New to Forum, new Kid, testing it out

[Jacotenente]

Hi - Just installed my new Kid from NAWS. I was using a Tracer 3215N 30A with optional meter and now have the Kid. As you can see from the attachments, I am running six Renogy 100D panels over 100' of 10AWG cable into the Kid (24v array system). The Kid is charging my six 29DC Deep Cycle Marine batteries (using 8-gauge wire to the batteries, 12v system). The batteries are in parallel using 1 AWG cables. The 12v routes up to my Powerbright 3,500 watt inverter using 0-AWG cable. I use the inverter to power garage electronics...mostly one fridge and one deep freezer. It works well.

Question: I set up the Kid per owners manual and today I am running around 26 amps at about 350 watts (according to the meter, almost full sun). I assume since the panels are wired for 24v, wattage is lowered. You would think six 100 watt panels = 600 watts. Is this normal?

About me: Retired Air Force (21 years) living in Moore, Oklahoma. Originally from Michigan.

Chris

[Jacotenente]

Here are some pics for what I am talking about...

[ClassicCrazy]

When in Bulk the charge controller will let in as much current as possible. When it goes to Absorb the controller will decrease the current to maintain the batteries at the absorb setpoint. 

Watts stay the same - current amps will change depending on the voltage .  Watts = voltage x amps.

How do you have your panels wired up ? three strings of 2 panels per string ?  600 watts charging 12 volt batteries would put you over the 30 amp current limit on the Kid I believe.

It isn't always you will see the rated current from a panel even in bulk - it all depends on the temperature, sunlight intensity, etc. Crystaline panels put out more current when they are colder.  The black amorphos type put out more power when they are warmer I believe.

Just found this which explains differences in panel types.
http://energyinformative.org/best-solar-panel-monocrystalline-polycrystalline-thin-film/

[Free Energy Freak]

First, thank you for your service to our country.

... I am running six Renogy 100D panels over 100' of 10AWG cable into the Kid (24v array system).

Is the 100' round trip of #10 awg wire?


Also, you have 2 panels in series, and three strings of those panels in parallel?


It will not hurt the controller, but that is over the controller's maximum output rating for 12vdc (to the batteries).

I am just going off the top of my head here. But, I am thinking you need to use a line loss calculator to determine your power loss from the panels to the controller. Something tells me you are WAY small on the gauge wire you need for that run. Probably closer to #2? You need to be at 3% voltage drop, maximum. That #10 just ain't gonna do the job for ya, at a 100 feet run. (See attached wire run chart, below.)

The Kid is charging my six 29DC Deep Cycle Marine batteries (using 8-gauge wire to the batteries, 12v system). The batteries are in parallel using 1 AWG cables.

You have 6 - 12vdc batteries in parallel?

I would change that inverter for one with 24v input. Then, I would connect two each of your 12v batteries in series, making three strings of batteries at 24vdc.


I used the Midnite Kid Sizing Tool and came up with the following information. (See two attached pdf files, below.) File chris_01.pdf is, if I am correct, your current set up. Take a look at the second file, chris_02.pdf, to see how much of a difference it would make if you were to wire the batteries in series. They would charge more equally as well.

Question: I set up the Kid per owners manual and today I am running around 26 amps at about 350 watts (according to the meter, almost full sun). I assume since the panels are wired for 24v, wattage is lowered. You would think six 100 watt panels = 600 watts. Is this normal?

Watts remain the same. As voltage increases, amperes decrease, to achieve the same wattage.

[Jacotenente]

Wow - Thanks for the responses. Forgive me if I don't answer all the questions:

1) My panels are wired series-series-series-parallel
2) Six batteries are wired in parallel for 12vdc to the inverter
3) The PV cable is super thick 10 AWG or 8 AWG stranded

When I was running my Tracer 3215 with the meter, it would read over 30 amps at full sun. The Kid is reading around 25 amps in full sun (still new, still testing) and around 350 watts with the input voltage in the pictures I posted. Still not sure if this is correct wattage...

I am thinking about adding two more panels to the array...thoughts? This would give me eight.

Also, my garage is hot (like 97 degrees) and both fridges are running full tilt off the inverter...so, kinda like a "push-pull" deal going on. I am throwing amps into the battery bank, and at the same time pulling amps out to power the inverter.

