Battery isolator...

[Stay Frosty]

My head's spinning after looking at the various leisure battery installs and while many aspects are starting to appear as obvious I see pictures of owners installs featuring a battery isolator.
My question is what is the isolator actually isolating ie. is it the incoming starter battery or the leisure battery outgoing feed to the 12 v fuseboard arrangement?

 

[Loz]

Normally you connect the battery isolator as the first thing after the battery post to allow for complete disconnection if a significant fault occurs and secondary for long-term storage to prevent parasitic drain etc.

 

[Stay Frosty]

Cheers @Loz so effectively isolating all the outgoing 12v onboard accessories before their fuses eg. lights, fridge, water pump etc.
A lot if not most of the leisure battery schematics don't show isolators and I know I'm going to have to install one for the solar feed in so my mind was filling in all sorts of gaps!

 

[Pete C]

You don't actually need one. I have a couple of big fuses at the leisure battery - one for the fridge feed and one for the feed to the smaller fuse box.
I just pull those big fuses if I want to isolate things. I have needed to do this 3 times in the last 4 years.

Pete

 

[Loz]

Cheers @Loz so effectively isolating all the outgoing 12v onboard accessories before their fuses eg. lights, fridge, water pump etc.
A lot if not most of the leisure battery schematics don't show isolators and I know I'm going to have to install one for the solar feed in so my mind was filling in all sorts of gaps!

Correct, but as @Pete C said, it's not essential if you have fuses in place for safety. Just a convenience and belt and braces if it makes you feel safer.
The thing is, if you are doing the wiring yourself and you have the correct size cables and fuses you can be confident you will not get a fault that causes a fire.
If I was getting a camper built and I didn't get to see their work or fully appreciate what they have done, I probably would get one fitted for peace of mind. But I'm rather cynical like that..

 

[DXX]

Correct, but as @Pete C said, it's not essential if you have fuses in place for safety. Just a convenience and belt and braces if it makes you feel safer.
The thing is, if you are doing the wiring yourself and you have the correct size cables and fuses you can be confident you will not get a fault that causes a fire.
If I was getting a camper built and I didn't get to see their work or fully appreciate what they have done, I probably would get one fitted for peace of mind. But I'm rather cynical like that..

Plus you must have good connections that do not create resistance and heat, I’ve seen some terrible crimps and many strands missing on connections on vehicles. There are many DIYers who think that because 12v DC isn’t going to shock you easily it’s safe, far from it.
I don’t have a battery isolator but I will be fitting one in the next few weeks.

 

[Stay Frosty]

Cheers gents and unfortunately it pays to think the worst as even when you pay top dollar it seems to be a case of "that's near enough"
I'm trying to retain my Sargent EC 160 panel in the wardrobe as it's a tidy way of combining 230v hook up and 12v DC leisure battery power. However with my Redline conversion the Webasto and fridge feeds have both been taken directly from the leisure battery under the seat, the Webasto via a 20A (main unit) and 2A blade fuse (for remote control panel) and the fridge supply was wired unfused to the Sargent then back via a 20A fuse in the panel so the initial run of 2.5mm2 single cable was unfused behind the kitchen cupboards as were the slightly chunkier 12v starter and leisure battery feeds to the Sargent, not great.
At this rate it will probably be a tidier job to fit an isolator and small fuse panel on the front sloping face of the seat base to fuse the fridge, Webasto and Sargent supply and effectively bring the Webasto supply out from being trapped under the bolted down seat, the larger fuses from the starter battery and for the new fuseboard via the isolator will have to remain trapped under the seat.

 

[Dellmassive]

I've got one, it just makes it easier to turn off the Aux power when needed.

Battery --> MEGA fuse --> Isolator switch --> outgoing feed to master aux fusebox.


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[n10n]

I've got one, it just makes it easier to turn off the Aux power when needed.

I’ve been considering adding one like @Dellmassive has done to break the feed from main battery to dc-dc charger easily. My use case would be when I want to charge main battery as fast as possible I wouldn’t want the dc-dc charger to kick in topping leisure battery. At least CTEK kicks in just by having main battery voltage high enough.

 

[jimthevan]

Battery --> MEGA fuse --> Isolator switch --> outgoing feed to master aux fusebox.

What size mega fuse would you recommend? cheers

 

[Dellmassive]

What size mega fuse would you recommend? cheers

i used a 300A one

 

[Stay Frosty]

The main fuse you fit before the battery isolator needs to have a chunky cable too capable of passing 300A however it's your total current demand that's going to dictate cable and fusing sizes.
Bank on roughly 100A per Kw from an inverter ie a 2Kw inverter is about 200A at 13Vdc then add on any additional current required by the fridge, lights etc.

 

[jimthevan]

no inverter just fridge , led lights, USB ports, water pump, 12v Aux, hob ignition.
Split Charge supplied me with 10mm cable for the victron DC/DC 30a charger. I did query wether it should be 16mm but they said 10mm would be fine if its under 5m.