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

[mbryner]

Greg: Yes, the Midnight Solar charge controller would work great for this application, but it's expensive and I already have the MX80 for 3400 watts of solar.

Tom: 

1. You can't really adjust the sweep interval to a very high value if you are using the controller for solar panels, too. 
2.  In this very long thread we discussed using a 2:1 step down transformer to for taking 120 VAC to 60 VAC and rectifying, but the resultant voltage won't be adequate for equalization charging and you'll need a hefty transformer.
3.  I tried without the choke first, but the high ripple seemed to confuse it.   With the choke it works great.   
4.  You can make a simple breaker setup of 2 double pole breakers to switch between 120 VAC and 240 V AC modes.   I can post here the wiring schematic I figured out.
5.  I don't think the setup is limiting the amps pulled from the generator:  I'd need to find a power curve for a 6/1 but as the rpm's drop the HP drops pretty steeply IIRC.   3+ HP at 480 rpm is probably reasonable, so 1600 watts is appropriate.   Just guessing.   Overall, I'm overjoyed!   

[admin]

Marcus

in my humble opinion, you likely have it optimized to about 95% of whatever outcome one could get
if he had an unlimited budget, basically getting the last 5% is going to progressively more expensive.

you are coming in right at about 8kw/hrs per gallon, which is very good considering most get right at that
amount out of a 6/1 at full output AC, considering the conversion steps you have added, it is apparent to me
that you have done very well indeed.

there are losses from the rectifiers , losses in the mx80 which together likely net a bit over 90%

so the engine bsfc factoring in those efficiencies, works out to be what?  .127 gal/kw/hr x 90% = .114 gal/kw/hr     

thats probably about right for a 6/1 driving a st head at that level of output and engine speed

actually thinking about it, the setup is likely doing much better than that, considering  a 6/1 will come no where
near .125gal/kw/hr with a load of 1600watts AC, it will likely come closer to .160 gal/kw/hr or more, i would have to check my
notes to see what the baseline is.

i do know the first kwatt generated is the most costly in fuel consumption, the second is better and the third kwatt is the cheapest.

so overall i would be well pleased too if i were you

bob g

[mbryner]

bob g:  Thank you very much.  Your opinion is highly respected.

[mbryner]

And here are the promised pics:

The bridge rectifier (100 Amp 100 V) and 120/240 ST head mode selector box:
(disregard the "left/right" written on the box, it was cannabalized from our temporary house construction power pole)






Old transformer (must be at least 75 lbs) used as inductor.   "+" DC with ripple from rectifier in one side of primary and "+" DC cleaner output to charge controller from other side of primary.




Opened up DC side of Outback panel and temporary placement of choke on the floor below.  Charge controller is on the right.   The plywood box is the battery box.




The day's data on the MX80 display:




Yes, I need to clean up the wiring at the ST head now that it's proven to work.




And my unique rpm limiter: a tiny key-ring from a Swiss Army knife was just the right size and makes switch over back to 650 rpm a trivial task.


There, a short tutorial on how to make a Outback MX80 or MX60 charge controller get DC current from a standard ST generator head....

[Geno]

Marcus
I'm glad to hear it's all working out. It's easy to see you've been a very busy man. The house and its location are incredible.

My setup has been working as well.
Recap
(ST5/120v-->240v to 208v transformer-->rectifier-->MX60-->48v battery bank)

The Metal Film Caps on the rectifier seem to have eliminated the MX60 display problems but I haven't been running it at high amperage either. I bought a 2500 watt inverter and power a few loads with it. The old UPS was just too inefficient.

Thanks, Geno

[bschwartz]

Awesome setup!!!!  Is the charge controller necessary, or could it be bypassed in favor of just connecting the outback (for a grid tie setup)?

[mbryner]

Hi Geno,

I wondered how your's turned out.   You gave me the nerve to hook up rectified DC to the MX80 with your positive report (except the garbled display!).  So, your transformer takes the 120 v down to 104 V, making it safer for your MX60.   Good setup too.

Hey Brett,

You were the inspiration for this whole thing, when you separated the 4 poles of the generator into 60 V each.   Are you still using it?

Is the charge controller necessary for grid tie setup?   Don't know.   How would the inverters react to dirty DC?  Good question.   Anybody have a Sunnyboy inverter they want to use for this application?   Seems like very expensive backfeed to the grid, though, unless you get the fuel for free.   At farm diesel price of ~$2.80/gal, and generating at 7.76 kwh/gal, you're looking at $0.36/kwh.   Let's say you mix 75/25% WMO/diesel or WVO/diesel, and your WVO or WMO is free then your cost is $0.09/kwh.   Compare that to your power bill and see if the cost and hassle are worth it.

Great to hear from you both.

