Relay modification for ign sw discussion

Topic: Relay modification for ign sw discussion (Read 10429 times) previous topic - next topic

Relay modification for ign sw discussion

Reply #75 – December 24, 2012, 11:21:30 PM

Hey Foe,
If i were designing this for work, first thing that stands out is the 80CB, i think its too high and will allow the wire to suffer before the breaker trips.
Seems more reasonable to be a 60A ,, especially since my actual loads with a lot of encouragement yielded worse case around 35A for the RUN or ACCY ckt.
With low battery voltage, current would go up but i wouldnt want to expect more than 60A even at those conditions,,
thoughts?

Relay modification for ign sw discussion

Reply #76 – December 24, 2012, 11:25:14 PM

Another tid bit,
apparently the highest amount of load coupled with inrush is the following activities........

Power trunk solenoid spiked a hell of a lot of current, i will call it approx 15A
power windows are approx 10A each, doing them both at the same time yields about 22A.
just throwing this out there for more info.

Relay modification for ign sw discussion

Reply #77 – December 25, 2012, 08:20:38 AM

Maybe you could give them each their own 30A breaker. Those are easy to come by and they fit in an inline fuse holder.

Relay modification for ign sw discussion

Reply #78 – December 25, 2012, 11:50:22 AM

i think 30's are a little light,, considering low voltage, thats the conundrum, max size of the fuse before you change to a breaker. i was doing

if the gray wire can see about 20A, then 20A x 12.5v in run condition is 250w.
in a low voltage condition, lets say 10v, thats 250w / 10v is 25A.

to size the fuse / cb, that would be 25A x 1.2= 30A required ocp.

30A is on the cuff per relay... just my toughts,, would you do 30's?

i think the real issue is the voltage drop from the starter relay up to the yellow wires.

id be interested to see what my voltage is up to the gray Run wire now that im gonna feed it with a totally new feeder. Id like to see 13.5 to 14, that would get my current down.

Relay modification for ign sw discussion

Reply #79 – December 26, 2012, 02:29:53 PM

Quote from: jcassity;405345

With low battery voltage, current would go up

Quote from: jcassity;405363

if the gray wire can see about 20A, then 20A x 12.5v in run condition is 250w.
in a low voltage condition, lets say 10v, thats 250w / 10v is 25A.

I think you are breaking the law.

OHM's law

Relay modification for ign sw discussion

Reply #80 – December 26, 2012, 03:04:12 PM

Doing the math Voltage X current =Watts

So 20X10=200 WATTS

And 20X14=280 WATTS

Jay please explain your self as you keep saying as voltage decreases current rises. Not true

Soft touch is correct you are breaking the LAW!!

Relay modification for ign sw discussion

Reply #81 – December 26, 2012, 04:11:51 PM

I think what j is getting at is that @ 14v you'll need less current than @ 10v, but he typed the same current for both voltages which is, I hope, a simple error from typing too fast.
The example should have been 20A @ 14v, but 28A @ 10v which would support his assertion that in low V conditions, 30A might not be enough circuit breaker. Ohm can sleep soundly.

Relay modification for ign sw discussion

Reply #82 – December 26, 2012, 04:55:09 PM

Quote from: TheFoeYouKnow;405447

I think what j is getting at is that @ 14v you'll need less current than @ 10v, but he typed the same current for both voltages which is, I hope, a simple error from typing too fast.
The example should have been 20A @ 14v, but 28A @ 10v which would support his assertion that in low V conditions, 30A might not be enough circuit breaker. Ohm can sleep soundly.

Better wake Mr OHM back up again.
If the voltage drops, the current will drop if the resistance(load) is the same.
I=E/R
Looks like I better get myself out of the stone age. They are now using V (Volts) instead of E (Electro-magnetic force). But they still use I for current.
So lets make it I=V/R

Relay modification for ign sw discussion

Reply #83 – December 26, 2012, 05:47:36 PM

Time to eat some crow.
When motors are involved the rules change. I=V/R applies to a resistive load. Motors are an inductive load.
Voltage drop on motors will cause current to increase. I am pretty sure this applies to AC motors, not sure about DC motors.

Relay modification for ign sw discussion

Reply #84 – December 26, 2012, 05:52:50 PM

I know Tom will have kittens when he sees how I did mine, because it is different from how he'd do it, so it can't be right (kidding, Tom, although I'm almost certain you'll pick it apart anyway)...

