You connect the battery to the chassis and ground to the chassis or battery negative directly. This is different than signal ground, which is highly sensitive to noise due to the low voltages and requires a separate ground reference.
Best ground when jump starting is any stout metal engine part. The battery IS or should already be grounded on nearly all 12v starting battery installations.
If you think grounds can't be noisy, you're nuts. It's why oscilloscopes come with a number of different grounding options. Under the right conditions, that lead with the alligator clip on the end acts like an antenna, polluting not only your measurement, but also the performance of the circuit under test.
what active electronis in the battery need dedicated signal ground to omm.
If you think grounds can't be noisy, you're nuts. It's why oscilloscopes come with a number of different grounding options. Under the right conditions, that lead with the alligator clip on the end acts like an antenna, polluting not only your measurement, but also the performance of the circuit under test.
Battery is just to boot up the car. Alternator does the heavy lifting.
6 months ago
Bepis
Battery smooths out the voltage from the alternator as well. Modern cars do not run well at all with a dead battery but alternator still putting out >14V. The computers really don’t like power straight from the alternator.
>Fwiw, pretty sure dielectric grease like this “bulb grease” is just silicone, looks exactly the same as the plumbing grease and the stuff you use for foodservice equipment. I’m just going to get a big tub of silicone grease when these run out
Get "dielectric grease" in a can instead. It has superfine glass powder mixed into the silicone base which stiffens it up enough to make it not creep away the way that your pictured silicone grease can.
You talking about picrel? I thought about buying that can but I figured the can would go flat before I get halfway done with it since a little dot of dielectric grease goes so far.
6 months ago
Anonymous
>Battery smooths out the voltage from the alternator as well. Modern cars do not run well at all with a dead battery but alternator still putting out >14V. The computers really don’t like power straight from the alternator
Close but it's more about ac to dc. The rectifier doesn't really do it 100% battery helps a bit more. Least that's what I've been told. They say it's actually dangerous to old school test an alternator (disconnect battery if car shuts off alternator) cause it can brick the computer if the rectifier is busted as well. Never seen that happen though tbh
6 months ago
Bepis
I’ve worked on a handul of cars where the battery drops a cell or does some goofy shit and is reading 7V and you can jump the car with a strong enough jumper box, but computers will flicker and lights do weird shit and it might shut off on you when you come to a stop sign and slow down. Haven’t perma-wrecked a computer trying to run with the alternator supplying all the power, but have seen a lot of stuff wig out.
6 months ago
Anonymous
Yup, for sure I've seen that as well. First thing I do for any electrical diag is check battery connections and health.
If you think grounds can't be noisy, you're nuts. It's why oscilloscopes come with a number of different grounding options. Under the right conditions, that lead with the alligator clip on the end acts like an antenna, polluting not only your measurement, but also the performance of the circuit under test.
Mechanic here, probably not as much as you think. Or at least the electrical engineers designing the systems are smart enough to see what fricked up shit I'm going to do to that shit call it stress testing. You've gotta really frick some shit up b4 anything goes wrong is what I'm saying. I'd ground my welder right to the battery in a drunken bet with a friend to prove it. Is what I'm saying. I haven't done that but I bet everything would be fine.
6 months ago
Anonymous
Uh, no, there's definitely lots of sensitive electronics in there.
>Or at least the electrical engineers designing the systems are smart enough to see what fricked up shit I'm going to do to that shit call it stress testing.
It's 100% that. Automobile electronics are extremely well protected both mechanically and electrically so that they'll withstand environmental abuse and abuse from even the clumsiest of mechanics.
>I'd ground my welder right to the battery
Shouldn't cause any problems. Since all electronics are referenced to chassis ground and aren't connected to earth ground, the car chassis could be at thousands of volts and nothing would be damaged.
At any rate, that doesn't disprove the need for signal grounds in addition to chassis ground.
signal ground and chassis ground are bonded together, but hi-speed signals need dedicated grounds so that the area of the loop formed by the signal path and ground is minimized.
Large loops = (relatively) large inductance = lots of cross coupling, noise, and EMI.
