120VDC battery bank ?

audredger

We did not bring the “Kangaroo Special” Classic to Maine as Ryan does not have a 120VDC battery bank.

A quote from the progress report from Midnight Solar on the "Classic" charge controller.

Do those "Boys" down under really use 120VDC battery banks and, what for? Havent seen a 120 V Inverter or is there some other majic like a motor/generator set?

Cariboocoot

Re: 120VDC battery bank ?

I've been waiting for a 120 VDC inverter system for years! Did you know you can configure two MX60's to charge the banks? It's in the manual somewhere.

BB.

Re: 120VDC battery bank ?

There are higher voltage inverters out there---I have seen larger computer room UPS that work at >120 VDC...

NEC tends to frown on voltages > 48-60 volts and it becomes very difficult for a DYI person to "work" on their own products "legally/regulatory" speaking without special training/certification/tools/protective mask-clothing/etc...

Frankly, high voltage/high current battery banks scare the hell out of me already... Makes working on home wiring a picnic by comparison.

-Bill

audredger

Re: 120VDC battery bank ?

Frankly, high voltage/high current battery banks scare the hell out of me already... Makes working on home wiring a picnic by comparison.

Me too ... Remember, I TIG weld with 185 amps @ 17 volts. Just need a high freq starter and argon or helium gas to contain the plasma. House wiring, even small shop 220 v 3 phase, is a snap compared to high amperage DC.

So, what is the application where you would have a 120 VDC solar charge controller?

Cariboocoot

Re: 120VDC battery bank ?

audredger wrote: »

Me too ... Remember, I TIG weld with 185 amps @ 17 volts. Just need a high freq starter and argon or helium gas to contain the plasma. House wiring, even small shop 220 v 3 phase, is a snap compared to high amperage DC.

So, what is the application where you would have a 120 VDC solar charge controller?

Coincidentally there's a clue in that to the riddle of the 15V threshold I posed elsewhere.

Don't know what the 120VDC app would be; just remember seeing the digram for wiring two MX60's to charge the bank. Probably something in the telecom industry.

Funny how people who'd recommend a 24 or 48 Volt system get nervous about the thought of a 120 Volt one. I guess we all have our 'thresholds'.

Vic

Re: 120VDC battery bank ?

I am very nervous around the PV input to my system -- 106 Vmp and runs around 120ish VDC in Float. It can be very difficult ot get away from DC Voltage SHOCKS, unlike the AC ones. Healthy respect is a good thing. Vic

BB.

Re: 120VDC battery bank ?

Any shock that puts more than ~5-15 mAmps (0.005-0.015 amps) or more through your heart (human arm to leg current, but not leg to leg current, etc.) is enough to ruin your day...

Depending on how the electrical connection is made, typically above ~48 volts can drive enough current to cause problems. Below 12 volts would be very difficult (i.e., no sheets of aluminum foil + salt water wrapped around your arm/foot/etc. :roll: ).

-Bill

Cariboocoot

Re: 120VDC battery bank ?

I can tell you from experience that 50,000 Volts isn't any fun either.
But frankly the 120 VAC 'clips' did more damage.

boB

Re: 120VDC battery bank ?

Cariboocoot wrote: »

I've been waiting for a 120 VDC inverter system for years! Did you know you can configure two MX60's to charge the banks? It's in the manual somewhere.

Yep. 2 MX60s in series (60VDC each) with each having its own array. The main application that I dealt with was an off grid home in Massachusetts. There were other requests for that in the US as well which is why I put that info in the MX60 manual.

One such 120VDC input inverter is the Exeltech MX series of rack mounted inverters which is what the guy in Massachusetts used. There are (or were) other 120VDC input inverters.

I think that Exeltech calls this particular voltage a 108V but says 125VDC nominal and up to 149VDC maximum, which would be like 14.9V for a 12V nominal battery system.

