What is the max voltage of a 12v battery?

[peter2407]

Last season my battery state indicator was showing the cranking battery at 14 volts. Having taken the battery home and charged it with an "intelligent" charger, my volt meter at home is only showing 13.3 volts. Will trickle charging get this any higher?

 

[VicS]

14 volts is surprisingly high. Are you sure the regulator is OK? Or is an unregulated solar panel involved. Other wise suspect accuracy of the battery state indicator.
Even 13.3 is high unless immediately after charging

After charging let it stand with no load and no further charge for at 12 hours
then read the volts with a digital meter.

If the rested volts is over 12.7 it is effectively fully charged but refer to the graph below.

 

[pampas]

battery indicator reading high? should have shown a considerable drop when cranking.(If connected to starter battery)

 

[simonfraser]

When not using a charge controller I recently had 15V showing whilst wind & solar on, about 1.5A into 75 AH wet lead, for no more than a day at the most, would that be a prob long term ?

 

[charles_reed]

My batteries, when fully charged, i.e. when the Adverc or the MPPT controller have clicked off register 13.1v on a terminated voltmeter and 12.5v on an unterminated one.
The figures are very similar on float voltage with the mains charger - the two figures go up respectively to 14.0-14.4 and 12.8 when equalising charge is on.

 

[Plevier]

You might see 14V if you check immediately after charging but not on a sustained basis.
Voltage (per cell of course) at 20 deg C is (specific gravity of electrolyte + 0.85)V.
Most starter/leisure batteries have a fully charged s.g. of 1.270/1.280 so you would expect about 12.7/12.8V. (You'll notice that matches VicS's curve.)
The highest s.g. I know of is 1.300 (AGM batteries tend to use this) which should give you 12.9V.
There is a temperature effect but not much, maybe 1mV/degree C/cell (lower voltage at lower temperature)

 

[Bosun Higgs]

To charge a battery, the voltage of the charging unit has to be higher than the back voltage of the battery or no current flows. But as the battery gets charged up, its back voltage increases and it will go higher than the 12.7v which is typical of a fully charged lead acid accumulator.

When the battery charger is first disconnected from a fully charged battery, there is for want of a better way of describing it, some surplus leccy left on the plates and the voltage reading is higher than the 12.7. This erodes away over a period of time ( hours) and the battery settles back to its fully charged 12.7.

Typically your conventional charger will build up its charging voltage to as much as 14.5v to get the leccy into the battery reasonably quickly but when the battery is fully charged the charger will drop back to something like 13.4v as a maintenance lever - the level required to compensate for the fact that even a disconnected battery self discharges slowly.

So if your battery is reading 14v then you either still have the charger on or have just disconnected it. Dont worry - its normal.

 

[geoffatstanpit]

When not using a charge controller I recently had 15V showing whilst wind & solar on, about 1.5A into 75 AH wet lead, for no more than a day at the most, would that be a prob long term ?

My solar got my ordinary car battery up to 16 volts from time to time. It was OK for a couple of years but eventually the acid level went down and wrecked it. Check the level now and again and top up with distilled (I use the output from my winter dehumidifier).

 

[simonfraser]

Tnx geoff