When I did mine I was also adding a few options/features that the car never had, so I integrated these additions into the setup. I had a small 6-position fuse panel from a cop car (it was a factory Ford part), so I used that to feed the new circuits. My goals were these:

1) Remove the single largest draw from the RUN circuit (the blower motor). I used two relays to split circuit 687 into two circuits: Heater/blower motor and everything else. I also re-pinned the factory fuse panel so the blower motor still used the factory fuse, it was just fed from a relay instead of via the ignition switch.
2) Integrate a remote starter into the system. This was actually the catalyst for doing this whole mod. When wired the normal way (IE by the remote start kit's instructions) I would have to make sure the blower was on "LO" when I shut the car off, otherwise one of the the remote starter's two 30A fuses would blow after the car ran for a few minutes if I started the car with it. This was because circuit 687 draws more than the 30 amps the remote starter could provide it.
3) Integrate the driving lights that were added when the TC front bumper was added. Make them operate when the key is in "RUN" because Nova Scotia came up with a law that cars either have to have daytime running lights (standard on all Canadian market vehicles since 1990) or if it doesn't have them, the headlights would have to be used, and I'd never remember to use them and didn't want to risk a $270 ticket.
4) Integrate the power lumbar bladders that were added with the TC front seat swap.

Here's a simplified drawing, showing only the parts of the circuit that matter (for example only the part of the ignition switch that switches circuit 687 is shown, only the related fuses are shown in the factory fuse box, and only the part of the remote starter that feeds the new "split" circuit 687 is shown):

I didn't worry about any of the other circuits (power windows, locks, trunk, etc) because they are not long-term draws so they would not have much effect on the ignition switch's longevity. They also draw off the ACCY circuit, not the run circuit. The wipers also draw off the accessory circuit, and the rear defog has a built-in relay, so these aren't really big issues either. The worst-case scenario for the ACCY circuit would be to have the wipers on high while also putting both windows up or down and pressing the power truck button at the same time, an unlikely scenario. Even the windows/wipers scenario, which could happen, would only be a momentary draw as the windows will only be pulling current for a few seconds.

Which brings up another point: Don't waste time trying to figure out the maximum current of each load. You'd never be able to build a system that could handle it. The alternator, even with a 130A upgrade, could never feed all loads at maximum draw. Just like your house's main electrical panel could never feed all the branch circuits at full draw. Your car, and your house, are both designed to support their electrical systems with the knowledge that they will never have all loads puling maximum current simultaneously. Just add up the values for all the fuses in your fuse box and they'll add up to way more than what your alternator can put out, and this isn't even counting things that aren't fused in the fuse box, such as the headlights, fuel pump, ECM, etc. Same goes for your house - if you add up all the fuses/breakers they will add up to a much higher number than the main breaker/fuse is rated at.

One more thing: Tom, in your "relay fails no tow truck" drawing you show the load getting power whether the relay is turned on or off. Using typical Bosch relay terminal numbers I'm assuming the "load" to be on terminal 30, the aux batt to be on terminal 87A, and the "Batt" feed to be on terminal 87. It also appears that terminal 86 would be ground and terminal 85 would be "Batt". I see a few problems with this setup:

1) With "Batt" connected to terminal 85 and "ground" on 86, the relay is always on. There is no way of turning it off aside from disconnecting the battery. I'm thinking you probably meant to have terminal 85 fed from the ignition switch so that the relay would turn on when the key is on, but this still wouldn't work because:

2) With the load on terminal 30 and both terminals 87 and 87A being fed power (one from "BATT", one from "Aux BATT") it wouldn't matter whether you turned the relay on or off, the load always has power. I don't know what you mean by "Aux BATT" - do you mean a second battery, or a second feed from the main battery? Either way there would be no way to turn the load off except to pull the relay out of its socket. If the relay is off the load (terminal 30) is fed via terminal 87A (Aux BATT), if the relay is on, the load is fed via terminal 87 (BATT). With no way of turning it off, why have the relay at all?

Also, generally speaking, if somebody knows enough to install the relays in the first place, they would know how to get it working should that relay fail. A bit of wire or a cotter pin in the relay socket jumping terminals 87 and 30 would be all that would be required...

Relay modification for ign sw discussion

Reply #85 – December 26, 2012, 05:56:06 PM

Quote from: softtouch;405454

Time to eat some crow.
When motors are involved the rules change. I=V/R applies to a resistive load. Motors are an inductive load.
Voltage drop on motors will cause current to increase. I am pretty sure this applies to AC motors, not sure about DC motors.

It does. This is why you can burn the commutator bars out of a starter's armature by trying to start it with a dead battery. You can literally turn your brushes into little arc welders. I actually had it happen to an old Nissan truck years ago - the commutator bars liquified...

Relay modification for ign sw discussion

Reply #86 – December 26, 2012, 06:07:32 PM

I did that to my Jeep J10 in high school. Was the basis for learning how to rebuild a starter.

