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e46 M3 jump starting
07-07-2017, 01:52 PM
Post: #1
e46 M3 jump starting
So after 2 months of not driving my M3, the battery is totally dead (no real shock there, pun intended!) I tried to jump start with a e46 320i and the car just ticked over, but never really swung. I could just hear a ticking each time a tried to turn the key. I did rev the 320 a bit, but still nothing.
Previously when the M3 was flat I managed to jump start with my e92 335i? Is there just not enough power from a 320 to jump an M3? Is it worth trying with the 335i again?
I'm only going to driving the m3 for a week or so before going away for another 3 months, so don't want to buy a new battery. But I really really really want to enjoy the m3 again before going away.
Thanks for any pointers (o and the car is in a storage unit, so push starting isn't an option)
Ty

Current - E92 2008 M3
Current - E46 2002 M3
Ex - E92 2008 335i N54 FBO
Ex - E46 2004 325ci
Ex - E36 1996 318is
Ex - Ford Escort
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07-07-2017, 02:36 PM
Post: #2
RE: e46 M3 jump starting
I would actually consider replacing te vattery if it was completely dead. It's probably old and due. It should run flat in 2 months.

Jump starting a car depends on both the jumper leads you are using, and the donor car. With Thin jumper leads it can take a while
For the battery of the flat car to charge, and yes the chances are the 320i has a smaller battery.

2004 BMW 330i M-Sport 6MT
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07-07-2017, 02:49 PM
Post: #3
RE: e46 M3 jump starting
Use thicker jumper cables. Borrow for now if you must.

My 328i wouldn't jumpstart my moms Getz using a cheap cable. The plastic looks thick but if you pull it away a bit you can see how thin the wire actually is.

Brother came with better cables and it started immediately under the exact same conditions.

Current -1996 E36 328i Individual

Ex - 1998 E36 318iS

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07-07-2017, 02:49 PM
Post: #4
RE: e46 M3 jump starting
Had the same problem few years back. This usually happens when the cells are totally dead. You will unfortunately need a new battery.

2011 320d E90 - Current
2000 328i E46 - Ex

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07-07-2017, 04:34 PM
Post: #5
RE: e46 M3 jump starting
+1 On thick proper jumper cables. If you have two sets you can connect them in parallel to provide additional amp capacity.

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10-07-2017, 01:44 AM (This post was last modified: 10-07-2017 01:45 AM by Blueskys.)
Post: #6
RE: e46 M3 jump starting
Get decent cables + connect the donor car and then let the donor car run for 5mins while it's connected which will give the battery in the M3 time to get some charge, then try turning it over.

Or if it's garaged just buy a decent charger and charge it up. Midas has a reputable smart charger for just over R1k last I checked. Probably worth leaving the battery trickle charging if you won't be using it for months on end.
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10-07-2017, 06:49 AM
Post: #7
RE: e46 M3 jump starting
Car batteries are not designed for deep cycling as it drastically reduces the life of the battery. With a completely flat car battery it's almost impossible to revive to working order again. You will need to replace it with a new 668.
I fitted a battery kill switch on the negative terminal on my e36 so I just simply shut her off when not in use to save battery life.
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10-07-2017, 09:25 AM
Post: #8
RE: e46 M3 jump starting
Thumbdown its all about the Amps.
If you had any chance at all of reviving that Batt you would have had to keep it on charge for a long time.
I also believe the Batt is past due for replacement.

2011 120d Coupe (Black - Yin)
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10-07-2017, 06:32 PM
Post: #9
RE: e46 M3 jump starting
(10-07-2017 06:49 AM)Gizmo@GARAGE46 Wrote:  Car batteries are not designed for deep cycling as it drastically reduces the life of the battery. With a completely flat car battery it's almost impossible to revive to working order again. You will need to replace it with a new 668.
I fitted a battery kill switch on the negative terminal on my e36 so I just simply shut her off when not in use to save battery life.
How big is the switch to be able to handle the enormous current draw?
I have seen on boats the special isolation switches they have on the battery banks but those pretty substantial, not easy to squirrel away inside the engine bay or battery location.
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13-07-2017, 07:30 PM
Post: #10
RE: e46 M3 jump starting
Its not very big, they are used on race cars as a battery kill switch.

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