MacBook Pro A1990 Battery not recognized repair

Problem description
MacBook A1990 not recognizing the connected battery

Symptoms

 * MacBook not turning on.
 * Battery not recognized/charging

Solution

 * First, try a known good battery.
 * If it doesn't work, check the battery cable going to the board.
 * Sometimes there is corrosion here, sometimes the customer tore the bar on the connector off the connector.
 * In some rare cases the SMC still is a factor in battery recognition on this board.