E89 Battery Charging

F

Frankie169

Member
 North Somerset
As the car I just bought (20i) has been sitting at the dealers I thought I would give the battery a charge to make sure its up to speed

I use a Ctek CS One , question I have is do I contect to the battery terminals or the posts under the engine? Had a search and couldnt find the answer, Im either blind or couldnt see the woods for the trees!!! so to speak
 
Attach to post with red plastic cover near rear of engine bulkhead right of centre ..do NOT attach to the battery UNLESS its disconnected..do not unnecessarily disconnect as its easy to damage the IBS sensor/ wire!
 
Interesting - we have an E92 with the same IBS stuff.

What reason is there not to connect to the battery end of the under-bonnet terminal? I think the E92 even has a cut out in the positive terminal flap to allow connections to it
 
TriggerFish said:
Interesting - we have an E92 with the same IBS stuff.

What reason is there not to connect to the battery end of the under-bonnet terminal? I think the E92 even has a cut out in the positive terminal flap to allow connections to it
Click to expand...
You mean why not attach the charger direct to battery terminals?

It then bypasses the IBS sensor which talks every few seconds to the DME to tell the DME the amount of current that has passed though the battery either way..the DME then mis calculates the sate of charge SoC and then incorrectly over / under charges the battery for a while.. so then the DME may shut down early or late various systems which in turn cause 'false' errors and also the battery sustains damage which would not have occurred shortening its life.. finally the sensor and its wire are very sensitive to knocks et so cam quietly fail causing yet more mysterious battery related woes..part from that its OK..
 
Got it, thanks. So connecting to this would be fine, as it's downstream of the IBS, I guess (it's directly onto that terminal of the battery)

PXL_20260625_170442885.jpg
 
Oh, then I really don't understand, as the E92 jump post in the engine bay is share a bolt connected to a ground point. All the wires out are brown. I don't see how connecting to that post would be any different than to the battery directly?

Maybe the e89 is different and the negative engine bay terminal has a different arrangement, but I know this E92 has the intelligent charging system fitted (as I coded it a new battery).

PXL_20260625_201107338.jpg
 
Good chance the bonnet terminal is convenience.
Can't get locked out of bonnet opening like boot, battery low.
I bet, but haven't traced it, it goes under the body, seen if you take bottom panel off, to boot through the floor terminal post.
But should never remove positive off battery post to charge or battery out of car to charge, computer gets confused, charge state, etc..
 
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