48V charging via ST generator and solar charge controller (no ST mod)

[BruceM]

Bob, That SD5 might be a real sweet setup for someone's off grid system. 

[Halfcrazy]

Bob what would you be looking to get? I may be interested in experimenting although I did hook 120 vac to my rectifiers and fed that into my 250 volt classic charge controller and it seemed to work fine I didn't push it past 40 amps output yet I wanted to get some software updated to give me a U pick mode first I was running in standard solar tracking mode.

[BruceM]

What make and model is your "classic" charge controller, Halfcrazy?  That's pretty sweet that it can take straight rectified 120V.  Even if starting with 240V, it's easy to find 240 to 120 step down transformers.

[mobile_bob]

as for cost of one of the sd5 heads,, let me check with my biz partner
he has one, and i have two

seeing how he was the one that suggested their use for battery charging, i want to allow him the first right
of refusal to sell, and get a price should he decide to sell.

if he tells me that he does not want to sell, i will then price one for sale.

what i would really like to have is an st5 or st7.5core, and would make a nice swap deal that would be fair.

i am thinking of rewinding an st5 or 7.5 for 12poles and replace the rotor with a custom clawpole lundell type
for ~400hz 3phase, , basically an oversized version of a truck alternator.

i think i could get 15-20kwatts pretty easy, although i really have no use for that much power, i do have the inverter
capacity to take that kind of power at 48volts nominal and put out very pure sine wave and rock steady no flicker power.

and i think i could get the alternator efficiency up to 85% plus without a huge effort.

or have the ability to run it at 600rpm for 60hz output, which might be useful for listeroid folks?

because of my physical limitations i am thinking of moving more into component development as opposed to complete systems
which i am now thinking may be of no use to me.

just trying to think ahead a bit
and look at my future from a realistic view

bob g

[mbryner]

Hi everyone,

We were camping on our land for the past 2 days, away from the forum.    Poured the last lift on the concrete block (filled all the cells) today.   Big day.  Lot of fun, except for the rain.

Bob, your SD5 gen may be just the ticket for me.   I could be interested in a swap.   Do you have any more info on that SD5?

Marcus

[mobile_bob]

i don't think i have anything on the sd5, but from memory it max's out at 160 amps, but at what voltage
i am not sure. i suspect it is probably around 30volts at full 160 amp load.

will have to look around this weekend and see if i can find any doc's with one of the heads, it all depends on how deeply they are stacked away.

bob g

[Halfcrazy]

Bruce I have all three models of the Classic controller from MidNite Solar. these 3 beta units are beta units I have been testing for MidNite for over a year. The units will be available to the public around may 2010. I was quite impressed that I got no display garbling or anything from the straight rectified ac. to be fair the ac was from the power co not a generator but I don't know how much difference that will make? I do intend to experiment with ac from my generator soon I should have updated software next week that will allow me to pick the target voltage I did not want the classic to do a sweep like it would on PV so I had to be careful. This is another nice feature software can be updated via usb cable or even over the home network or internet.

[Geno]

I'll be interested to see how you set the U-pick option and how it works. I tried it on my flexmax for a while and went back to sweep for some reason. Exact reasons escape me but I think varying voltage coming out of the rectifier had something to do with it.

Thanks, Geno

[BruceM]

Thanks, Halfcrazy.  I should have remembered you are the Midnite beta tester.

Another interesting issue would be what is the PF of the Midnite unit (or any other PV charge controller) attempting to charge from straight rectified AC.  There would be no PF correcting in a design for a PV power source.

Halfcrazy and/or Geno - can you measure your generator AC power out and then your charge controller DC output? (Maybe Geno already did this and I forgot.) If not very close, that would indicate that the PF issue is significant, and the need for an inductive filter remains for these units.

[Geno]

Bruce, I haven't measured power the way you suggest but it would certainly be a good idea. I think I'll start discharging the batteries right now and do a test later.

Thanks, Geno

[BruceM]

Thanks, Geno! 
Bruce

[Geno]

Listeroid 6/1 ST5
Killawatt on a current transformer.

There is a 75' run of 10 gauge cable to a step down transformer. It then goes into the rectifier which feeds the flexmax.

Killawatt readings
1470 watts
14.9 amps
117.6 volts
61.3 hz
Power factor .84

Flexmax readings in bulk charge mode
1250 watts
73 volts in
17.5 amps in
23 amps out
Battery voltage 52.8

I don't think the losses are to bad but if I could reduce them I wouldn't complain.

