Best way to clean corrosion on terminals?

Discussion in 'Generation 1 Prius Discussion' started by adric22, Dec 22, 2009.

  1. adric22

    adric22 Ev and Hybrid Enthusiast

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    I see a lot of threads that mention the corrosion but none really talk about the best way to clean it off. The pack I'm dealing with right now has a lot of corrosion on all of the terminals, busbars, and little nuts. Obviously I could spend some time with a wire-brush or something and clean all of that off. But it would take quite a while, especially those little nuts. Are there any recommended chemicals that might make the job easier?

    I was sort of thinking of mixing some baking soda in some water and just dropping all of those little nuts in the solution for 15 minutes or so. Maybe the busbars too. Then maybe a wire-brush on the battery terminals?
     
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  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Toyota recommends using a boric acid solution (80 g boric acid mixed in two liters of water) to neutralize the KOH electrolyte.
     
  3. DonDNH

    DonDNH Senior Member

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    A light sprinkle of baking soda and a spritz of water. Repeat as needed. Also a light coating of petroleum jelly will keep the corrosion from returning.
     
  4. adric22

    adric22 Ev and Hybrid Enthusiast

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    That's weird.. Does that mean the electrolyte in these NiMh batteries is a base instead of an acid? I guess I better look that up because otherwise baking soda won't make a dent..
     
  5. Rhino

    Rhino New Member

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    "NiMH cells have an [ame="http://en.wikipedia.org/wiki/Alkaline"]alkaline[/ame] [ame="http://en.wikipedia.org/wiki/Electrolyte"]electrolyte[/ame], usually [ame="http://en.wikipedia.org/wiki/Potassium_hydroxide"]potassium hydroxide[/ame].For separation hydrophilic [ame="http://en.wikipedia.org/wiki/Polyolefin"]polyolefin[/ame] nonwovens are used[5]."

    From wikipedia - not always the most reliable. But it does seem like the electrolyte is a hydroxide, which is a base, which means it is basic and not acidic.

    I stated this in a redundant way to help the non chemistry majors.

    In contrast, lead acid batteries use an acid as the electrolyte.

    I didn't know about the potassium hydroxide either. So I learned something.
     
  6. adric22

    adric22 Ev and Hybrid Enthusiast

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    That would make sense why i saw somebody mention using vinegar (which blew my mind at the time..) Maybe I should try that since it makes sense now.
     
  7. dogfriend

    dogfriend Human - Animal Hybrid

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    The Prius Emergency Response Guide says the NiMH battery electrolyte is a mixture of sodium hydroxide (NaOH) and potassium hydroxide (KOH). pH = 13.5 (very strong base)
     
  8. kenmce

    kenmce High Voltage Member

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    If it's corrosion on steel, try naval jelly. There is also a product called dielectric grease that can go on after to coat the exposed metal. Available at any car parts store, don't know how it compares with petroleum jelly.
     
  9. Rhino

    Rhino New Member

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    The reaction for sodium hydroxide and iron (steel etc) is something like

    Fe + 2 NaOH = NaFeO2 + NaH + H or

    Iron + Sodium Hydroxide = some sort of iron oxide (rust) + sodium Hydride + Hydrogen gas

    So the reaction is self sufficient and does not require air etc. The idea of the jelly and grease is to coat the iron (Fe) and prevent the iron from touching the Sodium hydroxide or potassium hydroxide in the first place. Once they touch, it is hopeless. So you want some stickly waterproof (potassium/sodium hydroxide proof) grease that would coat the metal and repel the potassium/sodium hydroxide. What also falls out of the equation is that the reaction self sustaining. The sodium/postassium hydroxide is used up and will corrode no more. Without a fresh supply of Sodium/potassium hydroxide, no more corrosion can occur. So the coating may work. It may wear off so you have to keep applying it if you see fresh corrosion.

    So much for theory. I have a question on practice.

    Does the high voltage battery corrode on its own? You mean I have to keep an eye on it? I thought it is one of the things I never have to look at.
     
  10. dogfriend

    dogfriend Human - Animal Hybrid

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    My impression is that this is only an issue with the 1st Gen Prius (01-03) and there was a service campaign to clean the terminals on the HV battery on some of those cars. I'm not aware of any problems with the 2nd Gen or the current model.
     
  11. andyprius

    andyprius Senior Member

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    Have you actually seen any corrosion? This has been a very interesting thread as I didn't know the electrolyte was a base of 13.5 and neutralizer should be boric acid. I have not experienced any corrosion problems on my terminals ( HV ) Nor any on the auxilliary battery. Of course I havn't looked at the terminals and would not .....unless there seemed to be a symptom in that area. If I compare cleaning the terminals to lead/acid systems.: the plus and minus connectors are removed, cleaned, and same process with the terminals, ie: 2 ea. Now with the HV interconnections there probably are 50-100/ or more. Not really to be tackled for any frivolous reason. I assume that your project is outside of the Prius HV pack?
     
