Adding panels and Bats, HELP!

WD-40 · August 2010

Hello,
Great site!!
I am getting ready to add more panels and re-battery. I have been off grid in the mountains of California for over 14 years. What I have now is a xantrex SW PLUS 5548, 4 evergreen 180 watt panels using a outback mx60 pv mppt, also a air-x 48v. I have a 25kw propane backup generator plus two 7kw diesel generators.

They don't make the evergreen panels anymore so i guess i mix panels??
Should i buy a new charge control?
Batteries have always been four 8D flooded but now im thinking of going with 6volt bats with way more amp hours?

Over the years i have spent much time in the city working and also much time on my saiboat but now would like to spend more time at the ranch here but need more power and storage.
My freezers and fridge are both propane and my water well has a solar/generator SQ-FLEX setup and is not tied to the houses.
both the guest and the main house are heated by wood.

I am a hard head who always does everything himself.........i built the homes and power system myself. The power set up could be allot better so any help would be appreciated! Im not all that smart in this field.

Thank you,
WD

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Here i am making a reply to my first post,haha

Okay, my MX60 MPPT is 150 volt max and 60amp max charge. Are those values based on 12 volts? I am running a 48volt setup? I don't quite understand ohm's law and how to calc out what i need to do.

I now have 4 evergreen 180's at 25.9v/7.7amp wired in series @ 103.6v run to my MX-60. The MX-60 then converts down to 48v and how many amps, 15 ? So if i had 8 of these same panels two strings of 4 in series then ran in paralel to the MX-60 and still would only be 30amps at 48v?

WD

BB. · August 2010

Re: Adding panels and Bats, HELP!

The maximum input voltage from the solar panel is 150 VDC... From the solar array, which changes output voltage based on temperature and loading (cold panels, higher voltage--no loading, higher voltage)--Works out that you can have ~100 volt Vmp array on a 150 VDC never exceed input.

The larger, multi-voltage output controllers (12/24/48 volt) output MPPT controllers are rated for output current, not really output power. The power output (power = Volts * Amps) for 12/24/48 volt battery banks are:

14.5 volts charging * 60 amps = 870 watts into 12 volt battery bank
29.0 volts * 60 amps = 1,740 watts into 24 volt bank
58.0 volts * 60 amps = 3,480 watts into 48 volt bank

So, for solar charge controllers, the controllers can hand 2x or 4x the solar panel watts with the 24 or 48 volt battery banks vs a 12 volt battery bank (save costs on system as you need 1/2 or 1/4 the charge controller for a large solar array).

Also, MPPT controllers have the ability to control the maximum output current--so you can even add a few more solar panels (more current) without damaging the solar controller. Withe PWM, they cannot regulate output current and too many amps of solar panels can damage the controllers.

Adding solar panels to your charge controller is a bit confusing... And cannot always be done efficiently. If you do not match the panels' Vmp (withing ~10% for parallel) or match their Imp (again ~10% for series connections)--Many times, the only option left is to add a second charge controller to manage the new solar panels and parallel the controllers into the same battery bank.

Also, there is an issue for some new high Vmp panels (~50-72 volt Vmp) with a 48 volt battery bank... A single panel is not high enough voltage to charge the bank--And if you put two panels in series, their Voc (Voltage open circuit) can exceed 150 Volt never exceed input voltage.

In any case--measure your loads and then plan out your system. Buying parts before making sure everything fits your needs can be an expensive mistake.

Evergreen was great because they made high wattage panels at with low voltage battery system compatible voltages (and their panels are supposed to be very reliable too).

For Grid Tied systems, high voltage panels reduces current (and wire gauge size)--Great for GT inverters--Can be an issue for battery based off-grid systems.

-Bill

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Thanks Bill!

