Ideals to charge a 48 volt bank

[gww]

I have a 48 volt, 800 amp hour fork truck battery.  5600 watt solar array. 

I have a cheap 5000 watt generator and a 3500 watt generator.

I would like to keep my batteries from disconnecting during low sun periods due to low voltage. 

I have heard that cheap generators  are too dirty to use battery chargers on.

I was hoping this was wrong as I would like to eventually build a wood gassifier to try one of the generators with.

My system works fine for daily use but would not keep me going for more then one cloudy day if I ever had to count on it.

Any ideals?
Thanks
gww

[DanG]

Find room for an auxiliary set of thin film panels that still put out on overcast days? Crystalline typically uses visible light, CIGS from 390nm-1150nm and CdTe from 260nm-1700nm.; and thin film isn't picky about using scattered skyshine or oblique angled light as much...

Just a thought

[oztules]

Any generator that can put out up to 60v will do....... if worst came to worst you could even use a diode and lots of capacitors direct from the generator 110v ac outlet if you didn't have a charger..... not for the feint hearted, but works very well.....

The batteries could care less..... so long as you can provide electrons at a  potential a few volts higher than the terminal volts... they will charge.

How you handle the finer points, like float etc, is best left to the solar system.


...............oztules

[gww]

DAN G
Thank you for the thought.
My panels go from a 30,000 watt day to a 2000 watt day with a bit of cloud.  I may have my oreintation a bit wrong also as short winter days gave my 30,000 watts and long summer 24,000 is about my best.
Thanks
gww

[gww]

DAN G
Thank you for the thought.
My panels go from a 30,000 watt day to a 2000 watt day with a bit of cloud.  I may have my oreintation a bit wrong also as short winter days gave my 30,000 watts and long summer 24,000 is about my best.
Thanks
gww

[madlabs]

Does your inverter not have a charger built in? In my (limited) experience there are a few inverters that can be fussy but most of them are pretty tolerant. I use a medium crappy genny and have had no problems with the innverter's charger using it.

And if no charger in your inverter, can you get a forklift charger or similar? I have a forklift charger and it works fine and would work fine no matter how crappy the genny was. It isn't a smart charger and does a half crappy absorption stage. The batteries don't care about dirty, just that you don't charge 'em too fast or to too high a voltage. I don't think your cheap genny should be much of a problem.

Jonathan

[gww]

Oztules
sorry for the double post.  I thought about retifying the output to dc and running it through one of my charge controllers but they all have a 150 volt max.  I don't understand how your presented ideals work or I would try them.  I have enough solar to eventualy recharge so during low voltage times I would be willing to try unregulated power.  I just don't know enough about circuits to do it without a very simple sematic.

I have unregulated solar hooked srait to the battery now.  It gives me an extra 150 watts untill it gets shaded at about noon.  I plan to add another 150 watts to that.  I am using about 250-300 watts worth of homemade panels to get the 150 watts for a couple hours.  Yes, your panel building was very impressive.
Thanks
gww

[gww]

madlabs
I have outback gvfx inverters.  Most say you need an inverter generater to work with these inverters.
Thanks
gww

[oztules]

Gww,
 I was a bit tongue in cheek, as it is frowned upon by all and sundry, buy it is a very effective way to utilize a wild/any LV ac source and charge batteries at constant current, and is controllable  by the uf of the caps.

It simply uses the capacitive reactance to limit current, and the diode/s rectify the AC, so it solve the problems very robustly and simply...... it will be easier on the genny rather than a traditional charger due to the power factor problems charging batteries from a sine wave.

The type of generator will make a difference as well, as if it uses capacitive excitation, it may change it's characteristics.


So we go from the 110v line to the capacitors which are in series with the diode rectifier, which goes   (cathode end) to the battery +...... the 110v neutral gos to the negative batt..... and thats it.

The number of UF of the caps will control the current, and the batteries will pull the voltage down to whatever they need. They need to be motor run or similar caps ( AC )

A standard battery charger would be fine too......, but at a pinch this will do it.
Note, all the gennies I have seen do NOT connect the neutral to the chassis and call it earth.... the chassis is normally connected to the earth wire, but I have not seen it connected to the neutral as well..... this means the power is effectively galvanically isolated from ground, and reasonably safe to play with sensibly.


