A Hybrid Solar Home Power System

Actually I meant absorbed glass-mat (AGM) batteries. You list them in your post.

That is exactly the ones I meant:- costly, easily damaged and short lived......plus points are quickly charged, can be used at any angle and don't gas....unless overcharged......

Please post a link supporting your own thoughts on using them for Solar applications. I could find nothing that would convince me to either buy or use them.....

Thanks in advance.

They seem to be the standard in the industry given the price and performance. The sources are many on the internet, but I am open to something better. What is common in Germany?

I have been considering adding a PV system to my house at some point and the predominantly recommended battery system is AGM.

Golf cart LA batteries are another substitute, but not as good as AGM.

A lot of the battery performance depends how they are charged and discharged and to what levels. The 4 to 8 year duty life sounds about right for AGM.

Wiki does not seem to like them much.......

I have never used them myself, too expensive over here, which always put me off first....I am a patron of leisure batteries, which give me a great life span.......but thats just me......

Though reading around, unless some major improvements are made to AGMs, its most unlikely that I will ever want one. But each to his won preferred Type.

The killer from me would be firstly the price (here) and secondly the need I have to be able to occasionally "top-up" from a car alternator, which would damage an AGM. I stay on some campsites with no amenities at all, they are always the best ones.....

See here:-

Thanks. I am thinking that golf cart batteries are a better investment for my needs. I won't be hauling them around, I just thinking about backup power when we lose it due to storms.

Now that I must agree with, though they are less easy to find here....

But I am not in the Solar business, except to assist some friends from time to time. I am still of the opinion that Solar cells are simply not good enough yet....and I also believe that some breakthroughs in both price and efficiency are LONG overdue.

Though relatively recent improvements with water cooling (Solar cells do not like getting hot strangely enough!!) allows water to be heated for other uses and the Solar cells to be cooled!!! There are even cooling units designed to be added to older Solar Cell installations. These improvements alone improve efficiency dramatically!

You can read more here:-

Hybrid-solar-panels-convert- heat-stress-into-hot-water

The first sentence makes immediate sense to almost anyone:-

A new design that improves solar PV panel efficiency by turning "heat stress" into hot water is surprising, but perhaps only because we wonder why someone didn't do it sooner.

The efficiency improvements appear to be as follows:-

Water-cooled PV panels reportedly deliver efficiencies of up to 28 percent while also providing 140 to 160-degree (F) water (the normal setting on a hot water heater is between 120 °F and 140 °F).

In some countries, here for example, Solar companies are not surviving without government help, and that help is disappearing fast!!

The Chinese Solar cells are also often short lived......efficiency, never good, gets worse rapidly....but we still have fields and roofs full of them here.....

Wind and water power are still better bets to my mind, though water will not appeal to many, being impractical unless you have a lot of land.....and both work day and night, like we do......

The GC2 is ubiquitous and inexpensive because of the sales volume. I think the GC2 from Sam's or other similar retailer is probably your best A-Hr/$ going.

I switched out a Group 27 AGM on my travel trailer for a pair of GC2's. The first set (used from my Dad's boat) went six years before I needed to replace them. And we used the hell out of our trailer.

There are Lead Acid batteries specifically designed for solar applications.

Please have a look at this link,

http://www.exide4u.com/exide/JSP/masters/apnpro/solar.htm

Both VRLA and flooded batteries are produced for solar power purposes.

So I not sure why you infer Lead Acid batteries will degenerate.

If the battery bank is on float charging mode, will it get fully charged?

Really depends on the load and the capacity/current limit of your rectifiers.....but assuming the rectifiers are capable of supplying both the load and charging the batteries then float charging will eventually fully charge a battery if the juice is not interrupted. It's done on every cell site, telephone exchange, datacentre, diverse UPS, and other mission critical installations on the planet (assuming they are correctly designed, implemented and maintained that is) There are other examples.

A common eg.. the battery in your car is float charged and eventually fully charged when the engine is running even with all your lights and other electrical accessories turned on.....providing you do not exceed the alternator's current limit and you give the battery enough time to charge.

Fully charging every time, can age many types of battery.....faster than NOT fully charging......also, fully charging some batteries will drive off water and or chemicals....

You must read the manufacturers infos fully and compare types.....it is not safe to generalise too often though.....

Exactly. Economics would dictate the priorities as follows:

1. as much solar power as possible via the battery storage
2. utility to top-up the solar
3. generator if neither of the above is available.

Add a wind powered generator too.

...with the wind having the same priority as the solar in #15 above. Good point.

Hello Anindya,

Here is a sample system.

1.) 4 or 6-250 watt 60-cell modules (depending on budget) and 1 Midnight Solar Kid MPPT 30A. (Two Kids can run in parallel for a larger array.)

2.) One battery bank up to three series strings.

3.) Battery charger output included in inverter. #4 below.

4.) Outback Power GFX International Series Grid Tie Inverter/Charger, 24(or 48)VDC 120 Vac/60 Hz.

5.) Gen-set with auto start. Inverter with generator support like #4 above.

6.) Over charge protection is in charge controller, discharge protection is in inverter. These are both highly configurable.

This sample system is grid-tie (sell), with battery back-up, and generator support. It would work well with a net-metering interconnection agreement. Consult your local utility and read their renewable energy interconnection agreement before buying any equipment.

In this scenario the array would charge the batteries and maintain them, then excess power would be made available to the loads attached to the inverter to either be consume by the loads or (if sell is enabled) sold back through the meter (or consumed by other loads on the service panel). In the event of a power outage the loads on the inverter would be powered by batteries, if the batteries drop below 50%, the gen-set would start and run until they were charged.

The technology is available to accomplish what you are asking but using different methods. You will have to carefully select what loads will be powered by the inverter.

Start with your battery pack. This is the single most important component of your system. With a gen-set you can use a smaller pack. Size it based on how long you want to run your loads, during an outage, before the gen-set comes on.

A $2,500 USD battery bank example:

16-6 volt Interstate deep cycle FLA Batteries (6V, 216AH)

2 strings, 8 batteries each

216 amp hours at 48 volts nominal per string.

Total capacity: 432 amp hours at 48 volts. 20,736 Watt-Hours.

Usable capacity (50%): 10,368 Watt-Hours.

Size your inverter based on the loads you want to run on the system. Size your battery bank by how long you want to run the loads (without gen-set). Size your array based on how much you want to produce (PVWatts is a good tool to estimate production) and size your charge controller based on your array's voltage and amperage.

Hope this helps a little.