I have recently got a HJC helmet with intercom 50B (based on sena 50 hardware), in yesterday's motorcycle ride my intercom was running out of power and as I used to do with the intercom I had previously (also based on sena hardware) I connected a cable to the helmet and wanted to connect it to a power bank, which I would keep in my pocket but to my surprise I found that connecting the power bank to the cable turned off the intercom, I also tried changing the cable but did not solve it. 
Since the battery life of the 50B does not meet what is advertised, that it turns off when plugged into the power bank is a major limitation, is there a way to keep the intercom from turning off when powered.