Personally I think returning those batts was a bit premature. Even if the batts were the cause of the mmm failures, which I don't buy... you could easily work around that by cutting back on timing and brake power to make them work no problem. I just ordered the same batts and plan on running them in 5s with another 2s pack, slightly lower voltage, lower brake settings and lower timing and punch, but still plenty of power and run time. And for what its worth, with these settings if my mmm still craps out, I will be the first to admit the batts may have played a role, but I doubt that I will need to do that.