Kc has a panel that looks very close to the evergreen 180's i have,
Kyocera Solar KD185GX-LPU 185 Watt Photovoltaic Module
Max Rated Power (Pmax) 185 Watts
Voltage at Max Power (Vmpp) 23.6
Current at Max Power (Impp) 7.84 Amps
Open Circuit Voltage (Voc) 29.5
Short Circuit Current (Isc) 8.35 Amps
Length x Width x Depth (inches) 52.8 x 39 x 1.8
Weight of Panel (Pounds) 35.3
Connector Cable Type or Junction Box MC4 Latching Cables

The evergreen's are ES-180-SL 180 watt,
Pm2 180 Watts
P tolerance -2%
Pmp, max 186.1 Watts
Pmp, min 176.4 Watts
Pptc3 159.7 Watts
Vmp 25.9 Volts
Imp 6.95 Amps
Voc 32.6 Volts
Isc 7.78 Amps
Cells 108
Max. Series Fuse 15A
UL System Voltage Rating 600V
TUV System Voltage Rating 800V

Can i add 4 of these to the same MX-60 mppt? They look to be well within the 10%? Or would it be better to go with a second mx-60 or?

Thanks,

WD

BB. · August 2010

Re: Adding panels and Bats, HELP!

I don't see any issue with paralleling the Kyocera with the existing Evergreen... The voltages should be be close enough for good efficiency.

However--Have you monitored the array voltage? In theory, your 4x Evergreen panels in series is pretty much at 150 Volts (Voc--Voltage open circuit) near 0 degrees F. In real life--it is possible the loading of the charge controller my keep the Voc voltage a bit lower than predicted.

If you have extremely cold/clear weather--it is possible that the Charge Controller could log a warranty ending input voltage, or even possible damage.

Perhaps somebody else with more experience than I can talk to the issues of running that close to Vnever-exceed in cold weather.

-Bill

Vic · August 2010

Re: Adding panels and Bats, HELP!

Hi WS-40 Welcome here,

Bill has given his normal excellent summary for this topic.

I, too, run my Vmp fairly high @ 106-ish Volts, and given my lowest temps, my Voc maximum, as recorded by the MX-60 is 139.4 Volts, close to the limit.

I, too, am considering adding panels, and might consider something in the 80-to-90 Vmp range, as the MX's tounge hangs out a bit when in Float. In Float, my system runs about 120 Volt array voltage, and the MX's output is 53 Volts -- this large differential increases the internal heat in the MX. The MX's internal fan runs a bit at surprisingly low watts delivered from the MX -- have begun running A/C for the Power Room ... it has priority over the residence A/C !

So WD, You might consider running strings of three panels -- add 5 panels, making 9 total panels. This may not work out too well with your existing Panel racking, tho.

If your PV is a great distance from the Charge Controller, then the higher voltage is an advantage, but the MX would really like a COOL environment with this high an input V. AND, as Bill has mentioned, there is a reasonable liklihood that you could exceed the Max Ever Voc, which is recorded in Log 2 IIRC. Looking at your Avatar, your climate looks COLD in the winter ! You may wish to look in the Logs, and see what your Max Voc recording is.

Good Luck, Vic

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Thanks Vic!
Still a bit confused,hehe It looks like we have a few things in common in term of setup. And yes it stays in the 20's for week's at a time here at 6400'

WD

Vic · August 2010

Re: Adding panels and Bats, HELP!

Hi WD,

Well, yes, you should be confused, as my post was a bit wrong, as of course, adding 5 Kyo panels will not work well with the 4 Evergreens ... Dunno why I was not thinking.

I'd bet that your Max ever Voc is very cose to the 150 Volt max ever.

I had poked around on the net, looking for the specs on your current Evergreens, and was kinna thinking that there was a panel quite close to the specs of the existing panels you have ... BUT, did notice that the host of this site no longer had the panel I'd been kinna thinking of.

Sorry for my confusion ... will poke around a bit more. ... Later, Vic

BB. · August 2010

Re: Adding panels and Bats, HELP!

Probably taking the 4 Evergreens + 4 Kyoceras and rearranging them in strings of 3 is not going to work either (the Kyoceras in 3 series is not high enough to charge a 48 volt bank on any but a very cool day).