Thanks, Geno

[mobile_bob]

looks like your overall efficiency is actually quite good in my opinion

the flexmax i figure maybe 94%
that leaves about 88% for the transformer and transmission line

for an overall of 82.6%

not bad at all in my opinion for the distance involved, the transformer and the flexmax

the st head is about 80% so

80% x 82.6% = 66%

don't know how you can significantly improve on that, using all those components,

what is a very good 120 or 240vac charger for 48volts nominal these days in efficiency?

i guess if it is much better than 82.6%, maybe it would pay out over time?

probably take a very long time in light of how pricey they can be

thanks for the numbers

bob g

[BruceM]

Thanks so much for the lovely data set, Geno.  I know how much time it takes for this sort of thing and I know others, too, will also appreciate your efforts to share your pioneering work and data with us.

Your 75' cable loss should be negligible at 117V with only 14.9 amps on 10 gauge wire.

The PF (0.84) seen at the ST5 isn't bad.  The transformer inductance is helping here, I think. A choke filter would lower this, but how much of a difference in fuel consumption that would make is still not clear to me, since some say that those VA lost to power factor won't show up in fuel use.  Apparently I'm not alone in being dubious about that theory and Bill Rogers doesn't buy that yet either.

The transformer efficiency looks like 87%, which is what my textbooks predict for a good non-toroidal transformer of that size.  (Larger transformers are more efficient.) The transformer loss is made up for in part by it's positive contribution to PF.

The Flexmax efficiency is impressive- 95 or 97%.  There seems to be a typo on the input to the Flexmax (after transformer) data; I calculate 1277VA, you wrote 1250.  Either way, the Flexmax as a DC-DC converter is VERY impressive in efficiency.

So depending on whether you think VA's generated for PF losses are real ones, fuel wise, the total efficiency (1752VA or 1470 watts with .84% PF) is either 69.4% or 82.5%.

The PF could be raised with a choke filter, and the transformer efficiency could be improved 8% by going toroid, but it's pretty darned good as is.  Each  would only affect the total efficiency be a few percent. Without some proof on the PF-fuel issue, I wouldn't blow the dough for increased efficiency.

I do hope someday, some pioneer will nail down the PF-fuel use issue for us all.  One generator run (with measured fuel consumption for a fixed period of time) with a lousy PF and X watts load, one run with same X load but only resistive loading.

Thanks again, Geno, for your help on this.
Best Wishes,
Bruce M

[mobile_bob]

as it relates to pf for our sytems

where lower pf shows up as costing you in fuel is when you push the circuit to capacity with kwatts (real, that are doing work) and then add the reactive component, this starts to heat the conductors in the generator, the transmission line and in this case the transformer,, when this happens
you will note some increase in fuel consumption. if the pf is for instance .9 in a situation as describe, moving it up to .95 is likely only going to show up
as a decrease in fuel of about a half a percentage point and not the full 5% as one might expect

even going from .8 up to .95 seldom returns 1% in fuel savings in most cases, and

if the kwatts real power, plus the reactive component is below that of the total capacity of the generator, the lines and in this case the transformer
there will be virtually no added heating, and therefore the added fuel burned due to lower pf will be very hard to measure.

this from my reading, and what i have been able to observe directly through experimentation.

typically capacitance is added to improve pf, not inductance, at least from what i have read, but
i don't know for sure that inductance can't be used, however

one is well warned not to start to add capacitance to any circuit feeding inverters, or converters in meaningful amounts, the results are damaged
electronics from what i read.. whether this is always the case i don't know , but probably something one ought to have the oem engineers involved
in the design and use of.

also the pf of Geno's transformer will improve to near unity the more load he applies to it, a lightly loaded transformer or motor exhibit very poor
powerfactor that improves with added loading and will peak with peak load.

my transformers i am am using in the 3 phase testing start out at about .4 pf at no load and get all the way up to .98pf at full load.

the problem with altering pf for a transformer is its dynamic nature, as the batteries come closer to charge the load will reduce and the powerfactor
will get worse, dynamic powerfactor correction would be the way to go, but

it is unclear to me as well whether the increase in pf would result in a meaningful reduction in fuel consumption.

my thinking is if you are using a 5kva transformer with a 5kw st head, driven by a 6/1 there probably is no combination of factors that would result
in peak kwatts of real work plus reactive component that would equal more than what the generator, transmission line and in this case the transformer could handle without significant increase in heating.

might well be a different story if the prime mover was a 12/1 driving the st5 and a 5kva transformer on the same 10gage wire, with a
load that was near 5watts and a pf of .84, then i would expect some heating (and probably a damaged st head) and extra fuel being consumed
to cover this extra heating.

my favorite subject, power factor and its correction



bob g