Battery posts too small?

Lucky1 · 06-20-2022, 06:30 AM

Needed a new battery as the car would not start after a short drive. Removed the battery cover and found the terminals completely crusty and corroded.

Anyway removed old OEM battery. BMW recommended new battery part number 61 21 5 A40 E19 (I know, I am overpaying at the stealership). When I put both positive and negative terminals over this new battery posts even after tightening the nuts they can be pried off by hand. Put the old battery back in and its definitely tight on these terminals. What gives? Is the new battery's posts smaller in circumference?

Old battery and terminals for reference. Wondering if I should also bite the bullet and have them replaced; both negative and positive terminal cable rings are pretty corroded.

grannyknot · 06-20-2022, 04:23 PM

The terminals can be dunked and soak in a small container of vinegar for about a half an hour, that will clean them up so you can see if they are worth keeping or replacing.
As far as I know, positive terminal clamps are the same size as all positive posts, same for negative clamps and posts.
If BMW sold you the new battery that doesn't fit your clamps, take it back.
Napa, Carquest sell the same size battery.

cbpip · 06-21-2022, 04:14 PM

Just take a thin flat file and file down in-between the splits on the connector until you can get a good bite on the post. Clean them vinegar first as previously mentioned.

Lucky1 · 06-24-2022, 09:10 PM

Thanks guys. Did both and I think I have control of the situation. Need to file the positive terminal some more for a good firm hold but so far so good. Some battery acid leaked past the metal platform the battery rests on top so I'll probably have to remove it all to clean it up.

06-20-2022, 06:30 AM	#1
Lucky1 Colonel 647 Rep 2,051 Posts Drives: '08 128i Coupe SGM 6MT Join Date: Nov 2008 Location: Toronto iTrader: (0) Garage List 2015 Porsche 911 Ca ... [0.00] 2008 128i Coupe [0.00] 2006 Z4 M Roadster [0.00]	Battery posts too small? Needed a new battery as the car would not start after a short drive. Removed the battery cover and found the terminals completely crusty and corroded. Anyway removed old OEM battery. BMW recommended new battery part number 61 21 5 A40 E19 (I know, I am overpaying at the stealership). When I put both positive and negative terminals over this new battery posts even after tightening the nuts they can be pried off by hand. Put the old battery back in and its definitely tight on these terminals. What gives? Is the new battery's posts smaller in circumference? Old battery and terminals for reference. Wondering if I should also bite the bullet and have them replaced; both negative and positive terminal cable rings are pretty corroded. Attached Images
	Appreciate 0 Tweet Quote

06-20-2022, 04:23 PM	#2
grannyknot Captain 951 Rep 780 Posts Drives: 2008 Z4M coupe Join Date: Oct 2021 Location: toronto iTrader: (0)	The terminals can be dunked and soak in a small container of vinegar for about a half an hour, that will clean them up so you can see if they are worth keeping or replacing. As far as I know, positive terminal clamps are the same size as all positive posts, same for negative clamps and posts. If BMW sold you the new battery that doesn't fit your clamps, take it back. Napa, Carquest sell the same size battery. __________________ 2008 E86 M coupe
	Appreciate 0 Quote

06-21-2022, 04:14 PM	#3
cbpip Private First Class 151 Rep 198 Posts Drives: BMW Z4C 3.0si 3 pedal Join Date: Nov 2020 Location: MD iTrader: (0) Garage List 2007 BMW E86C [0.00]	Just take a thin flat file and file down in-between the splits on the connector until you can get a good bite on the post. Clean them vinegar first as previously mentioned.
	Appreciate 1 grannyknot950.50 Quote

06-24-2022, 09:10 PM	#4
Lucky1 Colonel 647 Rep 2,051 Posts Drives: '08 128i Coupe SGM 6MT Join Date: Nov 2008 Location: Toronto iTrader: (0) Garage List 2015 Porsche 911 Ca ... [0.00] 2008 128i Coupe [0.00] 2006 Z4 M Roadster [0.00]	Thanks guys. Did both and I think I have control of the situation. Need to file the positive terminal some more for a good firm hold but so far so good. Some battery acid leaked past the metal platform the battery rests on top so I'll probably have to remove it all to clean it up.
	Appreciate 0 Quote