Battery Powerline Protection

[vette]

Basically a circuit is a loop so aside from an overriding authority or governing body making a regulation you can put a fuse in the loop anywhere and if it opens due to overcurrent or short circuiting (which will create the overcurrent) it will stop the current flow. In automobile technology there is very little governing body that regulates what you do. All current going out of the battery has to return to the battery or it would not work at all.
Ok, having said all that, what happens to the potentially large amounts of current that the generator or alternator might put out if the battery cable between the solenoid and the battery were dead shorted. I have a pretty good electrical background having studied it in technical school and as a career electrician and a Metering tech for a large utility. I was the guy responsible to measure all types of power in the largest electrical installations in place. From generating stations to large industrial complexes. So, I really don't know the answer to my own question. It would take some studying of the components involved and some test measurements. But here is a possibility: In my first paragraph I described a simple loop with one power source, the battery. But if the alternator takes over and its cable is shorted then the alternator becomes the overriding power source. Forget about the generator, Austin Healey generators can't put out that much before they will just burn up their brushes and commutators. Since the alternator is also grounded to the car chassis, the circuit loop is now from the alternator BAT terminal down to the solenoid and continuing down the path to the battery until it reaches the point of short circuit. That would be the large cable shorted to the chassis. So here we have an alternator that is in a loop that has its BAT terminal shorted to the chassis and then continuous to the ground side of its own windings. A continuous loop and a short one with almost zero resistance. The alternator will try to go to max output.
The battery is almost completely out of the circuit so a fuse protection back at the battery will not stop the alternator from going to max and trying to feed the shorted loop. Now if the short in the electrical system is on any of the smaller wires, those wires will just burn apart and as some have said, will act like a fuse. They will burn open and the circuit will be open and the alternator will stop putting out. Could the small wires burn enough to cause a fire, they could. But that is why we are putting fuses on all our circuits.
But back to the large cable that could get shorted to the chasis. How do we stop that cable from really pulling a heavy current from the alternator? In previous post, I have said, it just doesn't happen don't worry about it. Well I'm still playing those odds, but, is there a way to protect that large cable. There is. You would have to design an installation that would fit, but the equipment and technology does exist. It's called a 'CT'. Stands for "Current Transformer". This is a transformer that step up or steps down Current. Not Voltage. We all experience Voltage Transformers because they are around us every day. The utility uses voltage transformer to step down the high voltage to the voltage (120/240v) usually to your house. Your door bell works off a voltage transformer, it takes the 120volts in the house circuit and steps it down to 12, 18 or sometimes 24 volts. But a CT steps CURRENT up or down and has almost no parasitic loss doing it.
Do you see where I am going with this. If a Ct could be installed around the large cable going to the battery, it could trigger a relay when the large cable reaches a current value of a specified threshold.

here is an example of what I am talking about but you would have to find one that had the right specifications. the large cable runs thru the center of this and the device senses the current in the cable.

I see two problems with this. 1. I still think it is cumbersome. 2. I don't know that it would react fast enough to avoid a catastrophic loss.

 

[RAC68]

Hi Vette,

Thanks for your comments and instruction. As I understand, the one device and situation that would appropriately require a high amperage draw the starter when starting the car...especially in cold weather. All other cases put a much smaller amperage demand on the battery circuit and/or alternator, I would guess around 30 amps at max. Yes, a dead short would stimulate the alternator to push out full device output, however a 30 amp circuit breaker could address the issue when the car is already in operation. The challenge then would be how to switch from no protection during the time when the starter is activated to fuse protection (i.e. 30 Amp or so) when the starter is not operational.

By separating normal maximum amperage draw into 2 conditions, each can be addressed separately and, in this case, the majority (non-starting) portion of total operation could potentially be addressed with a quick responding fuse or resetting circuit breaker. This does leave the time when the starter is activated and in operation when large amounts or amperage could be correctly called for from the battery.

Do you agree and, if not why? Do you have any ideas?
Again, thanks for your thoughts as I have continued to think of this but have no actual solution,
Ray(64BJ8)

 

[CaptRandy]

Ray not sure if it will apply but I have tow 25 amp fuses at my battery terminal connection of the smaller boat that are connected with a metal plate. Got them at a marina store. Will try to get a photo later today.

