Re: (ET) More Power Inverters

["Chapin, Tim" <tchapin bf umich edu>]

I have picked up a number of ups's from recycle centers free.  The
batteries go bad and people drop them off on the junk battery pile.
Most are small 1000 watt surge 650 normal. But have picked up 2500 watt
surge 1500 normal for $40.  Most are 24v some are 12v.  I use them to
run the TV/vcr/dvd a light and stove blower fan off off external
batteries that are setting around. We live on a lake, I always have boat
batteries around.  Pontoon boat is a hybred and has 4 12v deep cycles
for it.   The biggest problem is they will only kick to battery mode
when the power is interrupted.  I end up faking them out with a cheap
300 watt car inverter to get them going.  Kind of like the gas kicker
motor on the old John Deere diesel tractors. 

 This is for short term electrical outages (we get them a lot).  After a
day, the wife forces me to get out the gas generator to get water (well
system) and to flush the toilet and take showers (grinder/pump system).

-----Original Message-----
From: elec-trak-bounces cosmos phy tufts edu
[mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of
subscriptions aeolusdevelopment com
Sent: Wednesday, December 12, 2007 9:34 AM
To: elec-trak cosmos phy tufts edu
Subject: Re: (ET) More Power Inverters

Bill Alburty wrote
>I was probably nearly correct about the amps pulled by my furnace 
>blower ( I said it was 11). I had estimated 11, allowing for a big 
>surge. So I measured it. The start up surge went to 8.4 on my galvo 
>type meter ( but the actual peak, if displayed on a scope, could be 
>twice that for a very short time). Suppressing that surge may be the 
>key to making an inverter do the job without kicking circuit breakers.

>The run current measured only 4.7 amps, indicating that 115  X 4.7  = 
>540 VA would  handle the running current.

That's a lot better (nearly 7 hrs off of a 100Ahr pack).  Less due to
efficiency and load issues.  More since the pack is larger and you
presumably won't run the fan 100% of the time.

>A 1kw inverter is therefore probably enough to run a furnace, 
>refrigerator, a TV, and a few lights (for running current only). Would 
>a big capacitor handle that pesky surge?

Capacitors are not the issue.  The inverter's power semiconductors are
going to be the limiting factor in a surge.

>    Whats bothering me now is Russ's getting only 6-9 hours out of the
>36 volt pack. I was hoping for for much longer.

Call it a lesson in the energy density of a battery.  

You might keep the furnace running for a while but other than that you
would want to rely on time tested methods for making it through a winter
power outage.  Early to bed, leave the refrigerator closed (or use the
great outdoor fridge ), candles, lamps and radio.

Robert


--------------------------------------------------------------------
mail2web.com - What can On Demand Business Solutions do for you?
http://link.mail2web.com/Business/SharePoint



_______________________________________________
Elec-trak mailing list
Elec-trak cosmos phy tufts edu
https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak