Best practice Panel wiring for optimal performance for 24 Volt System

akaschmid

Hi all

I have 6 Multicrystalline Modules, with the following Specs, see below

I have a battery bank of 6 volts, 415 AH * 8 Rolls batteries arrange in (Series and Parallel)
To produces a 24 Volt System 1660 AH

My question is this ? How can I arrange or connect the Panels for optimal performance.

A tutorial or a link or guideline will be appreciated

Module Type LDK-250P-20
Nominal Power = (Pmax) 250W
Minimum Output Power 250w
Voltage at Pmax (vmp) 30.3V
Current at Pmax (Imp) 8.27A
Open Circut Voltage (Voc) 37.7v
Short Ciruit Current (isc) 8.69A

Thanks in Advance

Akaschmid

vtmaps

Re: Best practice Panel wiring for optimal performance for 24 Volt System

akaschmid wrote: »

My question is this ? How can I arrange or connect the Panels for optimal performance.

Welcome to the forum. You didn't mention what charge controller you have and what the distance is from the Array to the controller.

You have several configuration options for the panels and the optimal design will depend somewhat on the answers to those two questions.

--vtMaps

akaschmid

Re: Best practice Panel wiring for optimal performance for 24 Volt System

Hi vtMaps

Thanks for your speedy reply

The distance between the charge controller and the panel is 5 meters. I have the following


XTM 2400-24 (-01) XTM 2400-24 Inverter/charger Xtender
Output voltage = 230 Vac / 50 Hz
Battery voltage = 24 Vdc
Charge current = 55 Adc
Maximum current = 50 Aac
Power P30 / pNom = 2400 / 2000 VA
Power Smart-Boost = 2400 VA

XTS 1200-24 (-01) VT-80 VarioTrack MPPT Solar charge Controller
Output voltage = 230 Vac / 50 Hz
Battery voltage = 24 Vdc
Charge current = 25 Adc
Maximum current = 16 Aac
Power P30 / pNom = 1200 * / 650 VA
Power Smart-Boost = 1200 VA

The company that produces the equipment is : http://www.studer-inno.com/?cat=sine_wave_inverter-chargers&id=432&pId=1214&tab=1#ul

vtmaps

Re: Best practice Panel wiring for optimal performance for 24 Volt System

akaschmid wrote: »

The distance between the charge controller and the panel is 5 meters. I have the following

I assume the Variotrack controller is similar to other controllers in that it will be more efficient and run cooler if you minimize the difference between the input and output voltages. Your panels are Vmp = 30.3 and your battery is 24 volts. Putting all the panels in parallel will NOT work because a Vmp of 30 cannot charge a 24 volt battery. Your optimal configuration is two panels in series to make a string with Vmp=60.6. With 6 panels you can make 3 strings and put them in parallel (use a combiner). Each of the three strings will need a circuit breaker in the combiner box.

The only reason to configure differently would be if your panels were very far from your controller. Then you might want a higher voltage to reduce losses in the cable. Your panels are close to your controller (5 meters)... 10 gauge copper cable will handle the current with very little loss.

--vtMaps

akaschmid

Re: Best practice Panel wiring for optimal performance for 24 Volt System

vtmaps wrote: »

(use a combiner). Each of the three strings will need a circuit breaker in the combiner box.
--vtMaps

Thanks for your support

Can you please recomend any good Combiner box I can make use of ?


Akachmid

vtmaps

Re: Best practice Panel wiring for optimal performance for 24 Volt System

akaschmid wrote: »

Can you please recomend any good Combiner box I can make use of ?

I have this one and like it:
http://www.solar-electric.com/mnpv3.html

--vtMaps

Cariboocoot

Re: Best practice Panel wiring for optimal performance for 24 Volt System

akaschmid wrote: »

Hi all

I have 6 Multicrystalline Modules, with the following Specs, see below

I have a battery bank of 6 volts, 415 AH * 8 Rolls batteries arrange in (Series and Parallel)
To produces a 24 Volt System 1660 AH

Wrong. Eight 6 Volt 415 Amp hour batteries arranged for 24 Volts would be two parallel strings of four making 830 Amp hours, not 1660. Amp hours only add for parallel connections, Volts only add for series connections.

