2.5 kv inverter 2 200 ah gel batterys have been crank tested both good batterys drain in 1 hour with 100 watt load why would it happen

Because Lead Acid Batteries cannot handle being cycled and discharged so often.

The batteries may test fine but are probably kaput as you only get an hour out of them. You're better off investing in a suitable Lithium battery

How old are the batteries .

Lead acid should not be discharged under 70% 

Gel batterys should not be discharged under 50% 

So if your low cut off volts were set to low it does not take much to destroy lead or gel batterys . 

Also if your float volts are to high the battery boil and also does not take long to destroy them .

Ago is also part of the issue don't expect gels to last much long than 2 years 

With the right setting I had gels last still the 2 hours load shedding with 350w constant after 4 years .

So the right setup is very important