Do you have a voltmeter to see exactly what voltage the batteries are reading at the beginning of your trip, and also just before the motor cuts out?
Do you have an ammeter to measure the actual current being drawn from the batteries?
Do the controllers cut out under light load or only under heavy load?
What is the maximum battery drawn current settings on the controllers?
If the controllers are cutting out because the battery voltage is too low
(which is what they appear to be doing) it may be due to one of the following:
- The batteries are completely exhausted (100% discharged) and the controllers are simply protecting the batteries from being further discharged
- The batteries are unable to produce sufficient current for the motors without excessive voltage drop (current draw exceeds their maximum discharge current)
- The main battery wires are too thin to carry the required current over the length of wires(resulting a significant voltage drop under load)
- A poor battery terminal or controller wiring connection
I think that disabling the "Clear undervoltage state while throttle off" would mean that you wouldn't be able to use the motors again once they had cut out due to low voltage without powering off the controllers and turning them back on again.
It's much easier to simply throttle back to reset the under voltage condition.
As you are using Lead Acid batteries, it might be worth setting the "Low voltage triggering current reducing (V)" to
(48V) to try and extend the remaining 30~40% battery capacity, but I don't know how much it actually reduces to current by.
Bear in mind that 200Ah lead acid batteries will be able to supply 10Amps continuously over a 20 hour period
(C/20), but they will not deliver 200A continuously for a whole hour
(1C).
If you look at the above graph you can see that when discharged completely over a 1 hour period, the actual capacity is only around 62% of the rated capacity
(~124Ah for a 20Ah battery).
Completely discharging a 200Ah battery over 90 minutes would obtain a maximum capacity of ~140Ah @ ~93Amps continuous current draw.
If your motors were drawing a constant 50 amps each
(a combined power consumption of 4.8kW, with a total combined power output of just over 5HP @ 80% efficiency) your battery would last
less than 90 minutes on battery power alone
(assuming it was fully charged to begin with).
Also, discharging your batteries to 38V
(9.5V per each 12V battery) is very bad for lead acid batteries, and it is likely to reduce the number of battery cycles available before the batteries need to be replaced.
I suggest 42V should be the
minimum value for the low voltage protection setting with 48V lead acid batteries.
Alan 
