ENOS Wiring problem

[Ohio Blue Tip]

GREAT QUESTION maybe it can be put in a new thread so as to allow it to be saved in the tech section.

thanks jim[/quote]

Good idea, I'll start a new post.  Frank will hve to delete this one because it's to late for me to delete.

[HOTRODSRJ]

Since you folks seem to be well versed in electrical systems, what and where do you recommend master fuses or fusible links and what capacity for general street rods.  I would like more of this protection incorporated into wiring systems and as I do most jobs from scratch, I would like to know capacity and location that would be best to protect most rods.
Thanks, Ken

I would like just to throw my general response in for this purpose.

First, automotive wiring has become more and more complicated as it grows toward the more modern auto designs with the likes of power everything, EFI and high capacity batteries, charging systems and wiring to go with and even EMI/RFI and sophisticated alarm issues coming to the surface.  As we all know it used to be a simple 8 or 9 circuit issue and pretty straight forward.

I would like to address the subject of capacity first and I could easily write many pages on this, but others I am sure will chime in with their experiences and takes as well.   This depends more or less on your system's design or application's demand.  As I have pointed out, some applications such as roadsters and others with little or no auxillery power needs, have a very simple demand and relatively light loading compared to modern day vehicles.  The way I figure demand is do a balance sheet of peak load then add another 50% for main fusing. Lightly loaded systems often require no more than a 100 amp fuse (keep in mind that I ONLY USE mini starters and do not use the old boat anchors/starters of yesteryear which take more current ...alot more current!).   I jump from there to a 150amp main fuse on most applications up to 100amp peak/nominal DC current loads.  I locate all my main fuses within 18" of the battery itself regardless of location. This protects all but 18" of the main feed wherever it goes.  

My 57 Belair is just about as power burdened as you can get and I have never exceeded 100 amps peak (I actually have a DC shunt that can easily measure this accurately) nominally.  This includes a 25 amp cooling fan, 1200watt stereo, six-way power seats, high wattage headlights, air, yadda yadda yadda.  The 150amp main fuse is what protects the total system.

But, fusible links or the more modern maxifuses are necessary too to compliment the main protection system. Again, the capacity of the fusible links depends on the alternator and bus demand.  I put my links nearest the feeding source. This protects the whole bus branch.  So my fusible link from the alternator is at the alternator. My maxifuse(s) is located at the source of the feed for the fuseblock and/or relay bus.

I do have some wiring/electrical system suggestions to keep things more with modern OEM designs and specifications. These are MY suggestions.

1. Always located your main fuse within 18" of your battery....actually the closer the better.
2. On-off switches offer no practical protection for system dynamic situations.  Plan accordingly.
3. Aux relay any circuits that are over 10 amps external to the interior, if possible (you will have brighter headlights, more output from fans and less voltage drops due to length of wire and connections).
4. Always use fusible links or maxifuses accordingly.
5. Use high quality automotive/appropriately rated wire/insulation for all circuits. This includes battery cables. (and this will open up a can of worms...I know alot of guys out there using rubber coated welding wire/cable and while these are great conductors and very flexible cables.... if not installed correctly with the ends completely sealed from the elements they will wick water up in the cable itself and eventually fail...quickly.  Notwithstanding that fact, the coating/insulation is NOT rated for fuel fires and/or heat and can easily be compromised in a high heat or fire situation adding another problem in a simple fuel fire to becoming an electrical issue as well. There is just too much other engineered cables for this purpose and I highly recommend them albeit more $$$).
6. Use only quality crimping tools, skip the cheap ones.  Usually gas tight connections are wanted for all applications. With quality crimps, soldering is not necessary at all!
7. When replacing an old battery, consider a newer technology such as a spiral-cell technology (Optima). These do not leak acid, no gassing, provide a longer shelf charge (meaning no tender necessary), and can be mounted in any attitude you can invent.
8. Dump your old fashion field-wound starters.  These take tons of current, are hard on your battery, require large conductors/connectors,  heat soak easily, weigh a ton and are now relatively huge compared to perm mag starters....what else do you need to know?
9. Use quality automotive relays that are rated at least 30 amps and most preferably 40amps and in some cooling fan situations....70amps! Pay attention to the nominal currents of these devices for reliable designs.
10. Use "bucking" diodes on cooling fans of more than 15amps. This will eliminate large inductive spikes on your system.
11. Relay sockets (not PC board ones!) are preferable to just relay wires with terminal connections.
12. Do not put any mechanical stress or torsion or at least minimize such on any electrical wire or connection.
14. Screw clamping/termination type fuse blocks are prone to heat cycling issues and failure. I highly recommend against them.  The GM block designs/types are as good as it gets.

I am sure others will have more to offer on this subject.

[Skip]

Lead acid batteries aren't used in production vehicles anymore.  Lead acid batteries are the kind you have to periodically add water to.

Newer batteries require higher charging voltages than lead acid batteries.  That's why it's not uncommon to see a voltmeter in the 16 volt6 range on a newer vehicle.

