For the electrical wizards... buggman ne - Electrical Tech - Tech Section

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Do Not Touch The Trim!

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I may ban myself for posting a non ranger thread, but it's in the ranger family (kinda) so I'll let it slide for now....

In my 03 Explorer I'm trying to find a 12v source that only gets power when the vehicle is running, not when it's off & not when the key is in accy (or on since it doesn't have a normal accy spot like my ranger does).

I've been through the chilton's manual a million times, searched online forever yet I still can't get anywhere.
The only Run Only power I've found is the small wire at the alternator, think it's the "exciter" that tells the alt to charge. It seems to be controlled by the PCM & I'm weary about tapping it although I'd run a diode & small fuse to prevent any voltage feeding back through the circuit.

All the fuses I've tested under the hood that are supposed to be "hot run only" are hot when running & when the key is on which defeats my purpose.

The simple thing would be to run a switch that's key switched, but I'd like to have something that comes on automatically when the truck is running & shuts off when it's not running.
Whatever I tap won't have any noticeable load, only a few mA of current to trigger a relay. This relay will be powered directly from the battery (fused at the battery also).

I know a few of our members work at Ford dealerships, hopefully someone has ran into this before or could check their manuals.

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Posted: Wed May 9th, 2018 08:50 am

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RCR4V3N
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The issue is the circuits are controlled by the switch position (off-accessory-run-start). Your best bet is to get an aftermarket voltage sensing relay that activates at 14v to trigger with alternator voltage instead of the battery/switch position.

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Posted: Wed May 9th, 2018 09:25 am

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410customs

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There should be a few ACC circuits for you to choose from
You will likely find one behind the radio or at the ignition switch

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Posted: Wed May 9th, 2018 11:53 am

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Scrambler82
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I am thinking, out loud, that the Interior Fuse Panel won't have that circuit in it, more of an Accessory Panel.
Have you checked the Fuse Panel under the hood for an open circuit with the characteristics you want ?
There seems like there is always an open circuit to play with.

Next would be to trace back the Engine Run Circuit to the Fuse panel, check the load of the circuit and the fuse size and then determine if it can handle the extra load, also dependent on the size of the wire and the length of time it will be drawing the extra current.

Ford has a habit of using only the gauge wire that is necessary to run what it wants, nothing extra in gauge of wire.

My first pass would be the Circuit Panel under the hood, there has to be be a run only circuit there somewhere ?

Is there a Schematics on that fuse panel, send me a link, can't promise anything but I will look through it !

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Posted: Wed May 9th, 2018 03:13 pm

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JAMMAN

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Think "if". If rpm then relay on. I would use the tach signal to trigger an OK for a relay.

If you haven't figured it out in a few days I could dig in to it but I have a mechanical job to be done first. I'm "carless" right now.

Truckless would better describe it.

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Posted: Wed May 9th, 2018 03:17 pm

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JAMMAN

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RCR4V3N wrote:
The issue is the circuits are controlled by the switch position (off-accessory-run-start). Your best bet is to get an aftermarket voltage sensing relay that activates at 14v to trigger with alternator voltage instead of the battery/switch position.
That would work also, though it would fail if the alternator went down. You could set it to 12.9V I've never seen a battery at 12.9V but I have seen an alternator drop down to 13.3 or so with a full charge on the battery.

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Posted: Wed May 9th, 2018 09:00 pm

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Dusten
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JAMMAN wrote:
RCR4V3N wrote:

The issue is the circuits are controlled by the switch position (off-accessory-run-start). Your best bet is to get an aftermarket voltage sensing relay that activates at 14v to trigger with alternator voltage instead of the battery/switch position.
That would work also, though it would fail if the alternator went down. You could set it to 12.9V I've never seen a battery at 12.9V but I have seen an alternator drop down to 13.3 or so with a full charge on the battery.
My lightning is routinely at 13.6-13.9

Buggman, I don't think other than the exciter wire on the alternator you'll find what you're looking for. The vehicles electronics don't differentiate between running and off.

Another option would be to find a source like a cam or crank sensor and use that voltage to trigger a relay.

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Posted: Wed May 9th, 2018 10:18 pm

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I was thinking of a digital infrared motion sensor pointed towards the radiator fan. It would trigger a relay to apply power to a circuit.

About $6 for a sensor (DFROBOT SEN0018 Gravity), $5 for the relay (12V 30 40A Spdt Bosch ), and the cost for wire and loom. You pull power from a key-on accessory fusebox to power the sensor (needs to be be dropped to 3 volts- $2 varistor can do this) and relay operations.

