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Discussion Starter · #1 ·
In the spring I thought I might put some thick sticky silicone grease on my battery terminals, the grease was purchased on line from an outfit that deals with scuba gear and I needed the grease for some o-ring application.
I removed the battery leads and applied the grease to the posts and re-connected the leads and all was well until last week.
We had a really cold spring, actually our home heating was on in mid June so the V50 t5 AC was not on full wack until last Thursday.
I was driving up the road when the dreaded Power System - Urgent came on. I did the errand I needed to do and drove home, about 15 KM round trip.
I opened the hood and got a whiff of burning from the alternator and the battery tested below 12v with the engine off and the same with the engine running.
That's a knackered alternator right? So I ordered a re-worked unit right away from RockAuto. I then disconnected the battery and put it on charge to see that it was still good. After charging the battery, I wiped all the silicone grease off the posts and the clamps and re-connected.
This was on Friday, my afternoon to meet the lads at the bar which was about 10KM away so I thought I would take a chance. I took my meter with me and drove with no AC, radio or fan and when I got to the bar I checked the voltage and it had not changed, so on the way back from the bar I put the ac, fan and radio on and when I got home the battery had not lost it's charge.
The next day, yesterday, I took the leads off the battery, cleaned everything with paint thinner and give them a bit of a sand and went shopping. Today we went to the country, about 140km round trip and the voltages measured spot on when we got back home.
I read on line that silicone is dielectric, an electrical insulator.
I have to try to send the alternator back when it arrives, it was not the cost, rather the work involved of getting the old one out of a t5 and getting the new one in.
So guys do not use silicone grease on your battery, even if that prick Scotty Kilmer says it's OK
 

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What type of grease was it? I only use the ones that say dielectric. Regular silicone grease is an insulator and putting it on battery terminals is no different then having the terminals barely touch the posts, very poor contact all around. That spray silicone stuff is no good either cus that turns into nasty gunk after a while.
 

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I'm not sure where to go with this - if your post attachments are functioning correctly - you should be squeezing 95% of it out of the top/bottom of the post. Why is this an issue? Metal-Metal contact isn't gonna be hindered by squeezing the silicone out when tightening it? I mean is it really that big of an issue or is this another issue being disguised as what OP's issue had?
 

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Yes, the silicone is an electrical dielectric (insulator) this is exactly what you DO NOT want on the posts before you attach the battery cables. Instead, you want clean metal to metal contact between the battery posts and the cable ends. After the cables are connected then you can apply the silicone grease if you wish. Personally, I use CRC battery terminal spray after the cables are connected. There are also treated felt pads that can be placed under the posts to prevent corrosion.

By the way, according to the VIDA instructions for disconnecting and reconnecting the battery:
Disconnecting - The ignition switch should be in position "0".
Connecting - The ignition switch should be in position "II". This sounds odd but I have run into issues with ABS light on and sunroof not working if I did not follow this procedure.
 

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Discussion Starter · #5 ·
Actually I put Dow Corning High Vacuum Grease on the posts, I now remember I could not find the online grease I purchased, which I have now found.
There is a difference between the 2, the Dow grease is a lot stickier and a lot more expensive, not for me, my old company supplied it.
 

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By the way, according to the VIDA instructions for disconnecting and reconnecting the battery:
Disconnecting - The ignition switch should be in position "0".
Connecting - The ignition switch should be in position "II". This sounds odd but I have run into issues with ABS light on and sunroof not working if I did not follow this procedure.
Today I learned! You'd think that would be in the owner's handbook since battery replacement is usually something the consumer can handle.
 

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By the way, according to the VIDA instructions for disconnecting and reconnecting the battery:
Disconnecting - The ignition switch should be in position "0".
Connecting - The ignition switch should be in position "II". This sounds odd but I have run into issues with ABS light on and sunroof not working if I did not follow this procedure.
Today I learned! You'd think that would be in the owner's handbook since battery replacement is usually something the consumer can handle.
That has nothing to do with the sunroof or ABS light. It is a safety precaution in case you were working on the SRS system (or near its wiring) to prevent the airbag from blowing off in your face if you somehow shorted just the right wires.
 

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I'm halfway surprised the dude from Finland didn't come into here and say "Congratulations. Wrong grease." again haha.

