Author Topic: (8) 48W panels aquired, how to hook them to 48V bank  (Read 6868 times)

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Jedon

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(8) 48W panels aquired, how to hook them to 48V bank
« on: July 27, 2009, 04:06:42 PM »
Siemens M75 48W 600V 3.35A short, 3.01A rates, 19.8V open, 15.9V rated, class C, 5A fuse.


Right now they are mounted to to pole mounts, 4 panels per array with all the positives hooked together and all the negatives hooked together then into a Trace C30+ 12/24V solar charge controller.


An electrician neighbor who is also off grid said that I could probably just wire each array in series + - + - then hook them in parallel right to the battery bank since we don't get enough sun here in Northern California to overcharge the batteries.


The battery bank is 16 Trojan L-16's fed to 2 Xantrex 5548 inverters.


Thanks!

I'm looking forward to running the generator less!

-Jedon

« Last Edit: July 27, 2009, 04:06:42 PM by (unknown) »

ghurd

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #1 on: July 27, 2009, 11:10:09 AM »
Yes, wire them +-+-+-+-,

repeat on the other array,

connect the 2 outputs in parallel,

connect them to the 48V battery.


Myself, I would use a blocking diode on each individual string, before they are paralleled.


I agree with neighbor.  They have a low chance of overcharging that much battery.  No need for a solar controller.


Be careful.  Open circuit of the seriesed PVs can be almost 90V.  It bites hard.

G-

« Last Edit: July 27, 2009, 11:10:09 AM by ghurd »
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Jedon

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #2 on: July 27, 2009, 11:46:57 AM »
Thanks!

So I would need two diodes? Like this?

MBR1645 8 amp 45 volt Schottky blocking diode

I have a 500A shunt and a Doc Watson to put on the hot side to keep track of the panels activity, should I also throw in a fuse/breaker?

-Jedon

« Last Edit: July 27, 2009, 11:46:57 AM by Jedon »

ghurd

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #3 on: July 27, 2009, 12:12:05 PM »
The 16 is 16A.  The 45 is 45V.


They need to block maybe 62V sometimes?  So they are not good.


The gain with a Schottky in this particular set up will not be much at all.

The 33 cell panels will overcome some of their deficiencies because it is a 48V system.


If it was me, I would use a 35A 200V bridge rectifier (or 2) on a fat heat sink.

Probably because I first tend to think in terms of what I have on hand, or what is Cheap.

The total real Vf difference between that Schottky and a 35A bridge will be minimal in your system.


Can use 1 bridge.  One array's + to the bridge on an AC (~) terminal, other array's + to the other AC (~) terminal, bridge + terminal to to the 48V +.


Can use 2 bridges.  One array's + to both AC (~) of a bridge.  Other array's + to both AC (~) termials on the other bridge.  Both bridges + to the 48V +.


Yes.  Use a fuse, very near the battery.  It will most probably not blow fast enough to save the meter, but it may blow fast enough to save something else (like your house).

It should Never Ever blow, so being a cheap SOB, I wouldn't use a breaker.

G-

« Last Edit: July 27, 2009, 12:12:05 PM by ghurd »
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Jedon

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #4 on: July 27, 2009, 01:19:06 PM »
« Last Edit: July 27, 2009, 01:19:06 PM by Jedon »

ghurd

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #5 on: July 27, 2009, 01:50:44 PM »
That's what I would use for the diode (except I'd sell it to you for less if S&H is included, and include some heat sink compound too).

ghurd.info

I believe a metal case is an indication of the quality.


Panels in series will make the same amps as ONE panel.  

A 5A fuse per string is what the factory calls for, and you will have 2 strings.

Arguable if you should use 2 x 5A fuses or if a single 10A is fine.  I would fuse each string individually, so 2 x 5A fuses.


I would probably use an ATC holder (or 2) something like this, but from the auto parts store to avoid $7 S&H on $1.50 or $3 in parts.

http://www.allelectronics.com/make-a-store/item/FHP-25/WEATHERPROOF-ATC-BLADE-FUSE-HOLDER-/1.html

« Last Edit: July 27, 2009, 01:50:44 PM by ghurd »
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Bruce S

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #6 on: July 27, 2009, 02:03:29 PM »
Jedon;

   I'd be careful with the Doc Watson, it can take small spikes above the 60Vdc max but not sustained, unless it's one of them that's been modded to aceppt a higher voltage.


G- is correct open voltage can go a bunch higher. Loaded while connected to batteries might hiold them down , but at full charge even the batteries are going be sitting around 58Vdc. That would be a little too close for my comfort.


