Annual report pursuant to Section 13 and 15(d)

Consolidated Statements of Stockholders' Equity (Deficit)

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($)	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Private Placement	Private Placement Common Stock	Private Placement Additional Paid-in Capital	Interstate Battery Transaction	Interstate Battery Transaction Common Stock	Interstate Battery Transaction Additional Paid-in Capital	2016 Public Offering	2016 Public Offering Common Stock	2016 Public Offering Additional Paid-in Capital	Officers and Directors Plan	Officers and Directors Plan Common Stock	Officers and Directors Plan Additional Paid-in Capital	Johnson Controls Agreement	Johnson Controls Agreement Common Stock	Johnson Controls Agreement Additional Paid-in Capital	Ebonex IPR Limited	Ebonex IPR Limited Additional Paid-in Capital	2017 Public Offering	2017 Public Offering Common Stock	2017 Public Offering Additional Paid-in Capital	Over-Allotment Option	Over-Allotment Option Common Stock	Over-Allotment Option Additional Paid-in Capital	2018 Public Offering	2018 Public Offering Common Stock	2018 Public Offering Additional Paid-in Capital	Restricted Stock Units (RSUs) Common Stock
Balance at beginning (in shares) at Dec. 31, 2015		14,137,442
Balance at beginning at Dec. 31, 2015	$ 33,665,000	$ 14,000	$ 48,356,000	$ (14,705,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation - stock options	1,060,000		1,060,000
Warrants issued for consulting services	138,000		138,000
Cashless exercise of warrants (in shares)		15,203
Exercise of options to purchase common stock (in shares)		4,500
Exercise of options to purchase common stock	19,000		19,000
Common stock issued (in shares)					719,333				702,247			2,300,000
Proceeds from common stock issued					$ 4,778,000	$ 1,000	$ 4,777,000	$ 4,370,000	$ 1,000	$ 4,369,000	$ 21,542,000	$ 2,000	$ 21,540,000
Proceeds allocated to warrants issued and beneficial conversion feature in connection with Interstate Batteries Agreement	4,975,000		4,975,000
Net loss	(13,557,000)			(13,557,000)
Balance at end (in shares) at Dec. 31, 2016		17,878,725
Balance at end at Dec. 31, 2016	56,990,000	$ 18,000	85,234,000	(28,262,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation - stock options	1,081,000		1,081,000
Cashless exercise of warrants (in shares)		1,173,296
Cashless exercise of warrants		$ 1,000	(1,000)
Exercise of warrants to purchase common stock (in shares)		2,500
Exercise of warrants to purchase common stock	$ 15,000		15,000
Exercise of options to purchase common stock (in shares)	284,370	284,370
Exercise of options to purchase common stock	$ 1,071,000		1,071,000
Common stock issued (in shares)															2,404			939,005					7,150,000
Proceeds from common stock issued														$ 8,000		$ 8,000	$ 10,472,000	$ 1,000	$ 10,471,000	$ 2,149,000	$ 2,149,000	$ 13,759,000	$ 7,000	$ 13,752,000
Net loss	(26,580,000)			(26,580,000)
Balance at end (in shares) at Dec. 31, 2017		27,554,076
Balance at end at Dec. 31, 2017	58,965,000	$ 27,000	113,780,000	(54,842,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation - stock options	$ 1,201,000		1,201,000
Exercise of options to purchase common stock (in shares)	0
Common stock issued (in shares)															2,034											1,072,500			10,085,500		65,600
Proceeds from common stock issued														$ 4,000	$ 0	$ 4,000									$ 2,103,000	$ 2,000	$ 2,101,000	$ 26,646,000	$ 10,000	$ 26,636,000
Common stock issued for consulting services (in shares)		152,727
Stock Issued During Period, Value, Issued for Services	$ 423,000		423,000
Modification of Interstate Batteries Warrant 1	1,002,000		1,002,000
Net loss	(40,254,000)			(40,254,000)
Balance at end (in shares) at Dec. 31, 2018		38,932,437
Balance at end at Dec. 31, 2018	$ 50,090,000	$ 39,000	$ 145,147,000	$ (95,096,000)