I've got a high powered stereo system in my 2004 Prius, so I want to increase the diameter of the wire from the 12V battery negative terminal to chassis ground up to 4 gauge. As y'all probably know, the Prius battery has "pencil post" sized terminals which are significantly smaller than the standard 12V terminals on most every other car. The OEM negative terminal is extremely corroded, and the wire looks like 8 gauge. So even if I replace it with a new OEM terminal/wire assembly, it will still be 8 gauge not 4 gauge. I'm leaning toward going this route despite the wire being smaller than I'd prefer because... I tried a highly-rated standard size terminal from amazon, along with an insert set that converts the pencil post terminal to standard diameter. It just won't tighten all the way; even after tightening the terminal as far as it will go, I can still rotate the terminal on the post with my hands easily. I've spent hours searching the web for a terminal that would go on the pencil posts without inserts, and have come up empty. So I thought I'd just double check if anyone here has a secret supplier. Otherwise I'll go to my Toyota dealer, pay whatever they are extorting for a new terminal/wire assembly, and keep the stereo turned down so I don't melt the 8 gauge wire.
not sure if this works p-161-4205 or you could replace the battery with something more robust with standard terminal posts
Isn't that ground wire all of maybe a foot long? Changing a foot of wire from 8 ga to 4 ga will reduce its resistance from 0.000641 Ω to 0.000253 Ω. What's the most current you anticipate your stereo pulling, if you don't keep it turned down?
Just replace the corroded stuff with same stuff. OEM is more than a sufficient gauge and your high voltage battery & inverter is handling the power supply not the 12v, which just turns the computers and relays on when you hit power button. Unless you have to sit on your windshield to keep it from popping off at full power to your amps and sub, you're barking up the wrong tree.
Wire ampacities are not inherent properties of the copper; they have to be calculated according to how much heat will be produced at what current, what temperature the insulation can withstand, and how well the environment can take away the heat that's being produced. Most of us who have seen wire gauge and ampacity charts have seen the ones for house wiring, which is based on insulation rated for 90 ℃ and running inside insulated walls, or conduits with several other wires. Toyota's ground wire is pretty much in free air in the back of a car near a ventilation outlet, and auto wiring generally uses insulation with a higher temperature rating. About the highest continuous current you would plan for back there would be the 125 A or so that Toyota fuses the circuit for. At 125 amps, that one foot of 8 ga will drop 0.08 volts. At 0.08 volts and 125 amps, 10 watts of heat are developed in the wire. So the question is, will 10 watts of heat raise the temperature of a foot of 8 ga copper, in automotive insulation, in free air, above its insulation temperature rating? I'm thinking it would be ok. But a person could also borrow a thermal imager and just have a look at that wire while carrying the maximum planned current, and see how warm it gets.
I had the same issue. Used the lead expanders over the pencil post. I tried 3 different multi connection negative terminals before one tightened properly. I'll send a pic. Posted via the PriusChat mobile app.
Very good electrical advice on previous post. I would add protect your own health, happiness, hearing, the environment and do others a big favor and don't turn the sound up enough to attract attention to yourself. If others can hear your stereo outside your car you are damaging your hearing while in the car. Loud Noises: Health Dangers (healthline.com) Noise Pollution | National Geographic Society The Many Health Effects of Noise - Consumer Reports
This was in my other car. It allowed me a 4 gauge to my amp and a extra ground to the car. Bought this 20 + years ago. Don't know the brand. Maybe efx. Posted via the PriusChat mobile app.
Scosche SCLAMPN High Quality Negative Battery Terminal 8/1/0/4 Gauge Out 33991023895 | eBay Posted via the PriusChat mobile app.
SCOSCHE SCLAMPN EFX NEGATIVE NEG CAR BATTERY TERMINAL CAR POST CLAMP 8 0 4 GAUGE 33991023895 | eBay Cheap one that looks like the same design that worked for me. Made by the same company. Posted via the PriusChat mobile app.
Excellent points about wire gauge being more than just where the electrons travel, but also how well insulated their traveling is. I recently restored a small 2K watt sauna and did a bunch of shopping around for the best power cable for it and was wondering why the different options were more about thickness and quality of insulation type and less about wire gauge. It's impressive how much cooler the same gauge wire runs with heavy duty insulation compared to standard extension cord thickness of near same gauge wire.
