automotive type PMG thoughts

[bschwartz]

Anyone have any thoughts about using one of these for direct feeding a grid tied inverter (with a battery bank buffer)?

http://cgi.ebay.com/MAXAMP-PMA-Permanent-Magnet-Alternator-Generator-PC1212-/250733051557?pt=LH_DefaultDomain_0&hash=item3a60dabea5#ht_5926wt_1140

The seller emailed me and said that the  model #PC1212  will make 62 Volts at around  3600 RPM

[mobile_bob]

yes, but at how many amps?

without knowing the alternators capability in both amps vs volts you cannot tell squat about the alternator

that ad copy is so full of misleading info it isn't funny, he is careful to not cross the line and all out lie, but
he words things so carefully that he has an out when the units don't produce what is claimed

there is no way that machine will make 300amps at 12volts let alone 24, 48 or 60volts

his assertion that you need his pm machine because you lose up to half your generated power energizing the field?

what bullcrappola!  a typical alternator at full field maybe uses 50-75 watts tops and that is at full alternator output
the only way it would come even close to half the generated watts is if the output dropped to maybe an amp?
then the residual magnetism of the rotor could probably support that output.

as an example, my test alternator which are all wound field units, only consume around 40watts max and produce between
2.88 and 4.1kwatts of DC output (one is 28.8volts the other is regulated at 57.6volts). the claim that field current is hogging
a significant amount of generated power is laughable, the lower output machine consumes less than 1.5% of generated output
for field current needs the higher output unit works out to less than 1% of generated power.  i would gladly trade 1-1.5% of my generated power to have the ability to have effective and accurate control of the charging voltage.

take a look at the applications he has illustrated, all using a single A size belt?  and tiny oem pulleys? he would be doing
good to transfer 1000 watts long term with that puny little drive, but we are to believe this thing is capable of massive amounts
of power?

depending on your expectations, it might be ok, that is if you want maybe 20amps at 60vdc, but expect to spin it up
to 5krpm plus to get there, and you have no effective means of regulating the voltage other than engine rpm which in my opinion
is only a small step above no regulation at all.

i wouldn't touch that damn thing with a ten foot pole, not unless i was on a desert island and it was the only option i had
and i didn't have to trade my lunch money for it.

buyer beware, very aware

bob g

[mbryner]

So what is a good alternater that would produce 55+ V for battery charging?  Aren't they all very expensive?   

Not trying to argue, but for kicks, even if this e-bay listing's claims are inflated, if you can charge a 48 volt battery bank at 2000 watts, at the current bid it doesn't seem like a bad deal.   Then again, as long as the input is greater than 55-60 volts DC, my Outback MX 80 can use it for charging and having a regulated voltage isn't a big deal.

Marcus

[Tom Reed]

Brett's making one out of an ST5. On a 4 pole alternator we have 4 poles/coils of 60vac each. Run a rectifier on each pole and you've got an excellent dc source for battery charging.

[mbryner]

Yes, I've made one out of my ST 7.5.   Worked great until the rectifier burned out (probably overheated due to inadequte heat sink).

[bschwartz]

Oh, I plan on doing the ST head deal too....  I ordered some bridge rectifiers from the bay (sorry Ron, I may have overpaid $11.38 including shipping for 4   ).  
Only half of what I do is for practical use, the other half is just my hobby.

So, back to the cheapo PMG.  I was hoping for a realistic 2kw output  At 50v that is 40 amps which I thought could be possibl.  I hadn't thought about running it through the FM-60 (ordered and on it's way).  Could I run the output of one of these in parallel with the solar panels?... Will I be able to run the output of the rectified ST in parallel with the solar panels?  Should I just run the ST or PMG directly into the battery bank and let the outback inverter do it's thing?

I love the experimentation, but the cost of frying the inverter or charge controller makes me nervous.

[bschwartz]

Did you run the plain rectified output from the ST directly to the input of the charge controller?  Was it paralleled with any other input?  Did you have a switch of some sort to choose the input source?

[mbryner]

Hi Brett,

I talked about this on the 15-16 page long thread about using a ST head for battery charging.   One of the last pages has a few pics of the setup but I'll describe here again.    I was planning on making a diagram and posting it here anyway.  

The solar panels are diode protected so you don't have to worry about them when running parallel into the charge controller.  

