...Or if you already have a charger, like any car enthusiast would, you can buy the smallest car battery at costco. They even come now with carrying handles, at half the price and use it to jump start a car with a dead battery or to get extra amps in the coldest mornings by plugging it in parallel with the existing battery. But if +/- if not your forte' then the B&D is the magic box for you
Or, even more simple, carry jumper cables and ask someone for a boost
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I received a Canadian Tire version as a gift a couple years back. Never used it, tried to keep the charge on it by plugging it in every once in a while, but after just over a year it was shot. I found it to be too much of a hassle.