You should be running a 6S battery.
With a 1555 and 4S you are getting 430 grams of thrust per motors at 50% throttle. That comes out to 1620 grams total. The aircraft is under powered and that causes high current and significant voltage sag. I’d guess hover throttle is around 60%. That’s not “bad” but you are cutting into the amount of throttle you have left for attitude control.
If you run 6S, at 50% throttle each motor will make about 820 grams of thrust for a combined total of 3280 grams and the aircraft will be overpowered. To get closer to a hover throttle of 50%, go with a 1344 on 6S. You will get 550 grams per motor for a combined 2200 grams (2.2Kilos) of thrust.
To get a better handle on this we need to know what the DRY (no battery) weight is. Then we can play with battery weights and give you recommendations that will give you the most flight time using the 1555 props. My thinking is a 6S 10000mAh.
I have a slightly stretched Tarot 650 Sport. I’m running 350Kv motors on a 10000mAh LiPo swinging 1655 props:
Aircraft Dry Weight (No Battery) (g) 2085
AUW (with Battery (g) 3305
Battery Capacity (mAh) 10000
Number of Cells 6
Battery Weight (g) 1220
Battery energy density (Wh/kg) 181.9672131148
Number of Motors 4
Thrust per Motor (g) 826.25
Motor Efficiency (g/W) 7.87
Expected Flight Time 31.7181240545 minutes
Flight Time with 20% Reserve 25.3744992436 minutes
Tarot 650 Sport Stretched to 662mm
Pixhawk w/GPS
3DR 915mHz Telemetry
XT-Xinte 5010-350Kv Motots
1655 CF Props.
Tarot Retracts
FlyTron Navigation Strobes
Craft&Theory Telemetry
6S +12 volt BEC
6S +5 volt BEC
OLED Display
3 Axis Gimbal w/ STorM32 Controller
GoPro Hero 3+ Black
Tarot “Carbon Look” Canopy
MavLink OSD running MWOSD
200mw FPV Video Transmitter
RHCP Clover Leaf Video Antenna