6 months ago
Anonymous
>I agree with everything you say >but you're wrong about these things you made no mention of
PrepHole
6 months ago
Anonymous
But also I will say it now, you're probably wrong about that. You're probably talking best case scenario something you read somewhere I would bet a beer I can just ground it wherever makes sense and it'll be fine. I bet you tell pc builders its impossible to build a one without a grounding strap too.
6 months ago
Bepis
You don’t work on many Chrysler vehicles, do ya?
Well maybe not ground specifically, but I just had random ass electrical issues in two Daimler Benz era cars, a Chrysler 300 was going into limp mode randomly and shutting off at idle, and a Grand Cherokee was throwing transmission codes for high temp and going into limp mode. 300 got a flashed rebuilt ECU because frick you and Grand Cherokee got a junkyard TCM.
6 months ago
Anonymous
Right I'm not saying computers don't fail, I'm saying for you to be the cause usually takes a pretty massive frick up. Doesn't sound like you caused those to fail they just did. But actually you're right I'm speaking out of turn, I've seen an audi bricked because it was jumpstarted. Not even in a fricked up way was done on the posts provided up front because the battery was in the back buried under a bunch of shit. Dude jumped it, parked it, wouldn't start again
this was pretty normal afaik, I saw it in old trailer lights. Ground to chassis, and every bulb just right to chassis. Less wires to care about and prevents corrosion. Wouldn't surprise me if you did the same for old cars, except for starter cables that require high currents.
I mean starters only have one damn + cable going to them, there’s no fat ground cable coming off. The ground is the big metal face that sits on the rear of the engine.
If you need this much shit directly connected to the battery you're much better off with a secondary fuse box for the positive and a bus bar for the grounds mounted to the fender. You can directly ground that to the battery if you want if the fender isn't grounded as well it it should be.
people doing that usually drive the borderline scrapyard beaters
chassis made out of iron oxide is not the greatest conductor so they just pull a direct ground wire to the battery, whenever they need ground
I absolutely despise that shit. And of course all those wires end up getting corrosion all up in them because of the battery acid. Most people that do their own vehicle wiring should have their faces bashed in with a lead pipe...
That might work fine, but I use that for bolts and nuts that might rust or seize (or the ordinary gray anti-seize). For anything near the battery I spray a bit of pic related. Might make less of a mess?
Love this shit. Spray the terminals once and it's pretty much good for the lifetime of the battery.
It's good for nearly anything.
A tiny amount goes a long way. After I dab it with the brush, I use my fingers to spread it thinly over the terminal and lug.
I find those CRC sprays to be a pricier alternative. Sure, they work. Sure you do not have to touch anything.
>I find those CRC sprays to be a pricier alternative
Sure, but only relatively in this case. We're talking about 10 to 15 bucks for a can of terminal protector that will last you for decades. I have a can that's still about half full that I'd guess I probably bought like 15 years ago.
I have a blue can of some CRC electrical contact cleaner/protector and I have yet to really use it. Don’t know what it’s even like. The WD Specialist electronic cleaner seems to be like pure alcohol spray.
Fwiw, pretty sure dielectric grease like this “bulb grease” is just silicone, looks exactly the same as the plumbing grease and the stuff you use for foodservice equipment. I’m just going to get a big tub of silicone grease when these run out.
>Fwiw, pretty sure dielectric grease like this “bulb grease” is just silicone, looks exactly the same as the plumbing grease and the stuff you use for foodservice equipment. I’m just going to get a big tub of silicone grease when these run out
Get "dielectric grease" in a can instead. It has superfine glass powder mixed into the silicone base which stiffens it up enough to make it not creep away the way that your pictured silicone grease can.
6 months ago
Bepis
https://i.imgur.com/lNuhD13.jpg
Battery smooths out the voltage from the alternator as well. Modern cars do not run well at all with a dead battery but alternator still putting out >14V. The computers really don’t like power straight from the alternator.
[...]
You talking about picrel? I thought about buying that can but I figured the can would go flat before I get halfway done with it since a little dot of dielectric grease goes so far.
