Battery Testing Equipment for Hire

Battery testing splits between two complementary test methodologies. The right method for a given test depends on what the maintenance cycle calls for and what level of evidence the asset owner requires.

Internal resistance / impedance testing (BT3554-50 method)

Internal resistance testing applies a small AC signal to each cell or block, measures the AC impedance, and compares the result against a baseline value. The Hioki BT3554-50 uses the four-terminal AC impedance method to measure resistance from 3 milliohms to 3 ohms with a two-second hold time per measurement. As a cell ages or develops sulfation, dry-out (in VRLA), or grid corrosion, its internal resistance climbs. Comparing the readings across all cells in a bank reveals the outliers; cells reading 30 to 50 percent above the bank median are usually flagged for closer inspection or replacement. The method is fast, the battery does not need to be disconnected from its load, and the test is non-invasive. The limitation is that internal resistance correlates with capacity but does not measure it directly. A capacity-degraded bank can still pass impedance screening if the degradation is even across all cells.

Discharge testing (Torkel 930 method)

Discharge testing applies a known constant current, constant power or load-profile load to the entire battery bank and measures how long the bank holds above its end-voltage cutoff. From the test result the actual capacity in ampere hours is calculated and compared against the nameplate. The Megger Torkel 930 supports battery systems from 12 V to 500 V, with discharge currents up to 220 A in standalone mode, and four test modes covering constant current, constant power, constant resistance and user-defined load profile. The Torkel 930 can discharge the bank in service, with the connected DC load remaining energised throughout, by using a DC clamp meter to measure total battery current and adjusting the Torkel load to maintain the target test current. Discharge testing is the only method that definitively proves a battery bank will deliver its declared duty cycle, and is the basis for end-of-life decisions on substation and UPS battery banks.

BVM cell voltage monitoring during discharge

On any discharge test of consequence, BVM (Battery Voltage Monitor) modules are connected to the Torkel 930 to log the voltage of every cell throughout the discharge. BVM modules daisy-chain to monitor up to 120 cells per loop, with a second BVM loop on the Torkel’s BVM2 port supporting up to 240 cells in total, and the Torkel 930 records the per-cell voltages alongside the total bank voltage and current. This allows weak cells that are dragging the bank toward end-voltage to be identified at the cell level rather than scrapping a whole bank because of a few bad cells. Megavar supplies BVM modules with Torkel 930 hires on request.

Expanding discharge capacity with the TXL870

For large battery banks where 220 A is insufficient to reach the test current called for by the IEEE 450 or IEEE 1188 discharge profile (for example, a substation bank rated for several hundred amps over an hour), the Megger TXL870 extra load unit connects in parallel with the Torkel 930 to add additional discharge load. Multiple TXL870 units can be paralleled, enabling discharge currents of several hundred amps depending on the battery bank voltage and the number of TXL units configured. The Torkel 930 remains the controller, with the TXL units providing the additional load capacity. This is the standard configuration for full capacity testing of larger transmission substation battery banks and BESS battery sub-strings.