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Posted: Thu May 10th, 2018 04:00 pm

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Do Not Touch The Trim!

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Well, I ordered a couple different undervoltage protection boards to play around with.
Hopefully they'll adjust the trigger voltage to 14v or just over the resting voltage of the main agm battery so it'll kick off when it's supposed to.
They have their own small relay rated at 10a but I think I'm gonna use that output to trigger a standard relay to power the isolator solenoid... it draws up to 8a spike when it first kicks on & 5a continuous) & I'm not sure how much I trust a $4 ebay part. Better safe than sorry :-)

Now it's just a waiting game for the boat from China to get here with the goods.

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Posted: Wed May 23rd, 2018 11:27 pm

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Finally got in one of the voltage protection boards to play with. So far I have mixed feelings with this.

I set a turn on voltage of around 13.8v and a turn off voltage of around 12.8v and it works on my bench power supply, but if I adjust the voltage slowly, I notice that I can make the relay continuously cycle if I hit just the right voltage. I'm not sure if this will happen when installed in the expo as the alternator voltage at idle was around 14v and battery resting voltage was around 12.8v, I'm hoping that the voltage will drop quickly enough when not running that it won't set at that quirky voltage load where it makes the relay go crazy. I couldn't really test the 1500rpm voltage at the battery by myself, but I know it should be over 14.5v but the idle voltage should be enough of a difference in the resting battery voltage.
Definitely don't want that 500a solenoid to be cycling that quickly.

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Posted: Thu May 24th, 2018 12:59 pm

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Scrambler82
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Im lost... a little !
What is going on with the circuit you want to build, what are you trying to do ?

Top Secret Stuff... ! If this circuit is a must have on, connecting it to the Alternator output voltage will work as long as the voltage output remains in the working range of the voltage sensing relay.
If the Alternator Voltage Regulator, loses some of its output and idles at a lower voltage than normal, then the relay won't trigger and do what it is you need done.

If the Circuit you are building doesn't trigger "On", will there be a problem ?

To me not knowing for sure what the circuit does, Im thinking a SPST Relay would work more reliable !

If the Circuit needs a delay "On", then there are delay on relays but once it is activated it will be on not waiting to hear from the Alternator to go live !

First... please straighten me out, (I guess I missed something) where is the circuit going to be used ?

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Posted: Thu May 24th, 2018 10:27 pm

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JAMMAN

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buggman wrote:
Finally got in one of the voltage protection boards to play with. So far I have mixed feelings with this.

I set a turn on voltage of around 13.8v and a turn off voltage of around 12.8v and it works on my bench power supply, but if I adjust the voltage slowly, I notice that I can make the relay continuously cycle if I hit just the right voltage. I'm not sure if this will happen when installed in the expo as the alternator voltage at idle was around 14v and battery resting voltage was around 12.8v, I'm hoping that the voltage will drop quickly enough when not running that it won't set at that quirky voltage load where it makes the relay go crazy. I couldn't really test the 1500rpm voltage at the battery by myself, but I know it should be over 14.5v but the idle voltage should be enough of a difference in the resting battery voltage.
Definitely don't want that 500a solenoid to be cycling that quickly.
It's not going to do that on the vehicle. I bet the relay is dipping the power supply when it comes on, the voltage lowers momentarily turning the relay off, lack of draw causes a surge in the power supply upwards which turns the relay back on.

If you aren't already use a diode for the flyback current. This is a must for all relays with the coil hooked to anything electronic.

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Posted: Thu May 24th, 2018 10:36 pm

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lol, i'm probably making this more complicated than it needs to be.
basically i want to switch on a relay whenever the expo is running but not when the key is on or not running. this will control my battery isolator solenoid (basically a huge 500a relay, but it draws 8a so i want to use a smaller relay to trigger the solenoid)

this will charge both batteries when running & the alternator is charging, but keep the batteries separated when off or if i want to listen to the stereo with the vehicle off.

the voltage controlled relays i got should do what i'm trying to do.
if i set the turn on voltage at around 13.5v it should kick on the isolator when the alternator chaarges the battery & by setting the turn off voltage at around 12.8v it should turn off a few seconds after it's shut off & the battery returns to resting voltage.
i'll probably have to play with the on/off adjustments until i get everything dialed in.

as a bonus, i found the voltage sensing relay modules have a "force on" connection where i can install a switch somewhere in the cabin should the main battery ever go down & not start, i can connect the aux battery for a quick boost.

