We are having trouble keeping the battery charged on the 52" walk behind that we swapped out engines on. It was a pull start before. It is now electric start and it only holds a charge for about a week. We have a battery charge that we hook up to it on a regular bassis to keep it charged. Problems is sometimes it dies in between properties when this mower is being used. Any Ideas on why it won't hold a charge. Do we need a smaller battery or a larger one. Maybe a thicker power wire or maybe even a thinner one. All ideas greatly appreciated.