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Battery Powerline Protection

RAC68

Darth Vader
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Hi All and Happy New Healey Year,

After discussing battery chargers/maintainers and, a while back, gear reduction starters, 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. Since this cable is routed to the exposed under the car and clipped to the side of the grounded frame, I often thought about what could happen if the cable insulation was breached in an accident, abrasion/ware, road debris penetration, or just a mistake.

A while ago, when working on my family car, I noticed what appeared (to me) to be a fuse-like component located near the battery that seemed to tie the battery’s power cable to the car’s main electrical systems and wondered if this could also be applied to the Healey. Although the power draw of an original Healey starter is far greater than that of a replacement gear reduction starter:

1. Can anyone recommend a way of cutting battery power in case of a short in the Healey’s main power cable (battery to starter)?
2. Is there an approach that could serve an original starter and be easily modified (tightened) to address the reduced draw gear reduction starter?

I appreciate that we have lived with this risk forever, however, after installing fuses and relays to reduce multiple individual circuit risks, this seems a major exposure not addressed or even talked about (that I am aware).

Your thoughts,
Ray (64BJ8P1)
 

Keoke

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HI Ray:

One method of doing this would be to use a reset-able circuit breaker they exist made for airplane circuits.
I think many years ago a RR came out with a board full of them.
However, I do not know if a battery protector was included.

To size your circuit breaker you will need to firmly establish the cars worst case normal current load.in Amperes.

Your circuit breaker rating then in Amperes should be 1 1/2 times that worst case normal current load.
Hope this helps you
 
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Ray--

I always try to protect long power runs at or near their source--in this case at or very near to the positive battery terminal. For a fusible link that will easily handle your loads see:

https://www.westmarine.com/buy/blue...E05-0747E2BF3D33&cm_sp=Onsite-Recs-_-MB-_-PDP

You can probably buy it cheaper online but if you are near a West Marine store you can get or see one there.

Alternatively you could use an HD circuit breaker such as this one that you could mount on or very close to the battery which would also give some theft protection:

https://www.delcity.net/store/Bussm...XjOcRVfTwk1RqmLrIJ9uANBpa_fh8nVEBXhoCzz7w_wcB
 
OP
RAC68

RAC68

Darth Vader
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Thanks Guys,

This is the direction I needed. By your comments, it seems this is a situation more commonly addressed in Marine and Air Craft. The fuse links examples referenced look reasonably simple to install and can pass the amount of power required to handle even our original high-draw starters.

Michael, I intend to look further into the units referenced and identify the level of amperage required that is required to be passed, per Keoke's suggestion. I would expect, if retaining the original starter, the upper power (amps) demand could be safely calculated by using the amount of power drawn by the starter.

Again, I appreciate your responses and thanks again,
Ray (64BJ8P1)
 
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Ray--

For sure it was not addressed on Healeys!

I have each appliance/circuit separately fused via a multi-fuse panel where the original one was mounted on the firewall.

Though some folks think it is okay to put a fuse holder anywhere in the middle of a circuit I try to place fuses as close as possible to the power source so as to protect both the circuit and the appliance. Light 18-20 gauge wires will sometimes melt at the point of a short before or even as the downstream fuse blows. (Hmmm--what's that smell?)
 

vette

Darth Vader
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Keoke

Great Pumpkin
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Light 18-20 gauge wires will sometimes melt at the point of a short before or even as the downstream fuse blows. (Hmmm--what's that smell?)

If this is the case the fuse was the wrong type or was located in the wrong position of the circuit.
Such that the wire becomes the fuse and protects the FUSE.
 
OP
RAC68

RAC68

Darth Vader
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Hi Vette/All,


Just to be clear, my intent in opening this discussion was to find a simple, although partial, approach toward isolating the battery and severing power cable connection, even if only for a High Amperage (>starter amp) draw, during a shorted main.

I would still favor the switched 2-fuse approach (high-starter, low-operation), I suggested in the past thread you referenced. Possibly because of my limited skill or knowledge, I have not been able to implement this approach at the level of simplicity and low cost I believe is required and, therefore have not determined the extend of reliable operation this non-obtrusive architecture would provides.

As a result, I have decided to look into the benefits and possible implementation of this single high-amperage Circuit-Breaker/Fuse approach and, again, have looked to the Forum for suggestions.

Would it be best to install a high-amperage fuse on the power cable/post or on the grounding side of the battery and would this installation cut power sufficiently fast to eliminate the possibility of a electrical short induced fire or at least diminish its result substantially?

I did reread the last “Battery Fire” thread to see if I missed anything.
Ray(64BJ8P1)
 
Last edited:
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Keoke said: "...or was located in the wrong position of the circuit.Such that the wire becomes the fuse and protects the FUSE."


That's my point--no sense putting a fuse for the license plate light in the boot!
 
OP
RAC68

RAC68

Darth Vader
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Michael,

Now I am confused as the license plate light fuse is located in the boot at the point it separates from its power source (the tail light circuit) on my BJ8 P1 and is meant to protect the tail light circuit, but more importantly, act as a gate to stop a shorted plate light from causing damage back to the tail light circuit.

Also,

During our last Overdrive Switch thread, we discussed the use of a fuse to protect the circuit and solenoid and a high amperage fuse was required when installed near the Solenoid due to a high induced draw by the unit. I later mentioned that I had installed a 10-amp fuse on the white wire extending from the #3 terminal on the fuse block feeding the C1 terminal on the OD relay that I understood, provides root power to the OD circuit that hasn't blown the long time this fuse has been in place.
1. Is this 10 amp fuse doing its job protecting my OD Circuit, including the Solenoid as it has been placed at the source of power for this circuit?
2. Could it be this fuse has not blown because it is installed far enough away from the Solenoid and not affected by the induced power draw of the Solenoid?

