connect mppt to pwm?

[nemie]

I have a mppt 30amp regulator and a pwm 30amp regulator can I connect them together, as I was running 160watt but now I am adding another 240watt, so 400 in all and as far as I understand things, 30amp regulator can only do up to 360 watts.

This is a 12 volt system 5x80watt panels.

[Sunking]

Well for one if you are using a PWM controller I seriously doubt you would need 2 controllers @ 30 amps. With PWM controllers they do not specify maximum panel input power, only voltage and current. With a PWM controller input current = output current. If you are using standard 12 volt solar panels each panel should have a Imp (current @ maximum power) = about 5 amps or less. So with 5 panels in parallel = 25 amps which is less than 30 amps.

As for MPPT you would not use 2-30 amp controllers, you would use a single 40 amp controller. But it really depends on the controller as some of the 30 amp controllers can handle 400 watts input just fine.

[computerpc101]

To make it simple.
It is not wise to use multi controller due to very hard to balance loading.

You should buy a MPPT 40A+ controller.
Since, you has 30A controller, It might be fine, you might test it before buying 40A controller.

1). Did you measure the maxium current from 160 watts panel at noon sun? Do you really get 13A? My understand is that, most panels product less power than their rating. My friend's solar panel, It is rated for 12A, He got 7.5A in real world at noon sun, He never see it over 8A.
2). you need to measure how hot your 30A controller with 160watt panel, If it is not too hot, It might be fine with 400 watts.

[nemie]

I went by written spec and did not allow for loss.

Right now I am using a MPPT 30amp (From china might be crap as far as MPPT goes) but was given free a pwm 30amp with the last three panels I bought, I should have them all this week, delay over Xmas and all that.

I have no idea how to measure the maximum current from 160 watts panel at full sun do I need a standard multi meter?


Thanks and happy newyear.

[computerpc101]

It is not a good idea to connect charging regulator in parallel to increase your current rating because they are not able to balance loading. it apply on both PWM and MPPT regulator. in your case, 30A regulator might be fine, Off course, It is better to use 40A+ regulator.

Solar panel's current rating is measured at sunlight 1000watt/M2, it is very strong sun, Most area, they get 70% of its rating current only.

You need to get a multi-meter to measure it to prove it.

http://www.mtmscientific.com/solarpanel.html

It is a better Idea to use MPPT regulator than PWM regulator. More power to your battery, Sine maxium power happen to solar panel between 17 volts to 24 volts while battery voltage is 12-13.5 volts.
Let assume maxium power happen at 20 volts. and solar panel's charging current is 10A
MPPT regulator, you get 20 voltsx10A power = 200 Watts power charging to battery , Aprom 15A current charging to battery
PWM regulator, you get 13 volts x 10A power = 130 Watts power charging to battery, Aprom 10A current charging to Battery

In very simple term, Real testing with solar panel
In strong sun situation
MPPT regulator produce 25 - 40% more charging current to battery compare to PWM regulator.
In Mid sun situation
MPPT regulator produce 40 - 100% more charging current to battery.
In Low sun situation
MPPT regulator produce 100% - 300% more charging current to battery.

[nemie]

I appreciate the information and the link, computerpc101.

[Sunking]

You need to get a multi-meter to measure it to prove it.
http://www.mtmscientific.com/solarpanel.html

That resistor kit they are trying to sell it just about useless.

[nemie]

That resistor kit they are trying to sell it just about useless.

I was looking at this one, would it work?

http://www.ebay.co.uk/itm/2-Ohm-2R-50W-Watt-Power-Metal-Shell-Case-Wirewound-Resistor-/150684443609?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item23157e23d9

[Sunking]

I was looking at this one, would it work?

It is a start but you need a lot of resistors. Max power point is a moving target, not fixed. In addition you would also need resistor to find the points above and below MPP.

Besides that resistor would be limited to 50 watt panel operating at 10 Vmp. There is no such thing as a 10 volt 50 watt panel I know of. For DIY purposes there is no real way to measure your panels maximum power with any degree of accuracy. You have no way to control temperature, humidity, or sunlight.

[computerpc101]

nemie, Please, Do not waste money to buy those resistor. Do not waste your time to measure maximum power point of your solar panel, They keep on change, Let MPPT charger take care of it, Are you using those Resistor to measure current?

