Weird Battery/Starter Problem (996 C2 3.4)

Hi, I've got an odd problem with my 1999 C2. I keep it on a trickle charge now, and have just replaced the battery (Bosch) so this isn't the usual issue about the battery running down quickly when not used (although i've been through that too, hence the trickle charger...). On a long drive, if I stop after around 2 hours of motorway speeds, I'll often find the car reluctant to start if I try soon after stopping (like after a fuel stop). It has a weedy attempt to turn over but fails to start. If I try again, even after 30 seconds or so, it (often, not always) manages to start, not eagerly, but turning over enough to fire up. On a longer drive (3 or 4 hours, including a fuel stop like the above) once I park up if I try to restart it again fails to turn over, and doesn't respond to a second or third attempt. BUT, if I just leave it for a few hours (without the charger) it will then start happily (i.e. turning over eagerly). Now I don't think the battery is magically recharging itself, so I suspect that this is something to do with heat in the engine bay, but beyond that I'm baffled. When driving the volts are running at around 13.5 v which I think is normal. Any ideas? Cheers

Most likely its a starter motor fault . If the alternator is working then its chargeing the battery , i cant see a totally dead battery in this situation and a discharge would not be this quick. It could be an earth lead fault to the engine .. o/s/r or a battery earth lead but from experience its normally a starter faulty .

Thanks. I did have the main earth strap cleaned up last time I had some work done on it, so that ought to be OK, but the starter motor or connection to/from it could be the culprit. Is this likely to be something that resolves itself when the engine cools down as happens with mine?

This sounds very similar to my recent problem Car had a recent new Bosch S5 battery, kept on a trickle charger and turned over slowly (and once not all) when warmed up Northway as a part of the next service diagnosed the starter motor as on the way out and changed it along with the live cable - now starts on the button every time now

Its normally when hot that the starters show signs of struggling with these so I reckon that's your issue.

mine has just recently started doing the exact same thing and just yesterday made me look a Kn*b at the petrol station straight after i received a "nice motor mate" comment hasn't actually failed to start but struggles when hot.