I have switched from AGM to Lithium batteries. I have read when in storage it is best to leave them at 80 %, so when in storage I will need to disconnect my solar panels otherwise they will be on 100% always.
I was thinking of putting a circuit breaker before the solar controller (I have a fuse there at the moment ) and just flicking it off, I have noticed the solar isolator switches I have seen online are 2 pole, ie switching off both positive and negative. Is it really necessary to switch off the negative ?
Peter_n_Margaret said
08:11 PM Jan 26, 2026
Why not? That is the requirement of AS3001.
A lightening strike (for instance) won't care which wire it follows. This is my new build under construction. 430W of panels per double pole DC breaker.
Good point, I never thought about lightning, not concerned about the cost, space is a bit tight in that area was my concern. Thanks I'll make room.
TimTim said
09:54 PM Jan 27, 2026
Ian G wrote:
Good point, I never thought about lightning, not concerned about the cost, space is a bit tight in that area was my concern. Thanks I'll make room.
Hi Ian,
A double pole switch will not provide you with protection from the huge power of a lightening strike. Some solar controllers such as Victron allow you to turn off charging thereby allowing you to isolate the solar panels.
Does this method comply with the Australian Standard referenced in legislation?
Yes it does because the applicable Standard is AS/NZ3001:2008, referenced by the Vehicle Standards Bulletins (VSB1 for trailers 4.5t and under) written under the Road Vehicles Standards Act 2018. Under that Standard there are no controls for Extra Low Voltage circuits.
7.3 Other electrical systems Electrical installations on a trailer that are intended for connection to an AC power system other than that of the tow vehicle must comply with Australian Standard AS/NZS 3001:2008 Electrical installations Transportable structures and vehicles including their site supplies.
Whilst it is a good idea to be able to isolate your solar panels I have seen a number of recent builds where manufacturers do not provide a method of doing so. Yes you can use a double pole switch and other alternatives are.
-- Edited by TimTim on Tuesday 27th of January 2026 10:00:20 PM
Ian G said
08:32 AM Jan 29, 2026
Thanks Tim, are you suggesting I put a battery isolator switch on my solar panels or on my battery ?
My initial question was, is it important to turn off the negative on my solar as well as the positive ?
Thanks Ian
TimTim said
02:46 PM Jan 29, 2026
On your solar panel side, the reason being is the majority of solar controllers require a connection to the battery before connecting to solar panels. If you put it on the battery side you would still be maintaining the connection from the solar panels to the solar controller.
My apologies, no they are not really necessary for low power circuits.
Good luck
Tim
-- Edited by TimTim on Thursday 29th of January 2026 02:53:52 PM
I have switched from AGM to Lithium batteries. I have read when in storage it is best to leave them at 80 %, so when in storage I will need to disconnect my solar panels otherwise they will be on 100% always.
I was thinking of putting a circuit breaker before the solar controller (I have a fuse there at the moment ) and just flicking it off, I have noticed the solar isolator switches I have seen online are 2 pole, ie switching off both positive and negative. Is it really necessary to switch off the negative ?
Why not? That is the requirement of AS3001.
A lightening strike (for instance) won't care which wire it follows.
This is my new build under construction. 430W of panels per double pole DC breaker.
They are not expensive.
DC 1000V Solar Mini Circuit Breaker Overload Protection Switch 6A/10A/16A/20A/25A/32A/40A/50A/63A 2P DC1000V Photovoltaic MCB PV - AliExpress 13
Cheers,
Peter
-- Edited by Peter_n_Margaret on Monday 26th of January 2026 08:18:08 PM
Hi Ian,
A double pole switch will not provide you with protection from the huge power of a lightening strike. Some solar controllers such as Victron allow you to turn off charging thereby allowing you to isolate the solar panels.
Does this method comply with the Australian Standard referenced in legislation?
Yes it does because the applicable Standard is AS/NZ3001:2008, referenced by the Vehicle Standards Bulletins (VSB1 for trailers 4.5t and under) written under the Road Vehicles Standards Act 2018. Under that Standard there are no controls for Extra Low Voltage circuits.
https://www.infrastructure.gov.au/sites/default/files/documents/vehicle-standards-bulletin-1-revision6-trailers-with-an-aggregate-trailer-mass-of-4-5-tonnes-or-less-july2025-pdf.pdf
7.3 Other electrical systems
Electrical installations on a trailer that are intended for connection to an AC power system other than that of the tow
vehicle must comply with Australian Standard AS/NZS 3001:2008 Electrical installations Transportable structures and
vehicles including their site supplies.
Whilst it is a good idea to be able to isolate your solar panels I have seen a number of recent builds where manufacturers do not provide a method of doing so. Yes you can use a double pole switch and other alternatives are.
https://www.jaycar.com.au/2-position-275a-battery-isolator-switch-with-afd/p/SF2249
Good luck
Tim
-- Edited by TimTim on Tuesday 27th of January 2026 10:00:20 PM
Thanks Tim, are you suggesting I put a battery isolator switch on my solar panels or on my battery ?
My initial question was, is it important to turn off the negative on my solar as well as the positive ?
Thanks Ian
On your solar panel side, the reason being is the majority of solar controllers require a connection to the battery before connecting to solar panels. If you put it on the battery side you would still be maintaining the connection from the solar panels to the solar controller.
My apologies, no they are not really necessary for low power circuits.
Good luck
Tim
-- Edited by TimTim on Thursday 29th of January 2026 02:53:52 PM