Battery condition / engine performance relationship?

[Liverpool Brick]

Hi,
Starting my RT is a bit hit and miss if its been standing because the battery is not good. It has been getting worse over the past couple of months and on Sunday it didn't have enough in it to start the bike although I had only charged it the previous morning. After charging again on Sunday it started and I went on the charity run as intended (Ancestors MCC annual toy run to Dundonald Hospital, Belfast).
Now here's the point - the bike seemed to perform better than it had done over the previous few months; smoother acceleration, reaching 100+ smoothly and with less vibration than I'd noticed before. Basically it seemed crisper, more sprightly and smoother. I was wondering if a dying half charged battery had an effect on the engine management that was noticeably improved by running on a fully charged battery?
Any experience of this?
PS BTW I'm picking up a new battery tomorrow
Cheers, Andy

[gogs01]

Hi,
Starting my RT is a bit hit and miss if its been standing because the battery is not good. It has been getting worse over the past couple of months and on Sunday it didn't have enough in it to start the bike although I had only charged it the previous morning. After charging again on Sunday it started and I went on the charity run as intended (Ancestors MCC annual toy run to Dundonald Hospital, Belfast).
Now here's the point - the bike seemed to perform better than it had done over the previous few months; smoother acceleration, reaching 100+ smoothly and with less vibration than I'd noticed before. Basically it seemed crisper, more sprightly and smoother. I was wondering if a dying half charged battery had an effect on the engine management that was noticeably improved by running on a fully charged battery?
Any experience of this?  PS BTW I'm picking up a new battery tomorrow
Cheers, Andy

I can't see why a fully charged battery would allow the engine to perform better since the generator should supply enough current and voltage once the engine's running.
Assuming your battery was 5 years old it's probably wise to replace it anyway, but I'm wondering if your problem might be a high resistance somewhere - battery terminals ?  frame earth ?  Might be worth investing an hour in tracking down relevant connections then cleaning and tightening them as you fit the new battery.

[David.]

I'm picking up a new battery tomorrow.

Are you replacing the battery with an OEM BMW one or an alternative.

[David.]

I was wondering if a dying half charged battery had an effect on the engine management that was noticeably improved by running on a fully charged battery?

Found this article on programmable ECUs and Engine Calibration, http://www.sae.org/students/presentatio ... rummen.pdf,
pages 14 & 15 are about Battery Voltage Compensation (BVC).

My interpretation of the information is that if the BMW ECU doesn't have BVC, then yes, the battery voltage could effect the performance of the engine.

[Liverpool Brick]

Hi Folks,
Due to unforeseen circumstances I haven't yet bought the battery but it will be an after market one. Thanks Dayglo for the link , I shall study it and let you know what I find but it may be a while.
Cheers each,
Andy