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Battery power


wwc's Avatar
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01-03-09, 08:25 PM   #1  
Battery power

I'm thinking about a DIY emergency power system for my home and i was reading a article on the subject and the guy made alot of sense to me untill it came time to doing the math,lol.

Here is what he has and says ....

accessory , hours used , amp draw , amp hours used daily

TV , 6.5 , 3 , 19.5

coffee pot , 4 , 2 , 8

4 light bulbs , 4 , 8.33 each , 133.33

small fridge , 24 , 2 , 48
,
total 208.83

plus 20% for inverter use and safety , 250.6

He says a 1600 watt atleast would be needed for a inverter along with enough batterys to store twice the amount needed daily.


I figure he would need atleast a 3000 watt inverter, am I wrong, please explain it to me.


Last edited by wwc; 01-03-09 at 08:32 PM. Reason: clarity
 
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Speedwrench's Avatar
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01-03-09, 08:40 PM   #2  
starting amps for the frig will be high enough to kill a 1600 watt inverter, also 1600 watt inverter will draw at least40 amps continuously which will kill a deep cycle batt in less than 24 hrs.

if we're not supposed to eat animals why are they made out of meat?

 
wwc's Avatar
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01-03-09, 08:46 PM   #3  
I think this setup is supposed to be used with about three or four good car batteries too. not even deep cycle.

 
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01-04-09, 04:55 AM   #4  
Posted By: wwc I think this setup is supposed to be used with about three or four good car batteries too. not even deep cycle.
If you have a normal or large size refrigerator it typically is impractical to run the refrigerator or heater fan off of car batteries or deep cycle batteries. The capacity of the batteries is too low; and typically youíre not going to get the full capacity out of the batteries because you deeper you draw the batteries the more likely they are to sulfate and become useless. The more deeper you draw down a battery the more likely it is to for sulfate; and the longer you leave it in a discharge state; the more damage it does to the battery. Thatís why most modern advanced inverters have voltage detection built in; so the inverter shuts down after the battery voltage starts to drop. This helps protect the batteries; but prevents you from getting the full capacity out of the batteries; if you donít charge the batteries up soon; they are likely to become significantly damaged anyway.

In most cases it is best to use a backup generator instead. With something like a refrigerator you donít necessarily have to run a generator for 24 hours straight; if you run it for about four hours every 12 hours it would likely be enough to keep your food from spoiling in the freezer and refrigerator as long as youíre not opening and closing them frequently with the power off.

As far as using standard automotive batteries to power an inverter; thatís really not a good idea. Regular starter batteries are not designed to be deeply drawn down. If you use a starter battery to drive an inverter it will lose a significant amount of its capacity in about 5 or 10 cycles; whereas a deep cycle under the same conditions will probably lose about the same amount of capacity in about 25 to 50 cycles. Whether it be a starter battery or a deep cycle battery; the deeper you draw down a lead acid battery the more you reduce the life and capacity of the battery; the longer you leave it discharged the more you reduce the capacity and life of the battery. A battery's shelf life if itís not used but kept charge is about four years. Considering all those factors; for most people a backup generator would be a more practical power supply for something like a refrigerator or and a house heating blower fan motor.

Sure yes it is possible to power an something like a refrigerator off of car batteries; but is likely to damage the batteries and not be very practical.

The math and the reality does not quite match the fantasy of running (and sustaining) a refrigerator off of car batteries and inverter.

 
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01-04-09, 08:12 AM   #5  
Posted By: wwc I think this setup is supposed to be used with about three or four good car batteries too. not even deep cycle.


You have to be careful when using car batteries for these kind of applications, they need ventilation and release gases which are dangerous if not ventilated properly.


For indoor applications it's much safer to use Sealed Lead Acid, even deep cycle batteries.


Tony,


Last edited by Shadeladie; 01-04-09 at 08:48 AM. Reason: Link removed. Advertising not allowed.
 
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01-04-09, 08:16 AM   #6  
Posted By: SchemeFighter If you have a normal or large size refrigerator it typically is impractical to run the refrigerator or heater fan off of car batteries or deep cycle batteries. The capacity of the batteries is too low; and typically youíre not going to get the full capacity out of the batteries because you deeper you draw the batteries the more likely they are to sulfate and become useless. The more deeper you draw down a battery the more likely it is to for sulfate; and the longer you leave it in a discharge state; the more damage it does to the battery. Thatís why most modern advanced inverters have voltage detection built in; so the inverter shuts down after the battery voltage starts to drop. This helps protect the batteries; but prevents you from getting the full capacity out of the batteries; if you donít charge the batteries up soon; they are likely to become significantly damaged anyway.

In most cases it is best to use a backup generator instead. With something like a refrigerator you donít necessarily have to run a generator for 24 hours straight; if you run it for about four hours every 12 hours it would likely be enough to keep your food from spoiling in the freezer and refrigerator as long as youíre not opening and closing them frequently with the power off.

