I recently purchased a Monterey 180 F/S which only comes with 1 battery. I'd like to hear recommendations for a jumpbox (battery charger) that I can take along with us when we go out...Any experience using these? Any good recommendations? I'd like to not "break the bank" when purchasing one since i'll only be carrying/using it in case of emergencies. I'm assuming they have kinds which I can charge at home, and bring along in a duffle bag on the boat and "jump" the battery should that become necessary. Thanks!