120VDC isn't quite dead yet. ( it got better )

boB

niel

Re: 120VDC battery bank ?

still listed on their website and you're right boB as it is in the mx series, but it's in some of the other series too.
[FONT=Verdana, Arial, Helvetica, sans-serif]Input Power[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Model Voltage [/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Minimum (Typical)** [/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]System (Typical) [/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Maximum (Typical)** [/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Typical Efficiency @ Full Power[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Peak Efficiency @ 1/3 Power[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]12Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]10.4/10.6Vdc*[/FONT]

[FONT=Arial, Helvetica, sans-serif]13.8Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]16.5Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]85%[/FONT]

[FONT=Arial, Helvetica, sans-serif]87%[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]24Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]19/21Vdc*[/FONT]

[FONT=Arial, Helvetica, sans-serif]27.6Vdc[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]33Vdc[/FONT][/FONT]

[FONT=Arial, Helvetica, sans-serif]87%[/FONT]

[FONT=Arial, Helvetica, sans-serif]89%[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]32Vdc [/FONT]

[FONT=Arial, Helvetica, sans-serif]26.5/28Vdc*[/FONT]

[FONT=Arial, Helvetica, sans-serif]36.8Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]44Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]88%[/FONT]

[FONT=Arial, Helvetica, sans-serif]90%[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]48Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]41.5/42.1Vdc*[/FONT]

[FONT=Arial, Helvetica, sans-serif]55.2Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]62Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]87%[/FONT]

[FONT=Arial, Helvetica, sans-serif]89%[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]66Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]57.5/58.5Vdc*[/FONT]

[FONT=Arial, Helvetica, sans-serif]75.9Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]91.1Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]88%[/FONT]

[FONT=Arial, Helvetica, sans-serif]90%[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]108Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]94/95Vdc*[/FONT]

[FONT=Arial, Helvetica, sans-serif]125Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]149Vdc[/FONT]

[FONT=Arial, Helvetica, sans-serif]87%[/FONT]

[FONT=Arial, Helvetica, sans-serif]90%

it didn't exactly copy and paste well did it?
[/FONT]

audredger

Re: 120VDC battery bank ?

Coincidentally there's a clue in that to the riddle of the 15V threshold I posed elsewhere.

Hint Please ... does this have something to do with throwing a spark? Air gap?

Funny how people who'd recommend a 24 or 48 Volt system get nervous about the thought of a 120 Volt one. I guess we all have our 'thresholds'.

High amperage gives me pause, high voltage not as much so. I have a 106 v pv string, I'm cautious but not apprehensive. Yes, something about high voltage and high amperage combined does give me pause. I would advocate 36 and 72 v banks if there was more equipment to support it.

Coot, you may be right, 375 amp battery bank @ 120 Volts just may be my threshold!?
An aircraft propeller spinning at 1,020 RPM or a turbine spinning at 13,820 RPM, you can see them and know they are going to hurt but, Trons, you can't see but, can hurt bad!

Cariboocoot

Re: 120VDC battery bank ?

"Spark" & "air gap". Oooh, you are getting so close! (Sorry if this is annoying people.)

Just think how easy the AC/DC Amp conversion would be on a 120 VDC system. For those of us too lazy to do real math!

ggunn

Re: 120VDC battery bank ?

audredger wrote: »

An aircraft propeller spinning at 1,020 RPM or a turbine spinning at 13,820 RPM, you can see them and know they are going to hurt but, Trons, you can't see but, can hurt bad!

It's kinda like how I felt watching the film of that guy walk the tightrope between the tops of the towers of the World Trade Center (RIP). It looked really scary, but really, what's the difference between doing it 1500 feet off the concrete and only 50 feet up, other than having a lot longer to think about it on the way down if you fell?

Brock

Re: 120VDC battery bank ?

Wind

But yes, what the difference between walking on a 8 inch painted line on a road and walking down a 8 inch steel girder 100 feet in the air

ggunn

Re: 120VDC battery bank ?

Brock wrote: »

Wind

But yes, what the difference between walking on a 8 inch painted line on a road and walking down a 8 inch steel girder 100 feet in the air

The penalty for stepping off the line, maybe? In the second case it's a fall to your death while in the first it's only a ride in a police car to the jailhouse.

niel

Re: 120VDC battery bank ?

