Intangible Assets - Finite-lived intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Gross	$ 5,224	$ 5,224
Accumulated Amortization	(4,729)	(4,433)
Foreign Exchange Rate Changes	(174)	(174)
Net	321	617
Amortization expense	300	300
Patents
Finite-Lived Intangible Assets [Line Items]
Gross	2,963	2,963
Accumulated Amortization	(2,642)	(2,346)
Foreign Exchange Rate Changes	0	0
Net	$ 321	$ 617
Estimated Useful Life (in years)	10 years	10 years
Developed Technology - 150 V
Finite-Lived Intangible Assets [Line Items]
Gross	$ 560	$ 560
Accumulated Amortization	(517)	(517)
Foreign Exchange Rate Changes	(43)	(43)
Net	$ 0	$ 0
Estimated Useful Life (in years)	6 years	6 years
Developed Technology - 600 V
Finite-Lived Intangible Assets [Line Items]
Gross	$ 1,701	$ 1,701
Accumulated Amortization	(1,570)	(1,570)
Foreign Exchange Rate Changes	(131)	(131)
Net	$ 0	$ 0
Estimated Useful Life (in years)	6 years	6 years