Waeco Polyfuse CF50

Mine has the seven lights but also has both the DC and AC sockets. My understanding is that it is my model that has the problem. The model before (no AC) and after (digital settings) mine don't have the problem.

I don't know if this might be the issue yet as I am going down the path of experimenting at this point.

When I try to measure battery voltage while the fridge is connected on a very short lead (say 1M from battery to fridge) the battery reads anything from 12.3V to 12.8V checking every five minutes. Battery was fully charged when connected. It is only a 18ah jobby so it won't take long to see where the waeco cuts out.

Next step will be upgrading the wiring and plug to the back of the wagon.

You need to check voltage while the fridge compressor is running.

Yes that is correct12/240v have a polyfuse (7 lights). The 12/24V don't (5 lights).

Dumb Question for you.

What is the best way to check voltage drop with everything plugged in and there are no exposed wires? Stick a couple of pins through the leads maybe.

BTW I am a DIY junkie however I wreck most things I have a crack at so have to be selective. $1,000 fridge frightens the !@#$%$^ out of me.

Not a dumb question and the idea of sticking pins through the two wires is an easy solution. (Sorry. Your idea isn't original!) Dress makers pins are best, spaced an inch or 2 apart so that they can't short together. Best to do this after disconnecting the 12V. The holes close up again when the pins are removed, but a smear of silicon next time you're using some is a good idea for waterproofing.

Obviously you don't do this with higher voltages! Could be a health risk.

Cheers

John

Dumb question? No such thing. Only answers and people (ie - not J&V!!).

To expand on the above...
Just a teeny weeny little bit...

Pins are fine - more below.....

For the record.... ideally an extension cable with taps/junctions etc.

Noting that all suggestions below are for this low voltage 12V DC example only - not AC systems etc.... (Yes John!)
And the next two text blocks can be skipped of you think pinning or wire-wrapping is achievable.

Where fuses are user replaceable, it can be "tapped into" with a thin wire etc - usually that's in the +ve supply (and -ve/gnd/earth is the metal chassis) - BUT that can be awkward, and if you do NOT know the internal connections, how do you know any drop is not caused by internal switches etc. Though fuses are usually the first electrical item - even before power switches.

Then there is the flying lead method - pins, nails and jumper-leads with alligator clips etc.
The main hazard is accidental shorting of the +12V & ground, but an upstream fuse should blow if the jumper lead doesn't melt & flame first (if the short is downstream of the jumpers - ie, at the fridge).
Another hazard is underrated jumpers that can get hot (and flame & melt insulation etc), but the ~5 Amps involved should be ok.
BTW - the voltage test is done at the end of the cable - not at the fridge: You are not interested in the voltage drop from the jumpers (unless it is so bad that the fridge does not operate).


Then the wire-wrap method: With THIN wires, wrap their conductors around the load's connector pins (since all loads should have male connections).
Insulated wires may not be necessary if there is no chance of shorting to chassis or each other.
They need to be thin enough to enable the power socket (lead) to be inserted properly.


Then, lastly, there is someone's brilliant suggestion of inserting pins....
This should not be done on voltages higher than (say) 50V.
This is probably the most common method used by the experienced that do not have a proper junction/splitter, and by clever else stupid DIYers.
If it is obvious which part of the cable is +ve and -ve it should be fine.
You then stick a pin through each insulation to hit the conductor (or pass through).
But do NOT pass a pin through one conductor into the other - that's a short circuit. Even though that should blow the upstream fuse, there is the ongoing problem of the insulation hole between the conductors, and possible contamination....
But other insulation holes can be plugged etc (silastic maybe?).
NEVER do this for domestic mains and other hazardous voltage appliances!


Above are the 5 common methods - the first is "approved"; the others may not be. And those others have their hazards.
BUT, the load/fridge itself should NOT be damaged by those hazards.
IE - the hazards involve shorting BEFORE the load. This is normally ok - you may blow the crap out of the battery or upstream distribution (fuses, cabling), but the load should be fine. Exceptions may include loads with large capacitors (ie, audio systems), and where repeated shorting occurs (ever heard "maybe a short blew your light bulbs"? - how does a short blow light bulbs? - except through repeated shorts or intermittent bad contacts that cause excessive thermal cycling etc... LOL (excluding inductance)).