I’m going to get down on a big tub of this shit for everything, plumbing and o-rings and batteries and all sorts of electrical connections and see how it goes
6 months ago
Anonymous
either one you posted is great tbh. I've had cans of the red CRC stuff around for years and they've never gone flat, although I have had them get squished in a toolbag and squirt their entire load without my consent
IDK why this shit tripled in price during covid and didn't come back down
You connect the battery to the chassis and ground to the chassis or battery negative directly. This is different than signal ground, which is highly sensitive to noise due to the low voltages and requires a separate ground reference.
Best ground when jump starting is any stout metal engine part. The battery IS or should already be grounded on nearly all 12v starting battery installations.
>low voltages
ground is 0v
vechicle body is enormous mass of metal meaning low impedance
try again
lol ur dumb
https://www.edaboard.com/threads/what-is-the-signal-return-line.70498/?amp=1
what active electronis in the battery need dedicated signal ground to omm.
if you are worried about comms used balanced line
Noisy ground can also cause problems in power delivery. Its why, for instance, the pwr/gnd lines to a fuel pump are often a twisted pair.
from a car battery?
Everything in a car is from the battery.
Battery is just to boot up the car. Alternator does the heavy lifting.
Battery smooths out the voltage from the alternator as well. Modern cars do not run well at all with a dead battery but alternator still putting out >14V. The computers really don’t like power straight from the alternator.
You talking about picrel? I thought about buying that can but I figured the can would go flat before I get halfway done with it since a little dot of dielectric grease goes so far.
>Battery smooths out the voltage from the alternator as well. Modern cars do not run well at all with a dead battery but alternator still putting out >14V. The computers really don’t like power straight from the alternator
Close but it's more about ac to dc. The rectifier doesn't really do it 100% battery helps a bit more. Least that's what I've been told. They say it's actually dangerous to old school test an alternator (disconnect battery if car shuts off alternator) cause it can brick the computer if the rectifier is busted as well. Never seen that happen though tbh
I’ve worked on a handul of cars where the battery drops a cell or does some goofy shit and is reading 7V and you can jump the car with a strong enough jumper box, but computers will flicker and lights do weird shit and it might shut off on you when you come to a stop sign and slow down. Haven’t perma-wrecked a computer trying to run with the alternator supplying all the power, but have seen a lot of stuff wig out.
Yup, for sure I've seen that as well. First thing I do for any electrical diag is check battery connections and health.
If you think grounds can't be noisy, you're nuts. It's why oscilloscopes come with a number of different grounding options. Under the right conditions, that lead with the alligator clip on the end acts like an antenna, polluting not only your measurement, but also the performance of the circuit under test.
your car is not a precise electronics, tho
Maybe if it's from 50 years ago, but modern cars are chock full of high-speed electronics that absolutely do care about good grounding.
Mechanic here, probably not as much as you think. Or at least the electrical engineers designing the systems are smart enough to see what fricked up shit I'm going to do to that shit call it stress testing. You've gotta really frick some shit up b4 anything goes wrong is what I'm saying. I'd ground my welder right to the battery in a drunken bet with a friend to prove it. Is what I'm saying. I haven't done that but I bet everything would be fine.
Uh, no, there's definitely lots of sensitive electronics in there.
>Or at least the electrical engineers designing the systems are smart enough to see what fricked up shit I'm going to do to that shit call it stress testing.
It's 100% that. Automobile electronics are extremely well protected both mechanically and electrically so that they'll withstand environmental abuse and abuse from even the clumsiest of mechanics.
>I'd ground my welder right to the battery
Shouldn't cause any problems. Since all electronics are referenced to chassis ground and aren't connected to earth ground, the car chassis could be at thousands of volts and nothing would be damaged.
At any rate, that doesn't disprove the need for signal grounds in addition to chassis ground.
signal ground and chassis ground are bonded together, but hi-speed signals need dedicated grounds so that the area of the loop formed by the signal path and ground is minimized.
Large loops = (relatively) large inductance = lots of cross coupling, noise, and EMI.
>I agree with everything you say
>but you're wrong about these things you made no mention of
PrepHole
But also I will say it now, you're probably wrong about that. You're probably talking best case scenario something you read somewhere I would bet a beer I can just ground it wherever makes sense and it'll be fine. I bet you tell pc builders its impossible to build a one without a grounding strap too.
You don’t work on many Chrysler vehicles, do ya?
