Extra electrical circuit

[B737]

thats exactly what I did too, its behind that boot in the photo.
The trigger for the relay was from the work light circuit, which is only active when the ignition is turned on. It is frustrating the AUX Circuit on the beach 2601 is rated so low, the BX and LX do not suffer from this.

Im trying to recall, on that ground at the starter, im pretty sure there is a wire to that bolt from the battery as well.

 

[BruceP]

should I connect it on the frame in the console where all other grounda lead? Or should I take it directly to the battery?

As I mentioned originally... your new ground should go to the ENGINE BLOCK. Preferably at the same point where the battery minus connects. This allows the dynamo/alternator to supply the current when engine is running. (most direct current-path)

We KNOW the battery minus goes to the engine-block otherwise the starter would not get enough current to crank engine.

 

[BruceP]

I plan on wiring the live on the starter also since it has a nice connection point.

This is a GREAT idea. From an electronics point of view, using the heavy wire on the starter (and starter ground) represents what we engineers call "mecca" points. Centralized points where ALL circuits originate.

Additionally, I prefer to not make connections right at the battery because it makes the battery-connections 'messy' (too many wires) and prone to acid-attack.

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As an aside, a machine I worked on many years ago was designed to measure FEMTOamps of current. ( that is 15 0s after the decimal point) That machine had 'mecca' points machined from 1 pound chunks of copper with threaded holes. ALL the circuits in the machine were originated at those large copper hunks. This was the only way to control where the current flowed within the machine. Just waving your hand past the machine would change the measured current so the entire thing was encased within grounded, steel casing.

That machine could almost count individual electrons as they flowed.

 

[torch]

@torch : a self resetting circuit breaker? That sounds interesting. Because my motor does work perfectly on the 5A light circuit but the fuses blow once the motor hits the resistance of the end of rotation of the chute. I've temporarily changed the fuse for a 7.5A (I know... Bad. It's just to test my motor) and that works flawlessly. So if I had a fuse that self resets, that would be perfect. I'll read up on that because I never heard of this.

Canadian Tire has a wide selection (as do most automotive parts stores).

 

[awesome]

I see that there is a 50A fuse in my electrical system and the WSM indicates that this is a slow-blow fuse that protects the battery. So if I understand correctly, this means that if I add a 15A circuit hooked up on my starter, then I'll still be protected from an overall draw above 50A right? But is there a chance that I could break the dynamo? I mean, in the off-chance that with my new 15A circuit I end up drawing 65A at some point, the fuse protecting the battery will burn, but will that hurt the dynamo?

 

[Henro]

BTW: Measuring a circuit with ohmmeter DOES NOT tell you how much current it can carry. The proper measurement is "voltage drop" with voltmeter while the current is flowing.

In theory, this is not correct, BUT in practice a great way to evaluate circuit performance.

The main issue is that precise measurement of electrical resistance, on low resistance levels, is not easily done with inexpensive equipment.

A more accurate measurement will likely be obtained (with homeowner level equipment) by taking a voltage drop measurement, as BruceP advises.

Even then, wire size would be determined by the rated load current. Here the question is the return path through the tractor frame though. Unlikely the frame would burn up due to heat developed in a poor connection. Small size wire a different story.

Net result of using accurate voltage drop or resistance measurements is the same. Once the voltage drop is known, the circuit resistance can be accurately calculated, within the accuracy of the voltage measuring device.

Or once the resistance is accurately known, the voltage drop for a given load current can be calculated.

Six in one, half a dozen in the other, with accurate initial measurements of course.

This is just splitting hairs though. I'll go back to my room now...

 

[BruceP]

I see that there is a 50A fuse in my electrical system and the WSM indicates that this is a slow-blow fuse that protects the battery. So if I understand correctly, this means that if I add a 15A circuit hooked up on my starter, then I'll still be protected from an overall draw above 50A right? But is there a chance that I could break the dynamo? I mean, in the off-chance that with my new 15A circuit I end up drawing 65A at some point, the fuse protecting the battery will burn, but will that hurt the dynamo?

In general, fuses are intended to protect the WIRING. (prevent fires) All additional circuits MUST have their own protection (fuse or self-resetting breaker)


You may be misreading the schematics.
I do not have the schematics for your specific machine in front of me. However, I have worked on all manor of equipment and have never ever seen a fuse between the battery-n-starter. This is because a starter can easily draw over 300 amps on a cold start. We want ALL the current available from the battery to get to the starter.

This is why the large connector on the starter is a GREAT spot to add additional circuits (with a fuse on each one). Connecting to the large wire at the starter is electrically the same as connecting right to the battery. (while engine is running, that wire is not even being used by the starter anyway)

To get to the root of your question "will it hurt the dynamo". I would like to think the designers of the charging-system have considered this. Besides, any load you put on the electrical system which the dynamo cannot handle will be 'backed up' by the battery which can easily handle the current. (until your fuse blows.)

One reason a fuse should be as close to the source as possible is to protect from chafed wires which may short to the frame. (It is poor design to place fuse at the 'load' end of the circuit...leaving the wires to deal with the 100s of amps the battery can provide)