Off Grid Home Forums Technical Discussion Tech help needed on homemade solar system Re: Tech help needed on homemade solar system


Sixsoxs I’m assuming you still check this forum from time to time.

Blazie made some good suggestions. How about responding so we know any advice is actually received.

I see several reasons why your system may have drained the battery bank. This advice is applicable to any person building their own system. Location by latitude is important to know. At higher latitudes you get much less solar input compared to the theoretical rating listed for the panel. If you are above latitude 45 the actual output of the panel could be as little as 50% during winter months. Secondly does the panel have isolating diodes. Several of the lower wattage panel do not because of the inherent voltage drop created by the diode itself. This means the solar panel actually drains the battery at night .

Thirdly that 35 watts for the music system amounts to nearly 2.9 amps X 12 hours or roughly 34.8 amp hours of consumption. In other words your music system is using all of the potential power the solar panel might be able to deliver but drain the battery bank of the charge in a couple of days. One week end in other words.

Not to mention which you are not going to get full output from that solar panel for the full period of daylight time. At most you can expect 4-5 hours of maximum output on a good day. Early morning and late afternoon is not going to deliver as much power no matter how much the sun is shining.

You mention using a 400 watt capacity inverter to run some night lights but do you shut off the inverter when not in use? The parasitic load will kill your fully charged battery in less than a week; even if the inverter is not driving any load.

The short answer is you need much bigger panel capacity. Secondly you need to understand where the hidden current drains can be found.

Forget the 7 amp charger it is not sufficient. It will barely handle the self discharge of the battery bank, let alone deliver 425 amp hours of real charging power.