The numbers show that it will take many seconds to charge up the banks then.
10+ seconds from 200A mains, 100+ seconds from a 20A breaker.
A typical battery load test is designed to discharge the bank at a high rate and then recharge at a much lower rate. Typically hours.
I also would be interested in more information on the nature and use of the battery bank in question. The voltage suggests something like a telephone exchange where the voltage is nominally 48V. They use large banks of batteries as backup.
Any other industrial /office UPS uses more like 450V+.
Weedpharma
Sorry for the long delay in replying. Weed is exactly right. The battery bank was a VERY large lead acid battery array consisting of hundreds of single cell glass batterys for a communications system. If I remember correctly the chargers were capable of 200 amps continious and the battery bank was rated for 500 amp talk battery load on a continious basis. The reason for the extreem load test was to quickly find defective cells in the array without shuting down comms for any long duration. We had to do the test and find the defective cells within 15 minutes and could only load the bank for 2 minutes per 5 minute cycle. The defective cells would drop to lessthan 1.9 volts within 2 cycles. Once found they were marked for replacement. The cells could be hot swaped as to not disrupt the power system.
Not sure if this helps but 30A @ 5V is 0.166 ohm resistance. If you can get current shunt that would work. A resistive dummy load might be a problem because a 0.166 ohm power resistor would need to be rated for at least 150 W. A 0.2 ohm ,200W would be easier to find. (or 0.1 x 2) (5V/0.2 ohm = 25A/125 W)
You can easilly find small resistances like that around the house.
A measured length of (speaker)wire has a known resistance.
It will last a long time in a bucket of water.
Double up the part that's outside the water.
Leo..