I second what Zimmy said about the Interstate brand. 5 years and still holding a charge on a 24V setup and they get abused a lot throughout the year. I do check the fluid about twice a year and add when needed. Typically only charge them after a trip but will leave them hooked up in maintenance mode for a week or so at a time when i know i will be fishing a lot. I have a 4 bank Minnkota charger but don't feel comfortable leaving it hooked up for extended periods.