What size dc isolator needed

[James Melville]

Just a quick question. We have a yard with no electric up there so using a 12v car battery connected to an invertor to power 230v lights. I'm wanting to connect a dc isolator from the battery to inverter so we don't have to keep connecting the clips to the battery and can use turn the isolator on. I know that the amps are alot more for 12v but what size dc rotatory isolotir would it need. 80amps

 

[Robson689]

All batteries are different I think there will be a rating on the sticker?

 

[James Melville]

All batteries are different I think there will be a rating on the sticker?

Did a quick calculation as its to power 800w inverter. 800x12v is 66.6 amps I think so anything over that should be fine I think

 

[Strima]

Why not use 12 volt lamps and a standard light switch?

Edit: Infact LED tape gives off plenty of light for little current draw.

 

[James Melville]

Why not use 12 volt lamps and a standard light switch?

Edit: Infact LED tape gives off plenty of light for little current draw.

Because we only recently purchased this and it already prewired lights and fuse board etc. Just need a simple way of switching the supply on and off instead of connecting the battery clips as I think if left on over night the inverter would slowly drain the battery

 

[James]

Err on side of caution, 1000w at 12v is 83A

So may as well be a 100A isolator.
What is it fused at?

 

[James Melville]

Err on side of caution, 1000w at 12v is 83A

So may as well be a 100A isolator.
What is it fused at?

Think the fuseboard has a 63amp rcd as main switch. But this is on the 230v output from inverter. Does it have to be a dc isolator or just a Normal 100amp rotatory switch OK to use

 

[Lucien Nunes]

Any AC switch or isolator is fine for 12V DC at the same current rating. A 100A main switch would suit here. Anything using 100A from a car battery will soon kill the battery though!

Note, the same is not true for higher DC voltages above say 24V, because of the arc. A normal 100A 400V rated AC switch carrying even 20A at 400V DC would probably turn into a fireball when someone tried to switch it off as the contact separation would not be great enough to extinguish the arc.

 

[Strima]

Just seems to be very inefficient to run it through an inverter if all your doing is powering some lights.

 

[James Melville]

Any AC switch or isolator is fine for 12V DC at the same current rating. A 100A main switch would suit here. Anything using 100A from a car battery will soon kill the battery though!

Note, the same is not true for higher DC voltages above say 24V, because of the arc. A 100A 400V rated AC switch used to interrupt even 10A at 400V DC would probably turn into a fireball when someone tried to switch it off.

Thanks. Won't be using anything like 100amp. Led laps about 10 so probably like 60w max. Just looking for something to turn battery off and on without having to remove and re attach the battery clips

 

[bill01803]

What about one of those you see on rally cars.

 

[PEG]

Hi,can you not leave the clips on the battery,and switch off at the inverter?

 

[Lucien Nunes]

Those ELV flag key switches are OK but very basic, and the cheap ones are rubbish. As you don't need the short term peak current capacity for starter duty, a regular 100A main switch is a better device cheaper than a good one. But, yes, doesn't the inverter have a soft switch or do you not trust it?

 

[Marvo]

If it's using a car battery you shouldn't drain it more than about 20%, cycling it any deeper will result in it failing in a few weeks or months.

To be honest, if this setup is a couple of lamps running from a camping type inverter in a domestic setup you could get away with using a recovered circuit breaker as an isolator even on the DC side. DC isolators are generally expensive and this doesn't sound like it's a critical application so it won't be a safety issue even on the off-chance the circuit breaker fails prematurely with the DC load....although I doubt it will. Also a 100A switch from an old CU as Lucien suggests or an engine kill switch mentioned above by Bill would all work great.