Well maybe not ground specifically, but I just had random ass electrical issues in two Daimler Benz era cars, a Chrysler 300 was going into limp mode randomly and shutting off at idle, and a Grand Cherokee was throwing transmission codes for high temp and going into limp mode. 300 got a flashed rebuilt ECU because frick you and Grand Cherokee got a junkyard TCM.
Right I'm not saying computers don't fail, I'm saying for you to be the cause usually takes a pretty massive frick up. Doesn't sound like you caused those to fail they just did. But actually you're right I'm speaking out of turn, I've seen an audi bricked because it was jumpstarted. Not even in a fricked up way was done on the posts provided up front because the battery was in the back buried under a bunch of shit. Dude jumped it, parked it, wouldn't start again
I did which is why I don't own one.
and yet, there's a single ground on the car battery - go figure
this was pretty normal afaik, I saw it in old trailer lights. Ground to chassis, and every bulb just right to chassis. Less wires to care about and prevents corrosion. Wouldn't surprise me if you did the same for old cars, except for starter cables that require high currents.
I mean starters only have one damn + cable going to them, there’s no fat ground cable coming off. The ground is the big metal face that sits on the rear of the engine.
If you need this much shit directly connected to the battery you're much better off with a secondary fuse box for the positive and a bus bar for the grounds mounted to the fender. You can directly ground that to the battery if you want if the fender isn't grounded as well it it should be.
people doing that usually drive the borderline scrapyard beaters
chassis made out of iron oxide is not the greatest conductor so they just pull a direct ground wire to the battery, whenever they need ground
I absolutely despise that shit. And of course all those wires end up getting corrosion all up in them because of the battery acid. Most people that do their own vehicle wiring should have their faces bashed in with a lead pipe...
Copper antiseize. Comes in a bottle with a brush. Apply a thin coat.
>Copper antiseize.
That might work fine, but I use that for bolts and nuts that might rust or seize (or the ordinary gray anti-seize). For anything near the battery I spray a bit of pic related. Might make less of a mess?
It's good for nearly anything.
A tiny amount goes a long way. After I dab it with the brush, I use my fingers to spread it thinly over the terminal and lug.
I find those CRC sprays to be a pricier alternative. Sure, they work. Sure you do not have to touch anything.
Love this shit. Spray the terminals once and it's pretty much good for the lifetime of the battery.
>I find those CRC sprays to be a pricier alternative
Sure, but only relatively in this case. We're talking about 10 to 15 bucks for a can of terminal protector that will last you for decades. I have a can that's still about half full that I'd guess I probably bought like 15 years ago.
I have a blue can of some CRC electrical contact cleaner/protector and I have yet to really use it. Don’t know what it’s even like. The WD Specialist electronic cleaner seems to be like pure alcohol spray.
Fwiw, pretty sure dielectric grease like this “bulb grease” is just silicone, looks exactly the same as the plumbing grease and the stuff you use for foodservice equipment. I’m just going to get a big tub of silicone grease when these run out.
Here’s the CRC… 2-26. Anybody use this shit? What is the actual sparky application of this shit? I remember that little can being quite expensive.
>Fwiw, pretty sure dielectric grease like this “bulb grease” is just silicone, looks exactly the same as the plumbing grease and the stuff you use for foodservice equipment. I’m just going to get a big tub of silicone grease when these run out
Get "dielectric grease" in a can instead. It has superfine glass powder mixed into the silicone base which stiffens it up enough to make it not creep away the way that your pictured silicone grease can.
I’m going to get down on a big tub of this shit for everything, plumbing and o-rings and batteries and all sorts of electrical connections and see how it goes
either one you posted is great tbh. I've had cans of the red CRC stuff around for years and they've never gone flat, although I have had them get squished in a toolbag and squirt their entire load without my consent
IDK why this shit tripled in price during covid and didn't come back down
Fluid film also works great and has many other applications than that crc stuff
Never tried that. Will have to. I've used just dielectric grease or even just plain ol' grease before and it seems to work bretty gud.
I’m guessing somebody had electrical gremlins and wanted to rule out a bad ground to the chassis?
Most battery terminal cleaner sprays I've run across are basically baking soda water...
Tell me you don't live in the salt belt, without saying you live in the salt belt.