My panels are as good as the day I built them, still pumping water in large quantities.


................oztules

[gww]

oztules
I still don't understand the caps, are we talking about the round things like on the outside of a 220 volt compressor motor that is atached to the motor? 

If I had a 5000 watt generator and 100 amp or above diode rectifier and an extention cord and I cut the cord and hooked one side to a wavy line on the rectifier and the otherside to the other wavy line and then hooked the positive from the rectifier to the battery pos and the neg to the neg, what would happen?

That would be about 170 volts dc held to say 50 volts by the battery? 

The generator has a 15 amp push button breaker at the plug at the generator,  would this breaker blow imediatly?

If it didn't blow,  would the generator run full blast trying to provide its max surge loading.? 

I don't know What a cap is but can look it up.   You are saying the cap goes after the rectifier on the pos. line?  If I use a extention cord that can be plugged into the generator to a rectifier, wouldn't both lines be hooked to the rectifier?.   Am I scaring you yet?  I understand the rf part of the cap and to look up ac motor caps, is my hook up sequence in the questions in this paragragh correct?

Thanks for your time.  I may not get back for a while as I am without internet and am headed home but am interested in your responce.
Thanks
gww

[oztules]

The caps are the motor caps you see on your motors.

The caps will limit the AC current going to the rectifier. You would need an armfull of caps to over load the genny.

So yes, if you cut the ext cord, and placed the capacitors in series with one of the two ac lines, and then connected to the bridge, you will have your 110X1.4=154v peak dc.

The batts will drag this straight down to their voltage the same as it loads a windmill stator.

The genny won't worry, as the current will only rise in line with the capacitive reactance of the caps... ie the caps will current limit it, and drop the voltage the batteries don't need over the caps.... they will not heat up like a resistor, as they are not dropping the voltage via resistance, but by the reactance instead.

This sounds rough and ready and it is, but is also used extensively in a small scale in tons of electrical equipment to provide small voltages to scr and triac circuits in particular, and lots of other even sensitive circuits in AC equiptment.

The down side is that it means in that equipment, the low voltage electronics must be double insulated from everything that a person can touch, as it is not galvanically insulated from the mains as in a transformer application.

In this application, the genny is not really grounded in the same sense as the mains... unless it is hard wired to one or the other of the floating 110v leads from the genny core.... and I don't see that in gennies over here, their earth lead goes to the chassis, but not to the designated N terminal of the machine.

I don't think you should go this route, as you don't have the necessary background to make sure that you are safe..... but that is how it works..... it is dangerous in the sense that the output from the bridge is 150v or so, until it is connected to the batteries....... so although it will work, I think in your case you should find another method.
Also it will need a lot of uf to make serious current.

Jerry ( from this board) charged his EV in this fashion for years, and i recollect he mentioned about 20uf per amp of current.... could be wrong, but rings a bell.

If you search this board, he has diagrams and information here. .... but it is best left for those used to playing with mains voltages on a regular basis I think.
Here is one of his stories on his charger.... this board is crap for older posts.. I see it mentions 24uf/amp.


................oztules

[DamonHD]

Impedance = 1 / (2 . pi . f . c) so current = V . (2 . pi . f . c) so depends on frequency as well as cap size, unless I'm missing something!

Rgds

Damon

[Bruce S]

I gotta go with Oztules on the recommendation of you NOT going this route.
Unless you are very well versed (or know someone who is) working with mains voltages and grounding, this could be a bit more dangerous than you really should be just learning with.
IF you know someone who is a HVAC person, show them this and let them build you one, just make sure they know you need to know what a floating ground is too.

Those who have played with voltages for a while know the risks, and have been bit a few times to hammer home what happens  when ya furget .

IF you go this route think safety, safety safety, then double check your work.

