Max voltage rating for Trailer plug (North American) - Page 1
Forum section: electronics / beginners

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 07, 2024, 12:18:02 am
content: Generally, these connectors are used to connect a vehicle to a trailer for lights, etc. The voltage is typically 12Vdc, but I wonder what the max rated voltage for such a connector would be. (excluding human safety issues)I've searched for a datasheet for these and have found nothing with any such details.But I've seen ones likethis "2 pin 1871"used for other applications at higher voltages (30V).Does anyone have an actual spec sheet with a max voltage and current rating, for this, or any other brand?

author: CaptDon
author_rank: Super Contributor
timestamp: August 07, 2024, 02:58:38 am
content: I suspect 'Not over 48 volts' and I would guess not over 6 amps per pole when clean and in good condition. Don't have a published spec however. I use the 7-Way R.V. style and the +12 volt 'always hot' battery blade always corrodes and breaks!! I have a master switch under the dash to disable the battery supply to the connector when not being used!!

author: SmallCog
author_rank: Frequent Contributor
timestamp: August 08, 2024, 03:33:08 am
content: I've never known these to be used for trailer lights, but I had a packet and figured I'd check to see if it had a voltage written on it, it doesn't.Checked the catalogue for the supplier and they're listed as "low voltage"https://www.wes.com.au/mediapub/ebook/wescat2023/1120/Here in Australia "Low Voltage" has a definition. I'm not sure if they're referencing this in the catalogue... I'd probably not use one for 1500VDChttps://www.energynetworks.com.au/assets/uploads/energy_networks_australia_list_of_definitions_0.pdfGiven that 24V nominal is not entirely uncommon in vehicles, and these charge at 29ish VDC I'd have no concerns at going a touch higher to perhaps 48VDCI'd certainly try and have the exposed terminal not be at a spicy potential however.

author: IanB
author_rank: Super Contributor
timestamp: August 08, 2024, 06:10:21 am
content: One might reasonably suppose that in such applications the wire insulation and plug design is intended more to provide mechanical resilience and protection than to provide electrical insulation. So increasing the voltage above 12 V is not likely to produce any kind of electrical leakage or breakdown.But there is also the environmental consideration mentioned above. Any electrical system exposed to dampness or rain (or worse, salty water from roads) is going to be subject to electrolytic corrosion, and the rate of this will increase at higher voltages due to higher leakage currents.So a "voltage specification" is not a simple property of the device itself, but rather a complex calculation from the application, use and installation environment of the device.

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 10, 2024, 03:31:39 pm
content: I case anyone else is interested, the only place I found a voltage spec was for a listing on Temu.QuoteThey even had a link to a poorly translated manual:

author: Siwastaja
author_rank: Super Contributor
timestamp: August 10, 2024, 03:47:11 pm
content: Exact voltage ratings forconnectors(at least non-hotpluggable) andcablesbelow legal SELV limits (which vary by region, but approx. 50-120V DC, I think it's 75V DC in EU for example) are arbitrary and irrelevant. It is practically impossible to manufacture a cable which survives 12V but somehow fails at 50V; same goes for connectors, so as long as you stay below the legal safety extra low voltage limit, it's OK.Now for fuses, relays and switches which need to open under load, there is possibly difference between say 12V and 60V DC, since latter is able to maintain a serious arc; there is a risk of switch/relay welding stuck on, and fuses could take too long to clear or damage the surroundings, therefore following datasheet ratings is important.

author: IanB
author_rank: Super Contributor
timestamp: August 10, 2024, 03:49:27 pm
content: I learned that this kind of connector is called an "SAE Connector" or "SAE Harness". Searching with this term produces dozens of examples. They are typically specified "up to 28 V" or "up to 36 V", but I found an exception below that says it is rated to 600 V, which seems to be for application with solar panels:https://www.sunpoweredyachts.com/product-page/mc4-to-sae-connector

author: Siwastaja
author_rank: Super Contributor
timestamp: August 10, 2024, 04:09:32 pm
content: 28V would be an arbitrary rating by manufacturer to be used in 24V car systems, as they have misunderstood from some random sources that such systems go up to 28V. In reality, 24V alternator, in cold weather, outputs 30V-32V continuous, not even to talk about conditions such as load dump, so these arbitrary ratings would be exceeded anyway. But it doesn't matter, they could have just said 40V or 50V or 100V or whatever.Things get different with voltages not under safety extra low voltage classification; those that can cause dangerous electric shock, and especially when high peak voltages are involved. Then it really does make a difference if a connector is rated to 100V or 600V or 1200V.

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 10, 2024, 07:50:23 pm
content: Quote from: Siwastaja on August 10, 2024, 03:47:11 pmThanks... Knowing more about SELV limits makes my search much easier.

author: ebastler
author_rank: Super Contributor
timestamp: August 11, 2024, 11:18:37 am
content: Quote from: Kim Christensen on August 07, 2024, 12:18:02 amBut the voltage ratingsareabout human safety, aren't they? The connectors do not protect users from touching the conductors, hence voltages must be safe to the touch.The nextvoltage-related safety limit would be to prevent arcing -- that would occur at much higher voltages and you don't want to go there due to the human safety considerations. And then there arecurrentlimits, to prevent the connector from overheating. (Due to resistive heating across the contact resistance, potentially exacerbated by oxidizing contacts.)