Bruce S

« Last Edit: July 27, 2009, 02:03:29 PM by Bruce S »
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Jedon

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #7 on: July 27, 2009, 02:14:55 PM »
If I can't find the bridge rectifier locally I'll get it from you.

Right, the voltage goes up, the amps stay the same, my bad.

Heck I probably have some of those ATC holders and fuses in my garage I can scrounge.

any common computer or electronics stuff have bridge rectifiers I could de-solder?
« Last Edit: July 27, 2009, 02:14:55 PM by Jedon »

Ungrounded Lightning Rod

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #8 on: July 27, 2009, 02:19:46 PM »
For 48V you really need the diode.  That's enough to break over on shaded cells and damage the panels.
« Last Edit: July 27, 2009, 02:19:46 PM by Ungrounded Lightning Rod »

Jedon

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #9 on: July 27, 2009, 02:21:34 PM »
Hmm I found the mods for the Doc Watson, doesn't look like something I want to mess with right now. I'm not sure what to expect out of the panels since they are nowhere near new and right now aren't even on a real mount. For now I'll just put some fuses in and keep an eye on the voltage via the Xantrex 5548. Will that not work since the batteries will pull the voltage down so I won't really know how many volts the panels themselves are putting out?
« Last Edit: July 27, 2009, 02:21:34 PM by Jedon »

richhagen

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48W panels aquired, how to hook them to 48V bank
« Reply #10 on: July 27, 2009, 02:57:37 PM »
I wrote a response that got lost due to the 50 charachter title limit, oh well, here is most of it:


I have several similar strings hooked up on a 48V system.  Hook them 4 panels in series, you will end up with two strings.  On mine, each string is run to a combiner box, and there is a fuse and a diode for each string.  The diode is a common 8 amp stud silicon diode with about a .54V forward voltage drop.  The voltage drop is of little consequence at this voltage, as the open circuit voltage of the strings is generally above 65V at any time there is appreciable current.  If I recall correctly the NEC now requires appropriately rated overcurrent protection for each string, and definitely requires a charge controller for all systems, should that be of concern to you.  I believe that it was SparWeb, Steven Fahey, who posted a link to the current NEC guidelines not too terribly long ago, and I printed it out and remember that it was worth reading.  


I doubt that you will cook your batteries with just the 8 panels and the batteries that you have, however I suspect that all approved charge controllers also prevent current from discharging into the panels.  If it were me I would probably E-bay your 12/24V controller and obtain a C40 or similar charger that can handle 48V banks at the current you have.    


Also, the bottleneck for the current for each string will be the panel that can handle the least current.  If you measure the current of each panel into a 12V battery under similar lighting conditions, you should be able to get more current into your batteries overall if you put the four highest current panels in one string, and the four lowest current panels into the other.  This is of course providing that both strings can reach the charging voltage.  Rich

« Last Edit: July 27, 2009, 02:57:37 PM by richhagen »
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ghurd

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Re: (8) 48W panels aquired, how to hook them to 48
« Reply #11 on: July 27, 2009, 02:57:43 PM »
Seems like almost everything has a bridge these days.

I would want at least 250% of the Isc, say 9A min?


Problem- Most of the AC powered stuff is rated way under 15A so it doesn't blow the breaker in an old house.  Not much chance of finding a suitable bridge in regular junk.


And most of the stuff rated below about 20A is not exactly suited to get rid of that much heat IMHO.

When taking about a system that size, worrying about $5 or 10 seems a bit silly.  Save a little money on aspirin required for the worry headaches?


Locally?  Remember to look for something in a completely metal case, if only because of my prejudices.  

If something half plastic is in a plastic&cardboard hang-tag package, question it.

All IMHO.

« Last Edit: July 27, 2009, 02:57:43 PM by ghurd »
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Jedon

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48W panels aquired, how to hook them to 48V bank
« Reply #12 on: July 27, 2009, 04:27:14 PM »
Thank you for all the info! Looks like I'll hide the panels when the inspector comes out! I will get a charge controller eventually, just putting all funds toward finishing the house right now so this is all a temporary setup ( famous last words? ). I'll also be adding in about 240W of hydro and probably some wind as well in the next few years. There is a box on each array where the wires come out, I bet there are already diodes in there, I'll check it out.
« Last Edit: July 27, 2009, 04:27:14 PM by Jedon »

ghurd

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Re: 48W panels aquired, how to hook them to 48V ba
« Reply #13 on: July 27, 2009, 09:55:40 PM »
Do not confuse the 2 bypass diodes in the box with a blocking diode.

They serve different purposes.  They can be the same part number though the functions are different.


