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Yumi single arm error 38200

Hello, 
we have a Yumi robot single arm 14050. Some week ago appeared error 38200 (battery backup lost). I bought a new battery and replaced it. Old battery was 3,5V so clearly discharged. I measured the new one and it is 7,2V so it seems to be ok. The problem is that the error is still there. Every time I reboot the robot the error appear and i have to recalibrate. Do someone know the reason? THere is something that i can check?