Homebrew emergency power system - advice needed please

Hi

I could use some feedback regarding a brainstorm of mine. I'm in the process of building an emergency power system for home use.

The main questios are regarding supply and re-charging.

For the supply, for now I'm using 12V starting batteries. The plan is to pick up 2 (or possibly 4) 6V 156Ah golf cart batteries.

For the charger I mated a 63A Delco alternator with internal 12V regulatioin to a gas snowblower engine.

I want to use a 1500W inverter to supply about 180 watts of AC, 8x IR LED surveillance cameras, and about a dozen 20mA LED lamps for emergency lighting all operating at their native 12VDC

The questions are:

Would I be able to use my alternator/generator to charge the golf cart batteries without damaging them?

Until I'm able to get the golf cart batteries, would the couple starting batteries I have work OK?

TIA

Bob

Reply to
bobvalli
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Will you need a clutch between blower motor and alternator? what sort of control system to monitor the starting and running of the motor?

Reply to
N_Cook

Is that really a good idea? Gasoline is dangerous to store, without special tanks you may have building code or insurance problems.

Propane is a much better choice unless you are in a very cold climate. No one seems to be upset if you have a large "bottle" of propane around for your gas grill, RV, etc.

In many places, you can have two of them strapped to the back of trailer and no one pays attention to them. Try that with gasoline. :-)

12 lead acid battery chargers are cheap enough. You can buy ones that will not cook your batteries.

You also want more than 12 volts to charge the battery, that's why car electrical systems are 13.8 volts.

Depends upon how often you use them, how you charge them and how low you let them go. If you discharge any lead acid battery, it will stop working.

There are devices that control the output of batteries and shut them off when they get to the point they will be damaged. You probably want one, but at some time may have to decide if you want light or batteries.

Another cheap source of stored electricity is the NiMH slow discharge batteries. If you buy a bunch of them for your battery operated devices and cycle through them they will come in handy. They can easily be charged, there are lots of devices to do it.

Though IMHO, you would be better off not buying any of this stuff and spending your money on Solynda solar arrays while you can still get them, especially if you buy them at "gone out of business sale" prices.

Geoff.

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Geoffrey S. Mendelson N3OWJ/4X1GM
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Reply to
Geoffrey S. Mendelson

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Thanks for the quick replies. As for the DC generator, the unit is belt driven and will be left outside. There are terminals on the generator that turn on the field once the engine has started. I explored solar but its too much for my budget, and again, for now this is for emergency use only. My idea is that with the 63A generator, that I'd like to get 6 to 8 hours of battery time (discharging the batteries to about 40%) and then use the DC generator to do a quick charge for an additional 6 to 8 hours of run time, ad infinitum. Monitoring would be done manually. My biggest question is whether this "quick charge" will destroy the golf cart batteries.

Reply to
bobvalli

You don't need a clutch. if the motor can't handle startup with the alternator, put a switch or time delay relay between the alternator & the load. Since the current output of the alternator doesn't rise at lower RPMs, the motor should have no problem coming up to operating speed without a clutch.

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You can't have a sense of humor, if you have no sense.
Reply to
Michael A. Terrell

Need similar system. Would you post a description of your camera system? Where you got it, costs, pros/cons, etc?

Reply to
Robert Macy

Need similar system. Would you post a description of your camera system? Where you got it, costs, pros/cons, etc?

Reply to
Robert Macy

Starting batteries don't last long if discharged below the 80% of charge level. The golf cart batteries will last much longer, but the best life will be achieved if the discharge is limited to 50% or less. The 63A altenator will only provide 63A if running at high speed (5000-6000 rpm) so you'd need to adjust pulley sizes to get full power when driving it with a 3000-3600 rpm engine. The rate of charge is also dependent on the battery's state of charge, so it's unlikely that your proposed setup will harm the golf cart batteries. The bigger concern is what the end of charge voltage of the golf cart batteries should be versus the end of charge voltage the alternator and its regulator are designed for. The golf cart batteries are deep cycle and *may* have a different end point voltage - check the manufacturers specs.

