3 wiper motors connection in parallel to lift 20kg

i m using 3 wiper motor at once to lift 20 kg of weight. but they are not working properly. but the single motor is showing more power. m using 2.5 guage wire with 12V and 80amp.all 3 motors are connected in parallel and just lifting only 7 to 8 kgs. but when i m connecting single motor it is able to lift 5 to 7 kg

link for my robot pic

https://www.facebook.com/photo.php?fbid=460492887350018&set=a.428922680507039.95791.428885363844104&type=3&theater

 help me to find solution

 

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1369295981_511384006_2-high-torque-100RPM-worm-gear-dc-motorfrom-TEAM-MOD-Secunderabad.jpg

1369295981_511384006_3-high-torque-100RPM-worm-gear-dc-motorfrom-TEAM-MOD-Tools-Machinery-Industrial_0.jpg

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all 3 motors are connected

all 3 motors are connected in parallel and just lifting only 7 to 8 kgs. but when i m connecting single motor it is able to lift 5 to 7 kg

Sounds like power supply to me

It sounds like your power supply is not able to dump the required current to drive all 3 motors.

What are you using for power?

power supply

its 12V 80amp 

 

 

80amp?

What exactly does that 80amp refer to? Is it 80 amp-hours, or is it capable of discharging 80 amps?

80 amp-hours

that the battery specification. 12V 80 amp-hours