 

[Bob_Spidell]

re: "... a dead short would stimulate the alternator to push out full device output ..."

I'm not sure, but I believe Healey generators--at least, on the 6-cyl cars--have a current limiting capability (that's why the regulator has three relays instead of just two like on the 4-cyl cars). At any rate, I think our Lucas generators are only capable of about 25 amps flat out; the source for 'unlimited' current is the battery.

 

[4tecdog]

This is really just a belt and braces precaution I would still be happier with a fuse/circuit breaker on the source of power as has been said before it is a standard practice on marine applications they usually have geared starters and are protected by a 90amp block fuse. I always turn the isolater off when parked don't like the idea of those little critters eating my battery cable. Have even spiro wrapped some of the more vulnerable areas and used strong nylon clips not those sharp metal ones. Maybe I can adapt a Marine block fuse on the negative cable. Those fused terminals are really cool could adapt one of those for the neg terminal and make a nice cover to stop those loose metal items in the boot touching.

 

[Keoke]

Well 4tecdog
For those marine applications that use a Single point ground system I think your approach is a go.

 

[vette]

Yes the generators are only rated at around 25 amps. And that is the later cars. I believe the early cars were rated around 15 amps. My opinion is that a car with an original generator would not supply enough current to create a catastrophic failure, but as Bob said, the Battery could. If the cable running alone the frame did get shorted to the chassis you would be creating two shorted circuits. If the generator/alternator was turning on loop would short out the generator/alternator and the 2nd loop would short out the Battery. I think the only way to try to protect against this is to have some type of protective devices in both loops. At this point I would think this would be a pretty daunting scheme. I could just envision converting your 2+2 rear seats or your parcel shelf into an electrical panel that would house the relays and relay operated breakers or circuit openers which would be able to sense the overcurrent and trjp the openers to open both loops.
Just for conversation sake, I just looked up the ampere draw of a starter on a 1960s era Corvette and it is about 80 to 90 amps. The generator for the Vette is rated at 60 to 65 amps. I believe the early alternators where rated about the same. A '60s era Corvette battery was rated at 62 Amp/hours. Watts rating was 3250w. That would equate to about 280 amps so I think that would be its CCA=cold cranking amps. Today we know that many batteries would have 500 or more CCAs. A #2 copper wire can handle about 115 amps. That's probably a little smaller diameter than the end of your little finger. So put 100 amp breaker in the circuit right at the battery and when the cable gets shorted that breaker will blow and keep the battery from putting out its full CCA. Once that blows, the electrical disruption to the system will probably be great enough that it will shut the engine off and the alternator/generator will stop turning and there will be no threat from that end.

 

[RAC68]

Hi All,

As I have understood from the previous posts in this thread, we have 2 power sources (battery, alternator/generator) that must be address and will need 2 separate protection approaches. Since a main-power short is the result of a power line coming in contact with an unplanned ground, protection must be applied to the power output side of the Battery and alternator-generator.

Placing a 30 amp. circuit breaker or even a 40 amp. fuse on the power output line of the Alternator/generator should provide a responsive termination of a potential runaway power generation flow. However, although this approach can also be used to brake the flow of power from the battery during on-going car operation, I don’t believe this simple single fuse approach would be sufficient to provide the substantial draw required when initially starting the engine.

So, in short, I see these Requirements and look:
1. A separate fuse is required for each Power Source (battery, alternator/generator) normal car operation.
2. Due to the high draw of the starter, it is not practical to implement a single fuse approach and the circuit should be switched to an unprotected state during this short period of starter activation.
3. A way to switch off battery fuse protection during the time of original starter operation.

Implementation:
1. What equipment, fusing, etc. will be needed for a practical installation?
2. What approach should be taken to switching the battery power line from fused (protected) to unfused during starter activation?

Please correct.

Ray(64BJ8P1)

 

[John Turney]

Let's go back to the original question:

I began to wonder if I could also install some sort of a protection (fuse, circuit-breaker, etc.) at the battery to protect against damage from a short developing in the long power line from battery to starter.

