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Trickle Charge AGM Starter Battery amp/hour to solar panel watts?

Arbee

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Dec 16, 2020
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Ok, sure, longitude, weather, the angle of the panel (which if on some vehicle roof is horozontal)....length of day, there is no one setup...

But that said, is there a basic rule of thumb regarding how big a solar panel in watts a person needs to, with an MPPT controller, trickle charge an AGM starter batter of size "x" amp/hours.

I'm not looking to charge my starter battery so much as I seek to keep it "topped off," as a shore plugged in trickle charger would do.

Thank you.
 
I have 30, 50, and 100 watt panels feeding PWM controllers for various batteries and has been fine for years. Set up one mppt with 480 watts on the MH. Will see what happened over the winter in April.
 
not looking to charge my starter battery so much as I seek to keep it "topped off
A lead acid starter battery will lose power due to self discharge and vehicle electronic standby power. Worst case, a 100 Ah starter battery self discharge will be 5 Ah per month, and vehicle electronics 10 to 20 Ah per month, say 25Ah per month, or 1 Ah per day , 12 watts per day. Suggests a 10 watt panel could easily carry out the task.
 
A lead acid starter battery will lose power due to self discharge and vehicle electronic standby power. Worst case, a 100 Ah starter battery self discharge will be 5 Ah per month, and vehicle electronics 10 to 20 Ah per month, say 25Ah per month, or 1 Ah per day , 12 watts per day. Suggests a 10 watt panel could easily carry out the task.
Thanks Mike. I'm not sure if in your reference to "vehicle electronic standby power," you mentally intended to include parasitic draw; which I'll loosely describe as power lost by the battery that doesn't serve legitimate purpose, that purpose even including keeping vehicle electronics in some dormant state.
 

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