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1988 Johnson 20 HP battery charging rating

E

emilkob

Member
What is the power output of the battery charging system on a 1988 Johnson 20HP (J20ECCA)? I am wondering how many amps can be pulled by accessory power with the engine running, and without compromising the charge on the battery.
 
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I just looked up the CDI replacement stator coils for this model and they are rated at 5 amps. I assume the stator coils deliver 5 amps at WOT. If my assumption is correct, and assuming WOT is approximately 5000 RPM, and I am running at 1000 rpm, would the charging system deliver 1000/5000 x 5 amp = 1 amp? How much of that is lost to the power pack driving the spark plugs? I am trying to understand whether running a considerable amount of accessory power (depth/fish finder, running lights, radio, charging the iPhone, etc.) is draining the battery when cruising at low RPM.
 
Get another battery and charge it onboard or at home, Once started an outboard does not use battery power
 
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There is no way that charging system will keep up with all that while trolling. You can help yourself by using Led lights but other than that either get the biggest starting/deepcycle battery you can or run 2 batteries like johnnygjr said.
 
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