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Topic: Relay modification for ign sw discussion (Read 10550 times) previous topic - next topic

Relay modification for ign sw discussion

Reply #120 –
your fine tom, im learning new stuff all the time,, just make sure to ask what the insulation type is please, that info you may already have handy.

btw, dc or ac , it does not matter because it all applies to the NEC and in this instance subject to low voltage.  either way the question i had is still there,
why is this design ok to source with an 80A cb?  just wondering.....seems kinda heavy to me for the actual loads.
I may be wrong, but i have not seen any statements in the NEC that waives the auto makers from being compliant, therefore when you have conductors in a wire loom, it no longer qualifies as free air.

perhaps the auto makers dont have to comply. 
I would bet the the answer you get is that the engineering is based on a huge / vast amount of derating which is understandable.

the motor your testing is non-linear loads,,

Relay modification for ign sw discussion

Reply #121 –
hey,, sometimes figuring out what the right question is,,, is part of my problem,,
here goes...

hey tom, what standard is applicable to automotive wiring?

Relay modification for ign sw discussion

Reply #122 –
From what i understand about electrical issues is this. If the voltage is below 50Volts it is not under any electrical codes. Example the low voltage lights my daughter installed on her walkway clearly stated they can be installed by the home owner. No electrical codes are required. Just saying. Their has to be a cutoff of codes and i think the number is 50V or under!!
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Relay modification for ign sw discussion

Reply #123 –
Oh, guys, you are still fighting about the current draw?

Here is the volt - amp characteristics of the resistor (red) and a light bulb (blue). The blower motor will be similar to the light bulb.

You can clearly see, that the current rises with voltage. The only thing where the current rises when the voltage is dropping is the switching supply, which WE DON'T HAVE in our cars.

Other thing is the load characteristics of the battery

U0 - no load (I = 0A)
Ik - short (U = 0V)

In other words, voltage drops with rising current draw.


PS: The inner resistance (Ri) of the battery rises with dropping voltage (that's the reason, why you can't start your car, if your battery is dead). That causes dropping current under the load.

Relay modification for ign sw discussion

Reply #124 –
Well whatever that language is i cant read it. But i definitely know that a blower motor on less voltage draws less current. That is unless my Extremely expensive  FLUKE meter went BONKERS and i doubt that!!!

I guess you are talking about a starter motor and a battery. But a fixed load the voltage drops the current drops. If you like i will make a video but i dont see any point in that as all you have to do is hook an ammeter to your blower motor and flick the speed switch on the dash. With that i dont care any more untill someone actually does this test. So do the test and see for yourself. Once again i dont think i fell off a turnip truck last night????
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Relay modification for ign sw discussion

Reply #125 –
tom,
this only becomes important when sizing your fuses or cb,,, thats all. its another ingredient in the design.
i did your test and i also did a test on headlamps just for my own entertainment,, took a lot of pictures to but concluded its a pointless thing to explain because i dont think its important anymore.  I probably have more tools than you to see this stuff like my midtronics tester, Biddle tester and plus the fact that "my" typical battery string i deal with weighs about 7900lbs consiting of 24) 2v cells.
Here is the deal just so you know that your meter wasnt bonkers........but your qty of stored battery is so small that a digital meter cant really catch what im talking about. 
When i tested the headlamps, the voltage droppped and i was able to see coupe de fout, but just barely.
what i saw happen in first 30seconds was a quick drop in voltage that lasted for i suspect approx 3 seconds during which time the current spiked but i missed the opportunity to catch it.

next the voltage went back up to about 11.97v thus dropping the current to about 4.1A (one headlamp bulb on high)
next the voltage started to drop and the current rose slightly to around 4.3 and held that point before it started to fall with the falling of voltage.

all batteries do this,, there is a moment in time in which the current will rise slightly (hard to see with basic tools) and this differential will be more visible to out typical tools directly proportinal to the stored ah rating of the battery itself.

as a result, im just simply stating that these events that take place and its wise to size things accordingly

ok, so lets let it go, its just a little thing that i happen to "prefer" to factor in.  with respect to switched power supplies, its more visual to a meter.

