# Maintenance-Free (MF) Car Batteries...

**URL:** <https://boards.straightdope.com/t/maintenance-free-mf-car-batteries/232545>\
**Category:** Factual Questions\
**Created:** [March 4, 2004, 5:29pm UTC](https://boards.straightdope.com/t/maintenance-free-mf-car-batteries/232545 "2004-03-04T17:29:40Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\
**Post date:** [March 4, 2004, 5:29pm UTC](https://boards.straightdope.com/t/maintenance-free-mf-car-batteries/232545/1 "2004-03-04T17:29:40Z")

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Should MF batteries come packed with electrolyte and be totaly sealed? My customers always whine that my batteries are not real MF because I have to open them and add the electrolyte (18% H2SO4 solution I believe…).

I know that MF batteries that come with the car are sealed, should this be the case with after-market batteries too? Are my batteries not really MF?

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**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\
**Post date:** [March 4, 2004, 5:48pm UTC](https://boards.straightdope.com/t/maintenance-free-mf-car-batteries/232545/2 "2004-03-04T17:48:45Z")

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BTW, the batteries I sell are made by Rocket ([http://www.gybc.co.kr/english/brand.asp](http://www.gybc.co.kr/english/brand.asp)). I can’t however find the same product numbers in their website. My battery codes have two letters, 5 numbers and then the letters MF for maintenance free, or nothing for plain batteries.

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**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\
**Post date:** [March 4, 2004, 7:11pm UTC](https://boards.straightdope.com/t/maintenance-free-mf-car-batteries/232545/3 "2004-03-04T19:11:28Z")

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I don’t know the official definitions, but I always equated maintenance-free with sealed, obviously having to come with electrolyte installed. My understanding is that modern batteries that are maintainable are low-maintenance or reduced-maintenance (compared to what was available decades ago). It has been decades since I’ve run across a dry-charged battery – I’m not even sure they’re available here in the States.

Nevertheless, I would say it’s theoretically possible to have a maintenance-free battery with removable caps. In such a case the caps would have to be of the maintenance-free design, specially engineered to virtually eliminate fluid loss over the battery’s lifetime. If the caps are the same as on batteries that are not maintenance-free, I would say the battery company is misusing the term.