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lmpdev

I get this a lot

I work at an electronics store in Australia

This week I had a customer dumbfounded why his 3,500W inverter almost caught fire

He was using 8-gauge wire (~56A max)

He needed 00-gauge (almost 300A max)

If he’d have run the system at 48V instead of 12V he’d have saved $200+ per metre on cabling his inverter

My advice on voltage selection for a vehicle is once you’re needing more than a few metres of 0-gauge, you should possibly increase the voltage of the system

High current cabling means expensive ANL, mega or other high performance fuses or other expensive circuit protection methods

I strongly believe that 48V systems are inherently safer than 12V systems when it comes to the public doing DIY work

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Back in the '80s I was helping a buddy upgrade the stereo system in his RX-7. The teenager down the street comes by and educates us that "you should be using really thin wire, like telephone wire, because otherwise the amp sucks all your power." My buddy was an electrical engineer at Hewlett-Packard.

Good look doing DIY work on the 48V network of a modern car, ICE or EV or 12, 24 or 48 V doesn't matter.

And the past 12 V systems are dead easy to work on. On older cars that is, as soon as you have electronics and bus systems DIY basically requires deep car electronics knowledge and skills.

Do you have examples of what kind of DIY work is hard?

I haven’t done a ton of work on newer cars, but at least adding wiring for a hitch on my Kona EV was just as easy as any wiring I’ve done on my old truck.

Is a job like adding amps and better speakers trickier?

I have a defender and added a bunch of stuff to it: cruise control, motor pre-heater, rear camera, working lights in the rear. I'll also add a diesel heater and more electrics at some point. On 12V it's easy, can't imagine doing work like that with 48V. Not sure how this works, and if you maybe just can use 12V anyway. But wanted to make the point of camper vans and overlanders and offroaders.

An old or a new one?

Ah right, should've specified that. Of course an old one ;) A Td5. I call the other one "New Defender"

And a TD5 is already modern-ish enough, but very nice regardless! Personally, I would be at a loss working in anything built after the early 80s, so for a Defender that would be the dual-carb V8s, and 200/300 TDis.

My 1982 Range Rover has all of three fuses, so electrically I'm fine! Except the mess previous owners did to the original wiring... No idea why it is so difficult to just make your own wiring for after market accesories instead of butchering the OEM one up beyond recognition. It works, so I don't touch it. I have no idea why it works so...

Yeah I don't touch anything in the box beneath the passenger front seat ;) The previous owner thankfully already fixed the "oil creeps up the wires" issue, so I can leave it. Nothing I'm too keen on, but simple enough I figure.

> I have no idea why it works so...

I know that feeling haha. Adding wiring is so much easier than ripping up existing stuff ...

When a mechanic from Land Rover saw the wiring, he said something along the lines of "just fault location would be 2k, none of the colors I see should be there". A mess... But hey, the 80s and 90s were a wild time, and it is rust free!

Depends on where you connect stuff. Directly to some wiring loom that is already there? Bad idea, not all connected equipment will take the aditional loads well. Going directly to the car battery with dedicated wiring? Doable, but since start-stop is a thing, battery management and other stuff migjt not like that very well neither. Second batery? A bitch since start-stopp.

Hence, one needs some good knowledge around that, what to connect where.

In the old days, well, just go directly to the main battery with your aftermarket wiring and Bob's your uncle.

And none of that, battery management, which equipment can be connected where, has anything to do with the voltage but rather with all the other stuff modern cars have (bus management, battery management, ECus,...) all of which might or might not accept voltage and amp fluctuations very well.

Dead easy is relative I guess, I once tried to track down an issue with the wiring loom of my 400cc motorbike and ended up giving up…

> as soon as you have electronics and bus systems DIY basically requires deep car electronics knowledge and skills.

So how is this done on cars? Dores each manufacturer have their own proprietary bus system (what i imagine), or is there a standard that everyone can use?

Nah there’s been mandated standards since the 90s eg OBD I/II/III

Protocols like CAN, LIN, SENT and XCP are all standardised point to point and bus protocols for automotive stuff

I personally think the standardisation is actually a bit limiting[1]

Just like SpaceX found massive cost savings in using networking tech over hard wired interconnects, I think there’s a good chance China or other manufacturers might catch on

[1]I think interconnect failure rates are so low out of factory it’s not unethical to begin making things more lean, obviously with sufficient human safety testing

But I’m not an expert, just a former engineer working in an electronics shop…

Thanks for posting this - I only noticed your reply now. Exactly this. Installing inverters for my own projects is what really highlighted the amp/volts/gaugerelationship. I quickly moved to 24V and will push for 48V for my next. As an aside I use Victron gear which I'm very happy with. Biggest install is for a film van and has dual 5KW inverters that can deliver 8KW continuous - and it's a 24V system.

Victron is an amazing manufacturer

I love that they don’t keep releasing new products so they can properly support their existing (extremely well made) lineup

Look into data centre infrastructure if you want to find interesting brands and solutions

A lot of automotive/DIY marketed gear seems to be reinventing the wheel and charging a much higher premium for it

I guess you work at Jaycar too? Always a fun conversation trying to explain voltage drop to someone who wants to cheap out on cable with our inverters and DC/DC chargers.

I'm sure a 48V bus would solve all those F1 errors too.

That's funny, I assumed the same.

Not an employee, but a very happy reoccurring customer.

Yeah my dude

Didn’t think there’d be more than one of us on here

Such a wild west company to work for. I enjoy meeting the many very bright people who work for us before they inevitably move onto other things

How do you integrate the 48V system with the existing 12V system when doing aftermarket/DIY work? Do you add a 48V inverter? A buck-boost DC-DC converter? between the battery (or main fuse block) and the 48V system?

You don't. 48V battery and separate circuits if it's an RV, otherwise forget it.

Do not attempt a hybrid system with different voltages DIY

In an industrial setting it can be done but you need an extremely well designed and made termination point for one system and an interconnect for another, I’ve seen customers using floating grounds (and negative voltages) to enforce it

If upgrading to 24V or 48V I recommend having a solid grasp on circuit protection first, and if you have concerns, pay the 30 minutes or so labour for an automotive electrician to inspect it

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