I have 4 batteries and have 2 for the TM only. One for cranking only, and the other is for acc. When you do this you need to connect the neg post of the cranking to the neg of the acc. This will allow your RPM's to work properly. I have a radio (Not marine just a CD player) installed and have had no problems with power. I also charge the 2 tm's and the acc battery as soon as I get home and they stay on the charger til I get ready to go again. First time on the lake at night and could not crank without help I decided to do this and have not regretted it at all.
Jody
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