Strange one today.I left my lights on the otherday without knowing went to go out on my F 650 GS Dakar yesterday and of course flat battery So I charged it all night and it read fully charged.Went for a ride this morning about 45 mins stopped the bike for 5 mins started it again it was a bit sluggish rode 100m got to a junction it stalled started it again went another 300 mters to a car park it stalled again wouldn't start???.I went to find a garage when I got back to the bike with the machanic I thought I just try it and it started and ticked over perfect??.rode it to the garage and put a multi meter on it,Not running it read 12.6 volts running 13.5 to 13.9.went and payed him 50CHF (Bloody rip off for 10 mins work).came back started it again but sluggish thought it wasn't going to go but it did.Rode home 45 mins no problem just cheacked it again 2 hrs later and started ?? any thoughts.

Your battery is on the way out.
From the web link shown below, this is a type of test that is worth doing - any good vehicle electrical place will have the equipment and will tend to do it for free in the UK on the prospect of selling a new battery:-

"Load testing is yet another way of testing a battery. Load test removes amps from a battery much like starting an engine would. A load tester can be purchased at most auto parts stores. Some battery companies label their battery with the amp load for testing. This number is usually half of the CCA rating. For instance, a 500 CCA battery would load test at 250 amps for 15 seconds. A load test can only be performed if the battery is near or at full charge"

https://www.batterystuff.com/kb/arti...-basics.html#6

Nevertheless, the symptoms you describe are of the same nature to a load test (high cold cranking demand on the battery while starting the engine).
It's all common enough at this time of year, cold weather blah blah. The multimeter will show nominally good voltage but the battery is well past its best and cannot provide high current.

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Dave

Thanks for the advice guess I'll be taking the battery back the it was new only just over a month ago.

In that case, it shouldn't be faulty, obviously. It isn't completely unknown for a new battery to be at fault, but it is unlikely.

Therefore, you need to get the supplier to check it over and see how it performs under test.

You haven't said what type of battery it is - see the earlier link for some discussion about some of the types of battery that are in the market.

There are a stack of pretty good threads in here about batteries and the related technology, all posted over many years as the technology has moved along at a pace.
Here's an extract for instance from an earlier thread that tells us something more about battery technology:

"Lead-acid makers have used AHr(capacity) ratings as shorthand to indicate cranking ability, rather than a real usable capacity. The lead-acid capacity rating itself is based on a complete discharge at a low discharge rate. Under actual cranking conditions they will deliver considerably less than spec capacity. And because lead-acid batteries begin sulfating when only a small percentage of the capacity has been used, and their internal resistance rises as they are discharged, the actual capacity which can be USED may be as little as 20% of the mfg. rating. Discharge in excess will not only damage the lead-acid battery, it may not allow proper starting as voltage sags.
Shorai LFX are based on a completely different chemistry. Not only do they have less than 1/3 the internal resistance per capacity than do lead-acid, they are also the ultimate "deep-cycle" battery. The internal "completely discharged" capacity of a Shorai LFX is 1/3 the rated "PBeq" capacity. For example, the LFX18 12V series have 6Ah cells internally. But the cells are capable of 90% discharge without damage and while retaining more cranking ability. As such, the USABLE capacity(or "reserve capacity") of an LFX18 12V battery is on or very near par with 18AHr-rated lead acid batteries, while providing superior cranking performance and a vast reduction in weight. The Shorai PBeq AHr (lead-acid equivalent) rating system therefore allows users to compare a very different technology from lead-acid, but on a close apples-to-apples basis when making a choice.

Shorai's explanation. Colebatch is correct, Shorai sell an equivalent 18 Ah equivalent battery which is 6Ah but will give the same or better real world performance as an 18Ah lead/acid battery FOR STARTING. A motorcycle battery is a STARTER battery and purposed to supply the required volts to start to engine and not to do any other task. Also remember, contrary to popular belief starting uses only a tiny amount of the battery's stored energy and is replenished within minutes. It's all the extras attached to the bikes electrical system combined with the inadequate OEM design of the loom R/R and alternator that stresses the battery."

Extracted from (and it saves a stack of typing) :
http://www.horizonsunlimited.com/hub...e-week-58445-2

It could be, assuming that your new battery is indeed OK, that you have a drain on the battery caused by some sort of issue in the bike itself, or the charging circuit may not be charging?
But, get the battery checked over first, especially with the cold winter we have at present.

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Dave

Thanks Dave some great Info,I should have just got a Lithum Batt in the first place.I am going to go over all the earths tomorrow and maybe have a look at the starter.Once I am sure it's not a problem with the charging/ starting systems I will invest in a new batt

Just took the battery back to the shop they drop tested it and it was reading 4 volts they said that is a problem and asked me if I wanted an exchange I said yes but only if the new one is tested first the tested, It and it was faulty so was the next 3 so I said thanks but no thanks got my money back and went to another shop got a battery 20 chf less than the one before charged it put it on the bike and problem solved..

Nice result!
It is always best to start with a good battery
Cancel what I said earlier about "the probability of faulty new batteries nowadays".

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Dave

Just a little up date,I can say after putting a new Batt that works on it the bike ticks over better revs a lot smoother and is more responsive I would never of thought the battery would influence these things Once the bike was running but it seems too?. So very happy.