Okay so question then, how does a flowable grease prevent metal-metal contact in a clamp like battery terminal? I get how it can fill gaps between spaces (it's not like the power arc's through these spaces anyways, so big woop), but what is it does the clamp not have enough force to push the grease out for metal - metal contact or something?

Me personally I use a lead based anti-seize on the posts - fills in the gaps and allows for maximum possible contact between the post and the clamp. Wipe off and reapply when removed/reinstalled.

I also put a plastic bag around the battery between the battery and the metal band that holds it down. All corrosion issues stopped entirely (mostly the by the bag of course). Been there for about two years now and not a hint of corrosion whereas without it it was maybe 90 days before white stuff started showing up and ran all the way down to the transmission.
 

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That has nothing to do with the sunroof or ABS light. It is a safety precaution in case you were working on the SRS system (or near its wiring) to prevent the airbag from blowing off in your face if you somehow shorted just the right wires.
Perhaps it was some weird coincidence when I reconnected my battery with the key out (ie position "0") and the ABS light came on and the sunroof would not function. I simply disconnected the battery for 10 minutes, put the key in position II and reconnected the battery. All was good after that.

Sometimes digital electronics can come up in an "ambiguous" states if they are not designed out.
 

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I'm halfway surprised the dude from Finland didn't come into here and say "Congratulations. Wrong grease." again haha.

Okay so question then, how does a flowable grease prevent metal-metal contact in a clamp like battery terminal? I get how it can fill gaps between spaces (it's not like the power arc's through these spaces anyways, so big woop), but what is it does the clamp not have enough force to push the grease out for metal - metal contact or something?
Ideally you want clean metal to metal contact for the lowest resistance connection between the post and the clamp. When starting there will be very significant current draw. That current draw through a resistance will result in a voltage drop (simply Ohms Law V=I*R). Sure the clamp can push most the grease out but a micro-thin layer can remain which will increase the resistance of the connection. Certain greases (ie wrong grease) may be corrosive or facilitate inter-metallic growth and further increase the resistance.

I don't follow why you would want the grease between the post and the clamp anyway? For best results; clean the post and clamp lightly with a battery terminal brush so there is bright metal on both mating surfaces, mate the connections and then add protectant if you like.
 

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Ideally you want clean metal to metal contact for the lowest resistance connection between the post and the clamp. When starting there will be very significant current draw. That current draw through a resistance will result in a voltage drop (simply Ohms Law V=I*R). Sure the clamp can push most the grease out but a micro-thin layer can remain which will increase the resistance of the connection. Certain greases (ie wrong grease) may be corrosive or facilitate inter-metallic growth and further increase the resistance.

I don't follow why you would want the grease between the post and the clamp anyway? For best results; clean the post and clamp lightly with a battery terminal brush so there is bright metal on both mating surfaces, mate the connections and then add protectant if you like.
Was just a question, I don't want grease there, I just didn't understand how some flowable grease would prevent the same metal to metal contact a clamp would experience, but the dielectric breakdown and metal interaction definitely makes sense.
 

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Electricity can not flow between the touching of two metals and it cannot flow through grease. The oxidation prevents electrical flow and grease is non conductive.

In order to get electrical flow the metal needs to be melded together.

Usually the pressure of the contact and the heat from the electrical flow is enough to create just enough of the metal to meld together. Unless your grease is rock hard the pressure just displaces it.

Grease is non conductive. The only use it has is to prevent air and moisture from corroding the melded joint.

Some people prefer anti-seize grease since the metal in it helps the joints meld together. For a battery lead is very soft so it is not necessary.
 

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I've used silicone grease with great success in the past but mostly on spade connectors, relays and the like.
The issue with coating battery posts is that the surface area is HUGE, and you need a helluva lot of pressure to get the grease to ooze out.

It's much better to clean the posts and terminals once a year, and maybe spray something on them after tightening.
 

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It's really not complicated. Disconnect the battery, clean the posts and cable ends with a terminal brush. Connect them. Apply whatever anti-corrosion spray or grease.
 

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Discussion Starter · #15 ·
In the spring the car started and ran OK with just the heater fan, running lights and radio, it was when the AC fan came on full blast on the auto setting on the first hot day.
Since cleaning off the silicone grease, the car is running just fine and we are having heatwave.
It has cost me about $50can to ship back the alternator to CA. I dread to think what a shop would have charged me, they would have probably just replaced the alternator?
 
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