As far as using standard automotive batteries to power an inverter; thatís really not a good idea. Regular starter batteries are not designed to be deeply drawn down. If you use a starter battery to drive an inverter it will lose a significant amount of its capacity in about 5 or 10 cycles; whereas a deep cycle under the same conditions will probably lose about the same amount of capacity in about 25 to 50 cycles. Whether it be a starter battery or a deep cycle battery; the deeper you draw down a lead acid battery the more you reduce the life and capacity of the battery; the longer you leave it discharged the more you reduce the capacity and life of the battery. A battery's shelf life if itís not used but kept charge is about four years. Considering all those factors; for most people a backup generator would be a more practical power supply for something like a refrigerator or and a house heating blower fan motor.

Sure yes it is possible to power an something like a refrigerator off of car batteries; but is likely to damage the batteries and not be very practical.

The math and the reality does not quite match the fantasy of running (and sustaining) a refrigerator off of car batteries and inverter.

There are UPSs designed for appliances specifically, such as fridges or furnaces. Usually they're dedicated specifically to the appliance.

The appliance style UPSs can handle a start up current from a fridge or a motor.


A fridge style UPS that can back up a fridge for 12-24 hours costs about $1K.


It might be worth while to invest in a generator!



Tony,


Last edited by Shadeladie; 01-04-09 at 08:49 AM. Reason: Link removed. Advertising not allowed.
 
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05-26-09, 01:24 PM   #7  
WWC-

Here's an option you might consider: Use a big (and I mean really BIG) inverter to power your house (you will need two to generate the 120/240 split-phase found in nearly every house in North Amercia) for only a short time, say, like two-three minutes. Since you will need a gen-set to power critical loads during a power failure, the DC-AC inverter arrangenent can serve as a "Bridge" from the instant AC power goes down until the Gen-set starts. The Generator can then slowly recharge the batteries once it's going, while powering your household needs. With a little thought, you can connect this Generator-battery-inverter arrnagement to your whole house and exercise good load management (turning off circuit breakers that are not absolutely necessary (like most electronics), and leave on the critical ones, like fridge, furnace blower motor, and a few critical lights. If you're interested, I could provide some more detail on how this is done, 'cuz I've been thinking of doing this to my house for a very long time.

Here's the scenario:

AC Utility power on- life's good. Utility power fails, DC-AC Inverter system kicks in within one-half cycle (typically 8.33mS), provifing an almost uninterrupted source of power. A momnetary flicker of the lights would be the only sign of a power failure. While this is going on, your stand-by gen-set's controller is deciding if this is a real power outage or just a brown-out. This usually takes anywhere from thirty seconds to two minutes before the gen-set actually starts. Once the gen-set starts (and auto-switches the house over to generator Power), the inverter shuts down, and the battery bank now re-charges of gen-power. Thi big thing hereis that in the event of a power failure, you have a truly uninterrupted source of power (or nearly so).

Hope this helps.

Steve

 
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05-26-09, 02:27 PM   #8  
thanks for the replys.
Steve, thanks for your help but i don't think i can invest in a system like you described.

I was looking into a dirt cheap emergency system , I checked into solar ideas and they are very expensive and it takes a lot of them to power anything it seems.
I would like to atleast be able to power by the sun a small bar type fridge on the cheap.

 
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05-26-09, 04:18 PM   #9  
As small as a bar fridge seems to be under normal circumstances when you try to power it up with any battery powered back-up system it becomes a huge current draw.
Using an inverter with batteries is an extremely short lived power source.
Adding other household devices to an inverter is quite frankly insane.

Everything will hum along great until the batteries die and you need as much power to recharge and maintain them as it would to just power up the appliances in the first place.
It is cost prohibitive to have large enough solar panels, home scale wind power or even a Gerbils on wheels to recharge the batteries quick enough.

Inverters are designed for short term power back-up as in many minutes or an hour or two as opposed for any sustained outage.
Under normal circumstances a battery powered inverter is designed to handle the instant switching of a load and a generator feeds as much power to the inverter as it uses to sustain itself over time.

I live in a rural area with occasional outages but having worked with large scale inverters in a casino and now with back-up systems in a hospital I still can't find a hobby priced, practical back-up system.

For me an inexpensive 5kw generator, a 12 volt back-up sump pump and an 800 watt inverter on a couple of large floor machine batteries will keep me going for as long as my gasoline lasts.

It is nice to dream about this stuff but put quite simply, back-up power is very expensive.


GregH.........HVAC/R Tech

 
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05-26-09, 04:39 PM   #10  
There was a series of articles a few years back in either PM or PS about a family who lived off the grid for a year. Had some great info about all the questions brought up in this thread.


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05-27-09, 06:35 AM   #11  
You can live off grid everyday
Off grid living is not difficult as you have to know how to correctly do it,,no your not gonn'a run your hvac.
Also there are vent kits for non sealed batteries.
1st step is cfl's than KVAR than choose what your going to run,,mainly lights and small loads,but yes tv and computer can be run to..
I can explain more later as I have to go to work,
Main thing is a Timer!!!!!! Too switch off utility at certain time and kick back to utility at certain time.

Off grid works !!!!
Great site by the way

 
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