Nissan Patrol 4x4 (Africa)

Peter Connan wrote:Ouch!

With 3% losses and an assumed cable length of 5m, this calculator:

https://www.solar-wind.co.uk/info/dc-ca ... calculator

Reckons you need 300mm^2...

Hi Peter.

The switch can handle a constant 500A draw through the unit, it does not necessarily need 500A to operate.

So I'm guessing I need to consider the highest amps draw and from auxiliary battery and match cable size for that.

Sent from my SM-G960F using Tapatalk

Forest wrote: ↑04 Jun 2020 09:09

Peter Connan wrote:Ouch!

With 3% losses and an assumed cable length of 5m, this calculator:

https://www.solar-wind.co.uk/info/dc-ca ... calculator

Reckons you need 300mm^2...

Hi Peter.

The switch can handle a constant 500A draw through the unit, it does not necessarily need 500A to operate.

So I'm guessing I need to consider the highest amps draw and from auxiliary battery and match cable size for that.

Sent from my SM-G960F using Tapatalk

I fully realize that it doesn't need the full 500A to work. However, in the features it notes that it allows paralleling the batteries when starting or winching. In that situation, it could easily draw the full 500A, without you having any control over it. If it melts those cables, that's a huge fire risk. I guess one doesn't need the high efficiency under those situations, but also I have no idea how small one can go before the whole setup becomes a fire hazard, but my guess is that 25mm^2 is well into the fire risk category.

If the system is such that you can control the paralleling, and decide never to use it, you can probably size the system to about 70A. But that means that, for the price of skimping on some cable, you have no self-recovery options for a flat battery situation...

Gents

I don't have time to show the calcs now, but in short : (pun intended)

Assume you have a fully charged very large main battery and a infinitely big alternator and very thick cables

If you now connect one flat (11.9V) 105Ah aux battery directly to that, the current flow from the charged system to the flat battery will very very unlikely be higher than 32A

Take my word for it....

NOW, using both parallel batteries simultaneously to start an engine is looking for trouble.....That can easily jump to 250A between the batteries, from aux to main

Peter Connan wrote:

Forest wrote: ↑04 Jun 2020 09:09

Peter Connan wrote:Ouch!

With 3% losses and an assumed cable length of 5m, this calculator:

https://www.solar-wind.co.uk/info/dc-ca ... calculator

Reckons you need 300mm^2...

Hi Peter.

The switch can handle a constant 500A draw through the unit, it does not necessarily need 500A to operate.

So I'm guessing I need to consider the highest amps draw and from auxiliary battery and match cable size for that.

Sent from my SM-G960F using Tapatalk

I fully realize that it doesn't need the full 500A to work. However, in the features it notes that it allows paralleling the batteries when starting or winching. In that situation, it could easily draw the full 500A, without you having any control over it. If it melts those cables, that's a huge fire risk. I guess one doesn't need the high efficiency under those situations, but also I have no idea how small one can go before the whole setup becomes a fire hazard, but my guess is that 25mm^2 is well into the fire risk category.

If the system is such that you can control the paralleling, and decide never to use it, you can probably size the system to about 70A. But that means that, for the price of skimping on some cable, you have no self-recovery options for a flat battery situation...

Thanks Peter.

The switch does allow for a manual override to force connect and disconnect of the battery.

Its seems I should go for the 50mm2.

When having to jump start yourself this is for a short period so I assume the cable temps wont get that hot. Winching may be a different story altogether.

Sent from my SM-G960F using Tapatalk

Nog nie heeltemal opened die regte plek nie, maar amper daar....

George, are you taking your Ratel in for some.... what do they call it?.... Rhinoplasty !!!... a little nose jobbie surgery....

ricster wrote: ↑05 Jun 2020 09:02 George, are you taking your Ratel in for some.... what do they call it?.... Rhinoplasty !!!... a little nose jobbie surgery....

Morning Cedric - long time no speak - goof to hear from you mate!! Are you well?

Indeed - a bit of plactic/metal surgery....

haha.... I am always well George... positive things happen to positive people !!

That is going to look really nice when done. Looking forward to the "post-op surgery photos"

ricster wrote: ↑05 Jun 2020 12:28 haha.... I am always well George... positive things happen to positive people !!

That is going to look really nice when done. Looking forward to the "post-op surgery photos"

Amen, that is the spirit Cedric!

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