equations

System

I'm new to all this. I've been lookin on you tube and all, and I want to buy cells, and build my own pannels.

I'm looking for a sticky here on the forum, or would like to know the general equation for how many cells/pannels to recharge (X ) ammount of (X) ammount Mah deep cycle batteries. I'm just guessing I will want something like 10 deep cycle batt. with a converter of some kind. Can someone give me a link to read? thankz

BB.

Re: equations

Here are a few threads on building your own solar panels:

Vacuum sealing solar panels
SOLAR CELLS - for sale on E-Bay?
DIY Solar Panels - materials?

And here is a thread on why we don't really have may DIY solar PV panel threads:

Do It Yourself--Why so many negative comments?

Regarding sizing of solar panels? Generally, we size the battery bank to your load (3 days no sun, 50% maximum discharge => basically somewhere around 6x your daily load). Assuming 20 Hour battery Amp*Hour rating.

For charging, we recommend around 5% to 13% of the 20 Hour Rating as another rule of thumb. Below 5%, it can be difficult to properly charge/equalize flooded cell batteries. Above 13% charge rate--you can overheat the battery bank and it is just a waste of money (lots of solar panels and no place for the power to go).

So, a 10% charge rate on a 500 AH battery bank would be ~50 Amp recommended charging current. (remember, you still need to return the amount of energy you consume from the battery bank over night--i.e., hours of sun per day * solar panel rating * ~50% end to end efficiency).

Note that AGM (sealed) lead acid batteries are a much better (and more expensive) battery type--higher current support, no water to check (if properly operated), low self discharge rate, and very clean (no acid mist in normal operation). They may not last quite as long as a high quality flooded cell lead acid battery though.

-Bill

System2

Re: equations

thanks bill. That gives me a great starting point.