Battery charging

Those 'magic eye' things on batteries are a bit hit and miss IMHO. I'd sooner rely on some form of metering.

Ok, thanks for all your help so far, much appreciated. What voltage should a fully charged battery read? We have had it on charge now for 24 hrs & it's reading 13.2v. Completley confused now...... 

Slightly difficult on two counts to be specific on this;

A battery just off charge holds what is called a "surface charge" making the voltage higher than the level it will settle to in time or if put on load. The 13.2 Volts is exhibiting a level of surface charge.

A full battery will settle in time, after the surface charge has dissipated to a value that reflects the trace alloying used within the lead the plates are made of. Typically this full charge will be between 12.7 and 12.9 volts, leaning in my experience more to the higher value with modern alloying.

 See what yours settles to and use that as your datum; the CTEK will have fully charged it.

Without a load placed on the battery the surface charge can take quite a few hours to naturally decay.

Flipping heck OCSID where as I appreciate your knowledge and obvious professionalism,you have just given me an headache and I am not much wiser now!.

liz1955. When you have finished recharging the battery leave it for a few hours. Then if possible test it's condition using a multimeter. Turn the dial to 20 volts DC and a full battery should read about 12.7 volts, half full about 12.4 and 12.2 is about down to a quater. The battery should hold the charge and not drop quickly. Hope this helps.

Flipping heck OCSID where as I appreciate your knowledge and obvious professionalism,you have just given me an headache and I am not much wiser now!.

Well, sorry about that but there is no unqualified answer to liz's question.

Put simply the battery's voltage when fully charged depends on its "brand" and you can't measure it for several hours after it comes off charge. For value see makers data sheets. 

Hint; it will be between 12.7 and 12.9 volts.

Ah well, battery performance is a complex subject but as ocsid says, you need to leave for a few hours after charging to get a true figure or you can apply a good load for a short period to clear the surface charge.

Our golf pro asked me if there was a device for measuring battery condition (for golf trolley batteries) and I did quite a bit of research. In practical terms the only way to measure the performance of a battery is to apply a steady load and measure the time it takes to go flat. Not very scientific but some golf clubs actually do this. Some garages will do a discharge test over a few seconds but I have never been convinced about the readings.

In terms of caravan or motorhome leisure batteries all you can do is check that after charging you get around 12.7/12.8 volts and that the battery will retain this voltage for a few weeks whilst standing idle. You then need to test it when using the van off of EHU and see what happens compared with what you might have experienced when the battery was new.

Ok, thanks for all your help so far, much appreciated. What voltage should a fully charged battery read? We have had it on charge now for 24 hrs & it's reading 13.2v. We've borrowed for now a C tek charger (mxs 3600) & it's showing fully charged with this unit, also checked it with a Ring multi stage auto charger & showing fully charged with this too. There is a battery condition window on top of the battery that should be Green if charged, this is Black which means it wants charging. Completley confused now......

You seem to have done better than I had expected, Liz. The best way to see if you’ve got any charge into your battery is to use it and you’ll soon find out. Try a slow discharge (one light for a day or two) and then recharge when it has dropped to 12.2V (no lower). The newer C-Tek chargers include a desulphation phase which may ‘clean’ the plates and improve the charge the battery will take. A few cycles, exercising it like that, may bring your battery back to life but I doubt you’ll get very far with it if you use a motor mover (you’ll need a new one). If it’s a sealed battery, it may be no good because you may have lost electrolyte that you cannot replace.

Ok, so after showing a full charge on 3 different battery chargers we left it to stand for 4 hrs. Result is 13.46v is this acceptable or not? We have planned to go away this weekend so if its not ok we'll need to get another battery ordered today for tomorrows delivery. Your thoughts once more please.

Ok, so after showing a full charge on 3 different battery chargers we left it to stand for 4 hrs. Result is 13.46v is this acceptable or not? We have planned to go away this weekend so if its not ok we'll need to get another battery ordered today for tomorrows delivery. Your thoughts once more please.

It is fully charged (expect the voltage to drop to 12.7 volts as soon as you apply load). Unfortunately you will not know if it s holding charge until you use it. If you are going to be on EHU then no problem, if stand-alone then you will discover fairly quickly whether it will hold its charge.