Hi guys I hope you can help me out. I have a hot tub that does not have a stereo so I built a box and used a 12 volt convertor to run the stereo. Its on a timer that also controls the lighting on the deck so its only good for 1 hour which is fine but the problem is the stereo does not retain the memory as there is no content power. I have a spare auto battery that I thought i could use in combination but i was worried it would cause a problem when the 12 volt convertor is used to listen to the stereo. The only solution is to activate the 12 volt convertor for 24 hr usage in the outdoor box that it is housed in and I don't know how safe this is. Can I go the auto battery way and use a charger to periodically charge the battery for memory used only. There is two lines one is the power ignition line and one is a memory line . Any help?