  12. adric22

    adric22 Ev and Hybrid Enthusiast

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    Well, just an update on this. I decided to do an experiment. I took half of the little nuts that attach the modules to the busbars (there are like 76 of these little things) and they were covered with corrosion, some of them worse than others. I dropped then in a bowl and filled it with vinegar. I could see them start bubbling immediately. After a couple of hours I strained out the vinegar and took each nut and ran it under the faucet. About half of them were very shiny and new looking. THe ones that had the largest amount of crust on them were still bad looking so I put them in a bowl of vinegar overnight. I just strained them out and tried the faucet again and all but 2 of them look nice now.

    However.. one thing I noticed, when comparing with the nuts I haven't processed yet, they are a different color. The original nuts look gold colored, like copper. THe ones I've soaked in vinegar look silver. But they don't look rusted or anything, as they are clean and shiny.. just a different color. Not sure if that will matter, probably not. I'm going to go ahead and do the other half.

    Now, the next thing I think I will do is take the individual modules and treat them in a similar way. I just need to soak the terminals where all the corrosion is, not the whole module of course. So I just need to figure out a way to suspend the modules so that one terminal is submerged in vinegar for a few hours, then turn them around and do the other terminal. I'm also going to soak the busbars too. This will probably take me all weekend, but when I'm done I think everything will look good-as-new again.
     
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I think it would be a bad idea to soak the battery module terminals because the acid might wick up through the seals and dilute the electrolyte. If I were you, I'd be content using a wire brush to gently scrape off the corrosion without damaging the threads.

    Regarding the busbars, as they have very fine sense wires attached to them, I do not think it would be a good idea to expose them to acid. The acid may be soaked up by the wires and eventually break. Again, I recommend that you be content by scraping off the corrosion via a mechanical method.
     
  14. ken1784

    ken1784 SuperMID designer

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    I believe it is better to stop leaking the electrolyte before cleaning the corrosion.

    [email protected]
     
  15. adric22

    adric22 Ev and Hybrid Enthusiast

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    I didn't think about that. So I decided I would just pop out all of the little sense wires from the plastic before soaking. It's a good thing too because I noticed that one of the sense wires is BROKEN! I'll have to resolder that back on, and no I didn't break it. So who knows.. that could have been contributing to some of the failure too.

    I did the bus-bars last night that do not have the sense wires. It helped some, but in the end I popped out all the little rectangular pieces of copper and ran them over a grinder with a wire-brush installed. That cleaned them up really nice. I'll do the same to the other side after it has had a good soak.
     
  16. The Electric Me

    The Electric Me Go Speed Go!

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    I currently own a 1993 Honda, that had a serious battery terminal corrosion problem based on a old battery (now replaced battery) and about 17 of overall years of useage.

    I know it's a sort of a cop out, but NAPA sells a battery terminal cleaner that does work really slick. You just spray it on where you see corrosion it foams up you wait a minute, where there was acid the foam turns pink, then you just use water to spray the foam off, and maybe in a few areas a brush...but remove the pink, and you are removing the corrosion. In my experience it easily leaves terminals corrosion free.

    I followed this with an application of Dielectric Silicone Compound also available at NAPA or any auto parts place to the terminals and areas inwhich I witnessed "pink" or corrosion happening. The compound acts as an oxygen barrier and does an excellent job of keeping corrosion from re-occuring.

    Trust me, my Honda with an aging battery had a more than a "normal" problem and the 10 dollar investment into those two products, and 1 application per year..has kept my battery terminal area corrosion free.

    Even though I have to admit, the biggest problem was I eeked every last bit out of my last battery. This winter I knew it wouldn't make it so I replaced in spring. But I was dealing with a battery that was at least 5 years + Old. Those products used in tandem kept the connections and terminal clean.
     
  17. donee

    donee New Member

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    Hi All,

    I would recommend using a brass bristle brush, rather than steel. The brass bristles should minize the amount of terminal plating removal, to that removed by the corrosion.
     
  18. andyprius

    andyprius Senior Member

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    Hello Pat, What are the sense wires for?
     
  19. adric22

    adric22 Ev and Hybrid Enthusiast

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    The sense wires allow the battery computer to monitor the voltage level on every "block" which is two modules in series.
     
  20. hybriddriveguy

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    This is a very common problem and the car will normally set a code P3030 Battery Voltage Detective Line Snapped

    Another thing to look for is corrosion wicking up the sensor wires towards the battery ecu. The terminals on the ecu side are gold plated and you can tell if the corrosion has traveled that far by shining a bright light into the back side of the orange connector.
    Make sure all terminals are bright and shiney. Once the corrosion gets on the ecu pins, it will have to be replaced.
    hope this helps

     
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