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Old 28-07-19, 21:27
scouse_surfer scouse_surfer is offline
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Default Fridge not working from battery

I have an issue with the fridge in my van. It’s a Waeco crx 50. It isn’t working on the leisure battery, it only works when I’m plugged into 240v hook up. It isn’t working when the engine is running either. The light inside it works, and the fridge sounds like it’s trying to work. The battery seems to be full charged and does work to power other items. Does anyone know if this might be a problem with the fridge or battery? The battery is around 2 years old so I’d like it think it’s still good. I was under the impression that these fridges worked off 12V only, so the hook up charged the battery, which in turn powers the fridge? Or is there a separate 240v and 12v supply depending on whether you’re using the hookup or battery? Thanks in advance for any information you may have
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  #2  
Old 09-08-19, 18:52
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T10ery T10ery is offline
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My fridge has a switch at the back which is used to select either 240 volt or 12v
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Old 09-08-19, 18:57
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T10ery T10ery is offline
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Oh and two separate supplies which need to be wired in. 240v via a fused supply to your hookup and the other again to a fused 12v supply to your leisure battery.
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  #4  
Old 09-08-19, 19:27
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Hoovie Hoovie is offline
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Default Re: Fridge not working from battery

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Originally Posted by scouse_surfer View Post
I have an issue with the fridge in my van. Itís a Waeco crx 50. It isnít working on the leisure battery, it only works when Iím plugged into 240v hook up. It isnít working when the engine is running either. The light inside it works, and the fridge sounds like itís trying to work. The battery seems to be full charged and does work to power other items. Does anyone know if this might be a problem with the fridge or battery? The battery is around 2 years old so Iíd like it think itís still good. I was under the impression that these fridges worked off 12V only, so the hook up charged the battery, which in turn powers the fridge? Or is there a separate 240v and 12v supply depending on whether youíre using the hookup or battery? Thanks in advance for any information you may have
The CRX-50 is normally a 12V Fridge only. You can get a 240V to 12V adapter for these which you may have.

Possibilities:
1) The Mains Adapter works by detecting when mains is available and uses the power via the adapter, and if mains is not detected, uses the battery power instead.
The auto-switching may not be working? But I would have expected no light in that case?

2) The Battery Voltage AT THE FRIDGE is not high enough to start the fridge compressor. A compressor fridge requires a BIG current to start and that causes the voltage to drop on the supply cable to the fridge. The thinner the cable, the bigger the drop.
It may be working when on the mains as the battery charger is stopping the voltage dropping below the level the fridge doesn't like.

Things to try:
Turn the fridge on when the mains is on. Then disconnect the mains supply while the fridge compressor is running (put the fridge at the coldest setting before pulling the mains to extend that time).
Does the Fridge carry on running or does it go off immediately? if it carries on, will it stop working the next time the compressor has stopped and tried to restart?

Plug the mains in but turn off the battery charger - doing this will have no affect on the fridge if it is using 240V input. If the fridge no longer starts even if the mains is connected then the fridge IS using 12V only.

Reason why the fridge won't start even though battery seems good? Inadequate cable gauge. The Fridge Spec says something like "3A when running" but doesn't mention very clearly the way bigger current spike when starting and many fitters use cable to deal with the 3A as they know no better.

You have given no info about the engine running bit other than it makes no difference - I guess you have a split-charge setup of some time. Have you checked the lesiure battery voltage when at rest, when engine is running and when the mains is plugged in? what are they?
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Old 11-08-19, 08:44
cl51ffe cl51ffe is offline
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Default Re: Fridge not working from battery

Great piece of information Hoovie ,

Do you know what is the lowest the leisure battery voltage can drop to before the fridge won't work ? Mine is also a weaco but as it's been hijacked by my daughter and is at the Harwood house vw show I don't know the model
Thanks

"It's only the help that matters"
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  #6  
Old 11-08-19, 10:30
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Hoovie Hoovie is offline
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Default Re: Fridge not working from battery

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Originally Posted by cl51ffe View Post
Great piece of information Hoovie ,

Do you know what is the lowest the leisure battery voltage can drop to before the fridge won't work ? Mine is also a weaco but as it's been hijacked by my daughter and is at the Harwood house vw show I don't know the model
Thanks

"It's only the help that matters"
Harewood House is a great show What a bummer about the weather

The fridges have a built-in low-voltage non-start that is actually put in place to protect the battery, which is a great idea but if the wrong cable is used to run to the fridge, it is the fridge that stops working. I had a look at the manual and all it says if voltage is "too low" but without a value. I have in my head 10.6V for some reason but don't know if that is right or not . It sounds very low but this is why even a voltage that low that can be a problem for an installation ...