Just for current measurement for one 160w Solar panel, you can buy Digital multi-meter with 20A+ Range for $few bucks from Ebay.

If you want a permanent nice looking gauge to monitor your solar system, you might buy "current shut" and "digital meter" for about $10 to 20, you can monitor your system charging and discharging.

Also, I am not exactly sure what you are doing, Just remember, Once you add 240 watts solar panel, you might need to really pay attention to wiring, With 30A passing wires, If you use thin wires, they will get really hot and melt the jacket.

[nemie]

3 x Brand New In Box 80w Photovoltaic Solar Panel with a 30amp regulator, and 5metre cable ideal for use with Motorhomes/barges/caravans

New specially designed shaped panel which reduces the heat effect and increases performance

Tuv Class Two IEC 612 15

Specifications:

PV Module with 80W maximum power

Cell: Monocrystalline Silicon Solar Cells

No. of Cells and connections: 36 series

Application: DC 12V System

Max System Voltage: 715V DC

These panel are all flash tested


Series Fuse Rating: 10A

Power Tolerance: +/- 5%

Surface max load capacity: 60m/x (200kg/sq.m)

Weight (approx): 9 kg

Dimensions: 122cm x 56cm x 3.5cm

Electrical Specs:

Max Power: 80WP

Open Circuit Voltage (V): 24

Short Circuit Current (A): 4.45

Max. Power voltage (V): 20

Max. Power Current (A): 4


Absolute Maximum Rating:

Operating Temperature: -40 to +80 Degrees

Storage Temperature: -40 to +80 Degrees

Temperature coefficients of Isc (%): 0.1/Degree

Temperature coefficients of Voc (%): -0.33/Degree

Temperature coefficients of Pm (%): -0.23/Degree

Temperature coefficients of Im (%): 0.08/Degree

Temperature coefficients of Vm (%): -0.33/Degree

Irradiance: 1,000W/m2

Temperature: 25 Degrees

Comes with FREE internal bypass diode to prevent backfeed to any batteries.

FREE Cable with MC4 Connectors this comes already attached to the back of the solar panels.

Comes with 30amp regulator

These panels are fully weatherproof and are ideal for use on Motorhomes etc

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[nemie]

My Goal is to upgrade 2x80watt panels with three more 3x80watt panels, total 5x80watt = 400watt.

Here is the design so far:

build 1_RESIZED_TO_600x349.jpg

I will be asking about wiring as soon as the panels arrive and I get better understanding of what route to take, i.e. the expensive route buy MC4 cable x3 10 meter

[computerpc101]

I am new to solar panel, I do have very strong Electronic background. If I am wrong, Please correct me.

From your Solar panel spec;

Maxium power happen at Aprom 20 Volts.
400 Watts panels output current is about 400W / 20 volts = 20 AMP @ Solar panels side
-----------------------------------------------
On Battery side using Mppt regulator.
20 volts - 13.2 volts(Battery) =6.8 volts
6.8 volts x (85% MFFT regulator effective )= 5.8 volts
(5.8volts x 20A) / 13.2 volts = 8.8A

Total current will be 20A +8.8A = 28.8A on Battery side
------------------------------------------------------------
Therefore Both PWM and Mppt battery regualtor will work fine.
PWM regulator = 20A current charging to battery (400 W input)
Mppt regulator = 28.8A current charging to battery (400 W input)

In Real world, There for many loses in the system, Wires resistance lose, High temperature lose Etc, you might really have about 350 W or less.

From your spec, Your solar panels have diodes in junction box, If you are using 12 volts system, you just need to connect them together with right polarity (+) (-) , Since each panel is 4A output, you don't really need thick wires, However, All bus wires, they carry near 30A, you really need very thick wires in those area.

Lose in wires. Assume wire resistance is 0.5 ohm.
For 4A single solar panel output, It loses 4A X 0.5 ohm= 2 Watts (Heat lose)
(Not bad here, so you can use little thinner/longer wires)

For bus wire to battery, It loses 28.8A X0.5 ohm= 14.9 Watts (Heat lose)
( Must use thick wires and as short as possible)

[Mike90250]

Look below in my .sig, for the link to the spreadsheet for the wire caculator (wire size and loss), that takes all the guesswork out of the wireing !