Mouse said:
Which would tend to reinforce my idea that the alternators output can easily become marginal. You only notice it if its winter + the batteries on its way out.
Which would tend to reinforce my idea that the alternators output can easily become marginal. You only notice it if its winter + the batteries on its way out.
Mouse said:Batteries' capacities are measured in amp hours. 12Ah means a battery could in theory supply 12 amps for one hour, or one amp for 12 hours.
That's not the whole story though, there are other important aspects of a battery that determine whether it's suitable for a given application. For example Cold Cranking Amps (CCA) - this is how many amps the battery can supply (for 30 seconds I think) when cold - in other words how good it will be at starting your bike first thing on a winter morning. The CCA for the Hawker battery is 200, not sure about the OE battery.
A 600W alternator can supply 50 amps at 12 volts. Of course the engine needs to be running at a certain speed for the alternator to do this. But, assuming that the battery warning light on the dashboard isn't on, the alternator should be supplying enough juice to charge the battery. Of course if the battery cannot hold this charge that's another matter.
I'm certain that the OE battery on my bike was a 14Ah model, so I guess BMW have used different batteries for different batches of bikes.
I agree with you that BMW should sort this out, but I reckon the Hawker battery is a good stop gap, at least for me anyway. And it may be a bodge but it was one of my better ones I think
Mouse
Thanks for the technical explanations - much appreciated.
Please don't take any offence from my use of the word "bodge", I merely used it as a reference to (a) a rectification not undertaken by BMW and (b) the requirement to shoe horn and make alterations to the battery to enable it to fit.
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