Are you saying that to be effective, the fuse must be installed to the unit to be protected or at the circuit's power source? Should the license plate fuse be installed close to the light and should the OD fuse be installed closer to the Solenoid. With regard to the Solenoid, per the discussion, a much larger or slow-blow fuse would be required to allow the Solenoid to operate properly and this placement would only protect the Solenoid.

Ray(64BJ8P1)
 

John Turney

Yoda
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Ray,

Fuses should be installed close to the power source, not near the load, if you have a choice. That way, if the short occurs in the wire to the load, the fuse keeps the wire from burning up.
 
OP
RAC68

RAC68

Darth Vader
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Thanks John,

That's what I always thought. Maybe I just misunderstood Michaels comments.

Ray(64BJ8P1)
 

Keoke

Great Pumpkin
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Should the license plate fuse be installed close to the light.

IN this case YES :

Here the fuse s positioned to isolate the circuit most likely to fail.
Looking at this from a reliability standpoint the parts making up the tail lamp and its routing contain the larger no of parts and therefore have a lower reliability than a single wire circuit.

Should the OD fuse be installed closer to the Solenoid. With regard to the Solenoid.::

Yes:
In this case we are attempting to protect the harness from failing in the event the solenoid fails electrically.

The slow blow fuse @ 10 amps takes into account the time rate of change of current during the initial pull in cycle while insuring that the Solenoid's transient characteristics are enclosed under normal functions and provides adequate fault protection when it fails.

OH!:
My schematic shows the power source for the solenoid is pin C2 of the overdrive relay.
 
OP
RAC68

RAC68

Darth Vader
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Thanks Keoke,

I appreciate your response. As I understand, in both cases the blown fuse acts as a closed gate, isolating the fault and stopping the propagation of further damage to the harness and attached components.

As far as the OD solenoid, C1 ties to the power source with C2 passing power to the solenoid. I see your point that if the Solenoid is considered the vulnerable component and a commonly found source for a short, then isolating the solenoid as soon as possible is a good move to protect the rest of the circuitry. Now I am wondering which approach is more effective and protective, a standard quick response low amperage fuse placed at C1 (the source of power to the full OD circuit) or a slow blow fuse placed near the solenoid to isolate the source of the fault...or maybe both?

Thanks again for the clarity,
Ray(64BJ8P1)
 

vette

Darth Vader
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I have been running a 10 amp fuse on my OD circuit for at least 2 years now with no failure. The fuse is in the new fuse box I installed under the dash just opposite the firewall where the old fuse box was. I believe inductive draw on a 12 volt circuit is pretty minimal to affect a fuse. If you want to see inductive draw you should see it when you close a switch on a 12,000 volt circuit.
 

Keoke

Great Pumpkin
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The inductive transient current on the initial engagement of the OD Solenoid is 19 Amperes but has a very short time interval..

The current home electrical 120V power installations are now using Ground Fault indicators at their load points in addition to circuit breakers at the power distribution panel.
Cuts the potential for fires down a bit--- :applause:


OH!
N Know what 28V DC will arc ina vacuum
 

vette

Darth Vader
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Keoke is correct in theory and acedemically but in practical application the surge of current of the pull in coil of the solenoind is not enough to blow a standard 10 amp fuse. I know this from not only my experience of my own car but others that I have seen. Also since I have just finished wiring my daughter and son's-in-law new house and have wired many house as a side line for 40 years, I can tell you that for at least 20 years now certain specific circuits in residential construction have by code been required to be protectec by a Ground Fault Circuit Interrupting device, GFCI, either in the form of a circuit breaker at the distribution panel or in the form of GFCI duplex receptical (wall receptical). But the circuit is to be protected by one or the other but not both. In recent years, probably not more than about 5, their is a new circuit protective device on the market. It is called an ARC Proof Circuit Breaker. Now by the requirement of the Nat'l Electrical Code (NEC), all other circuits in a residential dwelling not previously protected by a GFCI device must be protected by an ARC Proof device, with a few exceptions. Such exceptions might be things like a duo voltage cook top range or a microwave. The ARC proof requirement is applied to every lighting circuit and every receptical circuit not GCFI and then in actuallity protects recepticals in all bedrooms and living spaces. These devices are quite expensive and can double the cost of much material budgets for an average residential dwelling. Maybe Trump will rein in the fevor seen in these agencies of OSHA and the Nat'l Fire Protection Assoc. as well.
 

4tecdog

Jedi Hopeful
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In response to the original thread I am contemplating adding extra fuse protection to the circuits on my bj8, the lighting circuits are a priority and fairly straightforward however would appreciate a little advice on fusing the vulnerable feed to the starter. I have seen a very neat fuse block that sits in the battery terminal, used mainly in marine applications, however the car is positive earth and these fuse blocks are only made for positive terminals. My question is would this give protection if I fused the positive earth and not the negative feed.
 

Keoke

Great Pumpkin
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4tecdog:

Has seen a very neat fuse block that sits in the battery terminal, used mainly in marine applications, however the car is positive earth and these fuse blocks are only made for positive terminals.

His question is would this give protection if I fused the positive earth and not the negative feed.


It may Not ! , As the total fault current path may not pass through the fuse it would occur at the point of the fault.??
 
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