bobnollie

Yep...Walmart's the way to go for the new battery. You won't be needing to add water to your new sealed deep cycle battery but I would not leave the charger on constantly. I have a timer on mine to let it charge for no more than 4 hours a night when stored. I did however, improve on the venting system for my battery by adding a 12 volt, 1 inch, ultra-quiet, computer fan inside the outer vent plate. The fan is wired to the ignition wiring to run when the motor home is running/charging, plus a small 110vac to 12 volt DC "wall wart" supply hooked to the 110vac in to the coach charger. Power from the two DC sources is isolated by a diode to prevent the ignition from receiving any power when the unit is on shore power. Now all I need for my Horizon is a V8 engine.....LOL. Later good buddy.

You haven't stated weather the noise occurs standing with engine idling/racing or travelling at highway speeds. My 1988 Toyota Horizon had a whistle at highway speeds which turned out to be the overhead window weather stripping had shrunk, leaving a 1/4 inch gap at the top which acted as a very nice whistle/speed sensor.