Segment information (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net sales	$ 293,931,961	$ 244,166,312
Cost of Sales	237,056,725	196,792,444
Gross Profit	56,875,236	47,373,868
Lithium Batteries [Member]
Segment Reporting Information [Line Items]
Net sales	219,964,972	161,660,771
Cost of Sales	176,414,365	129,295,264
Gross Profit	43,550,607	32,365,507
Ni-MH Batteries and Accessories [Member]
Segment Reporting Information [Line Items]
Net sales	73,966,989	53,492,309
Cost of Sales	60,642,360	41,834,267
Gross Profit	13,324,629	11,658,042
New Materials [Member]
Segment Reporting Information [Line Items]
Net sales	0	29,013,232
Cost of Sales	0	25,662,913
Gross Profit	$ 0	$ 3,350,319

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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