My question is this ? How can I arrange or connect the Panels for optimal performance.

A tutorial or a link or guideline will be appreciated

Module Type LDK-250P-20
Nominal Power = (Pmax) 250W
Minimum Output Power 250w
Voltage at Pmax (vmp) 30.3V
Current at Pmax (Imp) 8.27A
Open Circut Voltage (Voc) 37.7v
Short Ciruit Current (isc) 8.69A

Thanks in Advance

Akaschmid

You need approximately 83 Amps peak to charge that battery bank. A 25 Amp controller is not going to do it. You need a big controller like a MidNite Classic to handle that much current.

Moreover your six 250 Watt panels will only produce about 48 Amps @ 24 Volts which is not enough to charge the batteries. That is a mere 5% maximum charge rate and far too meager for those batteries.

Otherwise the panels would need to be arranged as strings of two in series in order to obtain minimum charging Voltage, and then three such strings in parallel (each string should have a fuse or breaker in it to protect in the event of a short).

You need about double the amount of panel.

vtmaps

Re: Best practice Panel wiring for optimal performance for 24 Volt System

Cariboocoot wrote: »

You need approximately 83 Amps peak to charge that battery bank. A 25 Amp controller is not going to do it. You need a big controller like a MidNite Classic to handle that much current.

The VT-80 VarioTrack MPPT controller is an 80 amp controller. I agree that his array is a bit undersized, but I thought maybe he has grid... those inverters look like they may be hybrid inverters.

--vtMaps

Cariboocoot

Re: Best practice Panel wiring for optimal performance for 24 Volt System

vtmaps wrote: »

The VT-80 VarioTrack MPPT controller is an 80 amp controller. I agree that his array is a bit undersized, but I thought maybe he has grid... those inverters look like they may be hybrid inverters.

--vtMaps

The specs given make no sense at all:

"XTS 1200-24 (-01) VT-80 VarioTrack MPPT Solar charge Controller
Output voltage = 230 Vac / 50 Hz
Battery voltage = 24 Vdc
Charge current = 25 Adc
Maximum current = 16 Aac
Power P30 / pNom = 1200 * / 650 VA
Power Smart-Boost = 1200 VA"

I see "25 Amps DC" which is not 80 Amps by a long shot. Why VAC numbers are mixed up in this I don't know, and I'm not going to sort it out either. I can only say what would be needed for the batteries chosen.

It sounds like one of those all-in-one units which usually do not have satisfactory performance (or flexibility).

The array is significantly undersized and would require much charging from grid or generator to keep the batteries from dying.

vtmaps

Re: Best practice Panel wiring for optimal performance for 24 Volt System

Cariboocoot wrote: »

The specs given make no sense at all:
<snip>
It sounds like one of those all-in-one units which usually do not have satisfactory performance (or flexibility).

I think it's some very high quality Swiss made equipment.
controller: http://www.studer-inno.com/?cat=mppt_solar_charge_controller&id=2094
inverter: http://www.studer-inno.com/?cat=sine_wave_inverter-chargers&id=432

--vtMaps

Cariboocoot

Re: Best practice Panel wiring for optimal performance for 24 Volt System

vtmaps wrote: »

I think it's some very high quality Swiss made equipment.
controller: http://www.studer-inno.com/?cat=mppt_solar_charge_controller&id=2094
inverter: http://www.studer-inno.com/?cat=sine_wave_inverter-chargers&id=432

--vtMaps

That would make sense (and work) but does not explain the info in the OP's post.

zoneblue

Re: Best practice Panel wiring for optimal performance for 24 Volt System

Indeed, impressive specs. What do those go for?

---

Tracking efficiency: >99%
Conversion efficiency: >99%
4 step charger for longer battery life
8 predefined battery charge curves as standard
Free programming of the battery's load curve with the RCC-02/-03
Low self-consumption: <1W in night mode
Protection against incorrect wiring
Protection against reverse polarity
Fully configurable
IP54 enclosure
Comprehensive display, programming and data logging with the RCC-02/-03
Up to 15 VarioTrack in parallel on the same communication bus
Compatible with all PV systems
Optimal usage in an Xtender system with a synchronized battery management