View original topic: Solar Panel Size Question? Page: Previous  1, 2, 3
PDXWesty Thu Jun 12, 2014 10:25 am

Timwhy wrote: From Solar Blvd. Your panels may be getting more expensive soon.

Dear Friends,

On Tuesday, June 3rd 2014, The United States Department of Commerce successfully imposed increased duties of approximately 21.89 percent to importers of solar panels, asserting that foreign manufacturers had benefited from unfair subsidies.

The decision, in a long-simmering trade dispute, addresses one of the main charges in a petition brought by the manufacturer SolarWorld Industries America. While it is preliminary, the ruling means that the United States will begin collecting the tariffs in advance of the final decision, expected later this year.

What does this mean to you as a customer? Since you are not the importer on file, you will not be directly taxed for your solar panels. There will, however, be an increase of about 15 percent across the board on all solar modules in the next coming months.

Our goal at Solarblvd is to remain competitive. So, we will continue to offer you great pricing and unprecedented service in the coming years!

Thank you for your continued support.


I got the same email. Solar prices are set to go up soon. Get in while you can!

Howesight Thu Jun 12, 2014 11:18 am

WestyDreamer wrote: OK..
Since this topic has taken on so many variables and so many expertize has spoken and given there suggestions.

Another Question now has come to mind about standing Battery Voltage?

It was posted that a Solar Panel should provide Charge Voltage between 13.5 to as Hi as 14.8 Volts..

But after charging what should we see on a normal wet cell 12V Deep Cycle Battery? After I unplug my battery maintainer mine usually reads about 12.4 - 12.7 Volts. My charge volt meter usually reads 13-14 Volts but once disconnected the Battery Voltage drops to a steady 12+ volts. Is this Wrong.

I just don't understand how you squeeze 14 volts into 12

Just wondering if I should invest in a 14V Battery :lol:

Hi Westy Dreamer:

There are some very good information sources on how deep-cycle batteries work. Northern Arizona Wind and Sun has a good section found here:

HandyBob has an excellent thread on the practical side of correct battery charging and battery installation here:

The voluminous information in the resources above is very useful, but the short answers to your questions above are:

1. Standing battery voltage of a fully-charged deep cycle battery at approx. 70F degrees is 12.7 to 12.8.

2. But "standing" voltage is only accurately measured between 2 and 6 hours after all discharging and all charging activities have ceased. Batteries are electro-chemical devices and the chemical reactions continue for some time after both discharging and charging. For example, if your battery had been fully and properly charged, right after you remove the float charge of 13.4 to 13.6 volts, your battery will still read around 13.1 or 13.0 volts and slowly drop to 12.8 or 12.75 over the next several hours.

3. If your deep cycle battery reads 12.4 V after proper charging, it needs to be replaced.

4. The 50% depth-of-discharge (DOD) voltage is 12.2 V. You should not run your deep cycle below this level if you want it to last.

Here is the table that Northern Arizona Wind and Sun has in their battery FAQ:

State of Charge for a 12 V battery
100% 12.7
90% 12.5
80% 12.42
70% 12.32
60% 12.20
50% 12.06
40% 11.9
30% 11.75
20% 11.58
10% 11.31
0 10.5

I know you are probably thinking, if the battery has 10.5 volts, why is it "dead"? The answer is that at that state of discharge, it has no power to actually force electrons through a circuit. If you hook up a load to that 10.5 volt battery, it will essentially do nothing. Think of a tiny soap bubble with air pressure inside it. It has the pressure (analogous to voltage), but no appreciable volume of air to move when you pop the bubble.

MarkWard Thu Jun 12, 2014 11:37 am

A 12 volt battery at 12.8 full charged volts divided by 6 cells = 2.13 volts roughly per cell. A voltage reading of 10.5 volts could indicate one dead cell which is one way batteries can fail. Regardless, the battery is toast.

desertrefugee Sat Jun 14, 2014 3:56 pm

I just wanted to add a note of thanks to all the wisdom (and experience) shared in this thread. I've been looking for a solar system for some time. I am forever worrying about battery reserves in the field.

I do a lot of astronomy adventuring (plus lots of other camping). But, the astronomy outings are particularly power hungry. Laptop, three astro batteries, Westy auxilliary battery, lights - and the eventual TruckFridge. (Stock Dometic still ticking).

What really spurred me to action was the comment about new tariffs being levied against imported hardware.

So, today, I ordered a Renogy 100W mono' basic panel with 30A CC.

Pretty decent price. For now, this will serve my purposes, but I may eventually look to upgrade the panel. I will NOT hard-mount it to the roof, rather, my intent is to obtain a frame for setting it up remote from the camper. (We always strive to park in the shade in Arizona - even at elevation).

Again, thanks, and I think I made a much more informed decision based on a couple hours' worth of Samba reading. I was pretty solar illiterate before that.

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