The next, follow-on question is what are we trying to avoid? Igniting the battery cable? Igniting the battery? Burning a hole in the frame?

Let's start with maximum short circuit output of the three power sources:
A Lucas generator - ~25A - 30 A on a good day.
A replacement US alternator - Up to 120 A, but more likely 60 A, depending on rotational speed.
The battery - up to 1,000 A. Look at their cold cranking amp (CCA) ratings. Those numbers assume the battery current is passing through a starter, so short circuit current is higher.

What is the current carrying capacity of a #4 AWG battery cable? 130A steady state, much higher for short periods. Would it be damaged by a short if supplied by either a generator or alternator? No. A battery short? YES!

Would the battery be damaged by a generator or alternator if there is a short in the battery cable? No, current would flow from the generator or alternator to the short, then back to the generator or alternator through the frame, engine ground cable and engine. Even if the current flowed through the battery, it wouldn't be damaged in a short period of time. Would the battery be damaged by a direct short? YES!

Would a short in the battery cable be enough to burn a hole in the frame if supplied by a generator? No. Alternator? I doubt it. Battery? YES!

IMO, we need to be concerned by current from the battery if we have a short in the battery cable. A generator or alternator would be "small potatoes" in comparison, and the output wire from the generator or alternator would burn out first. But that's easy to fix. Put a fuse or circuit breaker on the generator or alternator output. The maximum output is known for each of those, and it's a reasonable number.

The problem has always been the short-circuit battery output. The "easy" solution has always been to move the starter solenoid near the battery, so that long, heavy cable only carries current while starting. Run a second cable capable of handling the normal, maximum running or charging current and fuse accordingly.

Does this introduce other sources of failure? Potentially.

1. The normal running wire could be damaged by accident, abrasion/ware, road debris penetration, or just a mistake. The fuses at the battery and generator/alternator would prevent catastrophic damage (unless being brought home on a flatbed is catastrophic).
2. The main battery cable could still be damaged by accident, abrasion/ware, road debris penetration, or just a mistake, but it would only be apparent when trying to start the car. Solution is to let go of the button.
3. The starting wire to the starter solenoid could be damaged by accident, abrasion/ware, road debris penetration, or just a mistake. See #1.
4. The fuse for the normal running wire at the battery could go bad through overload, poor connection, etc. Yes, but this wouldn't be catastrophic.
5. The fuse at the generator/alternator could go bad through overload, poor connection, etc. Yes, but this wouldn't be catastrophic.
6. Lose points in Concours. Yes, what's it worth to you?

Another solution, and I recall reading that the factory rally cars did this, was to route the battery cable in conduit above the frame, maybe along the inside of the sill.

 

[GregW]

The "easy" solution has always been to move the starter solenoid near the battery, so that long, heavy cable only carries current while starting. Run a second cable capable of handling the normal, maximum running or charging current and fuse accordingly.

Or move the battery to the engine compartment. Cars without a brake booster have a pretty good spot without much thought to battery size. Get a gear reduction starter and you could also get a smaller battery.

 

[vette]

Hi All,

As I have understood from the previous posts in this thread, we have 2 power sources (battery, alternator/generator) that must be address and will need 2 separate protection approaches. Since a main-power short is the result of a power line coming in contact with an unplanned ground, protection must be applied to the power output side of the Battery and alternator-generator.
I would like to give opinion as to semantics and concept. If the short is in the cable along the frame then for the moment ( until the cable may or may not separate or separate from the frame contact) both power sources will see the short. The battery protection can be applied at either battery post. The current going out of the battery would be the same as the current coming back to the battery and the object would be to stop that current flow.

Placing a 30 amp. circuit breaker or even a 40 amp. fuse on the power output line of the Alternator/generator should provide a responsive termination of a potential runaway power generation flow. However, although this approach can also be used to brake the flow of power from the battery
are you saying that a fuse near the alternator would stop current from the battery??? It would not.
during on-going car operation, I don’t believe this simple single fuse approach would be sufficient to provide the substantial draw required when initially starting the engine.
I agree with you Ray, one fuse near the alternator/generator would not keep the battery from doing its damage. But a 100 amp fuse or breaker at the battery would allow the starter to crank but would open upon a dead short of the cable and keep the battery from putting out max amps.