Now, if you're still running a lead acid battery, 16 volts is cooking your battery.  If you're running a low maintenance battery, 12.5 volts is too low and you want to be up around 13.6.  For maintenance free batteries you want to be close to 15.

which battery is under the hood?

[HOTRODSRJ]

Lead acid batteries aren't used in production vehicles anymore.  Lead acid batteries are the kind you have to periodically add water to.

Newer batteries require higher charging voltages than lead acid batteries.  That's why it's not uncommon to see a voltmeter in the 16 volt6 range on a newer vehicle.

Now, if you're still running a lead acid battery, 16 volts is cooking your battery.  If you're running a low maintenance battery, 12.5 volts is too low and you want to be up around 13.6.  For maintenance free batteries you want to be close to 15.

which battery is under the hood?

Okay Skip....I see what you are talking about.  Yep...I agree.  Thanks for clarifying this.

For the most part if you are above the full charge voltage of a battery at 12.65 is good.  16 would be too much for most common batteries.

[hotrodbob]

Wow, I sure started a interesting thread.

Lemme explain the situation I have. The new wire harness instructions had us hook up the ammeter so that it only shows charge. If I turn on the lights, fan or anything the meter will not show a discharge. By my way of thinking, this is dumb. ENOS did not agree. I use my guage (OEM 1948 Plym) to check brake light operation before I drive as well as other systems to ensure they are working. As ENOS has it, I can't check anything as the guage will not show any electrical action other then charging. Even at idle with everything turned on the system would not show discharge. That bothers me. My alternator is only a 30 amp GM unit.Based on the info you guys have provided we will rewire the guage and I will add a new ground for the rear mount battery.

The info on this thread has been great.

[PeterR]

I knew while typing up my early post which attempted to hose down some of the hysteria surrounding ammeters it would open a can of worms but the silly boy that I am still pressed the "send" key.  But I have learned my lesson and this is my last post on this or related topics.

Most of the discussion has revolved around catastrophic fault conditions, and while fault conditions should be taken into account, they should not cloud the normal operational situation. I illustrate this with an unfortunate accident.  

A friend of mine was working under a truck with the front end supported on jack stands.   A mechanic working on the engine dropped a spanner which fell on the starter solenoid, the engine cranked over, drove the truck off the stands and onto the person working below.   Neither his widow nor the coroner suggested the world should ban starter motors and revert to crank handles to start engines.

A couple of contributors have related stories of trunk mounted batteries causing fires as though that determines everyone of them to be unsafe, but do not blink an eye at rear mounted fuel tanks and high pressure fuel lines running the full length of the vehicle.    

There has been condemnation of remote shunt ammeters because they can cause problems --if not installed correctly.

Failure of idiot generator lights was mentioned.    Over a period of almost 50 years working on motor vehicles I have never seen an OEM idiot light fail, but have witnessed plenty of aftermarkets give up the ghost. The lamp used in an OEM application is under-rated and those of you familiar with life ratings of tungsten filament lamps will confirm that even a modest de-rating increases life enormously.  

The examples above are intended to illustrate that many of the problems described by others are the result of inappropriate materials and unsound practices not the particular equipment blamed.

Just to prove that I am a real masochist I will reiterate a couple of points Skip and I have endeavoured to convey.

To be meaningful a voltmeter must read the voltage at the battery terminals, this means running dedicated leads from the battery to the meter negating all the so called simplicity and "safety" of the device.   The meter then has to be calibrated to the particular style of battery and read to a fraction of a volt.

A correctly installed ammeter indicates the net charge rate and if showing a bit on the +side, then that is good enough, regardless of battery type or placement.

Three further comments then I will pull my head in.

1.  

Screw clamping/termination type fuse blocks are prone to heat cycling issues and failure

Screw connections with the conductor held under the head of the restraining screw have a high failure rate due to stress relaxation of the copper, however if the conductor is constrained within a tunnel they are fine as indicated by their near universal use in high current (1000A plus) applications.   Never, never, never ever tin the end of a conductor with solder if it is be terminated in a clamped connector.    Over time the solder "flows", the clamping force is reduced, the joint resistance increases causing heating, the solder softens and the joint progressively deteriorates.

2.

As ENOS has it, I can't check anything, as the gauge will not show any electrical action other then charging. Even at idle with everything turned on the system would not show discharge. That bothers me.

Sometimes ammeters are wired (incorrectly) to show the full alternator charge, not the net charge, presumably to give drivers a warm fuzzy feeling when they see all those amps running down the wire.

As Skip noted,

A correctly wired automotive ammeter will have ALL of the loads attached to the charging device side of the ammeter and ONLY the battery (at the starter solenoid end of the cable) connected to the other side.

3.

Use "bucking" diodes on cooling fans of more than 15amps. This will eliminate large inductive spikes on your system.

With the ever-increasing array of electronic equipment in motor vehicles this is becoming even more of an issue and it is good practice to clamp any inductive load, even relay coils.