ok, recap
upon initial discharge within the first few seconds depending on your battery type, coupe de foute will be experience where voltage drops **HUGE** while current spikes huge and then ......... the batt voltage recovers by going back up and levels off.
battery starts to discharge but the voltage recovers to around 12v bringing down the current.  all this happens in just a couple three or 4 seconds in a car battery.

current demands on the battery will seem to appear to be steady to a tad high (or even rise slightly) during the 12v to 11.5 v range.
the voltage drops but the loads will still demand the same amount of current until eventually the current starts to fall with voltage.

these considerations are what effects your wires ability to carry the demand.

i should have never brought this up.......but,,,,,,,, my next post may brighten the subject back on track

Relay modification for ign sw discussion

Reply #126 –
ok,,
got the relay bank built...
A few things im doing a little different.
I am using the 80A cb to feed a 100A rated buss fuse block
IGN sw RUN will e managed by a 30A fuse  / 40A relay(I hope this is enough)
IGN sw ACCY will be managed by a 30A fuse / 40A relay (i hope this is enough)
Marker lamps will be managed by a 15A fuse / 30A relay
Headlamp Hi & Low will be managed by a 30A fuse / 40A relay x 2
**i forgot to jumper out the headlamp stuff to do "thefoeyouknow" opiton and will fix my screw up tomorrow.

I have some overhead in this design so i can power my remote power strip for things we use in the car, as well a spare realy , maybe two depending on how i go about it.

so , here is the build, in this condition each relay has its own dedicated fuse and relay but that will change tomorrow slightly.

This mod is going to be really nice.
i need to talk to you **TOM** about the redundunt layout,, i tried like hell to figure out what you mean,,, sorry,,, i just dont get it.

so here it is,,,, comments welcome.

Relay modification for ign sw discussion

Reply #127 –
and this is how we protect the copper buss work that bridges the 80A CB tom sent me to the 100A fuse block..........

going in the car tomorrow

Relay modification for ign sw discussion

Reply #128 –
Quote from: TOM Renzo;405771
Well whatever that language is i cant read it. But i definitely know that a blower motor on less voltage draws less current. That is unless my Extremely expensive  FLUKE meter went BONKERS and i doubt that!!!
Don't worry about the language. I wasn't able to find it in english and I was too lazy to edit the picture. So I wrote the most important info under the picture.
It corresponds to info you wrote earlier. The first graph shows, that the current drops (Y axis) with the dropping voltage (X axis) on the load (resistor, light bulb). The motor will be the same.
The second graph shows that the voltage OF THE BATTERY drops with the rising current. In other words, you will measure higher voltage on the battery without load, than with load.

Jay thought that the load current rises, when the battery voltage drops (the wattage is constant). That's a mistake. If this would be true, then you won't need to care about the battery voltage and the load would work on it's designed power. That's not true. Only thing which can do this is the switching power supply. But we don't have any in the car (maybe except your mobil phone charger). That's the reason why we can ignore it now.

I hope you understand this.

Relay modification for ign sw discussion

Reply #129 –
Quote from: Trinom;405853
That's the reason why we can ignore it now.

exactly,

130 posts later and finally someone who knows this is a possibility.
however , your not quoting me totally correct per my description of desicharge wtih time.  ALL batteries go through a coup de foute event for a very short duration where voltage drops but the current stays high or rises slightly before recovering.  additionally , during discharage the current will attempt to stay steady and slightly rise while voltage drops before**current finally follows the voltage, this second event depends on the ah battery type you have. 

these two events in a short period of time factor into how an over current protection device needs sized.
coup de foute for approx 3-5seconds = long enough for a fuse to react (can last for several minutes on a larger 2100ah battery system)
discharge from 12 to 11.x V= approx 1 min depending on your battery ah.

when voltage drops but the current is steady and / or up by .2 or so means your approaching AIC or SCCR,, if these are not considerations to sizing a fuse, the so be it.

to say generically that it just doesnt happen is not the case.

Relay modification for ign sw discussion

Reply #130 –
question:
on my connectors, i tried to heat shrink them and they did not shrink.
the brand is burndy,, pretty much the best money can buy (along with thomas and betts, 3m ect) but was wondering if anyone else has seen this happen.