Most real panels do Not have a built in blocking diode.  

It is assumed most panels will be connected to a solar controller, which takes care of the 'blocking'.

G-

« Last Edit: July 27, 2009, 09:55:40 PM by ghurd »
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Jedon

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Re: 48W panels aquired, how to hook them to 48V ba
« Reply #14 on: July 28, 2009, 09:35:56 AM »
I didn't mean the junction box the wires come out of each panel, there is a plastic box where the 4 panels that make up the array join together and I'm betting there are some in there otherwise why have a box? Then again it was connected to a C30 so I could be wrong!
« Last Edit: July 28, 2009, 09:35:56 AM by Jedon »

OuttaSight

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Re: (8) 48W panels to 48V bank
« Reply #15 on: July 29, 2009, 05:32:17 AM »
Morningstar will start to sell a MPPT version of their TriStar 45A and 60A charge controllers from September 2009.  They can handle 150Voc (not quite enough for your 8 panels all in series) but it will save you some wasted power when the battery bank is low.  If you use an ordinary controller (or no controller) the panels optimum power is achieved at 63.6V (above the 60V at which the 48V battery bank would boil up) but more importantly, when the bank is low (at 48V) you'll drag the array down to that voltage and only get 48 x 6.02A = ~289W (75% of rated output).

I've got a pair of the current 15A MPPT controllers they make but they are 12/24V only.  The TriStars will do 48V batteries.  They also claim that they've improved the conversion efficiency from about 97% to 99%.
« Last Edit: July 29, 2009, 05:32:17 AM by OuttaSight »

ghurd

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Re: (8) 48W panels to 48V bank
« Reply #16 on: July 29, 2009, 08:39:38 AM »
I do not believe the "Money Math" will work out with only 200W of solar.

Even worse when his friend wants the panels back.


The maximum gain would be about 25%, sometimes.  About 50W.

Cheaper to buy more panels and always have more output.


I do not believe 6A of solar will manage to overcharge, let alone boil, 780AH of battery.  It is only 3/4 of 1% of the capacity.

G-

« Last Edit: July 29, 2009, 08:39:38 AM by ghurd »
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ghurd

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Re: 48W panels aquired, how to hook them to 48V ba
« Reply #17 on: July 29, 2009, 04:03:00 PM »
The plastic box was probably to contain the connections.

There is really no other purpose for a box.


I doubt there is a blocking diode in the plastic box, as you are thinking about it.

With a C30 that would have been a bad design decision in most places.

G-

« Last Edit: July 29, 2009, 04:03:00 PM by ghurd »
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Jedon

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48W panels aquired, how to hook them to 48V bank
« Reply #18 on: July 29, 2009, 04:06:56 PM »
Could I hook the panels up for a couple weeks without the diodes? I got a metal box at Home depot with an on/off switch and two 15A fuses, they didn't have lower amperage fuses, is that going to be useless?
« Last Edit: July 29, 2009, 04:06:56 PM by Jedon »

ghurd

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Re: 48W panels aquired, how to hook them to 48V ba
« Reply #19 on: July 29, 2009, 04:44:01 PM »
This is not a great idea but it will work for you until you get something better.


Go to that dam Ratio Shak with $6 and get TWO 8A 400V full wave bridge rectifiers (#276-1181).

Use them like this,

"Can use 2 bridges.  One array's + to both AC (~) of a bridge.  Other array's + to both AC (~) terminals on the other bridge.  Both bridges + to the 48V +."

And put them on large aluminum heat sinks, like some kind of car part or cookware or chunk of scrap lawn furniture.


Return the Home DePot switch box thing and get your money back.

Take the money to an auto parts store.  Purchase an inline fuse holder with at least #14 wire, and a matching pack of 10A fuses.

Or buy 2 fuse holders with a pack of matching 5A fuses.


Could get the auto parts while at that dam Ratio Shak if so inclined, and wealthy.

#270-015 holder (x 2 if you want it to be mostly semi-permanent).  

#270-1201 (x 2 if you want it to be mostly semi-permanent).


Feeling a bit extra cynical toward RatShak today.  :)

G-

« Last Edit: July 29, 2009, 04:44:01 PM by ghurd »
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Jedon

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Re: 48W panels aquired, how to hook them to 48V
« Reply #20 on: July 29, 2009, 04:57:36 PM »
Thanks! I didn't think RatShack had that kind of stuff, I called the local solar place ( sierrasolar.com ) and hey don't even have any since they say to always use a charge controller.
« Last Edit: July 29, 2009, 04:57:36 PM by Jedon »

Jedon

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Re: (8) 48W panels hook them to 48V bank
« Reply #21 on: August 01, 2009, 11:18:56 AM »
I rewired the arrays, flipping every other panel so instead of - - - - they are now + - + - but in doing so the voltage dropped from 16V to 6V. This is opposite of the desired effect, any ideas as to why that would happen? I thought at first it was a loose connection or something but both arrays exhibit the same behavior so that seems unlikely. There are diodes between the panels and the wires, they look to have come with the panels since they are in the panel junction boxes.