Using an oversized inverter usually wastes battery power. Inverters have their "sweet spot" where they have optimum efficiency - usually somewhere in the 50%-90% load range. For longest battery life, you should replace the inverter with a smaller one - and look carefully at the no-load current requirement. Inverter idle drain isn't usually high on the list of features people look for - most people are looking at the maximum power they can get from it. I have a PowerStar UPG400 that idles at about 1 watt (that's about 0.1 amps). I would guess that your 1500 watt inverter idles at 6 watts (0.5amps) - probably more. The UPG400 was a serendipity buy - $24.50 plus shipping (couple of pounds) - from a closeout at hsc.com n Dec 2009. Until I did research, I had no idea that a 1990-91 vintage inverter could be so efficient. Only wish I had known more about it sooner and been able to purchase several.

I'm not an expert on backup/standby power, but I've had emergency generators (one 1850 watt and one 5000 watt) for some time. Two generators? Yes, the little one if rotating power to one item at a time -freezer, fridge, etc - is adequate, the big one if multiple appliances are needed simultaneously -i.e., furnace and microwave oven. The little gen runs a lot longer on a gallon of gas than the big one at the same load.

I've been doing a lot of research recently before setting up a small solar system (70AH battery, 45 watt solar array) for testing. I've even measured the drain the solar charge controller puts on the battery - while it's typically in the milliamp range, some use two or three times as much as others. Solar amps are expensive, so I'm looking to get as many of them as possible to the load, not the control electronics. Lots of LED's on the controller *look* impressive, but require a lot of milliamps to be visible in sunlight. An analog meter or an LCD panel with no backlight (or a switchable backlight) requires less power to operate.

John

Reply to
news

It's interesting how a bunch of individual stuff that seemed like a good idea at the time can get combined into a less than optimal solution. Been there, done that...lotsa times.

How often does the power go off and for how long? I got a great deal on an impulse purchase at a garage sale. Now, I have a 5kw generator and a DIY transfer switch. When I did the plan to install it, I discovered that the cost of the permits and inspections cost more than the generator. Reviewing the outage history, I determined that I only *needed* one thing. I didn't want the pipes to freeze in the winter. In 40 years, the power has never been off that long. The solution was to put a disconnect on the gas furnace air handler so I could run it off a MUCH smaller generator. "Just because I can" was insufficient motivation to continue the project. Anybody wanna buy a 5kw generator and transfer switch?

I've found that an effective strategy for dealing with a power outage is to take a nap. I don't need any power at all to do that.

Some things to think about...

Batteries have a temperature coefficient. The alternator's internal regulator probably compensates for that...for the designed battery chemistry. If the batteries and generator are in different locations with significant temperature difference, that may be an issue. Worth checking.

Golf cart batteries are VERY expensive. Capacity may be a significant function of temperature. Most people don't golf in the dead of winter.

If you do the math, you might discover that using the existing batteries for short outages and running the generator continuously for the long ones to be cost effective. The losses in the charge/discharge processes may be more than the difference in efficiency running the generator in spurts.

Harbor Freight will sell you a 800W 120VAC generator for $90. It's a crap generator and probably won't last long...but how long does it have to run? Probably a lot cheaper than golf cart batteries...and has other uses.

As a matter of curiosity... More than one person mentioned the security cameras. Unless you're prepared to confront the gang of pillagers with your trusty shotgun, what good is a security camera during a protracted power outage? The cops are gonna be busy elsewhere.

The 180W is an interesting number. Can't do much at all with

180W. And you can do almost as much with 90W or 30W. Attacking the load problem at the point of use might improve the numbers. You're gonna have to run separate wiring anyway...if you want to meet code. Might want to review your fire insurance to see if it says anything about "user installed" electrical stuff. The cost of meeting code and passing inspections was what killed my generator project.
Reply to
mike

Per mike:

As one with zero practical experience - but who has been dabbling in IP cams since being anointed to set up a surfcam for a local windsurfing shop....

They may want the still photos that some cams can take/store automatically - for later use.

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PeteCresswell
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(PeteCresswell)

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