Is my car ok if I accidentally touched the positive terminal

coolguy1o1 · 02-24-2018, 11:23 PM

I was installing my jb4 and made sure to disconnect the negative terminal from the back. I installed the red wire fine but when I was going to loosen the nut for the black and I guessed I touched the positive terminal and the nut which is ground. This caused the wrench to spark. How was this possible if I disconnected the negative terminal. The car starts fine but was definitely pretty scary.

bmwchue · 02-24-2018, 11:50 PM

Ground doesnt have to be the negative terminal. The whole chasis is grounded.

Soul_Glo · 02-25-2018, 12:06 AM

^ what he said.

Gen13 F36 · 02-25-2018, 12:10 AM

The car is fine. Battery terminal touches spark happens all the time.😁

Billfitz · 02-25-2018, 09:36 AM

The entire chassis is ground, but if the battery negative terminal isn't connected to that ground then current can't flow between the battery positive and the chassis. That's the point of disconnecting the negative terminal. If he got a spark then it wasn't as disconnected as he thought. It's always a good idea to double check with a meter if there's voltage appearing between the charging posts under the hood.

02-24-2018, 11:23 PM	#1
coolguy1o1 Private First Class 23 Rep 110 Posts Drives: BMW Activehybrid 3 Join Date: Feb 2018 Location: Mississippi iTrader: (0)	Is my car ok if I accidentally touched the positive terminal I was installing my jb4 and made sure to disconnect the negative terminal from the back. I installed the red wire fine but when I was going to loosen the nut for the black and I guessed I touched the positive terminal and the nut which is ground. This caused the wrench to spark. How was this possible if I disconnected the negative terminal. The car starts fine but was definitely pretty scary.
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02-24-2018, 11:50 PM	#2
bmwchue Captain 242 Rep 804 Posts Drives: 2013 bmw 328i Join Date: Oct 2017 Location: California iTrader: (0)	Ground doesnt have to be the negative terminal. The whole chasis is grounded.
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02-25-2018, 12:06 AM	#3
Soul_Glo Major General 13352 Rep 7,484 Posts Drives: G20 Join Date: May 2013 Location: Manhattan, NYC iTrader: (1)	^ what he said.
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02-25-2018, 12:10 AM	#4
Gen13 F36 Brigadier General 1599 Rep 3,748 Posts Drives: 428i Gran Coupe Join Date: Nov 2017 Location: Los Angeles, CA iTrader: (1)	The car is fine. Battery terminal touches spark happens all the time.😁 Last edited by Gen13 F36; 02-25-2018 at 01:33 AM..
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02-25-2018, 09:36 AM	#5
Billfitz Lieutenant General 8259 Rep 16,106 Posts Drives: '15 328iX GT Join Date: Jan 2015 Location: New Hampshire iTrader: (0)	The entire chassis is ground, but if the battery negative terminal isn't connected to that ground then current can't flow between the battery positive and the chassis. That's the point of disconnecting the negative terminal. If he got a spark then it wasn't as disconnected as he thought. It's always a good idea to double check with a meter if there's voltage appearing between the charging posts under the hood.
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