auto changer

Hi, I hope this helps.

Trying to replace the grid, in the average home, can cost $20,000+. The first part of any good solar plan is to trim the fat. High efficient bulbs, appliances, pumps, alternate heat, propane/gas stove, on-demand propane hot water heater, are all good starts. I purchased the book The Home Energy Diet from Backwoods Solar. A very helpfull book. One of their tips talks about phantom power. Some appliances actually draw power even when they're off. It adds up at the end of the month. A cheap switchable power strip solves that problem.

Once you calculate your minimum kilowatt (kW) usage from your power bill, you can start building your system.

The basic components include:

Solar panel(s) - Can be wired in series or parallel to produce 12, 24 or 48 volts. There are several reasons for picking the proper voltage but 12v works well with a basic setup and with wire runs less than a 100' to the charge contoller.

Charge Controller - All solar panels wire directly to the charge controller. The CC then regulates the amount of juice that goes into the battery(s). When the battery is charged, the CC backs off to a float charge, basically keeping it topped off.

Battery(s) - This all comes down to how much power you want/need in reserve. They come in many different flavors. I decided to go with a couple of sealed AGM (absorbed glass mat) batteries. They're about the safest battery to keep in a living area (no fumes).

Inverter(s) - Inverters convert the DC current from the battery to AC household current

There are many other options. You can add a generator to supplement battery charging on overcast days and add a power transfer switch. These switches can be manual or automatically switch among solar, generator, or grid.

Backwoods Solar is the place to dive deeper into the subject.

He is not on the grid and only want to know how to start the gen-set to charge the batteries when the battery charge is getting low.

Hi guest

The gen-set supplier should have just that.

If not one can use a battery low charge alarm ($10-50) and replace the buzzer with electronics to start the gen-set.

They are everywhere. You may have such an alarm on your mobile.

Hello Guest,

If I understand you correctly, an UPS, should help you? It has an auto switch.

Perhaps you can try this site?

Industrial Switches Automatic Changeover. If EB supply fails, this system changes to the Generator Mode Automatically. ... now a days in flats and apartments as a back-up ...

catalogs.indiamart.com/products/industrial-switches.html - 65k - Cached

Good luck and let us know how you get on please.

Have a great new year.....................

Dear Friend

If you have any control circuit in your system which provides an indication or alarm for low battery, then your job is simpler. If a volt free ( potential free ) contact is available then interlock this contact in series with the battery such that it acts as a switch to start the genset. Once generator is started make sure that this contact opens IMMEDIATELY. If this does not open, then the situation is similar to that of the car key kept in constant starting position.

I can suggest you some set points, if you can tell me the battery voltage and generator voltage.

With good wishes for a happy, prosperous and peaceful new year.

Thanks and regards.

Ashok Toshniwal, Bangalore, India.

Dear Mr Shakir

Wish you a Happy New year 2009, I am sure I could do the change for you . For that I owuld like to know the details of the power thats is being generated and the supplied . This would help to suggest the right type of application too.

trust you would respond at st.choudhary@gmail.com

Best Regards

ST Choudhary

Try Deep Sea Electronics (DSE):- http://www.deepseaplc.com/

they are suppliers of controls to the gen.set OEMs (Original Equipment Manufacturers)

or FW Murphy :- http://www.fwmurphy.com/

I assume you are looking for a UPS (your battery backup) monitor to auto start the gen.set when the DC supply is low. The gen.set will have its own dedicated battery isolated from your UPS / DC supply so it is retained in a charged state.

You say you have no mains / grid - so what is your 'battery backup' backing up? Are you purely on a DC supply or do you have AC from another source e.g. gen.set or inverters. I ask as most systems are designed to monitor an AC output, even when charging a battery UPS (Uninterruptible Power Supply)

I once worked on a back up / gen.set charger for a mobile batter pack / DC supply, we had to specifically design a system as there was nothing Commercial Off The Shelf at that time to meet our spec.

However I believe there are some COTS units that could be used; but as I mentioned they usually monitor an AC (110 or 220 / 240~) signal, but also have a remote start facility.

The remote start could be activated by a battery monitor (as mentioned by a previous contributor) The gen.set would have its own dedicated starter battery and the unit also auto-started / maintained at least once a week to keep this in good condition (and replaced every year) - depending on how important continuity of your power supply is.

A more basic system could start the gen.set on a timer and charge the battery bank (& starter battery) for a set time each day to cover your drain / load on the battery bank. This is more economical & eco friendly than having a DC generator running all the time. It is used on sites for a non critical DC supply if the load will allow (mobile traffic lights etc.) It depends if the site is manned 24hrs so someone can manually start the gen.set if the battery bank gets low.

Hope this is food for thought and a Happy New Year.

PS - late edit to CJMcGill : just looked at your link after I posted; should have done that first as it would have saved me the effort, you seem to have recommended a solution already!