You can find various voltage drop calculators on-line that dramatically illustrate why cable gauge can be so important. Here are some numbers from one of them.
Example - the CRX50 is rated officially by Weaco and declared in the manual as needing a supply rated at 5A (and really draws around 3.5A). a 1.5mm cable can supply 5A all day long If the battery was at 12.5V (pretty decent level, yeah?) and the cable from supply to fridge was 3 Metres (round trip distance so not that unusual at all), you would end up with around 12.2V at the fridge while the compressor was running and drawing 5A. That's fine

But when the fridge starts, the in-rush current is way higher that this 5A - could easily be 50A (My own 240V AC compressor fridge draws ~40W running but when it starts up hits up to 800W for a second or so!). Put 50A through a 1.5mm cable and it is perfectly fine for a few seconds but ... the voltage drop goes from a 0.3V drop to a 2.9V drop on a 12V system . That means you are now only seeing 9.6V at the fridge - not enough for the Fridge to want to start.
This is why thick cable is needed even though the device draws a low current for 99.9% of the time.
Upgrade that 1.5mm cable to 4mm and the voltage drop goes from 2.9V down to 0.4V. So the fridge sees around 12V from your battery. If you have a 3 Metre cable run, using a 6mm cable would be even better and the voltage drop would be under 0.2V.

So the eventual answer to your question "Do you know what is the lowest the leisure battery voltage can drop to before the fridge won't work ?" is it depends
How long is the cable from battery to Fridge and what gauge is it? the shorter the cable and the thicker the cable, the lower the battery can be and still allow the fridge to run.


It can be hard to spot the spike with a multimeter and when measuring the voltage at the fridge as it is so short - especially if the voltage ends up being too low to start the fridge.

To capture it, I filmed a battery monitor that was connected in line between my battery bank and my inverter to record the spike on my 240V SC Compressor Fridge.
Video starts at 0.45. check out the power jump and voltage drop at around 0:52 when the compressor kicks in and then the recovery when it is just running as normal.
https://youtu.be/T35lOd_prY4?t=45
I am using 16mm cable here from battery to the Inverter and I am still getting a big voltage drop. The inverter is a 400W unit and it is that inverter that makes the noise (not the fridge) as it goes into peak load mode to deal with this spike in power (the inverter is designed to work at upto 900W for upto 30 seconds, so this under 2 second overload is nothing to it)

Last edited by Hoovie; 11-08-19 at 10:33.
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  #7  
Old 13-08-19, 21:54
cl51ffe cl51ffe is offline
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Default Re: Fridge not working from battery

Thanks hoovie I get the gist of it and can see why they don't give you a precise voltage cut of point

My controller knocks every thing of if the voltage drops below 10.5 v but while away the battery showed 11.7 v after a short run but the fridge was of but I take it you meen it needs a greater voltage to start it back up then needs a lower voltage to keep it running

" it's only the help that matters"
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  #8  
Old 13-08-19, 23:13
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Hoovie Hoovie is offline
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Default Re: Fridge not working from battery

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Originally Posted by cl51ffe View Post
Thanks hoovie I get the gist of it and can see why they don't give you a precise voltage cut of point

My controller knocks every thing of if the voltage drops below 10.5 v but while away the battery showed 11.7 v after a short run but the fridge was of but I take it you meen it needs a greater voltage to start it back up then needs a lower voltage to keep it running

" it's only the help that matters"
Without being overly pedantic, not the voltage but needs a greater current to start it then to keep it running. But as I said above, in ELV systems like a Campervan, a higher current does result in a bigger voltage drop in the cable so I guess you could say you need a higher source voltage to counter that drop

Where the higher current becomes critical is if you run a 240V Fridge like I do off an Inverter. even though the fridge draws under 40W when running, you need a much bigger inverter than than to cope with the high in-rush current - one that can reliably deliver nearly 1,000W for a device that needs just 40W to run Frustrating on one hand, but on the other, you can buy a decent suitable inverter with the money saved by not buying a 12V Compressor Fridge and still have lots of change for beer to put in it
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