Thanks!!

-Jedon
« Last Edit: August 01, 2009, 11:18:56 AM by Jedon »

ghurd

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Re: (8) 48W panels hook them to 48V bank
« Reply #22 on: August 01, 2009, 11:24:18 AM »
Wow.  You did something wrong.

Have any pics? Or a sketch or something?

G-
« Last Edit: August 01, 2009, 11:24:18 AM by ghurd »
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Jedon

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Re: (8) 48W panels hook them to 48V bank
« Reply #23 on: August 01, 2009, 03:27:32 PM »
Here are a few pics:

http://picasaweb.google.com/jedon13/Solar#

All I did was flip the 2nd and 4th panels on one and the 1st and 3rd on the other.

If I disconnect the first panel from the rest I get around 16V, connected I get 4.5-5V
« Last Edit: August 01, 2009, 03:27:32 PM by Jedon »

commanda

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Re: (8) 48W panels hook them to 48V bank
« Reply #24 on: August 01, 2009, 03:48:13 PM »
Your panels were originally connected in parallel, so only 2 connection points.


To put 4 panels in series, you need 5 connection points.


Neg of panel 1 to battery negative.

Pos of panel 1 to neg of panel 2

Pos of panel 2 to neg of panel 3

Pos of panel 3 to neg of panel 4

Pos of panel 4 to battery positive.


Amanda

« Last Edit: August 01, 2009, 03:48:13 PM by commanda »

Jedon

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Re: (8) 48W panels hook them to 48V bank
« Reply #25 on: August 01, 2009, 04:54:59 PM »
Thanks! Like this?

« Last Edit: August 01, 2009, 04:54:59 PM by Jedon »

ghurd

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Re: (8) 48W panels hook them to 48V bank
« Reply #26 on: August 01, 2009, 05:13:28 PM »
That's correct.

Is that how it is while it is making 6V?


Not sure whats up with photo 3 of 6.

Looks like all the panels are connected to short each other out.

G-

« Last Edit: August 01, 2009, 05:13:28 PM by ghurd »
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Jedon

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Re: (8) 48W panels hook them to 48V bank
« Reply #27 on: August 01, 2009, 05:17:56 PM »
Yeah in photo 3/6 that's me messing them up bad. Brain must have been turned off.
« Last Edit: August 01, 2009, 05:17:56 PM by Jedon »

Jedon

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Re: (8) 48W panels hook them to 48V bank
« Reply #28 on: August 01, 2009, 06:10:11 PM »
Success! Thanks all! I don't have the diodes or fuses hooked up yet so I'll disconnect them before dark but they were reading 64V. The amps were really low like .38 or something ( as reported by Doc Watson), granted the panels are in shade right now but is that right?
« Last Edit: August 01, 2009, 06:10:11 PM by Jedon »

ghurd

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Re: (8) 48W panels hook them to 48V bank
« Reply #29 on: August 01, 2009, 06:51:05 PM »
The 64V sounds a little low.

Check it good sun.

The 0.38A sounds pretty good for panels in the shade.

G-
« Last Edit: August 01, 2009, 06:51:05 PM by ghurd »
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Jedon

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Re: (8) 48W panels hook them to 48V bank
« Reply #30 on: August 02, 2009, 10:43:38 PM »
68.7V now when not hooked to the batteries, getting around 220W into the bank while the generator is going, 52V charging. I can see why people use charge controllers but this works for now.
« Last Edit: August 02, 2009, 10:43:38 PM by Jedon »

ghurd

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Re: (8) 48W panels hook them to 48V bank
« Reply #31 on: August 03, 2009, 12:41:58 AM »
The 68.7V open sounds about right for 33 cell panels.


Congrats!  It works!

G-

« Last Edit: August 03, 2009, 12:41:58 AM by ghurd »
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Jedon

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Re: (8) 48W panels hook them to 48V bank
« Reply #32 on: August 03, 2009, 09:21:39 AM »
Woohoo!

Now I need to hook those bridge rectifiers up so I can leave it hooked up at night.

Do I hook anything to the - pole?
« Last Edit: August 03, 2009, 09:21:39 AM by Jedon »