how many panels can I run thru this CC to charge 12 volt battery bank?
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vibeline
Registered Users Posts: 24 ✭✭
Hi Everyone I'm new here and I'm new to solar...
I have been reading for 2 days now....... soooo much to take in...
I have an opportunity to buy some panels for $200 each, from a local guy going out of business but I must act fast so I need your help...
Panel info:
Nominal power [Wp] Pmpp: 235 watts
Voltage at nominal power [V] Umpp: 30.2 volts
Current at nominal power [A] Impp: 7.78 amps
Opencircuit voltage [V] Uoc: 37.1 volts
Shortcircuit current [A] Isc: 8.42 amps
My question is how many of these panels can I run thru this
Xantrex XWMPPT60150V Charge Controller (I can buy this from the guy for $500.)
Electrical Specifications
Nominal battery voltage: 12, 24, 36, 48, 60 Vdc
Maximum PV array voltage (operating): 140 Vdc
Maximum PV array open circuit voltage: 150 Vdc
Array shortcircuit current: 60 Adc maximum
We have a lot of power outages in my area and I have been wanting to get some solar panels for years now..
I would like to run my garage fridge off the batteries and maybe dump extra power (if any) into water heater (if possible)
I want to keep my 12 volt battery bank for the time being. (I will expand later need more cash)
I have six 6 volt batteries series/parallel hooked up to a 12 volt 3500 watt inverter right now.. (keeps fridge and freezer going during outages)
I also have an APC with two 12V boat batteries hooked to it that backs up my TV/PC/modem and router that rig runs my 55 inch plasma for over 4hrs.
If there is a better CC than that one for around the same money please let me know..
I would like to keep this under $2500 (wife is mad already)
Any help would be greatly appreciated.
Thanks,
Jim
I have been reading for 2 days now....... soooo much to take in...
I have an opportunity to buy some panels for $200 each, from a local guy going out of business but I must act fast so I need your help...
Panel info:
Nominal power [Wp] Pmpp: 235 watts
Voltage at nominal power [V] Umpp: 30.2 volts
Current at nominal power [A] Impp: 7.78 amps
Opencircuit voltage [V] Uoc: 37.1 volts
Shortcircuit current [A] Isc: 8.42 amps
My question is how many of these panels can I run thru this
Xantrex XWMPPT60150V Charge Controller (I can buy this from the guy for $500.)
Electrical Specifications
Nominal battery voltage: 12, 24, 36, 48, 60 Vdc
Maximum PV array voltage (operating): 140 Vdc
Maximum PV array open circuit voltage: 150 Vdc
Array shortcircuit current: 60 Adc maximum
We have a lot of power outages in my area and I have been wanting to get some solar panels for years now..
I would like to run my garage fridge off the batteries and maybe dump extra power (if any) into water heater (if possible)
I want to keep my 12 volt battery bank for the time being. (I will expand later need more cash)
I have six 6 volt batteries series/parallel hooked up to a 12 volt 3500 watt inverter right now.. (keeps fridge and freezer going during outages)
I also have an APC with two 12V boat batteries hooked to it that backs up my TV/PC/modem and router that rig runs my 55 inch plasma for over 4hrs.
If there is a better CC than that one for around the same money please let me know..
I would like to keep this under $2500 (wife is mad already)
Any help would be greatly appreciated.
Thanks,
Jim
Comments

Re: how many panels can I run thru this CC to charge 12 volt battery bank?
Welcome to the forum.
Well there is a better charge controller for about the same money: the MidNite Classic Lite: http://www.solarelectric.com/misoclli.html
That's brand new, with a warranty, functions better than the Xantrex (or anything else, really) and can have the LCD display added later if you wish.
A 12 Volt system on a 60 Amp controller basically adds up to a max of about (60 * 12 / 0.77) 935 Watts. So you could use four of those 235 Watt panels (940 Watts) comfortably. (The MidNite can handle up to 80 Amps without difficulty, by the way.)
That's enough charge power for 600 Amp hours of battery, so what size are your 6 Volters? Golf cart 220's by any chance? It would be in the right neighbourhood for that (660 Amp hours).
You would probably be best configuring the panels either all in parallel (in which case each will need its own 10 Amp fuse) or plan for expanding to a 24 Volt system by wiring two parallel strings of two in series (no fuses required).
A bit about array configurations: http://forum.solarelectric.com/showthread.php?16241DifferentPanelConfigurationsonanMPPTController
And another about battery configurations: http://forum.solarelectric.com/showthread.php?15989BatterySystemVoltagesandequivalentpower 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
Thanks for the quick reply Coot.
I wanted to buy 6 or 8 panels and keep my 12 volt set up until I save some more cash then buy a new 24V inverter
I have 6 volt golf cart batteries 195AH
Thanks for the info,
If you have any other ideas please let me know,
budget is $2500
CheersCariboocoot wrote: »Welcome to the forum.
Well there is a better charge controller for about the same money: the MidNite Classic Lite: http://www.solarelectric.com/misoclli.html
That's brand new, with a warranty, functions better than the Xantrex (or anything else, really) and can have the LCD display added later if you wish.