This is the problem of "balancing" panels from different vendors and trying to get them to work well in all conditions--It is not a trivial task.

-Bill

Vic · August 2010

Re: Adding panels and Bats, HELP!

Thanks BB,

I had been "thinking" about two Kyo 185s and one Evergreen per string, but this yield one Evergreen unused, AND wastes some of the IMP of the Kyos, plus it is not enough Vmp for warm/hot days ... other than that ...

Forgot to engage the brain.

Did poke around trying to find a fairly high voltage panel with Imp close to the Evergreen's. but not much joy there.

Not knowing the temps at the target site makes it a bit difficult to calculate the Vmp at Tmax.

Am a bit concerned that the Voc of four panels in series is somewhat too high.

The MX-60 may already be out of warranty -- they only had a two-year warranty from the factory, but sold an optional extension of three years IIRC. The MX is probably fairly tolerant of exceeding Voc by something like 10 Volts or so, as the Voltage Detector and open relay contacts are most likely the only components exposed to a Voc exceeding 150 VDC.

However, brain may still not be engaged. Vic

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Thanks Bill!!

Im sorry for being a pain in the butt!

Okay,
Lets take the evergreen 180x4/Mx-60 out of the equation. The unit has worked for 3 years. The low temps in the winter during the day can be in the 20's but with full sun it most likely is about 35 degrees.

On my 48v setup i would like to add another 1000watts of PV with another charge control unit in parallel.

Any suggestions?

Thank you,
WD

Vic · August 2010

Re: Adding panels and Bats, HELP!

Hi WD,

Have not forgotten, was still poking around with this puzzle.

Certainly, your last post makes the issue very much simpler, but, of course, more expensive.

Just for curiosity, are you at the off-grid site now ? If so could you look in Log2 (I believe it is there) for the HiVoc value, and let us know what that is ? Obviously, whatever the value is, it HAS been working for 3 years.

Also, just where is the site ?

Ideally, the added panels would need to have enough output voltage to be able to EQ the battery bank in the hottest weather ever expected, with the coolest battery bank ever expected under the hot conditions. Running the Vmp of each new string in the 85ish Volt range should accommodate the above, and still keep the Charge Controller happy and fairly efficient.

Choose panels that will rack easily for your site, and probably run 3 in series.

BB has a lot of experience in running the numbers. Also searching the site will give good guidelines. "Crewzer" used to do a lotta panel configuration calcs, here, as well.

Off to chores for now. Good Luck, will check in later. Vic

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Vic,
The LOG-2 high voc is 137.6. Guess that's close to being to high?

Area is Lockwood Valley Ca.

Thanks WD

Vic · August 2010

Re: Adding panels and Bats, HELP!

Hi again WD,

Thanks for the added info.

Personally, I think that your HiVoc is fine ... Others may not. It is quite possible that in the years your MX-60 has been operating, it has not experienced a severe cold snap, where you will see a higher Voc ... you never know the result, as Ms Nature can slap us around. The highest Voc conditions often occur around first light on very cold mornings -- usually, the Sun is not directly striking the solar panels, and the CC is applying no load.

Thanks for the location info, looks nice, and remote on the map.

Am a bit distracted, by going through a similar process of considering adding some panels at my existing off-grid location, while trying to moderate the impact of this new hardware on the design of the power system for a second location ... too many bees a buzzing around here.

The current generation of solar panels are targeted mostly at grid tied systems, so finding panels in stock to meet one's off grid needs is more difficult.

Others here are probably better suited to recommend possible panel for your environment.

One bit of advice, if you have used some of the many features of the MX-60, and marvel (as I do) at its capabilities, then you may want to AVOID buying a Xantrex SCC-150. My personal experience with that box could not be printed on a family oriented site. It seems to me to be a feature-free, dumbed down box that is easy to install, as there are almost NO extended functions, capability or settings. YMMV.

Midnite Solar is finishing up their new Classic Charge Controller (Midnite was founded by the guys who started Outback). So if you can wait some months, the Classic
should be shipping this year. It promises to be a very nice CC. They will have a higher Voc version after the 150 Volt Voc version ships, as I read it.

