Shares of A123 Systems ( AONE) have run out of juice and are down nearly one-third from their high of $28.20. It looks like the IPO hype has faded and the hot-money investors have moved on. Now it's up to the company to produce concrete results that meet investors' huge expectations. A much better way to play the lithium iron phosphate space is China Sun Group ( CSGH.OB). I haven't written about China Sun in a while because I wanted to wait for the company's customer test results to be released. They were released Tuesday and exceeded investors' already high expectations. Technical testing was completed by several customers and, as expected, China Sun's lithium iron phosphate product met the required technical specifications. More important, China Sun announced that it now has 21 customers undergoing technical testing of the product for their own use. Given that the product has already passed technical testing by leading battery producers Shandong Shengong and Beijing Zhongxinlian, I expect that this next wave of testing is just a necessary formality for the 21 new customers. The most significant part of China Sun's recent press release is that the company has signed a letter of intent with Beijing Zhongxinlian to jointly produce its new lithium iron phosphate-based batteries for use in electric vehicles under the registered brand name of "ShenKun." This news is tremendous. China Sun has effectively transformed itself into an end-to-end supplier in the lithium ion battery space, providing all parts of the supply chain from raw materials to finished product. Beijing Zhongxinlian is an existing customer of China Sun, has already completed its required testing and has been selected by China Sun to be their partner. As a result, I view this letter of intent as being much more substantial than a letter by otherwise unrelated parties. This feels more like a contract to me.