Tips for Paralleling EA-BT 20000 Battery Testers

The family of EA Elektro-Automatik EA-BT 20000 battery testers with regenerative energy recovery offers up to 30 kW of power. The family consists of two types of battery testing equipment – the EA-BT 20000 with a single output and the EA-BT 20000 Triple with three independent outputs. The single-output models range up to 2000 V with 40 A or up to 60 V with 1000 A. The triple output models include a 6 kW/channel model with 10 V with 600 A/channel and a 10 kW/channel model with 920 V with 40 A/channel.

The high power of the EA-BT 20000 battery testers, with their wide range of voltage and current, provides outstanding flexibility to test a wide range of battery packs. With 10 kW/channel and three channels/instrument, the BT 20000 Triple increases production throughput by a factor of three. The 3-channel models save equipment costs compared to individual single-channel instruments and can save a significant amount of floor space.

While the EA-BT 20000 models have high power capacity, applications such as testing a new EV battery, a backup battery system for an electric utility or a server farm battery backup can require even more power. Fortunately, several EA-BT 20000s can be connected in parallel to increase input/output capacity.

Increased capacity combined with safety

Connecting EA-BT 20000 instrumentation in parallel provides substantial power, up to 64 instruments to produce 1.92 MW. EA-BT 20000 Triple testers can parallel the individual channels to deliver as much as 1800 A with one instrument. Two EA-BT 20000 Triples can individually parallel the individual channels, yielding three channels with a maximum current output/channel up to 1200 A.

EA series 10000 and EA-BT 20000 instruments employ two buses for convenient and safe control when paralleling instruments. A Master-Auxiliary Bus enables one instrument to control all the other instruments and display the total delivered (absorbed) current and power. A second bus, the Share Bus ensures that each instrument carries an equal portion of the load current. The Share Bus prevents an instrument from getting overloaded and damaged.

The master instrument monitors the Master-Auxiliary Bus. If the master detects a lost connection to an auxiliary instrument, the master will send an alarm and shut down the auxiliary instruments. Also, if an auxiliary instrument generates an alarm, the master displays the alarm condition and will disable the auxiliary instrument’s output. With the Master-Auxiliary Bus and the Share Bus, the EA-BT 20000 can safely support high-power loads.

Figure 1 shows the Master-Auxiliary Bus, Share Bus and power connections for paralleling two EA-BT 20000 Triples to double the power in each of the three channels. Figure 2 illustrates paralleling the three channels of an EA-BT 2000 Triple to increase the load current capacity by a factor of three.

Figure 1. Rear panels of two BT 20000 Triples. Master-Auxiliary Bus (yellow cables), Share Bus (grey cables) and power connections (orange bus bars and cables) connect each channel of two BT 20000 Triple testers in parallel.

Figure 2. Rear panel of an EA-BT 20000 Triple. Share Bus (grey cables) and power connections (orange busbars) connect three channels of the BT 20000 Triple battery tester in parallel. The Master-Auxiliary Bus is internal to the instrument.

Making proper parallel connections for high-power programmable power supplies

The configuration works well as long as some guidelines are followed. Considerations when paralleling EA-BT 20000 battery testers include:

Paralleling different DC programmable power models

• It is best to parallel similar instruments, such as a set of all BT 20000s. You can, however, parallel different models with different voltage-current envelopes and different power levels.
• Use the highest power model as the master instrument.
• Connect only two EA-BT 20000 Triples if the individual channels are paralleled. They must be identical models.
• Make channel 1 the master channel when connecting individual channels on a Triple in parallel.

Proper cables and connectors

• Use the same type of wiring to connect all power supplies together and to connect to the load. This ensures that all instruments have essentially the same load and helps with load balancing among the instruments.
• Separate the EA-BT 20000s from the battery-under-test with a DC contactor. The DC contactor should not close until both the polarity of the battery has been verified for proper connection to the BT 20000’s and the voltage of the EA-BT 20000 master is equal to the battery voltage. These steps avoid damage to the battery and the EA-BT 20000’s.
• Use 50 Ω BNC cable with a length of no more than 0.5 m for Share Bus wiring.
• Use CAT5 Ethernet cabling for master-auxiliary connections.
• Ensure correct cable or copper bar sizing for load connections based on the maximum load current. Keep power cables as short as possible to limit cable inductance.

Safety considerations

• Install the paralleled instruments in a cabinet to protect personnel from exposure to live voltages.
• Tighten all wiring connections to ensure all instruments are properly connected.
• Ensure the busbar connecting the paralleled instrument outputs is physically supported so that the instrument connectors do not support the weight of the busbar. Having a busbar support prevents the busbar from falling and creating a dangerous short circuit.

Actions to avoid when paralleling DC programmable power models

Some actions can cause damage to the paralleled set of instruments or to the battery-under-test. These steps can also prevent the instrument system from working properly. Avoid the following:

• Do not connect a battery-under-test to EA-BT 20000s without matching the EA-BT 20000’s output to the battery voltage. A spark or an arc can occur when the voltages are at different levels.
• When combining EA-BT 20000s with different ratings, ensure that the settings of the master instrument do not exceed the ratings of any auxiliary instruments.
• Do not attempt to program an auxiliary instrument. The master is the only instrument that you can program. In Master-Auxiliary mode, the auxiliary instrument is under the control of the master instrument.
• Do not use ethernet crossover cable for Master-Auxiliary Bus connections. The Master-Auxiliary Bus requires straight-wired CAT5 cables.

The EA-BT 20000 offers battery tests, simulation and recycling solutions.

Simple steps safely generate up to 1.92 MW

Following our guidelines will enable you to build a wide range of high-power battery test systems by paralleling EA-BT 20000 battery testers. The EA-BT 20000 testers not only ensure safe implementation with the Master-Auxiliary Bus and the Share Bus, but the programmable power supply instruments also save utility costs with up to 96.5% efficiency on returning absorbed energy to the power grid. A parallel set of EA-BT 20000s provides the necessary power with an excellent return on investment. Learn more about the value of the EA-BT 20000 battery testers at Triple Output Battery Tester EA-BT 20000.