Bussed Relay Bank for Electrical Upgrades

[Randy_Lahey]

Hi everyone,

I'm working on my '68 Charger.  I'm still in the process of upgrading my alternator to a 130 amp Power Master unit.  This has been a huge process because I'm also updating all the wiring under the hood, including making a new under hood wiring harness that goes to the bulkhead.  I'm making several modifications to the electrics and to the car.  At present I'm also installing dual 13" cooling fans and an external controller.

My problem is this:  the controller and the relays it came with aren't waterproof.  I don't plan to regularly drive the car in the rain but I'm rebuilding this car with reliability at the forefront of thought.  I'm thinking I'll mount the controller under the dash, by the glove box, and have the wires for it go through the open bulkhead connectors in the plugs.  I don't want to mount the relays in the cabin because this defeats the purpose of having relays; I don't want major current like that traveling long distances through the firewall.

I'm wanting to mount the relays on the front of the radiator support.  Because my relays are SPNO and have 2x 1/4" and 2x 3/8" terminals, I can't make them work in any universal relay banks.  The relays have resistors so I can't just go grab any 70 amp waterproof relays and use those instead to fit the relay block.  They're 4 terminal relays.  Oh, and while not necessarily required, I'd give huge bonus points if the relay box was "bussed" so it would only need one large power wire feeding all systems fed from the box.  I was thinking I'd run at least an 8 gauge wire from the distribution block where my alternator will join with the battery and starter (to save physical space on my starter relay because I'll now have 2 gauge battery cables).

Apologies for the novella, but what are your guys' thoughts?  I've been reading about this for hours here and elsewhere on the web, while also looking at options and I'm still empty handed.

Thanks,

David

[Nacho-RT74]

If you are keeping ammeter, get the buss power from alt side, don't feed from batt post. Is INCORRECT to feed anything from batt side if the ammeter is on use.

I'd run a parallel path between batt and alt up to ammeter ( check stikied thread on here )

Check ammeter conditions, not just outside but inside.

You could install the relays and controler at a side of your horn relay and horns. Even they are not waterproof. Thats an area very well protected. Your stock horn relay is not waterproof either and has hold all these years there.

[b5blue]

I'll try to get you some pics of what I have that may help. (Soon)

[John_Kunkel]

Is INCORRECT to feed anything from batt side if the ammeter is on use.

Have to disagree, many devices such as fans draw more current than the ammeter is rated for. The factory routinely powered high-draw motor load devices (power windows, power seat) from the battery side of the ammeter.

[Nacho-RT74]

John, please read the stickied thread i wrotte up. Just because the reason you expose, is incorrect to source anything from batt side!

NOTHING on a car with ammeter ( but the starter motor ) is sourced from the batt side of the ammeter, so that's an incorrect statement.

When you increase the load requirements on car due accesories added, you need to increase the alt output to feed those and hook them up to the alt side of the ammeter. That's what will keep safe the ammeter!

[John_Kunkel]

John, please read the stickied thread i wrotte up. Just because the reason you expose, is incorrect to source anything from batt side!

Sorry, just because you wrote it doesn't make it gospel.

NOTHING on a car with ammeter ( but the starter motor ) is sourced from the batt side of the ammeter, so that's an incorrect statement.

You oughta study the FSM before making statements like that. I will repeat, the factory routinely powered high-draw devices directly from the battery bypassing the ammeter. The pic below from the FSM shows a typical power window breaker (red arrow)  powered directly from the ammeter RED (battery side) terminal (red arrow) that powers the power window relay. I can show numerous other examples over the years.

The reason for this is obvious, high-draw devices (usually motor loads) running through the ammeter would overload it and cause huge deflections of the needle which would alarm drivers.

[Nacho-RT74]

well on that case could be just because they are ocasional loads given for an instance, but not constant operational devices. An instant load sucker like power windows is not a headache for the charging system to get the batt recharged, just like the starter motor is ( also on batt side of the game ), but any constant power needs to stay on alt side with a good upgraded alt of course

a constant load sucker on batt side will make the load going throught the ammeter constantly like charging the batt where is not but actually sourcing that device and adding an unnecesary stress on ammeter

[JR]

This maybe an unnecessary argument.

I would assume, if the OP is going through this level of upgrading his electrical system, he's likely upgraded to a voltmeter and ditched the ammeter.

I've got 3 relays in front of my core support. (High and low beam plus fog lamp relay). They are mounted in line on a flat piece of steel, with not much in the way of water protection.  My car gets driven in occasional rain, and I've never had any issue.