So, in short, I see these Requirements and look:
1. A separate fuse is required for each Power Source (battery, alternator/generator) normal car operation.
2. Due to the high draw of the starter, it is not practical to implement a single fuse approach and the circuit should be switched to an unprotected state during this short period of starter activation.
3. A way to switch off battery fuse protection during the time of original starter operation.
I don't believe a dual scheme (protected state/unprotected state) is necessary. Two fuses as stated above would do it. The equipment to install such a dual scheme would be pretty cumbersome. As I think about this i don't see any advantages to trying to accomplish a dual scheme. It would add more wire and more exposure for damage. If you wanted to run a heavy cable just for the starter, which you already have, then you would need to add additional small circuit wire to run the car absent from the starter. If you put this protection back at the battery, then the small circuit wire would have to originate back there and run forward. "More Exposure". If you put this protection at the front of the car, then the cable to the battery is still hot and the original exposure still exist.

Implementation:
1. What equipment, fusing, etc. will be needed for a practical installation?
2. What approach should be taken to switching the battery power line from fused (protected) to unfused during starter activation?
I leu of what was said above, you could install a manual 3-way switch at the battery. This should be a fused switch with 2 output terminals and 1 input terminal. The main cable coming along the chassis would be connected to both the output terminals and the battery would be connected to the input terminals. One position of the switch would connect from the input terminal to one of the output terminals and this position would have a fuse in it. The other position would connect from the input terminal to the other output terminal and would be straight thru with no fuse. You would manually switch this switch back and forth each time you wanted to start the car. You could do this with a very large and heavy relay but then you are adding all the encumbering to the system. One problem with this ideal is that after you start the engine you would have to switch back to the fused protected side of the switch, and upon make this move, the engine might stall.
I like putting the 100 amp fuse at the battery or letting the whole thing alone. Just put a tough cable between the battery and the solenoid.

Please correct.

Ray(64BJ8P1)

I keep getting messages that are too short. If anything my post are too long but it won't post.

 

[vette]

Let's go back to the original question:

The next, follow-on question is what are we trying to avoid? Igniting the battery cable? Igniting the battery? Burning a hole in the frame?

Let's start with maximum short circuit output of the three power sources:
A Lucas generator - ~25A - 30 A on a good day.
A replacement US alternator - Up to 120 A, but more likely 60 A, depending on rotational speed.
The battery - up to 1,000 A. Look at their cold cranking amp (CCA) ratings. Those numbers assume the battery current is passing through a starter, so short circuit current is higher.

What is the current carrying capacity of a #4 AWG battery cable? 130A steady state, much higher for short periods. Would it be damaged by a short if supplied by either a generator or alternator? No. A battery short? YES!

Would the battery be damaged by a generator or alternator if there is a short in the battery cable? No, current would flow from the generator or alternator to the short, then back to the generator or alternator through the frame, engine ground cable and engine. Even if the current flowed through the battery, it wouldn't be damaged in a short period of time. Would the battery be damaged by a direct short? YES!
John I agree with your premise, but a short to the cable would also be a short to the battery. I'd hate to be standing near by when that happens.
Would a short in the battery cable be enough to burn a hole in the frame if supplied by a generator? No. Alternator? I doubt it. Battery? YES!

IMO, we need to be concerned by current from the battery if we have a short in the battery cable. A generator or alternator would be "small potatoes" in comparison, and the output wire from the generator or alternator would burn out first. But that's easy to fix. Put a fuse or circuit breaker on the generator or alternator output. The maximum output is known for each of those, and it's a reasonable number.

The problem has always been the short-circuit battery output. The "easy" solution has always been to move the starter solenoid near the battery, so that long, heavy cable only carries current while starting. Run a second cable capable of handling the normal, maximum running or charging current and fuse accordingly.

Does this introduce other sources of failure? Potentially.