Also, the Kid is performing it's charge/absorb similar to the Tracer 3215 I just took off. At night (no sun, no charging) the fridges are both still on full tilt. By early morning, the battery bank voltage sits at around 12.3 to 12.4 vdc. And then the charging/powering kicks back in as the sun comes up. I am thinking a couple more 100 watt panels would be nice.

[Free Energy Freak]

Wow - Thanks for the responses. Forgive me if I don't answer all the questions:

1) My panels are wired series-series-series-parallel
2) Batteries are wired in parallel for 12vdc to the inverter
3) The PV cable is super thick 10 AWG or 8 AWG stranded

When I was running my Tracer 3215 with the meter, it would read over 30 amps at full sun. The Kid is reading around 25 amps in full sun (still new, still testing) and around 350 watts with the input voltage in the pictures I posted. Still not sure if this is correct wattage...

I am thinking about adding two more panels to the array...thoughts? This would give me eight.

Also, my garage is hot (like 97 degrees) and both fridges are running full tilt off the inverter...so, kinda like a "push-pull" deal going on. I am throwing amps into the battery bank, and at the same time pulling amps out to power the inverter.

Was your original post correct, 100 feet run of #10? I still say you need to address that distance. Can you move your panels closer to the controller? No matter how "super thick" #10 wire is, it is still only #10, or maybe #8. Either way, you need to look at the chart, or a voltage drop calculator to see what I meant about that.

I would not increase the number of panels until you increase your wire size, relocate your panels (or controller) closer to each other, or increase your battery bank (system) voltage to 24v.

The maximum amperes the Kid can send to the batteries, regardless of the amount of watts of PV, regardless of the wire size, is still going to be 30 amperes. That's it. How you increase the total power sent, is by increasing the voltage:

12v x 30a or
24v x 30a or
48v x 30a

It's still going to be limited to 30 amperes.

I have, in my mind, given you the best advice I can regarding wiring, cable size, and battery orientation. Feel free to ask others for their input, both here and on other forums.

[Free Energy Freak]

I am thinking a couple more 100 watt panels would be nice.

Brother, it looks like you have made up your mind what you want to do, regardless of what advice anyone gives you.

So, I will now tell you what you want to hear. Buy two more panels and put them in series / parallel with the other six. That will be perfect. It will do exactly what you need it to do. Don't worry about all the power you are losing along the way. Adding more panels will make up for it.

[TomW]

Just a note that The Kid will regulate itself to a maximum of 30 amps out to the battery even if there is more power available. So you cannot "overpower" it but you still need to respect the source voltage limits.

At least that is the info I have.

Going too far over the power limits will not harm The Kid but will waste a lot of potential power production. May not be a big deal?

Tom

[Jacotenente]

Copy that...thanks all for the responses. 

- 30 amps is plenty of charging power right now...with more panels, more time maxed out, more absorb time
- The PV cable run is through the attic out to the backyard pergola. So, moving things closer would be better, but not feasible at this time. Actual length is about 80-85'
- My set-up was designed for emergency back up for power failures (after the 2013 tornado that took out 1/3 of Moore). People were running power generators and getting sick, constant re-fueling, and noisy. So, I came up with this idea and it has proven it's worth on a small scale. Now it runs 24/7.
- Long PV cable runs are not ideal, I know that, but space is limited (small house, garage)
- A 24vdc inverter would be great and I might do that eventually along with the battery bank.

Again, thanks.

[Resthome]

Electrical Specifications
Optimum Operating Voltage (Vmp): 18.9V
Optimum Operating Current (Imp): 5.29 A
Open - Circuit Voltage (Voc): 22.5 V
Short- Circuit Current (Isc): 5.75 A
Maximum Power at STC: 100 W
Operating Module Temperature: -40°C to + 90°C
Maximum System Voltage: 600 V DC (UL) / 1000 V DC (IEC)
Maximum Series Fuse Rating: 15A
STC: Irradiance 1000 W/m2, module temperature 25°C, AM=1.5;

This appears to be the specs on your panels. And from your description you are running 3 panels in series and have two parallel strings.

Your wire runs from the PV to the Controller are undersized and you should be using a larger gauge wire from combiner to the controller as other have stated. Remember for DC you have to measure the distance round trip, so you have to double the one way distance to calculate the voltage drop in the wire. Looks like the distance from the controller to the batteries is reasonable from your photos. Even at absorb voltage of 14.5V you would only see 435W with the Kid.