since we are talking of odd voltages and not just the 120vdc i would like to kick it around just a bit. 36v and 72v were mentioned and i'm semi-surprised more options for 36v aren't out there. 36v is used primarily it seems in the small scale mobility areas and i believe would be another good option below the nec designated high voltage area of 50v and up. i suppose this is why 60vdc didn't catch on as it is just over that threshold and if you are over it anyway then common sense says why not just be higher like 72v or 120v and the benefits are better in terms of reducing amps and wire losses?
anyway, back to the low voltage area for a moment i feel that most figured to just keep going in a x2 mode to double things so to speak. doubling 48v does put us at 96v and if you're that high you might as well be at 120v imo. it isn't always easy or feasible for many of us to jump to 48v and 24v may not be as well suited for some and as such 36v is a good compromise area that there isn't much in inverters for so we deal with what's there. let's face it manufacturers would be hard pressed to offer nearly every 12v multiple.
so now why not more in the 120v range? i could speculate here by saying you need too much to accommodate that voltage as it would be either 10 12v batteries or 20 6v batteries and you'd need the pvs to match. upgrading here also is a big undertaking as these are large strings of both batteries and pvs. i would think this range to be good for say some really high power systems that are on battery backup. some could probably use it, but there wouldn't be a great demand for it. it does stand to reason it would see more use than is presently if controllers had a strong presence in that odd range. the future classic is said to have a version that would fit that bill.
so in general do i think there should be more options? yes, but what would be a viable voltage or voltages that would hold enough popularity that manufacturers can justify it too? do we go straight to 120v or keep the x2 trend for 96v (8x 12v batteries) or even compromise between say 120v and our present 48v systems such as 84v (7x 12v batteries)?
i know i got carried away with kicking this around.:-)

Cariboocoot

Re: 120VDC battery bank ?

And sometimes 'arbitrary' standards have to be set so that everyone is on the same page.
For instance North America's standardizing 60Hz current back in the '50's and the EU's recent 'adjustment' of power so that Voltage is 'the same' (plus or minus some wide tolerances) across Europe.
How many times already have I mentioned that 'standard' power used to be anywhere from 105 to 135 VAC?

But Neil is quite right about inverter power; there is opportunity to look at what sort of Voltage is really useful, rather than just going by multiples of the standard 12V car battery (which is what it amounts to). Maybe we should look at multiples of 8V or the cell standard 2V. After all, those are just nominal ratings anyway and every system has an operational range of at least 4VDC.

I still have my 36 Volt 'Alpha' inverter with the 'sun transformer'! Made more noise than power (600 Watts I think). Too heavy to take to the scrap!

audredger

Re: 120VDC battery bank ?

I agree with Neil, 36 v would be a good bid point between 24 & 48 volts ... just no support.

the original question why a 120 v charge controller?

and what is the magic of 15 v threshold?

niel

Re: 120VDC battery bank ?

well i'll let the one who brought up about 15v being a threshold explain what was meant.

as to the 120v cc, it is an option and i did give a potential reason for it.
"i would think this range to be good for say some really high power systems that are on battery backup. some could probably use it, but there wouldn't be a great demand for it."
also note the high voltage could overcome some of the longer distance wire losses as some have indicated here they have that problem in overcoming large distances. edit to add this last comment isn't so much about the classic's ability to output 120v, but more its ability to handle a higher input voltage to downconvert. now i don't know if the classic will be able to do extremes like 210v input to say 12v or 24v output. this of course would be at a lower efficiency if it could and at a lower current handling ability due to the limitations of the fets involved.

don't forget the gt crowd also said they want the ability to tap their high voltage arrays for when the grid goes down and it has been said a few times here on the forum. the classic won't tap some of the higher voltage arrays, but would suffice for some designed on the lower end of things. i don't know what good it would do to tap after the grid is down as they would not have a good battery bank to charge due to the lack of maintenance with it being disconnected for the higher grid efficiency to be connected. to keep the battery bank charged means a battery backed gt system and a loss of efficiency so what some of them will do with this ability they would need to say.

BB.

Re: 120VDC battery bank ?

For the 15 volt question, this may have been the answer (note: Google cache, original document no longer available--I guess) Marc was looking for:

An arc ignites in similar manner upon contact break. As the contacts begin to separate, less and less contact area carries load current. Load current begins to funnel into this constricted area and I²R heat begins to increase. The very last point of contact melts and, as the contacts continue to separate, a thin bridge of molten metal is stretched between the contacts. The air in the gap begins to ionize. The I²R energy in the bridge generates so much energy that the bridge literally explodes, showering the gap with metallic ions. Again, if contact voltage is sufficient, an arc will ignite.