OK am done for now, off to dinner. Will check in later. Vic

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Vic.
Thanks for the info! I am going to buy another outback CC and panels in the morning. Any thing i need to know about running both CC's on one battery bank?

Any thought?

After 15 years off grid i will never go back! I have 30 acres here, very nice. Kern county leaves you alone unlike Ventura and LA counties.

WD

BB. · August 2010

Re: Adding panels and Bats, HELP!

You can connect them together digitally with a "Mate" (4 or 10 port) and have them share a single battery temperature sensor plus change states (bulk, absorb, float) together (plus the Mate can manage/program your Outback inverters too).

I am not very knowledgeable about Outback--Others can probably tell you more about the Mate or Mate-2 (there is also a FlexNet which is a Battery Monitor system/option too).

-Bill

Vic · August 2010

Re: Adding panels and Bats, HELP!

OK WD, BUT,

You need to be a bit careful about the minimum Vmp the panels put out when HOT, vs the Max VOC when they are cold.

Not being too pushy, but do you have a target panel/configuration ?

Back in a bit ... And, I know nothing of the Mate and other OB giblets. Vic

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

VIC,
I would love to do another 4 panel set as it would keep some symmetry going at the panel location on the back roof of my log cabin?.

Thank to you too BB i will look at the mate setup for the CC's.

WD

Vic · August 2010

Re: Adding panels and Bats, HELP!

OK WD,

Nice to see you here, and good luck on your upgrade. Let us know how you are doing. Vic

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

okay,
Will a flexmax-60 and a mx-60 work together in parallel? What "Mate" would i buy to control both?

Thanks again!!!!!!!

BB. · August 2010

Re: Adding panels and Bats, HELP!

Pretty much any pair of solar charge controllers can be connected to the same battery bank in parallel (run cables from each charge controller to the +/- battery bus connection point--do not share the wire run). For MPPT type charge controllers, do not share the Solar PV array well.

I cannot answer the the Mate question (should be compatible). Perhaps a call to the place you are thinking about ordering your controller from and/or to the Outback support line would help.

-Bill

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Bill,
what does this mean "do not share the Solar PV array well" it's the "well" part, did you mean "as well" ?

thank you again bill

BB. · August 2010

Re: Adding panels and Bats, HELP!

Many PWM controllers can share a single solar array... Some people do this so they can charge both the RV house battery and the RV's starting battery.

With MPPT controllers, they are (once every few minutes) changing the loading current on the the solar array to find the maximum power point--Basically, using the equation of Pmp=Vmp*Imp

If you have two MPPT controllers, they are each going to try and vary the current and "solve" the equation... But the two controllers will confuse each other as each attempts to find the Maximum Power operating point--and most likely, neither will find the optimum operating point.

Also, at least one MPPT Charge Controller uses the negative lead of the solar array to measure the current (Xantrex MPPT 60 amp--I believe)--If you have any other wire/load/device attached to the array that can divert current--it will prevent the MPPT controller from operating correctly (not a problem with the design--just an engineering choice).

So the not "well" meaning does not work well at all--As opposed to a a degree of success as in not "as well"...

For others that may ask, there is at least one PWM solar charge controller that is designed for the RV battery charging dilemma with one solar array shared among two battery banks. At least a couple people have used it here and find it works well

:

Morningstar Dual Battery Charge Controller 25 Amp

-Bill

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Thank you BB! Like energy well!!!!!

I use the Morningstar Sunsaver Duo on my sailboat, seems to work well!

A wealth of knowledge you are and i am very grateful you have chosen to share it with me!
ty,

William

BB. · August 2010

Re: Adding panels and Bats, HELP!

You are very welcome William.

Also, I fixed some of the more egregious spelling and grammatical errors in that post.

-Bill

WD-40 · August 2010

Re: Adding panels and Bats, HELP!

Thank you,
Spelling and grammatical errors are numerous in my post history, oh well

WD

Adding panels and Bats, HELP!

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