Alkaline cells in your back up pack will last longer than NIMHs. I know the charts say otherwise, but a good brand of alkaline batteries like the "coppertop" ones (no brand names here, lol) will outlast the charge on the rechargeables. Fortunately, if you have a full charge on your NIMH, it should last four - six hours, which is enough for most guys for a days hunt. The only thing I don't like about the V3 battery system is that it doesn't give you the low battery warning soon enough. This is because of the way the NIMHs seem to hold a high voltage up until they're almost discharged, then suddenly the voltage drops. With my XLT using either NICADs or alkalines I could hunt another 30-45 minutes after the low battery warning started coming on. With the V3 and the NIMHs, one minute all is well, the next the detector shuts down and the battery is almost dead - not even time to make it back to the car. You are forced to carry the back up on your person if you're gonna be any distance from the car. Back to your problem, though, the rechargeable should last longer than what you are indicating. Whites will no doubt resolve your problem.