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Thread: Z3M Roadster battery. Are we suppossed to be checking water levels?

  1. #1
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    Z3M Roadster battery. Are we suppossed to be checking water levels?

    Z3M Roadster battery. I have only had my car around 8 months so I'm not familiar with everything yet. Are we supposed to be checking water levels? Do you?

  2. #2
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    Depends upon the battery. If I can, I do. If I can't, I don't. Does that help?
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    Blue Ridge Mountains
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  3. #3
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    Generally with modern batteries you don't really need to check the water levels on them. I occasionally desulfate batteries if I've had them for awhile, as that will prolong their life, but I've never needed to add water to a battery in any of my BMWs.

  4. #4
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    Thanks guys. I will have to go look at the battery in the car. I think it is a BMW OEM battery. I did not know if they were maintenance free. I guess if it has round dials to open and water in them I will have my answer.

  5. #5
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    Maint free <> don't check water levels.

    Although it is unlikely that a maint free battery will need (distilled) water, there are events that might cause water levels to drop -- overcharging, alternator problems, voltage regulator failure, etc.

    On all wet cell batteries there will be some kind of vent and there will also be a "cap" that you can remove and check water levels. This will not be the case for sealed AGM, gel or spiral cell batteries (like Optima, for example).

    Short story, unless you're having starting or charging problems, I'd probably leave a maint-free battery alone. That said, if a wet-cell battery is reluctant to take a charge or won't stay charged, first thing I'd check is the water level.

    WEAR SAFETY GLASSES IF YOU'RE GOING TO REMOVE THE CAPS. The acid is very dangerous and you do NOT want to get even a tiny drop in your eyes.
    Last edited by emoore924; 12-28-2014 at 06:38 PM.

  6. #6
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    Up until this past weekend i have always taken the position maintenance free was just that. 30 months ago bought 2 new autozone maintenance free batteries for the 850. One died. Upon removal found fluid was down below the plate level on 5 of 6 cells. The other battery was low. I will be checking with each oil change from now on.
    Dan "PbFut" Rose

  7. #7
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    If the battery has inspection caps, you should check the level occasionally. Once a year should be sufficient if there aren't any problems.

    The correct level if typically just touching the bottom of the vent cap rim. That's might seem low, but the goal is to just cover the plates without risking acid coming out the vents when on a steep hill.

    Modern batteries have chemistry (e.g. alloys with calcium) that reduces the 'boil off' (electrolysis) of water during recharge. Some even have recombining catalysts, which help decompose any generated H2 and O2 back into water. But they will still lose a little water over time, even if only from evaporation and 'breathing' from the vent with temperature and pressure changes.

  8. #8
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    I looked at my battery today. It is a BMW battery. It is white. I did not see anyway to check the fluid levels. There were 2 factory stickers on the battery. They may have covered up a place to lift off and look at the levels but I could not be sure. It has a window to check the battery. I did not see any color in there. When I drive my vots say 14 plus. Whe I turn the engine off my volateg meter shows 12 plus so I think I'm good for now.

  9. #9
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    Quote Originally Posted by PbFut View Post
    Up until this past weekend i have always taken the position maintenance free was just that. 30 months ago bought 2 new autozone maintenance free batteries for the 850. One died. Upon removal found fluid was down below the plate level on 5 of 6 cells. The other battery was low. I will be checking with each oil change from now on.
    I had one of these go bad on me a few years ago, but got a pro-rated replacement for about $45. Duralast, with the ever so slightly smaller positive terminal that make it hard to get the + lead tight. I used a lead shim. Never though to check the water level though, so thanks for the tip. I assume you just carefully pry off the large rectangular covers?

    OP, if you have the BMW battery, the 6 caps are located under the sticker on the top. Pull off the sticker until you can see the caps. They are flush with the top and can be screwed out one by one to check levels. And of course like mentioned, be careful to protect your eyes and don't spill any of the acid - I recommend wearing cheap latex or other rubber gloves. Do not put the wetish caps on any paint. Also, don't smoke or make any sparks. Enjoy.
    Steve
    '02 Z3 3.0i

  10. #10
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    Just replaced my 08 date yr. - BMW battery in my 00 z3 roadster,that's seven years on a battery here in Fla. Replaced it with a Autocare dry-cell battery. No venting,no fluid battery,drop--in.... no problems.Lets see how long this one lasts....?

  11. #11
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    Quote Originally Posted by 2002Z3 View Post
    I had one of these go bad on me a few years ago, but got a pro-rated replacement for about $45. Duralast, with the ever so slightly smaller positive terminal that make it hard to get the + lead tight. I used a lead shim. Never though to check the water level though, so thanks for the tip. I assume you just carefully pry off the large rectangular covers?

    OP, if you have the BMW battery, the 6 caps are located under the sticker on the top. Pull off the sticker until you can see the caps. They are flush with the top and can be screwed out one by one to check levels. And of course like mentioned, be careful to protect your eyes and don't spill any of the acid - I recommend wearing cheap latex or other rubber gloves. Do not put the wetish caps on any paint. Also, don't smoke or make any sparks. Enjoy.
    Thanks for the explanation. I guess I will put that on my to do list. I just hate cutting the pretty label lol.

  12. #12
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    I was able to peal mine back enough to get to the caps with very little, if any, damage to it. I've had a lot of practice pulling labels off beer bottles... After testing, I found one cell dead. The "eye" was still green, but all that means is that one cell is good. You can theoretically have 5 bad cells and still have that thing green. Best of luck.
    Steve
    '02 Z3 3.0i

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