 pm

Well that was an unusual problem to solve.

I was measuring the difference between the terminal voltage and the voltage at the din plug that the fridge will see. With the original wiring I would see a ~0.5volt drop at the terminals (to around 12.4v) when the compressor came on, this would drop to around 11v at the plug.
What I couldn't work out was why the new fat wiring wasn't making things better. However,what I didn't originally mention, as I was doing a bit of rewiring I took the opportunity to move (to make battery charging more efficient) and change the solar charge controller to a fancy one with a remote display that lets me keep an eye on the Ah and get a feel for how charged the batteries really are. What I hadn't done was turn the load output on properly! #-o It's a bit unusual as the load gives some output when off (around 11.2v...sound familiar) but gives full output when turned on properly. Now with no real significant voltage drop.
So,turn on the fridge...leave it a bit to check it's all running fine...and it starts cutting out intermittently again!
I get desperate, start wiggling wires and checking connections, all fine till I get the 12v connector on the back of the fridge. Give it a bit of a jiggle and the fridge starts to turn off and on. So, out with the screwdriver, off with the plastic cover for the compressor and there you have it, a split in the solder attaching the positive lead to the back of the switch! Quick bit of soldering later and it's good to go again. This time without any cutting out 8)
So there you go, a dull tale of minor mystery involving utter stupidity solved by desperation and blind luck :wink:
At least I have a properly wired van that shouldn't lose too much hard won solar power to unnecessary voltage losses.

Thanks for everyone's help.
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Re: Waeco CF35 - Voltage Drop Problem

Post by Dodgey » Tue Jun 25, 2013 11:20 pm

:-) Glad you got it sorted. The compressor fridges will not tolerate any bad connections or thin cables.

I've experimented and found, for the Bongo LB to half way down the length of the vehicle (i.e. a mid or side conversion) you need around 35-ish Amp cable (I've used 2 x 17.5Amp automotive cable successfully). The bigger the better really. As you go down in size the low voltage cut off of the fridge kicks in too early. Way too early.

Make sure if you are using the load outputs on a solar charger that the wires from the solar charger to the battery are also the same thickness.

The on/off element of these solar chargers is odd. If you read the instructions it actually tries to point out in "Chinglish" that the switch only affects the display and not the actual circuit - though I have found the same as you - if you turn the load off, appliances still work, but nothing heavy duty (like a fridge) will!
http://www.solarcampersolutions.co.uk Solar panel solutions for campervans
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Re: Waeco CF35 - Voltage Drop Problem

Post by Dodgey » Tue Jun 25, 2013 11:23 pm

roosmith wrote:I'm afraid I don't have answers however I do have the same fridge. I initially had similar issues when using the fridge through a 3 way adaptor, from the back socket. I also have solar panels but connected to leisure battery, then the original cabling to the rear socket. The adaptor was too clever for its own good and it was cutting out when the compressor cut in, as it saw the voltage drop. For me, I took that out and plug in directly it works just fine.

I haven't measured mine but I don't think the voltage drop you're seeing would be unusual when the compressor cuts in, momentarily at least. Does it not pick up again after starting up, or does it cut out immediately? Also which setting do you have the fridge on (high or low battery protection)?

Hope you get it resolved. Our first trip away before I discovered what was wrong with mine was very frustrating. On the drive there I had the setting too low and everything froze, then everything defrosted again with the 3 way adaptor issue! I know how frustrating it is to pay for panels, then a fridge, then for it not to work!!
Frustrating! - I'd be inclined to run a dedicated live back to your fridge (and run the earth to chassis). The standard wires to a Bongo 12v Socket won't let the fridge run nearly as well as it should do. They are far too thin.
http://www.solarcampersolutions.co.uk Solar panel solutions for campervans
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