Lights out in the Snow....

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That's interesting. Can someone check these calcs or correct if you already know.
Assuming headlight @ 60w and 12v Power=VxI so I = 60÷12 = 5A
assuming sidelight @ 5w and 12v = 0.42A

Soooooo, 5+5+0.42+0.42 = 10.84A max current draw

I put 12A in to that calculator on a run of 4m and get a voltage drop of 0.27v which is 2.25% and within the acceptable 3-4% The return run to the earth should be less than 4m, so well under.
Does that sound about right? If so, why does the harness have 40A fuses?


What size wire did you use?

Cheers
 
OK,

Yeah, I just went thru it and calculated it out. What you have there is correct.

Not sure why the boomslang uses a 40A fuse, what size fuse does the Landy use for each bulb?

I did not wire the sidelights into the loom I made as I think they are a waste of time, They come on only because I am turning on the driving lights, if that makes sense.

Cheers
 
Found an example in the rave for the 50th anni model.


upload_2017-12-10_10-33-34.png


Cheers
 
TBH I haven't looked to see if the boomslang harness incorporates the side lights, but as you say they're not that important in the scheme of things.
 
7.5A each. With 15A in that calculator that wire is still well within specification. :)

Looking at my schematic, I used 15A for the fuse going to the relays and then 7,5A for the fuse for the relay to the individual sides of the bulb.

My theory was that when you "flash" the lights both parts of the bulb light up so the amps required will be higher.


Cheers
 
That's interesting. Can someone check these calcs or correct if you already know.
Assuming headlight @ 60w and 12v Power=VxI so I = 60÷12 = 5A
assuming sidelight @ 5w and 12v = 0.42A

Soooooo, 5+5+0.42+0.42 = 10.84A max current draw

I put 12A in to that calculator on a run of 4m and get a voltage drop of 0.27v which is 2.25% and within the acceptable 3-4% The return run to the earth should be less than 4m, so well under.
Does that sound about right? If so, why does the harness have 40A fuses?
Yes, you have the basic principles correct but need to use about 13.5/14v as that is what the system will be at with the engine running (it will actually reduce the current flowing through the wire). Cant say I've studied the boosting system but you also need to consider the worst case scenario which is running on dip beam and then holding the headlight flash on. In this case you will have 2 x 55w AND 2 x 60w on at the same time, a total load of 230w which equates to about 17Amps. Another thing to bear in mind is the voltage drop over the cable, they will have chosen a larger gauge cable to reduce these losses, as a consequence of that they will have increased the fuse rating, generally fuses are there to protect wiring and not the end device (the bulbs in this case). If they have to include a fuse they may as well increase the size to save nuisance tripping if someone is running (illegal) 100w mains.
 
Hence the 40A fuses then.
Even so, for the sake of argument, say high and low beam both pull 5A each. That's a max of 20A if you flash the lights. gives a drop of 3.83% which is just within spec for those infrequent and brief moments.
Correct.

Cheers
 
Yes, you have the basic principles correct but need to use about 13.5/14v as that is what the system will be at with the engine running (it will actually reduce the current flowing through the wire).

I agree, which is why I tend to use 12V as it is a worse case scenario with regard to the amps.

Cheers
 
don’t want to start messing around with the alternator connections , if i’m being honest i can’t see it making any difference anyway if i connected it at the alternator or battery , but thks anyway of the idea

still got to get round fitting my split charge system in my D3 , now that is going to be fun, lol
In reality the difference would be minimal, however it saves you adding the additional wire and getting it to the battery box. The less wire and connections you have the less chance of something going wrong (cable chaffing etc)
 
In reality the difference would be minimal, however it saves you adding the additional wire and getting it to the battery box. The less wire and connections you have the less chance of something going wrong (cable chaffing etc)

firstly wished to apologise as i thought it just said connect to the battery

was just looking at this chart and it comes up 8awg

wondering if it may be better to install this cable, maybe abit of an overkill but then at least it’s an extra bit of protection

http://circuitwizard.bluesea.com/



https://www.12voltplanet.co.uk/63-amp-single-core-thin-wall-auto-cable.html

confused, i am now, lol

670AFC7D-AEF9-4023-975C-944F6DFD7122.jpeg
 
firstly wished to apologise as i thought it just said connect to the battery
was just looking at this chart and it comes up 8awg
wondering if it may be better to install this cable, maybe abit of an overkill but then at least it’s an extra bit of protection
http://circuitwizard.bluesea.com/
https://www.12voltplanet.co.uk/63-amp-single-core-thin-wall-auto-cable.html
confused, i am now, lol
View attachment 136688
I think the previous 50A 6mm sq wire you were looking at will be fine. I'm no auto sparky, but picking useful info up from Kwakerman and neilly. If that 50A wire wasn't up to the job they would have said 'don't use that', I'm sure.

Yes, you have the basic principles correct but need to use about 13.5/14v as that is what the system will be at with the engine running (it will actually reduce the current flowing through the wire). Cant say I've studied the boosting system but you also need to consider the worst case scenario which is running on dip beam and then holding the headlight flash on. In this case you will have 2 x 55w AND 2 x 60w on at the same time, a total load of 230w which equates to about 17Amps. Another thing to bear in mind is the voltage drop over the cable, they will have chosen a larger gauge cable to reduce these losses, as a consequence of that they will have increased the fuse rating, generally fuses are there to protect wiring and not the end device (the bulbs in this case). If they have to include a fuse they may as well increase the size to save nuisance tripping if someone is running (illegal) 100w mains.
Kwakerman's calcs would indicate the 50A wire is ok, even on that 10 foot run. That'll do for me.
 
I think the previous 50A 6mm sq wire you were looking at will be fine. I'm no auto sparky, but picking useful info up from Kwakerman and neilly. If that 50A wire wasn't up to the job they would have said 'don't use that', I'm sure.


Kwakerman's calcs would indicate the 50A wire is ok, even on that 10 foot run. That'll do for me.

cheers, always good to double and triple check , seeing we want things installed and done on our landies 100% , especially when it comes to wiring

there should also be the wiring spec on the boomslang loom ;):D
 
firstly wished to apologise as i thought it just said connect to the battery

was just looking at this chart and it comes up 8awg

wondering if it may be better to install this cable, maybe abit of an overkill but then at least it’s an extra bit of protection

http://circuitwizard.bluesea.com/



https://www.12voltplanet.co.uk/63-amp-single-core-thin-wall-auto-cable.html

confused, i am now, lol

View attachment 136688
Personally I wouldn't use thinwall unless I had to, it's designed to reduce weight and cable loom thickness as the insulation is thinner than usual (hence the name) and is a lot less robust when it comes to surviving chaffing damage etc. With regards to actual wire gauge, as long as your cable gauge/current rating is on par with (or slightly larger) than the boomslang loom then you shouldn't have any issues.
 
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