A 12 Volt system on a 60 Amp controller basically adds up to a max of about (60 * 12 / 0.77) 935 Watts. So you could use four of those 235 Watt panels (940 Watts) comfortably. (The MidNite can handle up to 80 Amps without difficulty, by the way.)
That's enough charge power for 600 Amp hours of battery, so what size are your 6 Volters? Golf cart 220's by any chance? It would be in the right neighbourhood for that (660 Amp hours).
You would probably be best configuring the panels either all in parallel (in which case each will need its own 10 Amp fuse) or plan for expanding to a 24 Volt system by wiring two parallel strings of two in series (no fuses required).
A bit about array configurations: http://forum.solarelectric.com/showthread.php?16241DifferentPanelConfigurationsonanMPPTController
And another about battery configurations: http://forum.solarelectric.com/showthread.php?15989BatterySystemVoltagesandequivalentpower 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?Thanks for the quick reply Coot.
I wanted to buy 6 or 8 panels and keep my 12 volt set up until I save some more cash then buy a new 24V inverter
I have 6 volt golf cart batteries 195AH
Thanks for the info,
If you have any other ideas please let me know,
budget is $2500
Cheers
Buy 6 panels from the guy.. buy the Midnite Solar Classic 150 for $620 (brand new) from NAWS (forum sponsor).. and be able to pump about 8090 amps thru it.. The Xantrex 60 is rated for a max of 60 amps.. which limits the amout of panels to like 4 like Cariboocoot stated..
You will need a combiner box with fusing.. as putting 3 or more panels in parallel will need fusing or breakers on each parallel 'leg'.
Midnite makes a MNPV6 which can hold upto 6 breakers.. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
Agree with all the above  the Midnite is the BEST currently available Charge Controller. It is far superior to the XW SCC. The XW needs an optional accessory to update the firmware, the XW SCC has a history of very BUGGY firmware, AND the XW Scc has lacked a very improtant function  a CC status output indicating that the batteries are fully charged, and excess PV power could be used for another purpose. This funciton is called an "Auxilary Output", and several CCs like the MidNite have the CC is in Float function builtin.
IMHO, there is no better CC than the MidNite Classic, it is by far the best, has the most functionality, and is constantly getting better with thoughtful and timely updates to the Firmware, via USB, or soon via Ethernet (both of these interfaces are builtin).
I have an XW SCC, which in my experience is a REAL SLUG of a CC.
Midnite Comparison Chart comparing CCs currently on market:
http://www.midnitesolar.com/pdfs/comparisonChart.pdf
Midnite Classic Brochure:
http://www.midnitesolar.com/pdfs/fullPage12Sept10a.pdf
This Thread on this Forum has a discussion of the attributes of the Classic Lite vs the standard Classic CC:
http://forum.solarelectric.com/showthread.php?16043NewMidniteClassicLiteannounced
I am very partisan regarding all of the functainality that the Classic CC brings to the Solar game, but I have no association with the company, other than being a very happy owner of MidNite Solar equipment. Just my opinions. Good Luck, VicOff Grid  Two systems  4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S530s, MX60s, MN Bkrs/Boxes. 25 KVA Polyphase Kubota diesel, Honda Eu6500isa, Eu3000ises, Eu2000, Eu1000 gensets. Thanks WindSun for this great Forum. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?Midnite Comparison Chart comparing CCs currently on market:
http://www.midnitesolar.com/pdfs/comparisonChart.pdf
Similar one but slightly longer from Home Power:
Attachment not found. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
Thanks for all the great input folks..
I will buy 6 panels, and the midnite classic 150 Charge controller
I will also buy the midnite disco combiner, extra buss bar and 6 breakers from NAWS....
Is there anything else I need???? other than cable 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
OK. I bought 6 panels.
Nominal power [Wp] Pmpp: 235 watts
Voltage at nominal power [V] Umpp: 30.2 volts
Current at nominal power [A] Impp: 7.78 amps
Opencircuit voltage [V] Uoc: 37.1 volts
Shortcircuit current [A] Isc: 8.42 amps
Now I need a CC
I like the Midnite Classic (not sure which one to buy 150/200/250)
I want to buy the right one keeping in mind adding 6 to 12 more panels to my system.
the first 6 I will put on my house thats all I can fit facing south...
If I add 6 or 12 more they must go on the shed which is about 150 feet away from my Generator, AC Panel and Battery bank.
I read Cariboocoot's posts about battery and panel wiring.
For long runs high volts low amps is best..
Could I wire my first 6 panels all in series = 222 volts into the midnite classic 250
then later (November) add another 6 into the mix? At that time I will add 6 more batteries and go up to 24V.
Thanks again Folks..
P.S. I'm new to this, all input/advise is welcome 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
I KNOW 6 in series will put you over the limit.. for a 12v battery bank..
Try this http://www.midnitesolar.com/sizingTool/index.php
Use the numbers from the back of the panels and then play with the battery bank and string's at the bottom..
