fridge amps

[96terrano]

Ok so about to wire my 12S socket for my little Hyundai, what's the best amp wire to use for the fridge power feed? I've already got wire for the charging circuit as it came with the SCR for charging my AUX battery in the spare wheel well, but will need a permanent live for the fridge

Just want to know what the best amperage of +ve and earth cable I should use

Thankies!:D

[judd750]

depends on the fridge, absorption or compressor type ?

[SPARKIEDOO]

What the rating of the fridge ........you will find that on the Data badge :augie
Then you can work out what size of cable / fuse you will need :clap

[SPARKIEDOO]

depends on the fridge, absorption or compressor type ?

Don't confuse the boy :lol:lol

I was going to ask Ryan if he knows if what the Delta T is between Super heat & sub cooling ......but that may be a Question to far :naughty:naughty

[zippy656]

Caravan fridge pull upto 10 amps

15amp fuse is fitted

Use 20amp cable

[96terrano]

actually, i'll just use a 12v cool box when i go on camping holidays, they're about 10/15 amps i think, designed to run off a standard 12v ciggy lighter so will store that in the trailer :D

[96terrano]

Caravan fridge pull upto 10 amps

15amp fuse is fitted

not as much as i thoght then:)

[briggie]

current ( in amps ) is voltage divided by resistance ....... or power in watts divided by voltage .

[judd750]

i only asked as i fitted compressor type fridges in motorhomes i worked on last week,
don't know how they slept for the noise on a night !

[zippy656]

current ( in amps ) is voltage divided by resistance ....... or power in watts divided by voltage .

Its all triangles to me:naughty

[jims-terrano]

Its all triangles to me:naughty

Oh good one Zippy:thumbs

[jims-terrano]

Don't leave the fridge or cool box running direct from the car battery without the engine running.

[zippy656]

Oh good one Zippy:thumbs

Carfull.

I might try another joke

[jims-terrano]

Carfull.

I might try another joke

:doh

[96terrano]

Don't leave the fridge or cool box running direct from the car battery without the engine running.

no, will be running it direct from battery but relayed off the ciggy lighter, so ignition fed:thumb2,

[briggie]

no, will be running it direct from battery but relayed off the ciggy lighter, so ignition fed:thumb2,

ciggie lighter sockets are normally rated around 10 amps as far as im aware ..... best to check :thumb2

[96terrano]

ciggie lighter sockets are normally rated around 10 amps as far as im aware ..... best to check :thumb2

aye, but ciggy is suplying the low curent feed to the relay coil:thumb2

ohh and the 12S socket is all wired, didnt need to make use of all the terminals, just the earths and fridge, battery and some other stuff for the split charge

wiring courtesy of my old SWB terrano :lol

https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-ash3/577293_692839787410111_119140134_n.jpg

[solarman216]

the answer is so simple, run your fridge and monitor the voltage, 12 volt fridge requires 12 volts you will be surprised what size cable you need to supply this voltage at the length of run you need, voltage drop on even 2.5 sq mm cable will be high, and your average tow bar cable does get near this size, Rick

[96terrano]

the answer is so simple, run your fridge and monitor the voltage, 12 volt fridge requires 12 volts you will be surprised what size cable you need to supply this voltage at the length of run you need, voltage drop on even 2.5 sq mm cable will be high, and your average tow bar cable does get near this size, Rick

Yeah, ill be fitting onboard voltmeters in the dash for both the Hyundai's own battery and the boot mounted leasure battery

[96terrano]

Yeah, ill be fitting onboard voltmeters in the dash for both the Hyundai's own battery and the boot mounted leasure battery

Will I need really thick cable, also, what is voltage drop and how does it occur?

[solarman216]

depends on your fridge, if it is the 12v compressor type it will draw 5 amps, if you use say ( and I am generalising here, as I have not the numbers i front of me) 2.5 mm cable for the length of your car plus distance to fridge on van, starting at 12 v at the battery by the time it gets to your fridge you would be lucky to see 10 v, so increase the cable size to 6 mm you still will not see 12 v at the fridge but it will be a lot better, see wot I mean, Rick

[briggie]

Will I need really thick cable, also, what is voltage drop and how does it occur?

all cable has resistance , whenever you pass a current through a resistance you will encounter losses ( ohms law ) .... the higher the resistance ( longer the run , and thinner the cable generally ) .... the greater the losses ., this is voltage drop in simple terms .

[96terrano]

Thanks guys:thumb2, ill up the cable size a bit

[rayf3262]

Example:

For a 10M cable run carrying a load of 5 amps
.75mm2 Loop voltage drop = 2.24V
1.0mm2 Loop voltage drop = 1.68V
2.5mm2 Loop voltage drop = 0.67V
4.0mm2 Loop voltage drop = 0.42V
6.0mm2 Loop voltage drop = 0.28V

[96terrano]

Example:

For a 10M cable run carrying a load of 5 amps
.75mm2 Loop voltage drop = 2.24V
1.0mm2 Loop voltage drop = 1.68V
2.5mm2 Loop voltage drop = 0.67V
4.0mm2 Loop voltage drop = 0.42V
6.0mm2 Loop voltage drop = 0.28V

cool, i understand now:thumb2:bow

[Thomas-the-Terrano2]

volts = amps x ohms ie V=IR

watts = amps x volts ie W=AV though was taught to me as P(ower)=IV

[96terrano]

volts = amps x ohms ie V=IR

watts = amps x volts ie W=AV though was taught to me as P(ower)=IV

Now your just confuzzling things :augie:duno:

[rayf3262]

Now your just confuzzling things :augie:duno:

Nope, no confusion,.. He is trying to tell you how as an auto electrician you can work this stuff out for yourself.

