Absolutely Necessary Entries; Important Tips On Testing Batteries; Additional Comments - Bosch BAT 121 Betriebsanleitung

What you should be aware of and observe when testing a starter battery | BAT 121 | 15
4.2

Absolutely necessary entries

Cold start current and test standard
The battery tester requires the cold start current in
amps and the test standard (IEC, DIN, SAE, EN, JIS) as
a reference value for the purpose of assessing a bat-
tery. A meaningful battery test is contingent upon the
correct entry of this reference value.
Battery temperature
The start performance of a battery is greatly dependent
on temperature. In order to arrive at a reliable test
statement it is absolutely essential to enter the tempe-
rature range of the battery (< 0 ºC or > 0 ºC) next to
cold start current and a test standard. Of significance
when selecting the temperature range is the battery
temperature, not the ambient temperature.
4.3

Important tips on testing batteries

On vehicles fitted with the latest technology, equipment
may still be electrically actuated for up to 15 minutes
after switching off the engine. The battery voltage
fluctuations this causes may make it impossible to
perform battery testing during this period. The battery
test should therefore not be started until the electrical
equipment has stopped being actuated.
New, ready-for-installation, charged starter batteries,
which have been in storage for a lengthy period, will
generally achieve their full starting power after a few
weeks use in driving operation.
Dry, charged batteries reach their full capacity only
several hours after being filled with battery acid.
!
Testing a dry, charged battery after filling can lead to
an incorrect assessment of the battery.
Any charging operation or current consumption activa-
tes electrochemical reactions in a battery which persist
after charging/consumption.
The battery test delivers the best results if no charging
or current consumption has taken place on the battery
for at least one hour prior to the test.
i
Charging the battery leads to a temporarily excessi-
vely high voltage and the Battery-Test would assess
the battery with a result that is too critical.
i
If the Battery-Test were be reversed, the battery
would be assessed as being good during a load or
shortly after discharging a high current.
Robert Bosch GmbH
Battery testers provide a snapshot of the battery's
condition. Each charging or discharging procedure
influence the battery condition. If a battery condition
is located within the good/unserviceable border, then
two successive tests on the same battery which in the
meantime has been charged or discharged, may see the
test fluctuate between a good and unserviceable result.
If the steady-state voltage lies below 12 Volt over a
lengthy period of time then one can assume that the
battery has suffered previous damage. A steady-state
voltage below 12.4 Voltpoints to a permanent battery
charging fault. The possible causes of such a lasting
charging fault are, e.g. a faulty generator or current
regulator, transition resistance through loose or dirty
battery terminal cable, loose V-belt or the vehicle fre-
quently driving short distances.
i
If the test result indicates "Replace battery" for
batteries, which are not older than 3 years, then we
recommend always testing the cold-start current,
charge circuit as well as the charge balance (e.g.
deficient battery charge through short-distance
driving).
As long as the sulfate layer of a battery has not set,
reduction of the sulfate layer causes the battery condi-
tion to change during charging. That is to say, a battery
assessed as "Battery unserviceable" prior to charging
may be assessed as "Good" after charging.
4.4

Additional comments

Hairline cracks in the connectors of the lead plates:
Very fine cracks in the connectors of the lead plates
(hairline cracks) may under certain circumstances be
detected only when the battery is under high current
load (such as a battery test under load). In a battery
test under no load (such as with BAT 121) such hairline
cracks are not detected in borderline cases. The occur-
rence of such cracks is extremely rare in modern-day
batteries.
Acid coating in the battery:
On lead-acid batteries with liquid electrolyte an acid
layer may under certain circumstances occur. The me-
chanical construction of a lead-acid battery means that
acid lifters can only indicate the acid density of the
upper electrolyte layer. This means that determining the
charge condition of a battery with the acid lifter entails
a high degree of inaccuracy.
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1 689 979 792 2010-02-24