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Psuk72 avatar image

How many amps should my 100 watt solar panel produce on a sunny day ?

It’s currently producing 17 volts but only 0.8amps ? Is this correct ? It does not charge my leisure battery very well

Solar Panelamps
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Paul B avatar image

Well this will depend on a few things, and so its cant be a cut and dried answer.

Ie system Voltage and the state of charge of your batteries, Mppt Panel out put and what goes into the battery

So if the Battery system is a 12 volt system then.

1. if the batteries are FLAT ie under say 12,5 volts then on a good sunny day at the peak of the day you would get say 8.0 amps (100/12.5) based on a 100w panel. going into the flat battery.

However the panel voltage maybe still 17 volts so out of the panels this would be 5.9 Amps but into the battery would be 12.5 and 8 amps (less losses etc)


2. if the batteries are full then the regulator should be reducing the current to close to zero or enouph to hold float volatage and supply any loads.



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I think you should clearify your answer. When talking Lead Acid battery gain a higher resistance as it charges. The last 90% top end in Lead takes forever to finish the charge. Li Ion do not work the same way as they have much lower internal resistance.

I am not an expert but the answer may be different based on battery chemistry. I see the poster did not state what type of battery system he is using or if he is using a PWM or MPPT charger.

On a sunny day my 400 watts (24-36 volt PV) of solar can pump out 12-18 amp hours to my Li Ion batteries. Of course latitude location, time of the year and cloud cover also effect how the charger works.