Battery Monitor does it all! Charge up a battery and maintain the charge with just one unit. Its built in 3 step charge allows for charging up to 90% capacity at 2.7amps, then switching to a timer controlled charge at 14.7 volts to bring the battery to full capacity and finally holds it there indefinitely with a float charge. Indicator lights show each charge step. 12 volt battery only. Read \" How-To Maintain Car Battery Life \" from Technical Articles for some useful tips to keep your car battery stays healthy.