Re: [pvusers] Need advice on using UPS as inverter

[Christopher Witmer <cdwitmer@spamcop.net>]

Robert Warren wrote:

 >  What is it you are really trying to do? [SNIP]

 >  . . . the whole point of your search for an inverter is to marry it 
to a PV charging source, is it not? Why fool around with an AC charger, 
as finding a 48 volt charger that will be compatible to the UPS as well 
as the batteries can give you other problems, mainly due to 
compatibility of the high voltage cut-off points.


Initially I need to be able to charge either from PV panels or from the 
grid (or a generator). In fact, initially I won't even have PV panels
attached. Ultimately I want to rely primarily on PV as my power source. 
I'll be making the move away from the grid in several stages.

 >  I do not recommend trying to modify a UPS into home-made, off-grid 
inverters. It is far better to put in a few extra hours, earn the money, 
and buy something that was made for the job.


I can't thank you (and all the others who replied) enough for your 
excellent advice. I understand that this is not the best route for an 
inexperienced person to take. But decent inverter/chargers (such as 
those from Xantrex) for the Japanese PV market are SO-O-O-O expensive, 
and on the small side, so two units are required -- double the pain in 
the pocket book. A kludge solution held together with string and 
adhesive tape seems to be about all that I can afford. If I lived in a 
region that had a larger market and a better selection of relatively 
inexpensive inverters, I wouldn't give my proposed DIY approach a second 
thought. 50Hz/100VAC . . . what a stupid idea for a standard.

Gratefully,

Christopher Witmer

 > ----- Original Message -----
 > From: "kirk" <kirk@3rivers.net>
 > Date: Thu, 12 Sep 2002 21:05:19 -0600
 > To: "''Christopher Witmer''" <cdwitmer@spamcop.net>
 > Subject: RE: [pvusers] Need advice on using UPS as inverter
 >
 >
 >
 >>It sees a voltage source and has no idea what its capacity is. It 
doesn't know the size of the battery. This can be a problem if heatsink is
 >>inadequate and it relies on the battery being small enough that charge
 >>tapers and keeps thermal dissipation within available mass and 
surface area of sink. A large cell may keep charge too high for too 
long. Likewise time or duty cycle of operation may be too long for 
output heatsink if it is designed for 45 minutes at max power and you 
want to run it for hours and can with large bank.
 >>
 >>Hard to believe a pure sine for $60.
 >>
 >>Kirk
 >>
 >>-----Original Message-----
 >>From: cdwitmer@spamcop.net
 >>Subject: [pvusers] Need advice on using UPS as inverter
 >>
 >>
 >>In Japan I have been having a very hard time finding an affordable DC-AC
 >>inverter; however, it isn't hard to find a large UPS that needs
 >>batteries. For example, I just found a used APC Matrix 5000 (a pure sine
 >>wave unit) now being sold for the equivalent of about $60. (This
 >>particular unit is being sold without batteries.)
 >>
 >>This UPS is designed to work with any number of add-on battery packs,
 >>each 48v/17ah. (APC calls these "Smartcell" batteries and of course they
 >>have a multi-wire connector of a unique design.) Instead of the
 >>manufacturer's recommended battery packs, I want to use one BIG 48v
 >>battery string -- e.g., something in the range of 600-1000ah.
 >>
 >>I imagine I will have to overcome two obstacles: 1) to get the inverter
 >>to accept a different battery than it expects, and 2) to recharge the
 >>battery string without using the inverter's built-in recharge function.
 >>(It takes eight hours for this UPS to recharge 10 battery packs -- just
 >>170ah. That means it would take 35-60 hours to recharge the large
 >>battery string I'm contemplating.)
 >>
 >>I have access to a separate charger for the batteries, but does anyone
 >>care to speculate how easy it will be to get the inverter to accept my
 >>large battery string and function as I require?
 >>
 >>Basically, I'm worried that the UPS might have some built-in self-test
 >>function and when it detects that something is not just as expected, it
 >>will refuse to function at all, and I won't be able to override or work
 >>around that.
 >>
 >>Any thoughts? Thanks!
 >>
 >>Christopher Witmer
 >>
 >>
 > What will we do if there is another fuel shortage?
 > Did you know that there is a pollution free, completely renewable 
fuel which you can use right now in your own car?
 > Don't replace the engine, replace the fuel. Check out my website on 
making your own fuel:
 > http://running_on_alcohol.tripod.com
 > robertwarren@mail.com
 >
 >




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