[zoneblue]

The Kid clearly says input voltage is 27V. Thats either two in series, or very very  late in the day.

At 12V a kid can only accept and output  360W.  Hence you have maxed the controller out.

If its two panels in series, thats a hefty 9% voltage drop:

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=36&phase=dc&noofconductor=1&distance=100&distanceunit=feet&amperes=16&x=44&y=14

Ive pointed out the numerous other issues with this system previously.

[Free Energy Freak]

I'm glad I'm not the only one around here who doesn't know what he is talking about.

[dgd]

- 30 amps is plenty of charging power right now...with more panels, more time maxed out, more absorb time

As others have told you, six 100watt panels are too much for a 30amp controller.
A suggestion:
Connect only four of the 100watt panels to the KID, two parallel groups of two in series.
Connect the other two in series and into the Tracer controller.
Connect the outputs from both controllers to the battery bank via 30A breakers.

If you no longer have the Tracer a better solution would be to get  a second KID then use it for the two panels plus the two  more you mentioned adding.

dgd

[acorn]

It's still unclear to me whether Chris's system is wired with 2 or 3 panels series in each series string. If it's 2 panels, then it seems like it would make sense to suggest setting the panels up in series strings of 3 panels. This would give a higher voltage over the long cable run, reducing current and hence voltage drop. (The voltage drop table posted by "Free Energy Freak" looks to be for 12 volts, but we have either 24 or 36 volts nominal for this cable run depending on the series/parallel configuration). The Voc of the Renogy panels is 22.5 volts, so 3 in series should be within spec on the Kid.

Beyond that, Chris notes that his Tracer MPPT controller was able to generate 30A output with the panels in their current configuration. If we believe the instrumentation used for the measurement then it seems like the Kid should be able to do the same. However, the Tracer spec sheet for the 3215RN (note RN not N, not sure what's different, but I can't find specs for the "N") claims full output up to 45 degrees C ambient (113 F). Midnite only states "Controller will auto derate as temperature rises above 25 C". Chris states his garage is at 97 F (36 C), so perhaps the Kid is throttling output based on heatsink temperature. Maybe try pointing a fan at the Kid on the next sunny day at peak output time and see if you get closer to 30A?

Yes, the 600W of panels is over the input power that the Kid can effectively use, but then that power surplus should let the Kid achieve maximum output. Chris is okay with the power loss over the cable run, I suspect. He'd just like to see full output from the charge controller. Perhaps misconfiguration (hard to guess what), or my guess is the ambient temperature. Perhaps other Kid users can comment on how the Kid fares in high ambient temps and what kind of derating they've seen.

Caveats: we don't know what voltage the Tracer was maintaining at 30A, so we don't know the actual power, just the current. One poster commented that 360W is the Kid maximum output, but that would be at 12V, and we'll usually see higher voltages. At 13.7 volts a maximum output current of 30A would imply 411 watts. Since Midnite only specs a current output it seems like maximum power with FLA's should be around 14.5V * 30A = 435 watts. (Depends on your absorption voltage, but 14.5 is in the ballpark).

In short, if the Tracer could get the output using the same panel and wire configuration, it doesn't seem like it makes sense to blame the panels and wiring for lack of input power to the Kid. I suspect the temperature issue...

-Scott

[ClassicCrazy]

Copy that...thanks all for the responses. 

- 30 amps is plenty of charging power right now...with more panels, more time maxed out, more absorb time
- The PV cable run is through the attic out to the backyard pergola. So, moving things closer would be better, but not feasible at this time. Actual length is about 80-85'
- My set-up was designed for emergency back up for power failures (after the 2013 tornado that took out 1/3 of Moore). People were running power generators and getting sick, constant re-fueling, and noisy. So, I came up with this idea and it has proven it's worth on a small scale. Now it runs 24/7.
- Long PV cable runs are not ideal, I know that, but space is limited (small house, garage)
- A 24vdc inverter would be great and I might do that eventually along with the battery bank.

Again, thanks.

Yes - a 24v inverter would be a good investment since you would be able to get twice as much power from the Kid at 24v . Check out Samlex inverters - decent price, good quality sine wave line.  And like others have said if you can reconfigure your panels to higher voltage you will also have less power loss in  your existing input wiring.