What can I do with just one solar panel?

Re: What can I do with just one solar panel?

You can certainly start out in our host's webstore: Northern Arizona Wind & Sun.

For small/simple charge controllers--You can start with the Morning Star brand (they also happen to make very good MPPT higher end charge controllers too).

A couple charge controller FAQ's to read up on:

All About Charge Controllers
Read this page about power tracking controllers

A very simple 4.5 amp 12 volt charge controller can be had for $30. High end 60+ amp MPPT charge controllers--$530+...

Some of the options may include Remote Temperature Sensor (very nice to have for optimum battery charging). Also, some of the MS charge controllers have landscape lighting timers in them.

For a battery--AGM's are very nice (sealed, no mess, no water), but are about 2x as expensive and very sensitive to overcharging.

A couple Battery FAQs:

Deep Cycle Battery FAQ
www.batteryfaq.org

Simple flooded cell deep cycle batteries are cheap, fairly forgiving, and you can monitor the electrolyte for state of charge with a hydrometer. And you have to add water around once per month (too much water, you are over charging. Very little to no water--you may be under charging).

Sizing your battery bank is one of the more important things to do when designing your system... It is the only part of the system that will age badly if not treated well (over discharged, over charged, too hot, not enough water, stored with less than full charge, too much load current, too much charging current, etc.).

Ideally, we like to size the battery based on the loads--then size the inverter and solar panels to work well with the battery bank.

Batteries should be charged around a 5-13% (of their 20 Hour capacity). And should not be subjected to a continous discharge of more than 13% or so... And the surge current should be no more than C/2.5 or 40% of the AH rating.

That means, if you have a 65 watt solar panel, then the battery should be (assuming a 0.77 derating for panel "marketing numbers" and charge controller losses):

• 65 watts * 0.77 derating * 1/14.5 batt charge voltage * 1/0.13 = 27 AH
• 65 watts * 0.77 derating * 1/14.5 batt charge voltage * 1/0.05 = 70 AH

If you wanted to get a 300 watt surge from your inverter (assuming 0.85 efficiency, and C/2.5 or 0.40 max current):

• 300 watts * 1/12 volt nominal battery * 1/0.85 inv eff * 2.5 max current = 74 AH minimum rated battery

Notice that a 65 watt panel will just charge a 70 AH battery bank. And a 300 watt (surge) inverter will just work on a ~74 AH battery bank minimum...

So, we get these issues all the time of trying to match batteries/loads/solar panels for optimum system design.

By the way, the above are generic rules of thumb and will (usually) give you a nicely performing system. However, rules can be adjusted to needs (AGM batteries have much better surge capability than flooded cell batteries; if you use a lot of Watt*Hours per day, you will need a larger battery bank/solar array for satisfactory performance).

For an inverter... There are hundreds of inexpensive MSW (Modified Square Wave) inverters out there. For 80% of the 120 VAC appliances, they work OK. For 10%, MSW may cause the devices to overheat and/or fail (months, weeks, or even minutes to failure). It is not easy to predict which ones will work well or not.

If you have a bit of cash--I would suggest a TSW type inverter. Basically the same sine wave and voltage from your wall outlet. And the small stuff (like cell phone chargers, DVD player/TV/Computer wall transformers & power bricks) work fine... MSW is a toss of the dice sometimes.

I really like the Morning Star 300 Watt TSW 12 volt inverter. Has some high end features ("search mode" where it turns on for a moment, looks for 6+ watts of load, if no load found, goes to sleep for a short period; Also has a DC inhibit input--You don't need a big manual 200 amp switch to turn it off).

However, it probably is too large for a "small system" unless you accept the limitations (cannot run the inverter at 300-600 watts on a small battery--Cannot run large loads very long, etc.).

Exeltech and Samulex both make some smaller inverters (but still 10x the cost of a small MSW inverter). Look at the "standby" and no load losses--These can be significant on a small battery bank+solar panel system (part of your education).

You can read the Inverter FAQ's here:

All About Inverters
Choosing an inverter for water pumping

Beside the usual DMM (volt/amp/ohm meter--Try to get one that will read down to 200 mV scale)... Some other equipment to look at:

Hydrometer + Thermometer (for flooded cell batteries only)
Kill-a-Watt meter (measuring your 120 VAC loads and how much kWH per day they use)
a DC Amp*Hour / Watt*Hour meter (DC equivalent of a Kill-a-Watt)

When you get a full size battery bank/system--I really like to push a Battery Monitor--Roughly equivalent to adding a gas gauge to your car's fuel tank. (Victron Energy also makes nice battery monitors too). Probably too expensive for a small/experimental system (unless you plan on a larger bank in the future--tells you a lot about your charging/loads for your system).

If you eventually work with larger battery banks--A clamp on DC Amp Meter is really nice (something like this guy).

Here is a great thread that started from nothing and went through all of the issues/discussions for building a portable solar power center. Lots of information (not including building a PV panel).

Building an Emergency Solar Power system

And here is a thread that has pointers/information/links/further readings for anyone that has a "what if/what can I do with solar" type question:

Working Thread for Solar Beginner Post/FAQ

Most of us have made multiple expen$ive mi$take$ with solar systems... Everyone here is trying to be helpful and try to limit your costs and other issues. But, people want to experiment too...

I will stop typing here...

-Bill

By the way, neither of us Moderators (Niel nor myself) work for NAWS--We are volunteers here for Spam control (boy--lots of that in the last few weeks :grr).

Windsun and Rick are the only two people where with NAWS--The rest are also volunteering answers (and questions and opinions ) to keep the forum humming.

-Bill