39
Gossen Metrawatt GmbH
METRACELL BT PRO
10.6
Resistance Measurement
Voltages and internal resistances of the blocks of a battery are measured with the
RESISTANCE
measuring function.
As a special feature of the internal resistance measurement, “electrical resistance R
el
” and “charge transfer resistance R
ct
” are measured
simultaneously. R
DC
(direct current resistance) is arrived at by combining these two resistance values:
•
“Electrical resistance R
el
” represents strictly electrical losses. These losses occur at, for example, plate straps, plate grids and electro-
lytes. The battery delivers rapidly changing currents via this resistance, for example for switched-mode DC/DC converters.
•
“Charge transfer resistance R
ct
” is used to characterize the ability of a block to accumulate and release a charge. This makes it possi-
ble to identify battery blocks which are operating at a loss with regard to float.
Measurement is performed as a 4-wire measurement and Kelvin probes (accessory Z227D) are used in order to compensate for cable
resistance
Attention!
!
Caution: Sparking
During the resistance measurement, test current flows which may result in sparking.
Resistance measurement
– may only be performed for voltages below 24 V
– May only be performed where hydrogen concentrations in the air comply with DIN EN 50272-2
– Must not be performed immediately after the battery system has been charged – wait for at least 30 minutes
– May only be performed in well-ventilated battery rooms
The Kelvin probes (Z227D, accessory) are available.
Polarity is switched on.
Se-
quence
Description of the Measurement
Display
1
Connect the Kelvin probes (Z227D
28) to the sockets (
5) as
follows:
–
Connect the black cable with the double plug such that the plug segment with the red ring
is connected to S– and the purely black plug segment is connected to P–/COM.
–
Connect the red cable with the double plug such that the plug segment with the red ring is
connected to S+ and the purely black plug segment is connected to P+.
2
Press and hold the
FUNCTION
key for about 2 seconds in order to switch the battery tester on.
BTpro
<date>
<version>
<time>
3
Press any key to open the
main menu
.
If you’re already in another menu, press the
FUNCTION
key repeatedly until the
main menu
appears.
->
MEASUREMENT
DATA
4
Press the
OK
key in order to open the
MEASUREMENTS
menu.
The
MEASUREMENTS
menu is displayed.
->
MULTIMETER
FLOAT
5
Select
RESISTANCE
using the
▼ ▲
keys.
CHARGE
->
RESISTANCE
6
Press the
OK
key in order to open the selected menu for the measuring function.
->
START
SELECT.BATT
7
Before starting the measurement, the location, battery and limit value parameters must be set.
These can be:
–
Selected in the battery database via RFID
step 7a.
–
Selected manually in the battery database
step 7b.
–
Entered manually at the battery tester
step 7c.
START
->
SELECT.BATT
7a
A battery database has been created
The battery database has been transferred to the battery tester
You use RFID technology for your system.
The DUTs in the battery database are linked to the corresponding RFID tags
1. Select
SELECT.BATT
with the
▼
key.
2. Press the
OK
key
The battery database is displayed. An acoustic signal indicates that the RFID reader is
ready.
3. Read the RFID tag (
An acoustic signal confirms reading and the DUT is displayed.
4. Press the
OK
key.
The battery is selected. The battery tester returns to the
MEASUREMENTS
menu.
START
->
SELECT.BATT