Battery problem on Nissan Micra SE models?

Im about to spend £5300 on a 2005 Nissan Micra SE, low mileage but when I went to see in showroom on a dealership[not Nissan] the bloody car needed a jump start! Ive read reviews that say that the keyless ignition system drains the battery, but then Ive heard it doesnt and it has some great reviews! Im going crazy,... show more Im about to spend £5300 on a 2005 Nissan Micra SE, low mileage but when I went to see in showroom on a dealership[not Nissan] the bloody car needed a jump start! Ive read reviews that say that the keyless ignition system drains the battery, but then Ive heard it doesnt and it has some great reviews! Im going crazy, does anyone know anything?/ Thanks
Update: Thanks guys
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