Battery advice needed please?

[triumph2.5pi]

Hello
Could someone please advise on the state of my main battery?
The main battery ran down, so I've given it a full 12h slow charge. It's now reading 12.8v with the engine off and 13.6v with the engine running on tickover. A google search seems to suggest the 12.8v is fine, but should be reading 13.7-14.7v with the engine running? Does a reading of 13.6v mean the battery is on its way out? It seems to be turning the engine over fine at the moment.
Any advice much appreciated, thank you

[bigherb]

13.6V is low when the engine is running 13.8V is the minimum and is governed by the alternator output voltage. But it does also depend on how much charging load there is on the alternator. Checking the voltage immediately after starting the engine will give a lower reading as the alternator is replacing the charge taken out of the battery by starting the engine. Give it 10 minutes to stabilize. If the reading is still low without anything else switched on whilst the engine is running then check the alternator belt tension and the electrical connections to the alternator and starter motor if they are OK then it is likely a faulty alternator voltage regulator change it to a 14.2V or 14.5V one.

[triumph2.5pi]

Thanks so much for the info! Yes I had measured the voltage straight after start up so I'll give it a run and then try again. Ta!

[Mocki]

After you have done what is suggested above, take a reading actually at the alternator output , with your meter connected to the alternator case for neg .
Then again at the battery , if there is more than 0.5v difference , you may want to check the earthing of the alternator ( and the gearbox nose earth strap ) and if that hasn't shown any improvement , the main charge cable from the alternator to the battery could well be at fault .
Chances are it's the same age as the vehicle .

You don't say what engine , but if it is a WBX the short cable tween the alternator and the starter is a common fault point, it goes high resistance ( looks ok visually ) and often causes these symptoms and worse .

I just replaced the whole run from alternator to starter to battery on one of ours a couple of weeks ago, and solved the whole low charge voltage problem for £25

[ZsZ]

The charging indicator light goes out? Maybe the blue wire of the light circuit is broken somewhere.

[triumph2.5pi]

Thanks very much all for the info and help. I'll check this out over the weekend