Auxiliary Battery in Classic Prius - JIS type number S34B20L

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Specifications

Manufacturer:   Japan Storage Battery Co. Ltd.
Technology: Valve Regulated Lead Acid, with vent tube.
Nominal Voltage: 12 Volts
Nominal Capacity: 28 Ah at 5 hour rate.
Length: 197 mm
Width: 129 mm
Height: 203 mm
Height, including terminals:   227 mm
Bench Charge: Not more than 3.5 amps for not more than 10 hours.

S34B20L 12V Battery  -  Measured Discharge

Graph of measured discharge performance

Measured capacity to 10.2 volt end point was 26.3 Ah

The battery was charged as follows:

1) Constant current 660 mA until voltage reached 14.5 volts.
2) Constant voltage 13.2 volts until current fell to 50 mA.
3) Constant voltage 13.2 volts for a further 5 hours.

The battery was allowed to settle for 12 hours before being connected to the 2.5 ohm test load
as shown in the diagram.   Measurements were carried out at 15 degrees C ambient temperature.

See Post 2282 for the background to these measurements.

S34B20L 12V Battery recharged by DC/DC converter in Prius

Graph of charge absorbtion as a function of time

The battery was almost completely discharged when charging commenced (open circuit voltage was 10.54 Volts).

The Prius was brought to READY on the residual charge, then left in PARK throughout the five hour duration of
the measurements.  Ambient temperature was 8 degrees C at the start, rose to 12 degrees C after two hours,
then fell to 4 degrees C at the end of the measurements.

See Post 2338 for more information about these measurements.