[VAC] Battery charging and discharging rates

[Tom Howarth <howarth@xxxxxxxxxxxxx>]

Once a battery has been discharged 50% or more, permanent damage is
induced into the battery.  This induced damage will drastically shorten
the life span of the battery regardless of the type of battery.


Charge Rates:

Trace Engineering (http://www.traceengineering.com), manufacturer of
high quality inverters and inverter/multistage chargers, recommends that
for vented batteries the bulk charge is 14.7 Vdc with a float of 13.3
Vdc.  

They also state that the charger rate for gel-cell batteries and AGMs
(absorbed glass mat batteries such as Optima and Lifeline, see
http://www.dcbattery.com  for more discussion on these types of
batteries) the bulk charge rate is 14.3 Vdc and a float of 13.6 Vdc. 
These are the two options that can be chosen on their
inverter/multistage charger.

However, Concorde (the manufacturer of Lifeline AGMs, THE premium
battery on the market IMO) insists that correct charging for their AGMs
is: @77°F, 14.38V (bulk) and 13.38V (float), so there is a bit of
difference there.  Regardless of the differences for the float, the
charging of AGMs at 14.7 Vdc is clearly too high and will induce damage
in a much shorter time frame.


Discharge Rates:


For liquid lead acid (vented) batteries,

Open Circuit Voltage = 12.65 VDC, charge = 100%
Open Circuit Voltage = 12.35 VDC, charge = 75% 
Open Circuit Voltage = 12.10 VDC, charge = 50%
Open Circuit Voltage = 11.80 VDC, charge = 25%
Open Circuit Voltage < 11.50 VDC, charge = discharged


For gel cell and AGM (absorbed glass mat) sealed batteries,

Open Circuit Voltage = 12.85 VDC, charge = 100%
Open Circuit Voltage = 12.65 VDC, charge = 75% 
Open Circuit Voltage = 12.40 VDC, charge = 50%
Open Circuit Voltage = 12.20 VDC, charge = 25%
Open Circuit Voltage < 12.00 VDC, charge = discharged



Tom Howarth

'53 Flying Cloud with Trace inverter/charger (Trace 812/SB from '97 to
'00 and recently updated with Trace Legend I 1512/SB) and two Lifeline
4D batteries since 1997

WDCU/VAC/SKP/TCT
C2C'09