Estimated max amp draw on standard starter

[DRUMMOND]

Has anyone measured this? Estimate max amperage on a 70F degree day, 150amp for a 1.3 kw?

Any reason why fiat did not see fit to place a fusible link on such a long battery/starter cable?

Has anyone fitted a manual reset breaker to their starter/battery cable link? Double duty Safety/Disconnect.

All views welcome

[aj81spider]

Here are a couple of thoughts (which along with $2.00 will get you a coffee at Starbucks):

> If your starter draws 100 amps and you put protection on your wire that adds only 0.01 ohms of resistance (and that's a tiny amount considering you will have to go through two connections and the protection device) you will drop an extra volt in the wires when trying to start the car.

> If you don't trip until 1.3 kw are being drawn you're going to do a lot of damage before the protection trips - the protection may not actually do that much protecting.

[spider2081]

+! with AJ

The primary purpose of circuit protection is to prevent a wire from getting so hot it causes a fire. The battery wires on a Fiat Spider are quite large. It looks to me as though its at least a #2 wire. If this wire were to short to ground it would probably burn the metal it shorted to before the wire would burn.
Some people install battery disconnects at the batteries negative terminal. With modern radios this will cause them to loose the stored stations and clock. If a stock clock is in the car the clock will need to be rest each time the battery is reconnected.

I have worked on cars where the owners have installed the battery backward or connected the charge backwards. In those cases the small #10 wire connecting the alternator to the starters battery terminal burnt but there was no damage to the battery wire. It also shorted the diode pack in the alternator.

[nalle]

This is from my earlier post:

Starter solenoid current (peak value) 17,5A.
So if you want to put a fuse there 25 A is fine (as Bosch recomends)
Current will stay at 17,5 A as long as solenoid is pulled.

Starter current (peak value) 243 A.
This is the zero-speed current (DC-motor is not a motor when n=0, it is a resitance, EMF=0V)
Current will go down after starter begins to rotate.
If we estimate that starter is 2kW and battery 12 V => 166A.
So if there is a need to put a fuse in battery line these are the current values what have to be fulfitted by the fuse.
And on the other hand it had to be calculated will the "big fuse " ever burn if there is "weak" ground fault in battery line.
But as i have said earlier it is really uncommon to have a battery fuse in a car.

[spider2081]

Starter solenoid current (peak value) 17,5A.
So if you want to put a fuse there 25 A is fine (as Bosch recomends)
Current will stay at 17,5 A as long as solenoid is pulled.

I am pretty sure there is a high short duration surge current associated with a solenoid that exceeds its operating current. Fusing this type of circuit is often done with slow-blow fuses.
Personally I feel Fiat has considered the safety of their vehicles and the un-fused circuits should be left as designed.

[nalle]

spider2081, I agreed.

[DieselSpider]

There is a very large safety margin there. The factory wiring is supporting the over 2 KW starter on the DieselSpider along with the load of the Glow Plugs without heating up even when our roadway temps are nearing 120 degrees so with the much lower draw of the gas engines starter I would not worry about it. I was concerned when I first got the Diesel that the cable may not have been large enough however that has proven to be unfounded.