Strange behavior of limited current

Hello.

We use a 5065 BLDC Hall sensored motor having low KV (70KV) with 2x12V lead batteries. We successfully processed the wizard to configure the VESC. Motor absolute max current is set to 150A and it is configured for 50A max current : the motor can support it. The motor turns with small load (8A) using VESC Tool at 50A (!?).

When putting increased load, we notice that the current goes up to 13A and then decrease down to 0 depending on the torque applied against the motor. We don't undestand why.

Why doesn't the motor uses 50A while we are asking for so using the Vesc Tool Interface ?

Why is the VESC not delivering up to 50A when we increase load on the motor ?

Is there some pb with the batteries not able to deliver the current. (batterie ref : https://fr.rs-online.com/web/p/batteries-au-plomb/5375488/) we use them in serial to get 24V. It is said on the datasheet that it can deliver 105A during 5s. So there should be no pb.

Thank you for any help !

Emmanuel