Relay modification for ign sw discussion

Reply #87 – December 26, 2012, 07:26:42 PM

Well i am lost for words as to why when a blower motor is set to high it is bypassed by a relay and not fed through it's original power source. If current increases when voltage drops. This is the opposite of my belief as the blower motor slows down and current drops as it is slowed down. I will post current draws for blower motors at different speeds. just saying!!

Basically when a load is constant lowering the voltage lowers the current. Years back during the brown outs the power companies lowered the voltage to homes to decrease power drain from the utilities. I dont know if this is true but CL&P told us this was the issue. With that i am willing to bet the blower currents are the highest on high fan. Reason being it is slaved from the factory. Either way Thunder as i always said over building circuits is something i will never understand. And basically i have no idea how and why you did it the way you did. But that is none of my business. And i am getting a headache following this. Reducing the current draw through the switch is necessary. Reducing it to the point of non existant current going through it is a waste of time and energy. The switch can handle high currents just not the amount the Ford engineers designed it to do. With that will post current draws of blower motors tomorrow when i read them in the MIDNIGHTER. Thanks

Relay modification for ign sw discussion

Reply #88 – December 26, 2012, 07:36:27 PM

Also, generally speaking, if somebody knows enough to install the relays in the first place, they would know how to get it working should that relay fail. A bit of wire or a cotter pin in the relay socket jumping terminals 87 and 30 would be all that would be required...

Well i find this post a little disturbing. As i posted a redundant relay system that i use i find this statement very ODD. As to have a relay fail at highway speeds and have an engine flame out. I would think one would design a system a little better than this. Being as you designed a system that i am getting a headache trying to figure it out. You should have built the run section void of relay control or use relay redundancy with a set of double throw contacts. Once again it is only my opinion Thunder and being in the car business can you actually tell me that a relay never fails or gets intermittent. With that i stand corrected beaten and will bow out. Just me could be wrong. Thanks!

Also better think again why a starter melts on low voltage. With that a blower load graph is in the works with reduced voltage to control speeds. A starter is totally different than a blower motor. The loads are dramatically different. And yes a sluggish starter draws a hell of a lot of current. And its load increases as it cranks against a dead load such as an engine. not to mention it's design and how it is polled.

Just another thing Thunder does your rear defroster stay on when you shut the car down. I DONT THINK SO!!! It has a latching relay setup. Not argue with you as i once again am tired and i wont argue with you. Look at my print very carefully and by the way the long rectangular battery feed is the ignition switch. So i thought you would understand that. Do you think i fell out of a turnip truck!!!
By the way looking at your print i am very happy you are using the original factory wiring to the relays for power source YELLOW I AM ASSUMING IS THE FACTORY FEED TO THE IGNITION SWITCH FEEDING YOUR RELAYS ??.. At least you understand it is quite adequate. And to run battery cables all over a car to slave out circuits is over kill. But as i said it is your car and that is the bottom line. So tomorrow i will post blower current draws at various speeds. Any one want to tell me what those numbers will be??? Any guesses!! With that i bet you have a giant stack of relays Thunder. Thanks Tom and you will get no arguments from me!!

Thunder jay clearly said he did not want to rip in to the wiring harnesses or fuse panels. That is why a slave relay on the highest draw circuits was all that is necessary. If you want you car wired like a Saturn 5 rocket be my guest. Other than that if you left the window motors through the switch why waste your time with all the other relays and stuff. I explained to you that i remove the windows out of the switch and wire them directly to battery through a circuit breaker. You went through all this stuff and left the windows in . makes no sense to me. But as i said no arguments . By the way better look over my no tow relay setup as you are clearly mistaken as to how it woks.
By the way your print does not show your run circuits ETC. It is a basic print that i can understand but do not know the total loads you slaved out. just saying

Relay modification for ign sw discussion

Reply #89 – December 27, 2012, 01:05:48 AM

what i mean is that when the potential goes down on a device,, said device will draw more current to compensate,, that is ohms law.
softtouch was explaining EYE SQUARED R loss which is in respect the same but kinda different animal.

yes i was typing too fast but watts is watts, you cant really manipulate that.

in dc power,, where im pretty much an expert, if your voltage goes down while you are connected to devices,,,,, the current WILL go up.
in an instance we have a -48v power plant which floats at 54vdc.,, and lets say you have 10,000Amps,,
that same amount of equipment while running on "BATTERY BACKUP" instead of rectifier will draw the same amount of watts and the first thing that will go down is voltage,, the next thing that gives in is AMPS which goes up.

I usually explain things in "on demand",, and not the "flight of the arrows" so to speak like i think softtouch was doing. I totally understand where he is coming from but when you have a dc load and you reduce the voltage, such as a blower motor in the car, well, the blower motor will still try to stay as high as possible but yes eventually it will either reach its ISC or SCCR, or it will blow a fuse or it will absorb all that heat without a fault and eventually slow down and stop.