If interest rates are too high, it discourages investment because the interest rates are the cost of borrowing. They do encourage savings. Low interest rates encourage borrowing but discouage savings. If rates are high, a company will need to be pretty certain of getting a high return before they are willing to make any investments- since it cost more to borrow. If rates are low, they can take on riskier projects with lower potential returns because the costs of borrowing to finance them are lower.
The problem today is not a lack of funds to borrow for investement (savings to tap into and borrow from)- encouraging more savings will not increase investment today. Banks have vast sums of money available but aren't being lent or borrowed. They have an unprecidented $2.6 trillion dollars in excess reserves stashed at the Federal Reserve- and that does not count excess reserves they have in their own accounts and banks. Business is not investing becasuse they aren't seeing the economic growth yet to justify putting money into increasing their business.
The near zero interest rates we have today is not encouraging a significant increase in investment. Raising interest rates won't help either.
The monetary base is not really a measure of money. It indicates potential money. Monetary base is the sum of bank reserves at the Federal Reserve (that $1.6 trillion plus their required reserves) plus all the cash printed and in banks and circulation. If the banks reduce their excess reserves, the monetary base goes down. But that means that money getting borrowed and spent is going up finally and that increase in money chasing after goods and services could mean higher price inflation. It is not the rising monetary base which could cause price inflation- but its decline.