Purchased from fleabay...http://www.ebay.co.uk/itm/DS3231-AT24C32-IIC-Module-Precision-Real-Time-Clock-Memory-Module-For-Arduino-/300938576118?
Works and keeps time when connected, when on battery (new one) it loses time badly.
The boards does not appear to have a crystal?.. For refernce?
Any feedback welcome
Cheers
Peter
Look at the DS3231 datasheet. The crystal is integrated.
The blue ink splodge on the case is likely a factory-reject mark. Sometimes stuff from
china/hong kong on eBay is rubbish/knock-off, that's how it is. I know of a firm
that bought an X-ray machine to tell if the expensive chips they use contain a die
or not - saves wasting whole PCBs in production, and the entire shipment can be
rejected without opening.
MarkT:
The blue ink splodge on the case is likely a factory-reject mark. Sometimes stuff from
china/hong kong on eBay is rubbish/knock-off, that's how it is. I know of a firm
that bought an X-ray machine to tell if the expensive chips they use contain a die
or not - saves wasting whole PCBs in production, and the entire shipment can be
rejected without opening.
Some of the fake chips have fake dies in them: https://www.sparkfun.com/news/350 
MarkT:
I know of a firm that bought an X-ray machine to tell if the expensive chips they use contain a die or not - saves wasting whole PCBs in production, and the entire shipment can be rejected without opening.
I'd think that firm's sourcing methods would be open to question.
Yep. If you're using 'expensive' chips then you should be buying from reputable places and have a quality control system to prevent big production runs using bad components.
OK caveat emptor
fungus:
Yep. If you're using 'expensive' chips then you should be buying from reputable places and have a quality control system to prevent big production runs using bad components.
If I were buying "expensive" chips (or any other kind, really), my expectation would be that the manufacturer would have sufficient QC in place that I would not need to do incoming inspection and they should, as a regular matter of course, be able to demonstrate this with appropriate statistical analysis. They should have a formal quality system based on ISO9001 or whatever the current craze is.
Randcook:
Works and keeps time when connected, when on battery (new one) it loses time badly.
I own two of these modules (not purchased on eBay). Both are in operation for several months. Works on both Vcc and the battery power. Accuracy is admirable, much better than in the datasheet (approximately less than a second per month). So I am very satisfied.
Your module must be defective. Do you have performed measurements, whether it is good contact between the battery and the chip / ground?
You know what, I have several of these and other ic's for time keeping and each day they would drift a minute or so...
So I connected a lithium (old samsung battery) and in 3 days it was pretty much accurate!
I blame coin cell batteries!
I have replaced the battery, with a new one, but will investigate...
I can ask again about the issues, I doubt they would have gone to these
lengths without good reason.
I've got a 1307 based clock module (China, cheap) which has been laid around in the kitchen for the last nine months running off the battery. When I've tried it out today it has only gained about three minutes which came as a surprise. It doesn't have a regular watch crystal in a metal case, rather a white ceramic looking item.