Fridge wiring size

[Krankin]

The missus won't go camping without her hairdryer It takes her 8 minutes to dry her mop. I need to work out what size of inverter will cope with 1500+ watts for 8 minutes and how much amps it will suck in 8 mins. Anybody know?

Buy a genie for that sort of load...

My 500W pure sinewave inverter has a max 12vdc current draw of 70A @ 500w/240Vac output load.

Remember, that your 1500w hairdrier is a load on the 240Vac side of the inverter and not on the 12Vdc.
So 1500/240= 6.25A on the ac side.
Anyway you would need a min of 2000w/240Vac inverter to run your h/drier comfortably,
BUT,
you wont be able to carry enough batteries and a big enough alternator to run that kind of inverter in your nav, (as mentioned earlier), unless of course you dedicate your entire tub just for batteries and a rather large inverter,
again as an example my inverter is 1/4 of that 2000w and it can pull 70Adc at full load, it pulls 1.5 amp just at switching it on with nothing plugged in.

And to top it off, inverters dont really like resistive loads such as a h/drier.

A genie is the way to go.

 

[Krankin]

Can I suggest that those circuit breakers are likely to cause problems if something goes wrong?

100A is a LOT of power in a 12V system. D22 alternators can't put out that much power, and a D40 has to be revving fairly well to pump that much out. It's enough power to light 12 driving lights.

The circuit breaker should be enough to carry the maximum intended current and not much more. In mine, I have 26A heading for the brakes (30A thermal breaker) and 20A-> caravan power plus about 9A into the tub running through a second 30A breaker.

I could use a larger breaker, of course, but I need the thing to trip when there's a problem before it can cause damage to any other part of the system, and 100A is just too much problem.

It's a suggestion only, please don't think I'm telling you that you must do it! I do recommend going and asking an auto electrician and get their opinion, but I'm fairly sure they'll say that a 100A breaker on a line that really only needs to carry 20A - 30A at best - is too high.

I think he means he ran the 100A c/b's on the 50mm batt cables at the batt ends, which is fine...
much like you mentioned in a previous post,
(remember a starter can pull up to 400+ amps),

though it sounds like there is no protection for the smaller loads.

CORRECTION....he mentioned c/b's on the acc's.

 

[Old.Tony]

Told you I knew nothing I called a buddy and he explained how it works..
Starter battery -> Dual Batt Controller -> Circuit breaker -> Cable to Dual Battery (in tray) -> 2nd Circuit Breaker -> Cables running to fridge / cigarette points both have 30amp breakers or maybe 25... can't remember!

That sound a little more logical?

Certainly sounds a lot better like that, and safer, good stuff!

 

[Old.Tony]

I think he means he ran the 100A c/b's on the 50mm batt cables at the batt ends, which is fine...
much like you mentioned in a previous post,
(remember a starter can pull up to 400+ amps),

though it sounds like there is no protection for the smaller loads.

I can't imagine hauling starter current in from the tub, it's just too much current over those distances. You'd have to cater for "worst case" which is a very, very cold diesel that is going to beat that 400A by a good margin - and that's frightening.

 

[Krankin]

I can't imagine hauling starter current in from the tub, it's just too much current over those distances. You'd have to cater for "worst case" which is a very, very cold diesel that is going to beat that 400A by a good margin - and that's frightening.

A 50mm2 cable would do it easily though...
I have the battery in the boot of my HR with a 50mm2 welding cable running from the batt to the starter with no probs turning over my high comp chev V8.

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[Old.Tony]

A 50mm2 cable would do it easily though...
I have the battery in the boot of my HR with a 50mm2 welding cable running from the batt to the starter with no probs turning over my high comp chev V8.

.

That size cable will do it for sure, but snag the cable, get a sharp stone to nick it, whatever - it's a significant risk.

How do you protect the cables as they pass under the car?

 

[Krankin]

That size cable will do it for sure, but snag the cable, get a sharp stone to nick it, whatever - it's a significant risk.

How do you protect the cables as they pass under the car?

Its a road only vehicle, protected by running as well hidden as possible and in reality is in no more danger than a starter cable in the average engine bay.

On the other hand, in a 4wd it would pay to provide some extra protection, maybe some steel conduit or the like,
but then again nothing is 100% safe and probably more so in a 4wd enviroment.

Back to before... i'm not sure if "scarecrows" intention was to use his batts in the rear as kranking units as I noticed he has used cable "100A" protection at both ends which surely would open circiut upon cranking load.

 

[scarecrow]

Nah my second battery is just for my fridge, lights and some other stuff.