Hence ensure a reasonable sized fuse - say 5 or 10 Amps - enough to handle the fridge and any inrush current.

If a short does occur, there can be sparks, flying plasma & noxious fumes. Wear safety glasses. Consider a suitable fire extinguisher. Update your insurances or Ambulance Subscription. And Will.

And be aware that voltage measurements do not involve large currents - a hair strand of copper will do.
A typical powered DMM measuring 12V takes well under 1uA (one-millionth of an Amp).
Hence pins and tap-wires can be as thin as anything. If they break, you will measure zero or random voltages.
Being thin means a small current to blow the short. Hence skin and carpet burns won't be as bad. (Do not do this near unlit gas-venting stoves, near petrol-station vent ducts, in wheat silos etc.)


Too much ramble? You confessed to being and avid DIYer, so I gave you the lot FYI. (Good - there are like-minded people on this site! At least DIY minded - but maybe far more concise & verbally gifted!)
Assume the standard no-care and no-responsibility riot act (even if it means nothing LOL!).

Unless you are plagued by heaps of disasters, try it.

Next step - WHERE are the voltage drops - grounds? +12V? Protection (fuses/breakers etc)?

Hi Chip,

We've tested our CF50 on a number of occasions on low cutout (apparently 10.5v) and it showed that if my battery is at 11.6 V the fridge will cut out so in our system the voltage drops is about .9V.

I don't like taking the battery below 11.6 anyway so I'm happy with the high cut out voltage.

If we do run out of power we'll run the car for a while. We usually drive somewhere every few days so It's never been a problem for us with a 105Ah Battery.

Regards
Geoff

Thanks Geoff.

"I don't like taking the battery below 11.6 anyway so I'm happy with the high cut out voltage"
..... LOL! Only yesterday I was reading of someone that wanted to bypass the low-volts cutout altogether (obviously shutting off to often) - and I'm thinking that maybe the cutout is to protect the compressor - not the battery! (If it uses an internal inverter, you'd think they could operate far lower.)

I agree with the battery not going too low. But that's the battery's open-circuit voltage - it will be lower with a load.
[ I was surprised recently when a 7mOhm internal resistance (fully charged) AGM dropped from 12.7V to about 11.6V with ignition and headlights on - that's about ten-times what I expected. But she got home without an alternator with 11.0V measured ~1 hour later. This proved to be ~12.0V open circuit; hence the ~50% capacity I did expect from its estimated load. Batteries - as far from science as Biology LOL. ]

The good thing is that reducing cabling drops is usually easy - double up the cabling to half the voltage drop.

I use a dual-battery setup so the inter-battery voltage drop not such a problem (2nd battery in the rear nearer my 60W cooler).

I will be considering a ~110AH deep cycle. My 40AH batteries are somewhat limiting..... Tomorrow's 4t Aldi winch will discharge my 38AH AGM in ~10 minutes without a load! 5 minutes merely pulling my static 1t vehicle!
But of course I won't use polluting petro-chemicals to recharge my batteries. Hence I have decided to interface an alternator to my pushbike, and bring my girlfriend along.

Thanks HL. After 10 mins turbo the fridge did not cut out on full bore so I'd say the fridge is not the problem. Although on three lights it will put an ice chill on a stubbie which might be a thermostat problem unless others might think this is normal.

Next job is experimenting with the vehicle auxilliary wiring.

Can someone explain though why the voltage at the battery falls when the fridge is cycling. Not really a fridge question or a voltage drop question I don't believe. At the battery's current state it drops from 12.8V to 12.3V when the fridge cycles. What is the battery doing here and what useful information is this giving me if any? Power usage maybe? I undertand it is during cycling that all the voltage drop measurements should be taken/become meaningful.

Hi...
Mine does the same, with 3 lights on it will go down to Zero in the bottom of the fridge....
The voltage drop you are seeing at the battery is quite normal too, as the fridge can draw up to 6 amps when it is running (hence the problems with the polyfuse which were originally rated at 5 amps)

Internal battery & cell resistance, and the cells reduce voltage when they supply the charge.

has been going for 13 hours now and battery down to 12V under load.

I wonder what the result would be in 30 degrees ambient.