My failed attempt to reference
Monty Python. I think fully-charged battery reads higher than that. The one on my bike reads 13.8v and the car-battery on the ground reads 14.3v and the one in my car says 13.5v. Same readings on 2 different meters. I'm pretty sure others can post their readings. The meters are not off.
http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
"A voltage of 2.10V [per cell] at room temperature reveals a charge of about 90 percent."
That's 12.6v at 90% charged or 14v at 100%.
http://www.totalmotorcycle.com/maintenance/battery.htm
"12-volt batteries supply useful energy only through a limited range -- from over 14 volts (when fully charged and unrested) down to 10.5 volts in use/under load (when lights dim, your motorcycle is hard to start). No 12-volt battery will remain at over 14 volts for more than seconds unless it's being charged. The lowest limit is 10.5 volts (used in testing) and obviously unsatisfactory in practical use."
A couple of
days after fully-charged, the "resting-voltage" will be 12.6v. I'm sure if we disconnect nebulous's 13.4v battery for a couple of days, it will read 12.6v.
The first quote relates to a battery that's just been charged and not rested.
The second get into more particulars but says much the same thing.
Bottom line is that to get any kind of meaningful readings on lead acid batteries, they must be "rested" and have spent time off of a load and off of any charging.
From Wikipedia:
Voltages for common usagesThese are general voltage ranges for six-cell lead-acid batteries:
Open-circuit (quiescent) at full charge: 12.6 V to 12.8 V (2.10-2.13V per cell)
Open-circuit at full discharge: 11.8 V to 12.0 V
Loaded at full discharge: 10.5 V.
Continuous-preservation (float) charging: 13.4 V for gelled electrolyte; 13.5 V for AGM (absorbed glass mat) and 13.8 V for flooded cells
1.All voltages are at 20 °C (68 °F), and must be adjusted -0.022V/°C for temperature changes.
2.Float voltage recommendations vary, according to the manufacturer's recommendation.
3.Precise float voltage (±0.05 V) is critical to longevity; insufficient voltage (causes sulfation) which is almost as detrimental as excessive voltage (causing corrosion and electrolyte loss)
Typical (daily) charging: 14.2 V to 14.5 V (depending on manufacturer's recommendation)
Equalization charging (for flooded lead acids): 15 V for no more than 2 hours. Battery temperature must be monitored.
Gassing threshold: 14.4 V
After full charge, terminal voltage drops quickly to 13.2 V and then slowly to 12.6 V.
Note the last bit. And then note the first bit about individual cell charges vs total battery voltage. It's not simple math.
If you've been charging your batteries and then disconnecting them and waiting overnight before taking voltage readings and still getting 13.4 volts, then there's something wrong with either the battery, the charger, or the meter. Or some combination. There's no getting around that.
