OHH.. in a thread about this mod, I should also say... I heard secondhand that the reverse polarity protection doesn't exist... A guy in my local b&m told me his buddy's bit the dust in a rather violent way instantly upon installing batteries backwards. Don't know if it's true or not (he'd been trying to sell me a Sigelei for weeks just before I showed up with my Tesla, so credibility is a bit iffy-) but it made me mark all my 25r's with a Sharpie. Just passing along, better safe than sorry!