Dumbass 12v electrickery question
So dumbass questino part II
4x 55W halogen lamps on a 12v supply. About 3m of cable required.
Will 20A cable suffice?
How much total wattage will the 20A 12v cable take?
EDIT: richmars, missed your post. But that’s what I was wondering, 2 on + and 2 on – does that give me 20A total?Posted 4 years ago
Right – so that probably clears things up.
If I have a distribution panel that has, say:
4x 3W LED lamps
1x 1Amp 12v USB charger (Cigarette socket)
1x 20W incandescent bulb
2x 55W halogen lamps
4x 55W halogen lamps
and 2x 20W speakers driven by a nominal 500W mini amp
means that the peak draw from the panel if everything is on is 12+12+20+110+220+40W = 418W
Which in theory could require 34A of current if they were all on at the same time.
So if I were to wire 2x 20A cables to each pole to the panel and then single 3A, 10A or 20A cable as needed to each circuit that would be OK?
Chances of having all on at once are zero, but best to plan….Posted 4 years agoJAGSubscriber
4x 55W halogen lamps on a 12v supply
So…..Watts = Amps x Volts
Amps = Watts/Volts = (4 x 55)/12 = 220/12 = 18.333 Amps.
20 Amps will be enough.
Hmmm you’ve edited your post since I wrote the above. However the principle still applies and I’m sure you can work it out.Posted 4 years agoSumMember
Going back to the original question; Generally, if the cables are of the same size (gauge), same construction (stranding), same material, same length, same type of termination, run in parallel path, and are properly physically connected properly (clean terminals, no surface contaminant, same bolt torque, etc.), then there should be minor differences in the current carried by the individual cables, and so running two 10A cables in parallel should in theory give a 20A max rating. However if there is a slight imbalance between the two, e.g. one cable isn’t terminated quite as cleanly as the other or got pinched by accident and has a difference cross-section, then one cable would attempt to draw more than the other.
Can you separate the 4x 55W halogen lamps into two 2x 55w? Or use 20A cable for that circuit?Posted 4 years ago
Spent today working on rewiring my mates comp safari racer, well mostly undoing the mess of spaghetti vaguely disguised as wiring by the previous owner, ready to put the new stuff in next weekend. I tend to work on over spec’ing wiring, especially for lights. For instance the 100W spots are wired with independent supplies with 25A cable, and 30A relays (although the independence is for failure resiliance as much as load). Much better to minimise the resistance and hence losses between the battery source and the lights to maximise the light output. Do I recall you fitting lighting loom kit with relays etc to your transporter to improve the light output? Same princilple here.
As Sum says use one run of the right rated cable, safer in the long run if one of the cables/connections becomes a high resistance point.Posted 4 years ago
Cheers Sum & mark90
yes I did uprate the lamp cabling in the T4.
This exercise is for my Landrover 110. I’m putting together an auxiliary electrics panel to manage all the non-MOT stuff. I want to directly wire it to the battery with a panel power switch and then everything else on toggle switches from there.
Given the low chance of actually drawing more than 20A at any one time, I could just use one 20A wire, but since Im getting a roll if wiring two 20A wires to the panel (with idenitcal runs, connectors etc etc, natch) give more redundancy then it’s cheaper for me than buying some 30A as well.
thanks for the help.Posted 4 years ago
The topic ‘Dumbass 12v electrickery question’ is closed to new replies.