1. The normal running wire could be damaged by accident, abrasion/ware, road debris penetration, or just a mistake. The fuses at the battery and generator/alternator would prevent catastrophic damage (unless being brought home on a flatbed is catastrophic).
2. The main battery cable could still be damaged by accident, abrasion/ware, road debris penetration, or just a mistake, but it would only be apparent when trying to start the car. Solution is to let go of the button.
3. The starting wire to the starter solenoid could be damaged by accident, abrasion/ware, road debris penetration, or just a mistake. See #1.
4. The fuse for the normal running wire at the battery could go bad through overload, poor connection, etc. Yes, but this wouldn't be catastrophic.
5. The fuse at the generator/alternator could go bad through overload, poor connection, etc. Yes, but this wouldn't be catastrophic.
6. Lose points in Concours. Yes, what's it worth to you?

Another solution, and I recall reading that the factory rally cars did this, was to route the battery cable in conduit above the frame, maybe along the inside of the sill.

This would be a good solution. One that I considered when restoring my car. But the one thought that kept me from doing it was the possible water or moisture penetration that might eventually weep into the conduit.

 

[RAC68]

Hi All,

Well, I have slightly modified my originally submitted diagram which reflects additional research. The present implementation diagram for providing quick response protection:

1. 40A Circuit Breakers on Main power sources (Battery, Alternator) except for the short period when the starter is being activated by the key switch.
2. Uses the existing battery cable.
3. Can be almost completely hidden and easily reversed.
4. Retains original operation.

The remote starter solenoid has an “I” terminal that is switched ON (12V) when the solenoid is activated by the ignition switch and OFF (0V) when the ignition switch is in the Off or Run position. I am retaining my Healey’s original starter solenoid and plan to activate the original solenoid with power from the Remote solenoid’s “I” terminal. I am planning to disconnect the original red/white line to the original solenoid at the ignition switch and jump it to the “I” terminal wire. I will activate the remote starter solenoid by connecting the “S” terminal connection to the ignition switch replacing the original solenoid connection.



Hidden Implementation
In this approach, no modifications other then the addition of a hidden 40 amp resettable circuit breaker will be made and, therefore, look as original as prior to the installation ( I have an alternator and other modifications all designed to be removed to go back to concourse). As mentioned, the remote solenoid and circuit breaker can be placed under or incorporated within the battery box thereby hiding all boot-located modifications.

To Be Tested
Draw at the 40A Circuit Breaker during dual Solenoid (1st Remote Solenoid, 2nd Original Solenoid) activation?
Will the circuit breaker designed to provide 40A Max protected line power when the Ignition is in RUN or OFF be subject to a startup draw substantial enough to cause it to fault?

Comments appreciated,
Ray(64BJ8P1)

 

[John Turney]

Hi Ray,

Draw at the 40A Circuit Breaker during dual Solenoid (1st Remote Solenoid, 2nd Original Solenoid) activation? If I read your drawing correctly, there is a 20A fuse to the rest of the car from the original starter solenoid. That would be limiting during the dual solenoid activation since the current to the ignition switch goes through it.

Will the circuit breaker designed to provide 40A Max protected line power when the Ignition is in RUN or OFF be subject to a startup draw substantial enough to cause it to fault?
That will depend on: the wire size, resistance of the circuit breaker and the remote solenoid. The current in each leg will be inversely proportional to the resistance in each leg. If the remote solenoid develops a high resistance, the CB will likely fault.

The maximum alternator output is? The alternator fuse needs to be larger than that by ~25% but the wire size must support that, so alternator output wire size is?

 

[RAC68]

Hi John and thank you for your response.

I have a 65A Delco Alternator. I chose the 40A circuit breakers because the main power usage is the lighting and all else. All front lights are covered by a 20A fuse providing power for 3 relays (High, Low beams and driving lights). The other 20A fuse is to cover the demands of all else. Since I expect the alternator and/or battery will be called upon to satisfy a NON-startup draw much less than 40Amps, I felt this size circuit breaker would be more then sufficient.

Since the remote and original starter solenoids would be in very good or new condition, internal switched resistance should be non-existent. My thought was that when switched-in, power would flow through the remote solenoid through the original switched-in to the starter. The only time the amperage draw could exceed the 40A Max is during the initial startup when the primary draw is from the starter's operaton. In this case, the 40A fuse should be bypassed and flow through the remote solenoid without protection.