[kitestrings]

I have outback gvfx inverters.  Most say you need an inverter generater to work with these inverters.

gw,

Is that true?  We have the VFX, and I'm much less familiar with the grid-ties, but I thought they all incorporated built-in battery chargers.  We run the charger at times with our Onan gen-set.  It is a good quality generator, but it is not inverter based/VSD.  You also can program the current limit so as to better match the capability (or limitation) of a lower quality generator.  You might check the OB forum, if you haven't.

While not a perfect fix, a boost transformer can make up for a bit of ground.

My understanding is that the sine wave inverter chargers do much better with delivering rated output with lesser quality generators, but I don't have first-hand experience with this (e.g. Xantrex, Iota).  I have noted that their cost has come down quite a bit from when they first started appearing.

A PV source does this seemingly so effortlessly.  It makes you appreciate the wonder of it thru those painful days when supply doesn't meet demand.

Good luck,

~ks

[oztules]

http://www.fieldlines.com/index.php?topic=127768.5;wap2   ..... forgot the link to Jerry

But again, probably not for you at this point in time,
Jerry mentions some 900uf in his case... thats a lot of caps....... unless you bought big ones specially.... and  then a charger would be better.

Perhaps first try the charger function on your inverter, with luck the frequency/voltage window is compatible with the programming in your inverter.... depends on the program.



................oztules

[madlabs]

Yeah, try it first and see. If they really won't work, sell the two cheap gennys and by an inverter genny. If you look at the wattage of your charger in your OUtback, you likely won't need too large a genny to feed it. If you get a genny with about 25% more capacity than the charger needs you should get decent fuel economy too.

Jonathan

[gww]

I have read all the responces and will need more time then I have now to study what is said prior to responding.  I have frequented the outback forum for a couple of years.  I can't thank you enough for all your responces.  I am eventually going to have to break down and get a internet connection again if I am going to keep working on projects.  I'll be back
Thanks
gww

[gww]

oztules
Thank you for the posted link.  I do have a question.  If the caps have different uf values and are connected in series but add up to a total of 90 uf are there any worries?  I would salvage (find not buy) the caps if I ever tried this.  Also to the grounding point,  I have never used a ground when using a generator and also my solar is grounded at the pv aray and the turbines have no ground.  The inverter is grounded to the mains per outback instructions.  I dont see a large difference of the generator being to the battery in the same fassion.  I could be wrong.  The generator is self fused and without ground has been tripped while using it to weld with.  This should help with the isolation issues? 
Thanks

madlabs, kitesrings and bruce
The off grid is different then the on grid for outback per outback manuals and their forums but I may try it anyway.  I did self install my system and believe I have the proper wire and fusing.  Most of that is carpentry and wasn't that hard.  understanding caps and circuits is harder.  I built a ghurd charge controller that works fine but I couldn't tell you why.   

Damon
I don't understand what you are saying or the math.  My generator should be 60 hrtz.  I don't really need to understand if it works.  Anything to add on the above?
Thanks all
gww

[ChrisOlson]

Is that true?  We have the VFX, and I'm much less familiar with the grid-ties, but I thought they all incorporated built-in battery chargers

Outback does not recommend using the GVFX-series with a generator at ALL.  They say they are grid-tie only.  Some people have gotten them to work with inverter generators.  But their allowable input range for voltage and frequency is quite narrow, and non-adjustable.  The GVFX is a synchronizing inverter like the Schneider XW-series.  But it is considerably less sophisticated than the XW and is not able to sync with, and stay sync'd with, conventional generators.

[Mary B]

Maybe try a line conditioner after the generator to clean it up? http://www.tripplite.com/line-conditioner-2400w-avr-system-automatic-voltage-regulator-power-conditioner-ac-surge-protector-rack-mount~LCR2400/

[oztules]

gww... no.
Caps need to be paralled to make the uf increase..... if you series them you get higher voltage and lower uf

ie
 2 times 20uf 240vac caps in series yields 10 uf at twice the voltage.. 480vac

2 x 20 uf in parallel yields twice the uf ( 40uf) at the same voltage (240vac)

.............oztules

[gww]

oztules
Got it, Thanks

I am supposed to get a satilite dish for internet installed tomorrow.  I have mixed feelings about it but have solved many problims using the net.  It cost as much as the electric I am trying to save with solar and turbines.  Oh well all is good.
gww