rpi constant reboot

last night I tried to add an oled panel using i2c, along with the picoborg reverse and the ultraborg. I turned everything on, but after a few minutes (without doing anything, the diddyborg was just sat on the table) I got a rapidly flashing red light on one of the boards and so turned everything off. I took out all of the new cables (I did think it was all wired correctly, but am questioning myself now) and went back to just the battborg + picoborg reverse. Now whenever I turn on the pi I just get into a constant reboot cycle. The pi itself seems to be OK - when I connect using usb power, it boots up fine. But when I switch to battery power, (even just using the 5v and gnd pins) I get this constant rebooting. The battery pack power was still around 10V.

I just wondered if this was something you may have come across and whether you had any thoughts? Have I somehow fried the battborg or picoborg? I've ordered a new one of each, so I can try and track down what I have done, but if you had any ideas I would be very pleased to hear them!

Tonight I'll try just batteries, battborg and pi - see whether that works, then rebuild from there. Fingers crossed - piwars is getting close!

best wishes
Richard