John, I really appreciate your views,
Ray(64BJ8P1)

 

[John Turney]

"I have a 65A Delco Alternator. I chose the 40A circuit breakers because the main power usage is the lighting and all else. All front lights are covered by a 20A fuse providing power for 3 relays (High, Low beams and driving lights). The other 20A fuse is to cover the demands of all else. Since I expect the alternator and/or battery will be called upon to satisfy a NON-startup draw much less than 40Amps, I felt this size circuit breaker would be more then sufficient."

OK, but what about the charging current to the battery?

"Since the remote and original starter solenoids would be in very good or new condition, internal switched resistance should be non-existent. My thought was that when switched-in, power would flow through the remote solenoid through the original switched-in to the starter. The only time the amperage draw could exceed the 40A Max is during the initial startup when the primary draw is from the starter's operaton. In this case, the 40A fuse should be bypassed and flow through the remote solenoid without protection."

Yes, but the 40A fuse/CB isn't out of the circuit as far as I can tell. Did we ever determine what the starting current is? If the remote solenoid and the remote CB have the same (identical) resistance, and the starting current is, say 300A, then the 40A CB will see 150A. Can you find a solenoid that will remove the remote 40A CB from the circuit?

 

[vette]

Ray, I believe you have developed a very adequate scheme for this issue. And I agree with Johns point about high resistance in the remote solenoid. But I also agree overwhelmingly with you that the remote solenoids internal resistance across its large contacts will be small. I think this plan of yours will work. If I interpret your drawing correctly the ignition sw when moved to the start position will pull in both solenoids via the brown and pink wires. With both solenoids energized the battery power will go thru the big contacts in both solenoids and crank the starter. As the starter is cranking the ignition coil will get power from the 20 amp fuse off the front solenoid. ( i might have a problem with this fusing). When the ignition sw is released to the run position the big contacts in the solenoids are released and the starter stops cranking but instrument power is then pulled around the rear solenoid thru the 40A circuit breaker then up to the 20 amp fuse.
I think maybe the 20 amp fuse is not large enough if you consider any possible combination of auxilary equipment ex: driving lights, radio, GPS, cell Phone, etc. But I can't interpret the terminals on the front solenoid to be sure where you are connected. If I remember correctly the starting voltage to the ignition coil is pulled off of the starting terminal on the front solenoid but the run voltage for the coil is pulled off the ignition switch from battery power. So my concern with the 20 amp fuse is why bother. If you pull all the instruments, etc from the 20 amp fuse they will not be turned off with the ignition switch. But the hot wire running from your remote solenoid to the ignition switch which should be battery power to the instruments of the car, it is not fused at all? So to me you are endeavoring to protect some things and ignoring some others ??
This brings me back to my original premise that all this paraphenalia is encumbering and overpowering. To my mind (I'm a simplist), ya know the old KISS principle, you mount this stuff in a box with the battery and the next time the battery needs serviced you find that electrolyte has leak unto your relay and wiring and the wiring is in the way when you want to change the battery and etc, etc, etc. Then you have the extra wires run to the solenoids and the ignition switch and one day the car won't start. Well, I hope your in a good mood to pull out your new drawn out, lamenated wiring schematic, because the local repair shop down the road will take one look and say good-bye. Well this has been a fun mental exercise, but it seems to be proving that we all must have too much time on our hands. And I say this with all due respect. Really. All the respect to you guys but I wouldn't put this in my car if you paid me, and I wouldn't put this in a customers car if THEY paid me.

 

[RAC68]

Hi Guys,

John,
Sorry to have not responded immediately. First, the choice of 40A circuit breakers should be more then sufficient as I expect that my actual power use is well under 20 amps in total. Additionally, I expect that my 65A alternator will easily be able to maintain the battery within the limitations of the 40A circuit breaker and that level of circuit breaker will provide quick response if a short is encountered in the main circuit. It is not the alternators to function to charge the battery but to maintain its power and the only time a dead battery condition should be encountered in an operating Healey is if a short circuit is detected. In this case, I would rather cut the power from the alternator to save major components. Considering the upper charging capacity of an original generator falling within 25 amps and satisfying my Healey's power demands, a 40A circuit breaker limiting the output of my 65A max alternator more then envelopes my power requirements.