Ok.. either way 6 in parallel or 6 in series puts you OVER the limits for the Classic.. 46.68 amps into the MPPT can make 139.6 amps into a 12v battery bank..
Even 3 by 2 or 2 by 3 will put you over for a 12v battery bank..
A 24v battery bank will let you do 6 in parallel but NOT in series.. you can also do 3 by 2 (6 panels) or 3 by 3 (9 panels)..
Anything above 9 Panels in any combo I just tried with the Calc will put you over the Max VOC..
A Classic 200 or Classic 200 Lite with a 48v battery bank will allow up to 16 panels in a 4 x 4 configuration.. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
Things to consider for wiring panels in series:
Do you actually have a long wiring run between the array and charge controller? Measure the distance and then you can try some numbers in a Vdrop calculator.
Charge controllers work more efficiently when the nominal array Voltage is close to the nominal battery Voltage. The greater the difference, the lower the efficiency. If possible, staying with the 2X factor works best: 12 Volt battery with a 24 Volt array, 24 Volt battery with a 48 Volt array, 48 Volt battery with a 96 Volt array.
The biggest concern is with Voc of the panels potentially exceeding the charge controller's maximum input limit. In this case the Voc is 37.1 and all six in series would be 222.6. This would only work on the Classic 250, and if the weather gets cold Voc could reach 289 and would shut even that down (hyperVoc function on Classics allows up to system Voltage above the rating, so 298 on a Classic 250 with a 48 Volt system). The Vmp would be 181.2, which is way above any battery system Voltage.
So let's see what options there are for those panels with 150 wire run and a 12 Volt system.
Best for conversion: all six panels in parallel. Array @ 30.2 Volts & 46.7 Amps. You'd need 4/0 wire. Out of the question.
Middle of the road: three strings of two in series. Array @ 60.4 Volts & 23.3 Amps. Would need about 4 AWG which is rather unmanageable.
Easiest without fuses: two parallel strings of three in series. Array @ 90.6 Volts & 15.56 Amps. 8 AWG gives about 2.5% Voltage drop. Voc is 112 and even in cold temps any good MPPT controller should handle it (max < 150). This is acceptable.
Highest Voltage: all six in series. Array @ 181.2 Volts and 7.78 Amps. About 14 AWG would do. Conversion efficiency will suffer several % drop.
Output of six 235 Watt panels is likely:
1410 Watts * 0.77 efficiency / 12 Volts = 90 Amps peak current. A MidNite Classic 150 is rated at 96 Amps on 12 Volts maximum.
1410 Watts * 4 hours good sun * 0.52 overall efficiency = 2.9 kW hours AC per day.
900 Amp hour 12 Volt battery bank @ 25% DOD = 2.4 kW hours AC.
(Please note these are rough calculations, not precise.)
Personally I hate to see that much power being utilized on a 12 Volt system. The current involved is not easy to handle. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?Cariboocoot wrote: »Easiest without fuses: two parallel strings of three in series. Array @ 90.6 Volts & 15.56 Amps. 8 AWG gives about 2.5% Voltage drop. Voc is 112 and even in cold temps any good MPPT controller should handle it (max < 150). This is acceptable.
Highest Voltage: all six in series. Array @ 181.2 Volts and 7.78 Amps. About 14 AWG would do. Conversion efficiency will suffer several % drop.
This may work though the Calc for the Classic 150 says Excessive Wattage.. says upto 97.9 amps into that 12v battery bank after MPPT conversion from the 15.56 amps in.. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?This may work though the Calc for the Classic 150 says Excessive Wattage.. says upto 97.9 amps into that 12v battery bank after MPPT conversion from the 15.56 amps in..
This could be, however the Classic should be able to clip that extra power on the occasions it occurs.
On the whole I wouldn't be running that size array on a 12 Volt system anyway. Great for 24, though. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
Thanks for the input guys...and the concerns about Excessive Wattage...
I can rearrange my batteries into 24V
How much is a decent 2000 watt 24V inverter gonna set me back?
What inverters do you like?
Thanks Coot and ywhic....... 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
A couple of thousand for an Outback inverter/charger.
But there are options, especially if you don't need the builtin charger.
NAWS inverter section: http://www.solarelectric.com/inverters.html 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
Samlex makes a 1500w 24v model for like $550.. you can go for a 2000w model for $740.. 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?
I've been so close to pulling the trigger on a Samlex 24V 1500 or 2000W but nobody has real life figures for idle usage. It seems the specs for idle usage on inverters are almost never right! 
Re: how many panels can I run thru this CC to charge 12 volt battery bank?I've been so close to pulling the trigger on a Samlex 24V 1500 or 2000W but nobody has real life figures for idle usage. It seems the specs for idle usage on inverters are almost never right!
They are horrible enough on the Samlex that you can believe it.
Keep in mind actual idle current will depend on what you power and how often the inverter switches in/out of standby. These less expensive units do not have good numbers for power usage and are limited in their programmability for this function.
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