Different contact materials have different arc voltage ratings. For fine silver, the arc voltage is 12 volts. For cadmium, it is 10 volts; and for gold and palladium it is 15 volts. Let’s assume the contacts are fine silver. Within nanoseconds after the molten bridge explodes, if the material is silver and if circuit voltage is 12 volts or more, voltage break over occurs. If circuit voltage is less than 12 volts, break over cannot occur and there will be no arc.

-Bill

Cariboocoot

Re: 120VDC battery bank ?

Bill's got it! (Sorry; there's no prize money. )

15 Volts is what we used to call "arc point"; above that arcs become sustainable. Whereas that makes electric welding possible, it also makes handling higher Voltages more difficult and is one of the reasons why vehicles went from 6V to 12V but not to 24V. (Many industrial applications use 24V start/charge.) It's that bugabear about getting fuses and switches that can handle breaking the connection without frying.

In another post here there's reference to a fire starting as a result of a DC arc fault. This is exactly the problem; enough Voltage to sustain an arc, without drawing enough current to trip any sort of standard OCPD, becomes an ignition source for any handy flammable material. Like vinyl wire insulation.

As for the advantages of a 120VDC system; I may be wrong about this but doesn't the conversion efficiency go up the closer the Voltages are? Getting inverter efficiency above 95% would be great. (Getting battery and PV efficiency up would be even better.)

audredger

Re: 120VDC battery bank ?

Sooo Air Gap was close. Just not close enough!

Yes the higher the voltage the better the efficiency. A 48 v inverter is ~1% more efficient than a 24 v. But, I have never seen a 120 v inverter.

I was hoping someone would say " oh yeah you use a framasam. it's like a bridge rectifier, only opposite."

PS for those that don't know: a framasam is the part that is connected to the hurah valve. Kissing cousins to the "whats-a-ma-call-it"

niel

Re: 120VDC battery bank ?

yes, there is an inverter that qualifies if you see post #10. it is listed as 108v, but it works over a range of voltage.
btw, that's a whatcha ma call it.

BB.

Re: 120VDC battery bank ?

I have seen higher battery voltage UPS's (like 120 VDC)--Those were larger units (10kW or so) and installed as computer room backup power supplies.

I am sure there are a lot out there (the Priusups guy got his from Ebay)--but it probably requires a lot of digging around "other places" for that type of UPS information.

-Bill

audredger

Re: 120VDC battery bank ?

Ok ... corrected I am. Seems like a limited market but, I guess somone needs to cut the edge.

Frank

Re: 120VDC battery bank ?

As a general point, there's cross-overs from the EV world. I drive a converted Toyota pickup (120 VDC system) and have been trying to think of easy ways to tap that to dump charge our household batteries in case of extended powerdown. I think some battery chargers accept AC/DC inputs and that might be useful. I could take power from the EV pack through a charger to top off the household system (24 VDC.) The same charger might be useful to use our rooftop array (array #1 comes into a MX60 at 48 V for the 24V pack and array #2 is grid-tied) to recharge the EV pack. I'll probably never do any of this of course but it isn't outside the realm of possibility....

cavit

I live in Europe Romania I run. from 5yars ago 120 vdc battery banks on my household pv system at first 10 gel flat plate lead acid 120 ah approx 10 kwh now 10 12v blokcs in series OPZs tubular floded lead acid 100 ah, I built a pv charger 2 modules charger mppt whith shutdown in case of open dumpload and dump load voltage regulator based of 2 c3m0065090d silicon carbide mosftets for eaach module and inverters bridge input of 200v mosfets as irfp260 or irfp4227 or irfp4668, out stages c3m0065099d for 230vac single phase,2 kw out pv power 2kw, at inverters I encoutered diffculties whith bootstrap drivers as ir2110 ir2113 because can not drive fast body diode silicon mostets or some npt IGBTs despite in datasheet are specified imune to dv/dt but in reality they are not, they are brake down, but they work well on sic devices that have a smaller transconductance and are not proned to generate hi dv/dt oscillations, but irfp4668 in primary stage is accomodated only whith driver transformers.

 Now are available a lot of driving solutions, some of them may work but i have not tested them, AD prvides a pulse transformer link driver ADuM 3224 may work, or a hi speed optocoupler driver, from Avago acpl-w346 or several prefabricated driver boards.

FrankZ

I run a 120vdc solar system. Frank Z on youtube if you want to see