[Dino]

When I actually still drove my car... ... I drove it in the rain A LOT. No issues with any of the relays. I've got a few. I just added a fuse box next to the fender tag as well. It'll live.

[Randy_Lahey]

JR is right, I'm planning to replace the ammeter with a volt meter conversion gauge.

I think you guys are right, I'm probably overthinking the waterproofing requirement of the relays. I'll mount them in a line behind the core support. I would have liked to consolidate the main power wires so I don't have a bunch of extra wire. I'll just add a distribution post by them to feed them all.

[c00nhunterjoe]

If you run 130 amps through the factory amp gauge, your car will burn down. Period. They couldnt handle 50 amps, nor can the supply wire to them.

[Nacho-RT74]

If you run 130 amps through the factory amp gauge, your car will burn down. Period. They couldnt handle 50 amps, nor can the supply wire to them.

FAAAAAALSE!

Your load requirements  never changes no matter how much amps is able to put your alt.

If your car requires 50 amps to work, you can install a 500 amps alt and will never put out more than 50 amps. Amperage is sucked by the devices not pushed in by the alt! Just need to be sure the alt will be able to source everything at the minimal sped as posible. Once you get that, the ammeter won't EVER sense any load.

And all the loads ( or most of ) are between amp and alt. The ammeter just read what cames out from the batt when car is off or what alt is not able to provide while spinning... or goes in to the batt when is discharged, and still the amperage won't be pushed in. The batt will suck what the acid is able to catch taking its time. Is not able to suck more no matter how much amps is the alt.

So, once again, if loads requirements are between alt and ammeter ( like factory made ) no matter if you increase up to 80 amps by accesories added and alt is able to provide every ampere at any speed, your ammeter won't  EVER sense anything, so won't move, so it means no load going throught... no load throught, no heat there.

Of course, ammeter NEEDS to be in good conditions, and bulkhead checked and/or upgraded.

The "weakness" of the ammeter based just on amperage limits becomes dangerous just if your car still sucks 80 amps ( using the last example ) with engine off and everything correctly sourced by the alt side of the game. That's the only moment the ammeter will try to give you that reading being pushed over the limits... but, when does it happen that with regular car accesories?

[Nacho-RT74]

Just think on this, you charge your phone from the wall outlet sucking no more than 1 amp. But the local electrification system maybe is able to give up to 200 amps ( depending on your safety breaker ), and you still plug your cell phone charger at the wall outlet.

[c00nhunterjoe]

If you run 130 amps through the factory amp gauge, your car will burn down. Period. They couldnt handle 50 amps, nor can the supply wire to them.

FAAAAAALSE!

Your load requirements  never changes no matter how much amps is able to put your alt.

If your car requires 50 amps to work, you can install a 500 amps alt and will never put out more than 50 amps. Amperage is sucked by the devices not pushed in by the alt! Just need to be sure the alt will be able to source everything at the minimal sped as posible. Once you get that, the ammeter won't EVER sense any load.

And all the loads ( or most of ) are between amp and alt. The ammeter just read what cames out from the batt when car is off or what alt is not able to provide while spinning... or goes in to the batt when is discharged, and still the amperage won't be pushed in. The batt will suck what the acid is able to catch taking its time. Is not able to suck more no matter how much amps is the alt.

So, once again, if loads requirements are between alt and ammeter ( like factory made ) no matter if you increase up to 80 amps by accesories added and alt is able to provide every ampere at any speed, your ammeter won't  EVER sense anything, so won't move, so it means no load going throught... no load throught, no heat there.

Of course, ammeter NEEDS to be in good conditions, and bulkhead checked and/or upgraded.

The "weakness" of the ammeter based just on amperage limits becomes dangerous just if your car still sucks 80 amps ( using the last example ) with engine off and everything correctly sourced by the alt side of the game. That's the only moment the ammeter will try to give you that reading being pushed over the limits... but, when does it happen that with regular car accesories?

As your prior post stated "nothing from the car is sourced from the batt side of the ammeter" which means ALL loads will be going through it. So as i clearly stated- if you run 130 amps THROUGH the ammeter as you stated it needs to be wired, your car will burn down. I did not say anything about the capabilities of the said alternator. Lets look at this simply
Msd-7 amps
2 fans- 25 each
Stereo- 7 amps
4 std halogen headlights- 25 conservatively.
Park lights- 5
Elec fuel pump- 7

There is almost 100 amps right there to start and the factory single feed alternator was rated at 46 amps. The ammeter could potentially take 60 amps as could the fusible link. The feed wire connection through the bulkhead is an 18 gauge spade terminal. You do what you like, but i have watched many mopars burn to the ground following that advice.