 

[Krankin]

I can't imagine hauling starter current in from the tub, it's just too much current over those distances. You'd have to cater for "worst case" which is a very, very cold diesel that is going to beat that 400A by a good margin - and that's frightening.

Just venturing off for a minute Tony,
I haven't tested the HR starting current draw but have on my XF ute, with not much comp and 360k on the clock,
it came in at a max of 301A.

When I get a moment I'll do the 2.5 Nav and post some figures, ie: cold v hot engine crank amps.





.

 

[Old.Tony]

Glad that's your multimeter!

Be great to see those figures - then I'll know if I've had more BS thrown my way. I suspect probably not, but let's see.

 

[Krankin]

Glad that's your multimeter!

Its ok, its my Fluke Clamp meter, good for 1000A ac/dc.
Also logs min/max & inrush currents.
I bought for work but get much more use of it at home.



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[tommy222220_0]

How do you protect the cables as they pass under the car?

My dual battery wire runs through the middle of the chassis rails. And also has some plastic split tube as well. Should be pretty safe in there

 

[Krankin]

Glad that's your multimeter!

Be great to see those figures - then I'll know if I've had more BS thrown my way. I suspect probably not, but let's see.

Results in!

Test using 2008 STR '22, battery in very good cond.
Fluke 337 True RMS clamp meter on 12V+ cable to starter motor,
2" from +battery terminal post,
using short crank bursts with no warming periods for glowplugs.
16 deg Celsius @ 345m above sea level
****did notice though, the longer the cranking period, a dramatical rise in current.

COLD ENGINE:

inrush---------557A
crank----------520A


HOT ENGINE:

inrush---------595A
crank----------515A

.............................................................
actually surprised me, had to do a second time to verify.







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[Old.Tony]

Wait, so a hot diesel is harder to crank than a cold one? That's different.

The lesson here of course is that we should all have 800A jumper cables and never try jump-starting from a normal car. These things would just kill its battery.

Awesome stuff, thanks for doing that!

 

[Krankin]

Wait, so a hot diesel is harder to crank than a cold one? That's different.

The lesson here of course is that we should all have 800A jumper cables and never try jump-starting from a normal car. These things would just kill its battery.

Awesome stuff, thanks for doing that!

The only 2 explanations I can offer to that is,

compression is stronger i an engine at operating temp....
as,
by the way,
this is when you should perform a compression test, I mean when the eng is at operating temp.

Current does increase with a rise in temp, eg: i found as I mentioned before the longer the starter cranked, the higher the current draw and thus more heat

I should add, my test cranking periods while very identical in time each, where not actually precisely timed, and regardless the 'inrush' current would not be effected by time.


.

 

[Old.Tony]

I'm not that fussed on timing accuracy. Just the figures that you've given are brilliant to have.

Which reminds me, I need to change my jumper cables for something heavier.

 

[Krankin]

I think another important part of the equation would be the current draw of the glow plugs.
I dont know,(have no time atm to research) their rating, how/when/if/time period in relation to the actual cranking period they are controlled by the ecu,
but I would think they would contribute somewhat to those figures I posted earlier.


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[Old.Tony]

According to the manual, the fuse for the power side of the glow relay is a 60A fuse. There's a 10A fuse feeding power to the input of the relay.

So, knocking 60A (tops!) off the values and the old 400A cables still don't cut the mustard.

They are controlled by the ECU for some time, even after starting, until the engine reaches a certain temperature (I could get the figures out, if desired). The indicator light on the dash only shows that they have come up to temperature, not that they are now turned off.

 

[RustyNav09]

this has probably been covered but i cant seem to find it in here without the mixed confusion.

as most people know i am going through the stage f finally getting the dual battery stuff together. in that i am running the appliances off a fusebox into switches and plugs etc. now i am confused on what sized wire i should be using off the fuse box tot eh switches and plugs. obviously the biggest unit running off the block is the fridge. i have been told a wire size anywhere between 4mm(15amp)-6mm(29amp). can anyone shed some light on what is best?

Rusty

 

[KraftyPg]

I use the same cable from the fuse box to the fridge as from the main to the Aux. I do run the same cable from the Aux to the CB, DVD, 19v power supply but that's only because I don't pay for the cable. Personally I wouldn't bother running it for anything other than the fridge, but even for the fridge it's going to be overkill. The only time it wont be overkill is in one of those "what if" situations like if you get in an accident or something.

Know your own power ratings and you can make the decision for yourself, if you don't know the power of each item you run just use the biggest you can find, the cable makers love it.