The DC system is mainly composed of rectifiers and batteries. Among them, the role of the battery pack is particularly important. In the event of a grid failure, the load will be supplied directly by these battery packs, which is the last barrier to the DC system.
The closed valve-controlled lead-acid battery has outstanding advantages at the same time, but also brings inherent deficiencies, such as:
1, The battery is difficult to test capacity and cannot add water, which also need high the floating charge voltage and the use requirements and so on.
2. After the battery is put into use, due to factors such as the design, tooling equipment, quality control and other factors before the battery leaves the factory, as well as the floating charge voltage setting in use, the ambient temperature used, etc., it will lead to the phenomenon of active material falling off, deterioration, positive grid corrosion and vulcanization, which will cause the entire group of batteries to lose capacity, uneven voltage difference,  single batteries fault and etc.
This will bring great hidden dangers to safe production, when the power grid failure and  requires battery power, the battery cannot discharge the vicious accident, therefore, the maintenance procedures require the battery to carry out a check capacity test, the purpose is to test the actual capacity of the battery pack, find out the fault battery, eliminate hidden dangers.
Then the problem comes out, and the problems that THOMSON need to solve for battery maintenance in the actual work process can be summarized as:
1: Daily maintenance and testing of the battery to find out the unqualified or invalid battery.
How to check?  Experience alone?  
No, The professional "DFT-6101 battery internal Resistance Tester" will be your daily maintenance and detection of the right assistant, can help you find out the invalid battery by testing the battery's internal resistance and voltage, preliminary estimate of the battery capacity. This solves the problems of capacity testing