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Posted: Fri May 25th, 2018 11:18 am

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Look to motor home or marine setups - they often have starting and leisure batteries charged from the alternator but otherwise isolated.

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Posted: Fri May 25th, 2018 11:59 am

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Scrambler82
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buggman wrote:
lol, i'm probably making this more complicated than it needs to be.
basically i want to switch on a relay whenever the expo is running but not when the key is on or not running. this will control my battery isolator solenoid (basically a huge 500a relay, but it draws 8a so i want to use a smaller relay to trigger the solenoid)

this will charge both batteries when running & the alternator is charging, but keep the batteries separated when off or if i want to listen to the stereo with the vehicle off.

the voltage controlled relays i got should do what i'm trying to do.
if i set the turn on voltage at around 13.5v it should kick on the isolator when the alternator chaarges the battery & by setting the turn off voltage at around 12.8v it should turn off a few seconds after it's shut off & the battery returns to resting voltage.
i'll probably have to play with the on/off adjustments until i get everything dialed in.

as a bonus, i found the voltage sensing relay modules have a "force on" connection where i can install a switch somewhere in the cabin should the main battery ever go down & not start, i can connect the aux battery for a quick boost.
Buggman,

I understand... thanks !

I know you like to build stuff yourself, I do too to a degree, but why not get a standard Battery Isolation setup ?
Won't the standard Isolation Setup do what you want ?

Also, since an alternator only charges when the battery(s) need charging, will that interfere with the Voltage sensing relay or will the alternator actuate and start putting out a voltage because of the Relay Draw ?

Smell the smoke AGAIN !

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Posted: Fri May 25th, 2018 01:38 pm

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Tsquare
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What you are making is an automatic transfer switch with a manual override - correct?

I have seen this with duel generator or generator/shore power setups but nothing in a 12 or 24 volt power range that was electronically controlled. Marine duel battery switches are all manual. There are some controllers that will monitor voltage in battery #2 and when it drops below a set voltage it has the charging circuit turned on till it reaches upper threshold.

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Posted: Fri May 25th, 2018 02:28 pm

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I had a diode type battery isolator but it was only good for up to 200a & i now have a 250a alternator.
the diode style would have probably worked, even with the .8v drop.

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Posted: Sat May 26th, 2018 10:39 pm

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Scrambler82
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buggman wrote:
I had a diode type battery isolator but it was only good for up to 200a & i now have a 250a alternator.
the diode style would have probably worked, even with the .8v drop.
Just talking out loud.
I would have guessed there would be a Diode Type Isolator for almost any amperage.

I will back off with my suggestions.

An interesting Thread, I will keep reading.

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Posted: Sun May 27th, 2018 10:53 pm

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i never could find anything for over 250a. i'm sure somebody makes one though.

had a couple days to work on the project again... so far everything is working as it should.

the turn on voltage is set to 13.8v-14v & it turns on right after startup. i've been playing with adjustments on the turn off voltage & i think it's set to around 13.5v now. it kicks off within 30 seconds of turning the key off.

got the aux battery fused & connected now too.

next up will be charging the amp caps & tuning the amp.
it will be nice to finally have some sounds in there again.

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Posted: Tue Jun 5th, 2018 01:23 am

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little update on this project...

i have everything installed (for the most part) and the voltage controlled relay module is working about 93% perfectly.
i've noticed when i have the a/c on, wipers, headlights, etc. while idling, sometimes the relay wants to kick off like it's hitting the turn off voltage.

I have noticed that this alternator seems to have a "low" point at idle with lots of stuff on where i can hear the a/c blower motor slow down a few rpms.

I'm thinking it's just gonna take a few more adjustments to the turn off voltage pot on the board, so it's not a huge deal... just gotta wait till the evening when it's not so darn hot where I can adjust things.

Once I have everything ironed out, I'm definitely gonna but a kit together 'cause I know this is gonna be a handy mod for guys & gals who want to run 2 batteries but keep them isolated when not running.

Still waiting on a spare center console section where i can mount some voltmeters to keep tabs on both batteries.

One other odd thing i noticed is the pioneer double din radio wants to power up the amp turn on wire whenever the screen is on. Not sure exactly why it doesn't work like every other amp turn on wire & just turn on the amp when the head unit is actually in use, but i guess this is a "feature" of this pioneer.

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Posted: Tue Jul 10th, 2018 09:01 pm

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Sounds like you need to smooth out the voltage fluctuations that cause the cut outs. Could add a capacitor to stabilize the voltage (low pass filter).

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