I am trying to figure out the best way to hook up two 12v DC peristaltic pumps to run as close to the same speed as possible. The manufacturing tests had the pumps running within 10ml per minute which is acceptable; when I hook the pumps up in series they are not even close. When hooked up in parallel they are in sync however they run intermittently 1 second on 1 second off. I am assuming I'd need more volts or amps due to internal resistance of the motors? The individual motors are 12v 3a max 1.5a continuous. The power supply I was testing was the same 36w. Do I need to get a 72w(12v 6a) to run both in parallel? Also, what would be the best way to get the motors running dead in synchronized? I'm looking to use these pumps for a water exchange; pump old water out and new water in. Ideally the volumes are identical to keep parameters from creeping over time. Thanks for any advice.