[mobile_bob]

coordinate or schedule your genset run time to the time of day where you can use the waste heat to best effect
either heating domestic hot water or space heating in winter and your cost per kw/hr drops dramatically.

certainly well under the grid cost in most cases, most especially if you are living a very efficient lifestyle to start with
where all the addon costs on the electric bill raise the actual cost per kw/hr to in some cases twice the base rate, or more.

this is why i look to automation so heavily, it is my firm belief that i can remain very competitive with the power company rates
even burning 100% pump diesel year round

bob g

[bschwartz]

After getting the 60V output on the ST head, I kind of stalled on that aspect of things for awhile.  I'm currently in the middle of plumbing a FPHE inline with the engine coolant to an old cast iron radiator that will be mounted in my living room.

I just ordered one of the GVFX3648 inverters to try.  Although it can charge batteries, I want to see if I can connect it to the grid, and a DC imput and run my meter backwards.  The DC may be rectified from the ST, or from a large 48V DC power supply (3000W if I recall).

Does anyone know if the outback will work this way, or do I need to have batteries connected?

Ahhhh..... too many projects at once.  I'm sure no one here understands 

[Tom Reed]

Bob,

You were talking about paralleling all four poles into one bridge rectifier. Would it not perhaps be easier to run each pole into its own rectifier and then parallel the outputs of the rectifiers?

Bschwartz, I think you would want at least a small battery bank to smooth out your dc ripple. It would seem to make the inverters job really difficult to deal with fluctuating input while syncing to the grid. I am anxiously following your adventure as I plan to do a similar project except charging batteries. I would think that you could adjust the governor on your engine to keep the batteries around 54vdc and you would be good to go with the inverter.

[bschwartz]

Tom,  if it doesn't need the batteries, then the 3000 watt 48v DC power supply (I think I can crank the voltage up to about 54V) should just power it fine without any filters.  I think it was designed to power a computer setup of some kind.  The brand is KEPCO, rated at 48v 60A.  Inside of the box I think are two paralleled 30A units.  It won't be the most efficient with the conversion from 240v AC from the ST, to 48V DC in the power supply, back to 120V in the Outback, but losses while running on WVO, or WMO don't bother me.

[Tom Reed]

It might not need the bats, I'd just hate to think of letting the magic smoke out of a $2k inverter. I was thinking of a small battery bank, say 4 70 ah marine/deep cycle units. I don't think you would loose much if anything efficiency wise since the batteries would just be a buffer.

[mobile_bob]

i would not run the rectified dc from an st head directly into an inverter without the use of a battery buffer

my exeltech mx series system will take from 42 to 62 volts input (48volt nominal) but anything over 62 will cause a fault and drop out
and then takes a manual reset.

i would imagine any quality sine wave inverter will operate on the same principle,

when it comes to rectified power from something like an st head, without some form of regulation that is very fast
when there is a load dump the dc voltage will spike much higher than 60 volts which will cause the inverter to trip out, hopefully...

or worst case, damage the inverter.

a battery bank is very good at being a buffer and clamping for the most part when load dump occurs, and also has the ability to
provide a boost for starting heavy loads, depending on inverter capacity the 3kwatt limit of a 6/1 could become two, three or more times that limit for several seconds or minutes if need be.

lots to be said for including a battery buffer

if all the batteries are asked to do is provide a buffer and/or a momentary boost, i would look toward using standard automotive starting batteries, they are made to deliver massive amounts of current for several seconds, recharge more quickly than do deep cycle
and are cheaper because of economies of scale, probably a million car batteries are built for every one deep cycle battery.

fwiw

bob g

[bschwartz]

Bob,  I wouldn't go from the ST head to the Outback inverter directly.  Do you think the Outback would be OK taking its 48v DC from a 48v power supply that is powered from the ST head?
I'd think with a static load of just the power supply on it, the 6/1 with ST head should be stable enough to provide a constant 240v AC for the power supply which would in turn provide a stable DC voltage for the Outback.

Am I making any sense?
Maybe another cup of coffee.........

I guess 4 car batteries would be cheap insurance though.

I was also lucky.  Instead of it being a $2000 inverter, I found a factory refurb for $1161 !!!  So the magic smoke would be ...... nevermind still too much to imagine

[mbryner]

Update:

This morning I installed a 10 ohm Ohmite rheostat to the excitation loop in the ST 7.5.   Using the full 10 ohms brings the output voltage to ~93 VAC instead of ~115 VAC.   The DC output from the rectifier/choke combo is now in the 120-130 volt DC range.   Hard to measure precisely because as soon as I flip the breaker, the solar charge controller locks on and starts charging at ~2500 watts.   Perfect!!!  

The only problem: the toroid transformers I'm using are getting quite hot still, even though I'm running at full 650 rpm (60 Hz) now.   I'll need to find a real 5 kw 2:1 transformer.   The only real reason for the transformer is isolation of the circuit to allow for common ground between the generator and DC neg.   I can produce power via the 120 V gen head setup, but the toroids take the voltage from 240 to 120 on the standard gen config.   Is there such a thing as just a isolation transformer with a 1:1 winding ratio?   Time to do some google searches.   I'll post pics later tonight.

Also, I'll start a new thread later tonight with data on how my masonry stove is heating the 500 gallon water tank in the basement.   You'll be waiting with baited breath for sure.....