Toa VX-3000DS CE-GB - Manual (Page 28)

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Check procedure 2:
This measurement can be done with a slow voltmeter.
Disconnect the VA unit’s power supply from the DC output from the VX-3000DS and connect a load of 5 - 6 Ω /
600 W to the DC output (when the current of the connected system components is known), then take care that
the total current is approximately 5 A. Do not measure a too long time to avoid reducing the battery’s capacity
too much.
Measure the voltage of each cable path while the load is connected.
measuring Points
Touch the battery contacts and the screw tops of the battery connector of the VX-3000DS with the measuring
tips as shown above.
Do not measure the voltage at the cable clamps, because in this case the contact resistance is excluded from
the measurement.
Measure the voltage on each path (it may contain a fuse).
Add these voltages and divide by 5 (5 A current).
The result is the resistance. When it exceeds 0.004 Ω, then check the contacts, clean them if necessary and
tighten it. Alternative: max. voltage = 20 mV.
Example:
Current I = 5 A, measured voltages: 1 : 120 mV, 2 : 10 mV, 3 : 50 mV
Total voltage: 180 mV = 0.18 V. R = 0.18 V/ 5 A = 0.036 Ω > 0.004 Ω
The total resistance is too high. Since path 1-1 has a much higher resistance than path 3-3, its connection
should be checked.
When the resistance is below 0.004 Ω, then the battery can be defective (too old).
measuring the battery’s internal resistance
There are special but expensive measuring tools for battery impedances. Usually when the battery’s internal
impedance is double than typical, then the battery should be exchanged.
1
2 2
3
3 1
Battery
VX-3000DS
Battery