[Nacho-RT74]

No, the only way you get all the amperage going throught the ammeter to feed all what the car requires as far is being sourced correctly from alt side is if engine is off.

In that case, you wouldn't ( or shouldn't ) have electric fans, fuel pump, ignition system working, ( just the time you take from RUN to START, and that's if engine is hot, talking about the fans )


Aaaand halogen headlights don't suck that much. You in fact can feed all 4 high beams with a 20 amps relay and won't burn ( is the one on my car ).

I'm talking about regular circunstances and use.

Regular stereos doesn't suck 7 amps, maybe 5 at high volume. If it was 7 amps fuse could blown when you put turning lights and some other accesory, since normally everybody uses the stock provision for it which is linked to turning lights and several other.

Trust me, as far you source everything from alt side and get the CORRECT power alt ( not the factory one, which it was a HUGE mistake by MaMopar, being so poor ) able to source everything without needing to be  assisted by the batt, your ammeter practically will never sense any load under regular circunstances aside some small flicks caused by the time the reg takes to sense the power decay and send the order to the alt, because the batt will never get discharged so the load will never get back to the batt to be recharged. Battery barelly will request to be recharged. The only noticeable moment will be after the crank up, and the charge reading could take less than a minute at 5-10 amps and going down with stock starter motor... is my case, not my imagination. My own car can proove it and I have 6 relays, everyone INSIDE the cab, to feed the AC blower, one for each speed ( to save the blower speed switch which is WEAK ), plus the headlights and all relays are sourced from ammeter stud on alt side.... of course I have a parallel path to ammeter, saving the bulkhead conections, which are still there.

You wanna know what really sucks A LOT of amperes? The stock AC blower! It can be up to 30-32 amps at max speed

And source anything from batt post will be read to the ammeter as a charge process, an unnecesary stress for the system.

On everything of this, the only weak point to be allways checked and upgraded or getting mantenience would be wiring terminals on charging system

[Nacho-RT74]

Well in fact, a prove about a 130 alt won't burn your ammeter or anything of the system is you actually HAVE a battery able to give up to 400 or maybe more amps as cranking power, and you still get the dome light being sourced by the batt ( from alt side of the wiring ) with engine off... it doesn't burn because the high load capacity from the batt... right? Same example as the cellphone charger plugged to the wall outlet.

Please read my thread about that. I know is not in perfect english but ilustrations are really clear and easy to understand.

[c00nhunterjoe]

You are still overloading the system that was designed to handle 40 amps and 40 amps only. Period. The ammeter, connectors and wiring was never intended for any of the additional loads you are describing. The methid you posted simply bypasses the ammeter and the load is still on the subpar wiring. If you bypass the bulkhead connector, bypass the ammeter, and replace all of the factory wiring, then why are you even bothering to have the ammeter hooked up? It would be much simpler to just not hook it up and save the trouble and risk.

[b5blue]

  The gauge we are talking about here is labeled "ALTERNATOR" right? It monitors the alternator's function not AMPERE quantity. If you read the FSM's schematic the alternator gauge is reading between + post of battery and main harness + feed from alternator AFTER main fuse block splice. Think of the gauge as a degree of balance meter for the charging system not an AMPERE gauge per say.
  So in each of your ways your both right but no matter the gauge shows interaction differential as the system functions up to about 40 amp. 

[John_Kunkel]

No, the only way you get all the amperage going throught the ammeter to feed all what the car requires as far is being sourced correctly from alt side is if engine is off.

Don't forget the scenario wherein the battery is completely dead and the car is started with a jumper, as soon as the jumper cable is removed the entire output of the alternator will be flowing through the ammeter to charge the dead battery.

If for no other reason, this is why you don't want to run a high-output alternator with an ammeter unless the meter is shunted.

[b5blue]

  Exactly! Folks think just because their lazy a car can charge a dead battery, not so. Here are a few quick pics of added relays and mini fuse panel added for electric fans and A/C. By using control relays and mini panel added loads are not run inside car, just minor bit of control voltage from switch. Car has #8 (Blue) wire added per "Fleet upgrade" with inline fuse. I'm using a DENSO 120 AMP alternator that is capable of 50amp @ idle. (After fooling around with various fan setups I found a factory direct drive fan that eliminated the need for electric fan/s.)  