[96terrano]

Nope, no confusion,.. He is trying to tell you how as an auto electrician you can work this stuff out for yourself.

Ahh ok, I've never done much with watts, just volts and amps are what I understand just now

[Thomas-the-Terrano2]

Ahh ok, I've never done much with watts, just volts and amps are what I understand just now

all related, and would need this formula for spot lights, make sure have right wiring,
funny its the resistance one I used the least in real world vehicle applications.

[96terrano]

all related, and would need this formula for spot lights, make sure have right wiring,
funny its the resistance one I used the least in real world vehicle applications.

Aye, I've fitted spotlights to many vehicles and never had a problem with the wireing:D

[rustic]

Nope, no confusion,.. He is trying to tell you how as an auto electrician you can work this stuff out for yourself.

Ryan, As I have posted this link on your tow bar electrics thread, why don't you open it, read it, better really, to print the 12 pages off.

It explains what cable size, voltage drop and all the formulas you will need to calculate voltage drop. You will only need a simple calculator, as seen on your phone, to do the calculations.

http://www.caravantalk.co.uk/library/files/Beginners-Guide-To-Electrics.pdf


It also explains % charge available in a battery when it has been resting some time, so if you have a second battery, you will be able to understand what the voltmeter is actually telling you.

Remember voltage drop on a cable is on both the feed AND on the return, if you are using a return cable like in boat and caravan wiring.

If you are using the car body as earth return, then the voltage drop is minimal, on the return, but make sure you use star washers to cut through the paint, and some grease, vaseline, or waxoyl over the connection to reduce corrosion.

If you are using a return wire, and you are using it for several things, then you need to ensure that this cable is big enough for the return current for ALL items assuming that they could all be on at the same time. Otherwise the voltage drop could be considerable, not only that, the cable will get warm due to resistance of the wire. The wattage or heat output of the cable will be given by the formula IxIxR ( pronounced, I squared R) Current x Current x resistance in ohms.

An example where the return cable isn't big enough, is on trailer and caravan wiring. Watch the tail lights go dim, when the indicators are on, on the trailer or caravan, they dim in unison with the indcators.
Also seen on many ford cars, that use the galvanised metal circuit tracks on the rear light cluster. BAD EARTH, clean the contacts on the plug, bit of vaseline or waxoyl... sorted.
For Vaseline... Ryan is your man.:thumb2
For Waxoyl... I am your man.:thumb2

With my posts you always get more advice than you asked for.
Others say I go on a bit...:lol:lol

Rustic

[96terrano]

Ryan, As I have posted this link on your tow bar electrics thread, why don't you open it, read it, better really, to print the 12 pages off.

It explains what cable size, voltage drop and all the formulas you will need to calculate voltage drop. You will only need a simple calculator, as seen on your phone, to do the calculations.

http://www.caravantalk.co.uk/library/files/Beginners-Guide-To-Electrics.pdf


It also explains % charge available in a battery when it has been resting some time, so if you have a second battery, you will be able to understand what the voltmeter is actually telling you.

Remember voltage drop on a cable is on both the feed AND on the return, if you are using a return cable like in boat and caravan wiring.

If you are using the car body as earth return, then the voltage drop is minimal, on the return, but make sure you use star washers to cut through the paint, and some grease, vaseline, or waxoyl over the connection to reduce corrosion.

If you are using a return wire, and you are using it for several things, then you need to ensure that this cable is big enough for the return current for ALL items assuming that they could all be on at the same time. Otherwise the voltage drop could be considerable, not only that, the cable will get warm due to resistance of the wire. The wattage or heat output of the cable will be given by the formula IxIxR ( pronounced, I squared R) Current x Current x resistance in ohms.

An example where the return cable isn't big enough, is on trailer and caravan wiring. Watch the tail lights go dim, when the indicators are on, on the trailer or caravan, they dim in unison with the indcators.
Also seen on many ford cars, that use the galvanised metal circuit tracks on the rear light cluster. BAD EARTH, clean the contacts on the plug, bit of vaseline or waxoyl... sorted.
For Vaseline... Ryan is your man.:thumb2
For Waxoyl... I am your man.:thumb2

With my posts you always get more advice than you asked for.
Others say I go on a bit...:lol:lol

Rustic

brilliant, thanks for that:bow:bow

[Banshee]

current ( in amps ) is voltage divided by resistance ....... or power in watts divided by voltage .

Yeah I found that formula after I fitted my spots first time round and realised that my lights were drawing 5 more amps than the wire was rated :doh

[96terrano]

Yeah I found that formula after I fitted my spots first time round and realised that my lights were drawing 5 more amps than the wire was rated :doh

oops:doh