What gauge wire?

[Keith_Haw]

I'm going to be adding a second solar panel and need to know what gauge wire I need for 2/140w panels on a 35' run.

Thanks
Keith

[BFL13]

Found that old thread (was mitch)
and where this all came up before--scroll way down to the MPPT30, just above that there is a line in red ink saying in the photo of the circuit board there is no coil so it is not true MPPT. (I saw your note that it might not need a coil though)

http://www.chinasolarregulator.com/solar-controller-cm50-cm60-cm6048-cm5048-cm3048-mppt-10-20-30.htm...

Ok saw that video and same thing, he shows this same write up with the red ink warning.

[Salvo]

This video thinks it's not a mppt controller.

https://www.youtube.com/watch?feature=player_embedded&v=KA3X8XLxWHU

However I'm not 100% sure he's correct. The real check is to test it. He failed to do that. I've designed inductors where the windings is a spiral trace on the pwb.

[Salvo]

Yes, I've seen the discrepancy in current. He provided his phone number. Give him a call. I doubt he'll mind.

[BFL13]

Salvo, I can't see how that post shows the unit is MPPT. He says he was getting 8.9amps from 3-95w panels. If Isc is 6a then max expected amps in PWM would be 18a in parallel.

With those three in series amps would be 6a and 8.9a would show bucking 24-12, but are they in series? Total Voc would be about 3 x22=66 which is under the 75v limit so they could be. Did he change his panels from parallel to series or just change controllers from PWM to this unit?

Windynation also has one of these Solar30 looking things and there, it explains in the blurb somewhere it is not really MPPT IIRC. This came up when that lady (sorry, can't remember her name) was posting about her ISTR flexible panel ?? vague about it all now, and she bought one of these controllers.

[Salvo]

Harry Parsonage
Subject: Install of Qianqsun® LCD 30A MPPT Solar Panel Regulator Charge Controller 12V/24V
380W/760W With USB
Letter Mailed to:
Peng Jian Chu-YP
8th Flr Bldg 6F
Ju Yin Technology Industrial Park
Gan Li Road No. 1
Bu Ji Long Gang District
SHENZHEN GUANGDONG
CHINA 518112

I recently purchased your Solar Charge Controller via Amazon.com and installed it into my RV. I
have 3 – 95 Watt Solar panels on the roof and 4 pairs of 6 Volt – 225 Amp Hour batteries on the
coach. I used your controller to replace the Go-Power SC30 Charge Controller; which was working
just fine, but it does not have MPPT protocol for maximizing the charge of the batteries.
Even though I had a small place to mount your Charge Controller, I was able to do so in the same
footprint as the SC-30 controller.

I am not using the “Auxiliary Power Output – i.e. Load Control” feature of your controller, so there is minimal heat dissipated by the unit. I did however, mount the unit onto the control panel with ¼”
stand-offs to keep the base plate properly ventilated. Note: The space behind the face of the control center is about 3-1/2 inches deep, so there is adequate air space behind the MPPT controller.
Shown above is the remote display panel of the Bogart Engineering PentaMetric Battery Monitoring system. This device monitors the power flow of my battery bank, Amps Input from solar, Amps Input from on board Converter / Charger, and Amps draw by the 3000 Watt Inverter. The unit also collects historical data, so I can analyze the consumption of power on the RV over many months of use.
The system also collects data about battery state, voltage and amperage, during the different charging phases that your MPPT controller will apply to maintain the batteries.

The photo below shows the Input from the solar panel ( i.e. 8.92 Amps on Bogart and 8.9 on Qianqsun Unit) and current battery bank voltage level ( 13.6 as shown on both displays).

As you can see in the first photo above, I plugged in the short Temperature Thermister into the top of the unit. If I want to have actual battery temperature, what Thermister (i.e. 100 K ?? ) can I mount on the negative terminal of the coach battery which is about 20 Ft away from this MPPT controller?

Yesterday I ran multiple 110 Vac appliances ( Microwave / Convection Oven, Electric Hot Water Pot, TV and Satellite Receiver ) and as many of the 12 volt devices (i.e. Refrigerator on 12 Volt ) I could turn on in the coach. The peak load on the battery bank was 82 Amps, but the average was 16.8 Amps over the 8 hour day of use. Note: The instantaneous voltage, during the peak 82 Amps of draw, was a low of 12.3; returning to 13.6 on average. At the end of the day my battery was down about 10%. Today I checked and the battery has fully recovered to 100% just from solar input late in the evening and from early morning sunlight. So it appears your unit is working, and I will continue to monitor its performance over the next few months.