Do not run direct into a charge controller without some sort of pulse smoothing.   I tried taking the output of the rectifier direct into the charge controller.   Without filtering my charge controller would lock but immediately release and then hunt again, and repeat.   Then again, I think it was Geno who had good luck without smoothing, but his screen kept getting garbled.  Not worth the risk.  

Make sure you check the specs on your FM-60 for its Voc max. and remember diffs btwn AC and DC and RMS.    If the charge controller is rated for 120 Voc and you hook up 120 V AC (RMS) you could toast the charge controller.   Hopefully its electronics are smart enough, but you never know.   Before plugging in the rectified and smoothed DC into the charge controller, check the voltage (which you would do anyway -- just emphasizing)!!

The way I did it:  Since the MX80 is rated for 140 Voc DC input, I figured 70-80 volts DC would do the trick and safeguard against errant pulses into the higher V range.  To do that I just slowed down the 6/1 by putting a "jumper" in the spring of the fuel linkage.  (Actually just a tiny keyring from a little Swiss pocketknife was perfect).  That slows the 'roid to about 450-500 rpm = ~80 volts.  I took the output from a regular bridge rectifer (100 amp 1000 volt rated) and fed the hot leg across one coil of a big transformer.   The MX80 charge controller locked on quickly, loaded down the 'roid and held at 1600 watts.   Battery charging like that worked great for weeks until the B-R blew, I troubleshooted, accidentally shorted the ST head, locked it up while running, spun the bearing shells, etc.   You know the rest of the story.

That brings me to another point:  if I had a lockout on the selector switch btwn 120 mode and 240 mode, my problem would not have happened.   A sliding isolation switch for the breaker panel is one of the next things to build.

Marcus

Pics:
http://www.microcogen.info/index.php?topic=500.msg15361#msg15361

[mbryner]

P.S.  The only bad part is that the ground doesn't come out correctly if you set the ST head for 120 Volt mode.  It keeps tripping the solar input's GFCI.   The neutral always has voltage across ground (yes, very bad) in that setup, but ST manual says to pick one side or the other, i.e. U1-U6 or U2-U5, as neutral.   My next iteration of this will be use 2 rectifiers in 240 V mode.   Use center tap (bonded U5-U6) as neutral.   That *should* fix the ground problem.  The new rectifiers and large heat sink have been bought (e-bay, ~$50 total w/ shipping) and I'll post back to my original thread when it works.

Marcus

[mbryner]

One more thing:

Should I just run the ST or PMG directly into the battery bank and let the outback inverter do it's thing?

No, do not do that.  You only have a little battery bank buffer, correct?  You will have no way to regulate charge current and will damage your batteries.   I realize you want to sell back to the grid as fast as you are making power, but if something goes wrong w/ your inverter, or a breaker gets thrown, or, or, or......    Don't run that much juice into a little battery bank unless you have some sort of charge controller!

[d34]

Marcus, what type of avr/excitation are you using? My avr says 230vac connected to u1 and u2.  I was looking at setting up my st5 for 120v only but wasn't sure if the avr would work that low. I wouldnt mind doin the four 60vac windings but again was unsure how to setup the avr/excitation.

[mbryner]

I don't use an AVR.

Haven't had a problem w/ excitation, even going to down to 80 V by slowing Listeroid.

Thanks,
Marcus

[mobile_bob]

going back to the earlier question regarding whether or not the listed alternator would charge 2kw at 48volt nominal

i don't think it will, at least not on a continuous basis,  without presenting a serious fire hazard

you can't get 2kwatt output without an input of about 4kwatts mechanical, and that puny little A belt is going to be very short lived.

that is if it will last at all.

the question was asked what alternator can i use to charge 48volts

you can use a rebuilt 110-555jho that has had the rectifiers replaced with non avalanche diodes rated at 200piv
then turn it at ~6krpm and it will charge up to 60 volts and easily make 75amps, certainly 50amps continuous at 57.6vdc
which works out to about 2.8kwe continuous, it can then be controlled with a balmar (relatively expensive) or sterling (much better price on ebay) regulator that will give you rock solid regulation which will protect your batteries and any other connected equipment.

a rebuilt alternator such as the one spec'd should be available for 250-275bucks and the sterling regulator goes for about 110bucks or so, so for about 400 bucks you can have a real alternator that will do what is needed, has a real two groove pulley or 5,6 or 8 groove microgroove pulley if you like.

bob g

[bschwartz]

Okee Dokee..... all thoughts of the cheapo ebay pmg are out of my head....

Now I just have to wait for my bridge rectifiers, and find a really heavy duty choke for filtering....