ST head modification for 48 volt battery charging

[mobile_bob]

they average about 85% and some a bit higher at 88%
but so far i have never seen one of the larger ups systems over 88% efficient.

many of the big boys are tough as a tiger tank, and long lived, but not quite
as efficient as modern purpose built inverters.

bob g

[BruceM]

Power mosfets have improved so much in the last 5 years, I've thrown away all my old IGBT transistor and older mosfet data sheets.  The older UPS inverters are a bit less efficient primarily due to switching losses.  Switching efficiency and speed is so much better now that a higher switching frequency is also used, which allows smaller inductors; that helps (potentially) with resistive losses, and reduces overall size and weight, too.  Just in the last 3 years, high voltage Mosfets have improved dramatically.  It's going to be hard to find IGBT transistors in a few years, they used to rule the high voltage switching world.

[Jedon]

<quote>I wonder what it's efficiency is ?</quote>

Well they claim 90% for the FE series, this is the older FD series, Best Power got bought by Powerware who got bought by Eaton so docs are hard to find.

[mobile_bob]

you betcha docs are expensive

i bought a 15kva 3phase inverter surplus for 25 bucks, it weighed about 4k lbs with the battery cabinets, the power conditioner cabinet
and distribution cabinet

really clean unit needing new batteries, 240dc front end buss, yikes!

called eaton, which bought out exide, blah, blah blah

well they thought they might have a copy of the owners manual, hmmmm
why yes we do!!

how much?

1800 bucks and change!

oh really!!!

i can't imagine they have sold a single copy since i asked for one 4 or 5 years ago, and my copy has probably ended up in a shredder by now.

they sure were proud of a product that they no longer sold or supported!

i guess they got stiffed on manuals and decided they would recoup their losses all on me?



bob g

[mobile_bob]

why don't you tell us how your really feel?

i had a similar experience years ago with triplite, and to this day i will never use another of their products

the only thing i can say positive about them, was the engineering dept sent me replacement final drive transistors
so i could fix it, only to have it fail again later,

bought another and it lasted all of about 10 minutes, got it warrantee'd

that one lasted about a month till someone stole it,

to be honest i wasn't even that pissed off about it being stolen!

i figured the thief got the short end of that deal

bob g

[Jedon]

I got mine free from a buddy at work, it used to back up a bank. There are a bunch of AGM batteries in it, no idea if they are still good or not, I've never dared to hook it all up yet.
I'm trying to figure out if I should try and use it as is, take parts out for other projects ( transformer for the ST-5? ), or try and sell it.

I have a couple triplites that won't work with my inverters or generators.

[mobile_bob]

apc?

now that is one ups/inverter that i have had very good luck with.

the only ones that have failed have done so because of me trying to "hack" one of them.
(yes in this case, i would call what i was doing a "hack", because i had no clue what i was doing
and the results were less than expected)



apart from that, the vast majority of used apc units have worked just fine after changing out the dead batteries.

bob g

[Geno]

Well they claim 90% for the FE series, this is the older FD series, Best Power got bought by Powerware who got bought by Eaton so docs are hard to find.

I've got the paper back install docs for the FD series and a bunch of original paperwork that came with my unit. Once you get into the serial port there are all sorts of parameters that can be looked at and tweaked. Gotta know the right passwords though. I also have pdf files for the FE series but their pretty easy to find.

I only want $1799.00 +shipping We can start the bidding for the passwords on another thread

Actually I'll be happy to scan them in if anybody wants a copy.

Eaton obviously wants to sell new units, which is probably why they're hard to work with. They wanted $1500.00 to sell me the parts to convert mine from 208 to 120. I don't know about the FE's but these FD's never die. I had a few out in the field that ran great. I was there when the one I have was installed by a certified Best tech. I know for a fact it has survived multiple lightning strikes and never once required any maintenance. When I got it, it still had the original batteries which had very low capacity but would keep things running for a few minutes and still passed the daily self test. The cooling fans ran virtually nonstop from 1992-2008 when I got it.

Thanks, Geno

[Jedon]

Geno that's great that you have experience with the units and have the docs! I'll start my bidding at a few decimal places to the left :-D
So the real question is, say I hook this up in between my ST-5 and my inverters, or between the inverters and the house power?

[Geno]

If you don't need it don't hook it up at all. Mine is a 5.3kva and uses at least 300 watts doing nothing but sitting there. The only reason I'm using it is because it was free and I don't have a "real" inverter. It hums and buzzes like crazy also. I'm sure there are some good parts inside. The transfer switches are very high power. The ferroresonant transformer is a gem but probably pretty inefficient too. Others will be able to offer better suggestions on alternate uses for it or it's guts.

Thanks, Geno

[Jedon]

<quote>If you don't need it don't hook it up at all</quote>

Well I do have some problems I would like to solve, like the lights flickering when the generator is running and with the 6/1 & ST-5 the lazy governor giving me high ( 138V ) then low ( 104V ) depending on load. I know there are other ways to solve these issues but they all seem to involve a weekend and $500 or so 

[Geno]

Well, that's different. You could just set up the ST5 for 240 and plug it right into the UPS. The wiring labeling under the cover on the back is pretty self explanatory on my unit. If you go outside of the high or low voltage parameters it will bitch, got to inverter mode or shutdown. I wonder if it will keep the 120v legs balanced??? Either way you'll have steady, flicker free power.

Thanks, Geno

[BruceM]

Jedon,
138 to 104V is very bad, even for an ST head on harmonic.  Some of that is governor, as you suspected.  You didn't mention rpm or frequency variation.  Start with the governor.

The typical fix for governor is replacing the spring.  A set of springs from ACE that are slightly softer than the stock spring isn't going to set you back too much.  Inspecting and cleaning up the "Y" yoke piece that connects to the rack is also a good idea- this piece often binds.  I had to rebush mine, as the fit was so sloppy.

Georgia Generator has AVRs for $59.  That would keep your voltage constant regardless of load.

[bschwartz]

------ UPDATE ON THE BS-ST head mod ------

I've got the head back together with wires hanging out of the doghouse for testing.
I connected the coils 180 degrees apart instead of the stock 90.
Results so far are interesting.
Groaning on uneven loads seems much better (less groaning).
Unfortunately, the reason I abandoned the ST-5 head in favor of the 6.5 PMG still stands.
When one leg gets loaded more than the other, it's voltage drops, and the other leg goes up.
I haven't done any real testing as far as measuring loads etc., but I've already had one leg at 111v and the other at 127v.  Not horrible, but not the rock steady voltages I've had with the PMG.

As far as the original concept of modification for 48 volt battery charging, I'd rate the mod successful for now as I did separate the coils and can now get ~60v from each coil and externally connect them for 60v, 120v, 240v.  I'm sure if I wanted, I could connect two in series for 120v, and parallel the other two for 60v to rectify for battery charging or grid tie etc.

[mobile_bob]

127 volts is at the top end of the north american standard, while 108 is at the bottom end iirc
looks like even though they are uneven when one is loaded, it is still within spec's?

otherwise, good job !!

thanks for the update

bob g