Paul asked: Do you really put grease on a clean battery post before attaching the cable? In the Cleaning a Car Battery section, it says to prevent corrosion, you should put grease on the clean terminal post before you reattach the cable. Won’t this prevent a good electrical connection?
The 
grease that should be applied is white lithium grease. It is readily available at automotive stores. It will not interfere with the electrical connection, but will help prevent future corrosion by displacing the air in the surrounding space.
The idea is to apply the grease to the terminal after you have connected and tightened the battery cable. This will create a layer of grease between the conducting surfaces and the surrounding air and moisture, and thus, prevent corrosion. Always apply it to a clean terminal for best results.
It is also wise to install a pair of felt washers underneath the terminals. These washers are available in automotive stores, right near the batteries. The help prevent high-resistance shorts across the battery case (when batteries get really dirty, the layer of oil and dirt will sometimes be conductive enough to connect the two terminals electrically)
The conductivity of grease is irrelevant when you’re dealing with the 100 + Amp cranking current. All electrical joints – mains or automotive – require clean, dry mating surfaces for low resistance. Putting any sort of grease on terminals before connection will increase it. It’s often not explained clearly by people who should know better – even manufacturers.
Clean the terminals and clamps as people describe, secure the clamp, then apply grease all over the joint to keep air and moisture out. The grease can’t penetrate between the two conductive surfaces if they’re firmly secured.
I agree with Vincent; if the grease is not conductive, you should only apply it after connecting to the post. If you applied a non-conductive grease to the post prior to connecting the wiring, it will form an insulation layer between the electric connections.
The idea is to insulate the terminals from the air moisture, which will create the the salt and corrosion later on, and that could be achieved by applying the grease after making a good electric connection (by connecting a clean terminal to a clean post).
Shereen
Electrical Power Engineer
Saw another article by a EE HAM radio operator indicating that silicon dielectric grease had advantages over petroleum. Here, after applying Permatex silicon dielectric grease to cleaned battery terminals on old F150, and re-clamping, measured 12.67 V across the posts, across the clamps and (-) post to alternator casing. No change in potential. The EE HAM made the points that Vaseline has a low melting point and is a fairly good fire starter (think cotton balls saturated with the stuff); melting points of petroleum greases are lower than silicon and that any conductive material in petro grease is isolated from conducting by the surrounding lube, except in providing an arc path at very high voltages.
Seems to me, unless the product has a conductive component, it will act as a resistance component if applied to the two conductive surfaces prior to connecting the cable on the terminal.
I’ve found the best way to care for post terminal batteries is to pour the baking soda solution on the terminals and battery top, wait until it quits foaming, then rinse with hot water. Next, disconnect the ground terminal (neg.), then the positive. Since good terminal and cable end cleaner tools are not available anymore, I use an old pocketknife to carefully ream the cable ends to shiny metal. I then use a strip of shop cloth to clean the posts. Once everything is back together, I spray battery terminal protector on each connection. Lastly, I clean the top of the battery with window cleaner and a paper towel.
Metal to metal connection is the best electrical connection and least resistance. Dielectric grease is to protect a connection not make or enhance electron flow through electrical connection, only to protect from the environment. There are greases that are conductive, e.g. “No-ox”.
Lithium grease is non-conductive; it can be used to protect completed connection, but not make a connection. On an auto battery, clean the post and clamp, attach, and apply di., lith., etc., sealing the connection top and bot.
I have been using the grease that electricians use on aluminum wire. It’s a conductive grease that keeps corrosion away from aluminum wire. My ex-brother-in-law (an electrical contractor) told him to use it on battery cables that they would stay clean and it helps contact. It can be bought at any place that sells electric wire.
Hello all. After reading the posts, it came back to me; when I had older cars and corrosion on the battery terminals, I used Coke (the soda) and it would dissolve the acid corrosion and help in the cleaning of the posts and cables. I also remember using boric acid for the same cleaning. Coke is good also for cleaning out battery compartments of items that use reg. batteries e.g. AA, C, D… Just use it sparingly and don’t drown the compartments. Also, after cleaning the car battery posts, I would coat the terminals as well as the attaching the ends of the cables with either Vaseline (don’t remember if it was clear or petroleum) or lithium grease. One other thing comes to mind and that is I think I used to check the other ends of the cables (those that were attached to a “negative ground” and those that were attached to their “positive source” for corrosion build-up. Never had any problems after that. Hope this imparts some useful information. HAPPY HOLIDAYS!
How much grease to apply? A thin or thick coating? Is this done after you re-attach the cables to the posts?
Why do people say to stick a penny in between the connection?
Well!! I have been wondering about just this issue since I had to (trickle) charge my lawn tractor’s battery a few days ago, after it sat in a very cold garage all winter. I think my dilemma is more or less resolved with the “conductive grease” solution above; either that or using that white lithium paste. I have some reddish grease in a small packet labeled “battery protector”; it looks just like the heavy grease I use for all sorts of heavy mechanical lubrication/rust protection. Seemed to me that, if put on all metal surfaces, it would act more as an insulator than a conductor. So. . .I am happy to read this thread and will place felt washers where needed to prevent an accident. The whole system has been cleaned and scraped, and has been awaiting resolution of this conundrum. Thanks!
What about flammability of these greases? Are the fiber washers flame retardant? We handle these on production bases and wonder if they should be stored in a flame-proof cabinet?
Tye,
Both articles agree that grease should be applied directly on the terminal posts. Petroleum jelly is often used for cuts and wounds because it acts as a seal against oxidation, which is the same reason that people put grease on battery terminals. Some people prefer to use petroleum jelly simply because they have already have it on hand, it is less expensive than lithium grease and they can use it for other purposes. Either product will complete the task of protecting your car battery from corrosion, however white lithium grease is the recommended product that is used by professionals.
Source: WiseGeek – What is Petroleum Jelly?
Source: Wikipedia – Lithium soap
Source: Reader’s Digest – 5 Car Battery Tips and Tricks
Thank you.