[b5blue]

To avoid voltage back-feeding in any way and to allow A/C and/or Thermostat to turn on fan you can install a Diode. (Diodes allow voltage only in one direction.) The adjustable thermostat allowed me to tweak just how soon the fans came on, it's really hot here in Florida.  

[Nacho-RT74]

  The gauge we are talking about here is labeled "ALTERNATOR" right? It monitors the alternator's function not AMPERE quantity.

Thats the first mistake made by factory. The ammeter is a batt gauge not really alternator. You CAN NOT get discharge on alternator because IS NOT an accumulator. You can get discharge just from something able to storage something, ( load/amperes on this case ).

Ammeter gauge reads AMPERAGE COMING AND GOING FROM/TO BATT.

You can unplug the batt with engine running and ammeter will stop the readings. You can unplug the alt with engine running and ammeter will read discharge so will keep reading... what could mean that ? Think on that!

Guys, I can understand you are expert on mech/performance stuff and on those threads I just can give opinions, not experience, but please, I would appreciatte at least ON THIS stuff trust me, or give me at least the doubt benefit!

Make your own experiments about this and prove it by yourself

[Nacho-RT74]

No, the only way you get all the amperage going throught the ammeter to feed all what the car requires as far is being sourced correctly from alt side is if engine is off.

Don't forget the scenario wherein the battery is completely dead and the car is started with a jumper, as soon as the jumper cable is removed the entire output of the alternator will be flowing through the ammeter to charge the dead battery.

If for no other reason, this is why you don't want to run a high-output alternator with an ammeter unless the meter is shunted.

It can't be charged faster or higher amperage than the battery capacity to get the load absorved or captured by the chemical process. I Repeat, YOU CAN'T PUSH IN the amperes, they just can be sucked

In any case you SHOULD NOT make that and should be charged out of the car. In case of emergency on the road, you can save part of the load going to the batt just turning headlights on. That will save the ammeter and wires between amm and batt to get the extra load that long. Of course alt speed will be part of this.

Once again... guys I have made MANY experiments of this on my own car WHICH HAS BEING A DAILY DRIVER, because electricity is part of my main worries on my 74 being I know the charging system is a weakness on Mopars. Aside that I work allmost everyday with electricity due my job. Not saying I'm eletricity engineer, but I deal with that as regular part of my life.

[Nacho-RT74]

You are still overloading the system that was designed to handle 40 amps and 40 amps only. Period. The ammeter, connectors and wiring was never intended for any of the additional loads you are describing. The methid you posted simply bypasses the ammeter and the load is still on the subpar wiring. If you bypass the bulkhead connector, bypass the ammeter, and replace all of the factory wiring, then why are you even bothering to have the ammeter hooked up? It would be much simpler to just not hook it up and save the trouble and risk.

When you guys understand the deal on this is get an alt able to source every part of the car needs and being everything sourced by the alt at the minimun speed as posible and never by the batt ( or reduced at minimun ) will begin on trust on the ammeter as a safe gauge still being +/- 40 amps even with a 500 amps alt.

Would be better they were 80 amps gauge? Sure! Would be even better they were ALL shunted like later models? Sure too, but they didn't exist back in the days.

It was better our cars were equipped with airbags too and nobody talks about install aribags sytems on our Cars!

Keep or not the ammeter and make mods goes by each own, I just try to let you know how really works the system and how to keep it safe if wished to keep it on car in working order, but with the correct info, and not myths anymore ( or fears )..

The wiring upgrade and bulkhead terminals weakness is more toward due the car requirements than the alt itself. Of course are related, but as mentioned, if your car sucks 50 amps, and everything is hooked up to the main splice inside the cab, that's the moment the bulkhead and related wires are part of the problem on both sides. If you get the alt upgraded and your batt never get discharged, the only side will be in troubles is the black one between alt and splice. The red side won't have any problem

The burn spots on bulkhead on both sides is due the loads going back and forth constantly with alt speed.. with an alt unable to feed at iddle the system will suck from batt partially. Then increasing speed the alt will feed all the car and restore the load missed by the batt previouslly.

I don't know any other form to try to make you understand this. Just proceed by yourself with experiments if you really care about and will confirm by yourself how my diagrams on the stickied thread about the ammeter and loads work are totally true!

Don't be like a horse, please.

[b5blue]

I haven't had any issues in 23 years with most of that time my only car.