Leisure battery danger level

Check this out: https://www.thebatteryshop.co.uk/car-battery-voltage-guide-34-w.asp

Don’t be alarmed if your voltmeter reads 14+ volts, just means the battery is on charge. 

I was under the impression the battery voltage should not drop below 12.0 volts but really a battery is potentially flat around 12.3.

At these levels the battery will easily recharge,continuous  discharge could cause sulphation  to the plates at around the voltage given in your manual.

I would only use the USB battery meter as an rough indication,for more accurate readings you should have a digital multimeter which will have an extra decimal point.

There is a  difference in battery measurement between 12.60 (which could be 12.59 rounded up )and 12.69 

Battery at 10v doesn’t always mean the end. Weinsberg forgot to include a relay in the 12v supply to my fridge, so I had a couple of deep discharges before the penny dropped. Didn’t have enough volts to operate the central locking. Luckily the combination of a relatively new battery and quick recharge saved it. Three+ years in and the battery is still holding full charge.

OP.  If you go into 'My Profile' you can give yourself a nice screenname! 

Re your battery question; it really is quite simple: anything over 12.7v battery is fine; below that the battery is at various states of needing charging and at 12v it is pretty flat.  At 10v I doubt if it would even allow a light to be turned on (ie really flat!).  A battery should be kept pretty well at full charge all the time.  In winter I remove mine and store it in my garage checking the reading every couple of weeks using a multi meter and putting on charge if necessary.  So in summery any reading below 12.6v and I would put my battery on charge.

I believe the Sargent unit is a so called “smart” charger which means that on EHU the battery will be taken off-line and charged at up to 14.4 volts assuming you have a sealed battery. A standard charger floats at 13.8 volts - not enough to fully charge a discharged battery but not too much to damage it or the “12 volt” system.

Frankly, 10 volts and it’s as dead as a dodo and unlikely to recover. I would consider 12.3 volts to be the lowest to avoid the risk of reduced battery life.

A point about  Digital Meters if I may  ! 

Like all bits of 'kit' meters should be used with care & handled similarly.

To be absolutely sure of their accuracy they should be checked & calibrated annually BUT  they will give good service over many years without such expensive work only if they are treated with that care !!

Older style analogue meters need even more care & gentle handling.

I have an analogue multimeter which never leaves my premises, but is treated with kid gloves and is used purely to check on the digital meters at regular times.

If digital meters are mis-used they can be inaccurate to four places of decimals !!

Thanks to all for the helpful replies - we clearly have much still to learn!

Mike - that's better than a screenname!  Don't worry we all started sometime and you will get on top of this caravanning thing quickly.  If you have not yet been away in your caravan it is useful to go local site for a few days using everything in the caravan.  If you forget something you would not be too far from home.  Check lists for hitching up etc are in the Club handbook.  There are always many willing hands on site, and on this forum, to get help from and most, if not all, are only to willing to help..  Most important is not to forget bottle opener and sense of humour!

My take on this:

Our lead acid batteries age more if not kept fully charged, even more the deeper from fully charged they are and the longer they stay partly discharged.

So a rule of thumb is try and avoid them not being discharged or left there long, both the depth and duration getting progressively more damaging.

BIt of an issue, as using them so discharging them comes along with why we need them, but understanding the issue helps gets the best life from them.

Now differing technologies of build, the structure and materials [lead alloying], significantly alter how individual battery types cope with these damaging discharge issues, all battery types are far from equal.

Therefore, no one is going to be able to put a marker down about a certain level of voltage causing damage, its impact varies so much with type, but the ground rules always apply, the greater the depth of discharge and the longer there, harms all. 

We have an AGM battery in our caravan and it has recovered from being down to 5v when i forgot to turn off the 12v mast switch.  Not sure if AGM had better recovery rate than a lead acid battery?