Regards
Harry N. Parsonage
Gamma Infinity, LLC
1547 Palos Verdes Mall #404
Walnut Creek, CA 94597
(925) 945?0672

[BFL13]

Salvo wrote:
This person seems to believe it works as a mppt controller.

Qianqs controller

Salvo, always willing to learn, but not registered for that forum. Can you cut and paste here? Thanks.

[Salvo]

This person seems to believe it works as a mppt controller.

Qianqs controller

[BFL13]

Salvo wrote:
Here's a mppt controller for $48 including shipping. Voc = 75V

Qianqsun mppt

For $48 you can go serial, keep your existing cable and just swap out the controller. In addition you'll get 5% more current.

BFL13 wrote:
The $102 Eco-Worthy 20amp MPPT is the lowest cost "real" MPPT but it can only do about 42-45 Voc input limit, so it can do one big panel (250w max?) but not two 12v panels in series. (22 +22=44)


So the money does not work out for going MPPT in this case just to be able to use some skinnier wire.

Salvo, AFAIK that is a version of the Solar30 PWM controller. It has no inductor etc in its circuit board and somebody painted MPPT on it.

There are several of these "fake MPPT" controllers going for low cost. They are just straight PWMs that work with 12v panels

JiminDenver sometimes finds Eco-Ws going for less than the usual $102 at maybe $85 or whatever but that is the only case I know of less than $100

[Salvo]

Here's a mppt controller for $48 including shipping. Voc = 75V

Qianqsun mppt

For $48 you can go serial, keep your existing cable and just swap out the controller. In addition you'll get 5% more current.

BFL13 wrote:
The $102 Eco-Worthy 20amp MPPT is the lowest cost "real" MPPT but it can only do about 42-45 Voc input limit, so it can do one big panel (250w max?) but not two 12v panels in series. (22 +22=44)


So the money does not work out for going MPPT in this case just to be able to use some skinnier wire.

[pianotuna]

Hi Keith,

First, there are no stupid questions.

Since you have a Blue Sky Controller, you would buy the sensor probe from Blue Sky and follow their directions for placement.

Keith Haw wrote:

pianotuna wrote:
Hi,

#10 will be just fine with a pwm controller. I would add a temperature sensor.

Hate to sound stupid but, where would I find a temp sensor and where would I connect it?

Thanks
Keith

[CA_Traveler]

Keith Haw wrote:

pianotuna wrote:
Hi,

#10 will be just fine with a pwm controller. I would add a temperature sensor.

Hate to sound stupid but, where would I find a temp sensor and where would I connect it?

Thanks
Keith

Some controllers have a connector for the temp probe and it may be an additional item to purchase. The probe end is attached to a battery post or glued to the case.

Some controllers have a temperature sensor build in and if they are in the general area of the battery that's good enough. Note that batteries should be isolated from electronics due to their vapors.

Some controllers don't have a temperature sensor.

Knowing the temperature allows the controller to better adjust the amount of charge.

[Keith_Haw]

pianotuna wrote:
Hi,

#10 will be just fine with a pwm controller. I would add a temperature sensor.

Hate to sound stupid but, where would I find a temp sensor and where would I connect it?

Thanks
Keith

[Salvo]

You don't understand all the ramifications of lower voltage in a pwm system. We've had this discussion before. I had shown voltage is also important for pwm charging.

pianotuna wrote:
Hi Salvo,

You know that pwm doesn't control voltage so the top 2.6 volts on a 17 volt panel don't matter a hoot, assuming a 14.4 charging voltage. #10 wire is good for 30 amps. 280 watts/12.8 volts =~22 amps max.

[BFL13]

The $102 Eco-Worthy 20amp MPPT is the lowest cost "real" MPPT but it can only do about 42-45 Voc input limit, so it can do one big panel (250w max?) but not two 12v panels in series. (22 +22=44)

So that forces you to pay kazillions of dollars for MPPT just to run a couple of 12v panels and BTW you don't get any more amps with the MPPT unless you are at the North Pole. The MPPT method requires voltage and the panel loses voltage as soon as the sun gets on it, costing you amps. (you can't get anything with no sun and you lose when the sun is out!)

So the money does not work out for going MPPT in this case just to be able to use some skinnier wire.

Go parallel and PWM. You can wire it all sorts of ways, even use two PWM controllers (eBay $20 each) one for each panel and parallel them to the battery, or several other ways, doesn't matter, you will get your "expected amps" (two times the Isc of one panel)

My 130w panel got its expected amps (its Isc of 8.2a) even on hot days (which badly degraded the MPPT set but had no effect on the PWM set)), on 45 ft one way of #8 as an example.

IMO first try it on the existing wiring and if not satisfied, then get into improving the wiring.