Vette,
I appreciate not wanting to complexify the circuitry at the battery but the points you have made are not issues.

1st, I am using a sealed Optima battery and have built a battery box to take on the image of a non-modern battery.
2nd, I have a battery pan that would also protect anything mounted under the battery if I choose to place the components there.
3rd, the complexity of the installation requires both remote and original solenoids to switch simultaneously and 2 new switching wires routed from the Remote Starter Solenoid to the aria of the ignition switch.

Installing the Remote Starter Solenoid under the battery would be relatively easy and, as with the original starter solenoid, would not need much, if any, attention following implementation. The rear circuit breaker would be manually reset and could be mounted just behind and above the battery for convenience. At present, I have my subwoofer amp mounted under the battery and have found no problems with the location of that unit.

Keep in mind that the 20A fuse supporting the main circuits of the car is more then sufficient as I have separated the major power draws (i.e. Head/Driving lights, etc.) to relays powered by separate power sources and only use original components and lines to switching functions at minimal power draw. This separate power source approach has also been taken for the installed sound system, however the 20A fused line still provides power for the horns and rear tail lights.

It is possible to eliminate the involvement of the original starter solenoid and just keep it in place. In a single solenoid approach, power would only flow through the original battery cable during engine starting and an additional fuse-protected line of sufficient gauge would be required for installation to power the car during operation. Although this would work and be preferable to many, I find the approach presented as requiring the least alteration to the original wiring and be easy to reverse. The use of the power line from the battery would be a superior carrier of the 40A protected power as well as guaranty that power is cut to the starter when the original solenoid deactivated.

At the ignition switch, one wire would replace the original starter solenoid wire on the switch and the second wire would be connected to the original starter solenoid. A double connector on the ignition switch could eliminate routing a second wire from the remote solenoid altogether with both solenoids connected directly to the ignition switch. Depending on the power draw required to activate and maintain both starter solenoids during start-up, a relay could be incorporated to carry the power and to reduce the amperage passing through the starter switch to that of relay switching current only. Although this would be advantageous to prolong switch life, it does add an additional component that could be wired directly through the 20A fuse. To complete the installation of the remote starter solenoid, a short piece of battery cable would be required along with changing the battery end of the original cable to fit onto the remote starter solenoid.

All my electrical modifications are well documented, logical, and reversible (other then the in-line fuses covering all critical circuits). This is an easier implementation then the multi-relays of the headlights/driving lights or the implementation of an alternator. Since all can be reversed, the cost of doing so would be the approx. $50US component cost. Yes, something unexpected and unplanned for could go wrong but then which potential risk is higher?

I really appreciate your comments and feel I would be less confident if you guys didn't provide your meaningful critical review.

Thanks Guys,
Ray(64BJ8P1)

 

[Michael Oritt]

This topic certainly has legs and while we have come up with some interesting theoretical solutions I doubt they will be employed by many.

I do like the idea of simply moving the solenoid in the starting circuit from the starter end back to the battery and de-energizing the cable except when the starter is actually in use. I realize that when the batts are located remotely such as in Healeys this will still require a long run of relatively large wire for service of other house loads--lighting, horn, etc--but that can easily be protected by a fusible link and/or protected sub-circuits.

I wonder why, in modern cars where batteries are usually found very close to the engine, does the practice of mounting the starting solenoids on the starter--versus on the battery--persist? Since the battery cable must in either case be the same length factors of resistance, voltage drop, etc. should remain the same.

 

[Bob_Spidell]

... I wonder why, in modern cars where batteries are usually found very close to the engine, does the practice of mounting the starting solenoids on the starter--versus on the battery--persist? Since the battery cable must in either case be the same length factors of resistance, voltage drop, etc. should remain the same.

I think it's because most modern starters use the solenoid to both energize the motor and push the pinion gear into the ring gear (i.e. no Bendix drive).

https://en.wikipedia.org/wiki/Starter_(engine)#Electric