Thread: Traxide SC 80 cut out

Originally Posted by drivesafe

Hi again Landoman, temperature is not a major factor with the Cut-Out level as the unit will always be quite warm because the relays are powered up.

If you had a loose wire, the SC80 will actually fail-safe, it will cut-out at a higher voltage.

I have no idea what would cause it to cut-out at a lower voltage on one day then work perfectly.

If the SC80 was faulty, it would, one would expect, stay faulty.

I can only recommend you keep an eye on the voltage levels and see if the situation repeats it self.

Sorry I can't be of more help, but that is a strange one, and I suspect it is going to be something other than the isolator, but ?

Thanks Tim .......if it fails to cut out when the voltage on the cranking is below 12 volts then it would very much appear not to have tripped ........anyway I'll keep an eye on it and sees how it goes .....very strange ??

I understand that you would like to know exactly what is going on.

However, I'm not sure that 11.89 volts is a worry. When the previous battery in my Defender was on its last legs, I measured the voltage at 10.5 and was able to start the engine - just.

It was pleasantly warm weather at the time. It would have managed it if it was cool.

Originally Posted by vnx205

I understand that you would like to know exactly what is going on.

However, I'm not sure that 11.89 volts is a worry. When the previous battery in my Defender was on its last legs, I measured the voltage at 10.5 and was able to start the engine - just.

It was pleasantly warm weather at the time. It would have managed it if it was cool.

Thanks good to know .......guess my concern was that while the voltage had dropped below set cut out volts ( 12) the SC 80 did not isolate the cranker

......I keep an eye on it to see if the issue recurs

While I did manage to start with just 10.5 volts, if this chart is accurate then it seems that really is the limit.

I think Tim has posted something similar a few times in the past.



I am certainly not suggesting that relying on a battery with a low SOC is a good idea.

I remember being astonished the first time I saw Tim's chart at how much a battery is already down by the time it gets to 12V.

As I said, I understand that you want to know what is going on. While 11.9 volts may not be a problem, the question is how much lower would it let the battery get if the cut out is not doing its job.

Originally Posted by vnx205

While I did manage to start with just 10.5 volts, if this chart is accurate then it seems that really is the limit.

I think Tim has posted something similar a few times in the past.



I am certainly not suggesting that relying on a battery with a low SOC is a good idea.

I remember being astonished the first time I saw Tim's chart at how much a battery is already down by the time it gets to 12V.

As I said, I understand that you want to know what is going on. While 11.9 volts may not be a problem, the question is how much lower would it let the battery get if the cut out is not doing its job.

Precisely ......that was the crux of the matter ......if I had not checked it and found the voltage below the cut out .....and the the two batteries still connected with the SC 80 not tripped then My cranker would have reached too low to start ....
I'll monitor it to see if this incident repeats ......

Ps ....excellent chart ...good to know you can start your motor on 50 %
.......some people have argued with me that not possible .....but appears it is

Hi vnx and landoman, that chart has been around for decades and with good reason.

The GREEN area is the section of the battery that is able to meet the CCA rate of a battery.

Most people are unaware that the CCA rating of a battery is maintained by a battery till it is discharged down below 40% of it's SoC ( 11.9v ).

So with landoman's SC80 not tripping at 12.0v, he was still within or close enough to his CCA rating and would have no problems starting his motor.

But this does not explain the strange one time low voltage????

BTW, I have tested quite a few new and newish vehicles, not just Land Rovers, and all started with batteries as low as 11.5v.

My TDV8 RR ( when it was running ) could be started with a cold motor, using a battery discharged down to 11.5v.

But at 11.3v, I could not turn the motor over.

Originally Posted by drivesafe

...

My TDV8 RR ( when it was running ) ....

I really did want one of those at one stage.

Anyway, I love the explanations of how your gizmo works. I also have one in my Defender (ex Disco 4).

No issues so far, all works as normal.

I do have a big battery in the cargo area and I get at least 5 days use of the Engel starting the motor.