2 x 100w 12v Renogy output = 136w 10.2a <---Normal?

[problemchild]

I am new to solar and this is my first project. I bought a Renogy "kit" of 2 x 100w 12v panels with cables, terminators and PWM-LED charge controller. I was only getting 10a x 13.4v or 134w so I bought a Kid MPPT controller thinking I could harvest the balance of the watts I was losing. All the reading I had done said the MPPT were 30% more efficient. So I hooked up my Kid last night and today I have the exact same output. I tried each panel by itself and each puts out about 65w. I tried running in series and parallel. The series actually seemed to drop a few watts.

So is this "Normal" for 83854 zip Northern Idaho? My cables are 20' long. I tried tilting the panels at all different angles with the wife watching the watt meter and no joy!

[rhawkman]

problemchild, it sounds like you have the same system I was looking at. Your numbers look pretty much like what I would expect from it if I get it, also. I guess I should try to find a single 200 with MPPT for about that price.

[Sunking]

What size battery? If it is to small for the panels will limit current on its own internal resistance.

Try this. Discharge the battery down so the next day it demands charge. When you see the current top out 10 amps from the panels, turn on a load device that pulls 10 to 20 amps and see what happens. Assuming noon bright sun panels facing into the sun you get 15 to 16 amps from the panels. If that happens means you got more panels than batteries. Not a big deal and better than the alternative of not enough panel wattage on too large of a battery. You are just getting robbed of potential energy. You can remedy that to some extent by performing opportunity loads to run during peak hours to tap some of that unused energy.

[PNjunction]

This is a common mistake assuming the controller is bad, when the batteries aren't discharged enough. If the batteries are close to fully charged, they are in "absorb", and the batteries themselves are limiting the current draw from the panels.

Discharge the batteries a bit more, and then rerun the test.

And, at 200 watts or less, the difference in charging may not be THAT significant. Also note the "weasel words" that lower quality controllers may use like "up to" and so forth. Are you paying a huge difference for an "up to" increase of efficiency that only amounts to something like 2-percent?

Note that the "kid" is definitely NOT in the lower quality category!

[problemchild]

Yeah I made that mistake when I first got it. Battery was near fully charged and I could only get 2 amps out.

I did run a 165 amp load (Keurig coffee) while checking it and the battery (2x 6v costco golf cart batteries brand new) and I saw the amps jump to 11 input and watts were 138w. My panel voltage in is 16v and the kid says its in mppt mode not absorb.

Should I be getting 17 amps at high noon on low batteries?

Whats the best panel on the market now (most bang for buck) if I have to return these and get a 24/36v panel? Also is there a local vendor (NO SHIP) close to Spokane/Coeur D Alene Idaho?

I plane on growing my system but wanted to learn before I buy!

Thanks for the help guys.....

What size battery? If it is to small for the panels will limit current on its own internal resistance.

Try this. Discharge the battery down so the next day it demands charge. When you see the current top out 10 amps from the panels, turn on a load device that pulls 10 to 20 amps and see what happens. Assuming noon bright sun panels facing into the sun you get 15 to 16 amps from the panels. If that happens means you got more panels than batteries. Not a big deal and better than the alternative of not enough panel wattage on too large of a battery. You are just getting robbed of potential energy. You can remedy that to some extent by performing opportunity loads to run during peak hours to tap some of that unused energy.

[BrokerDon]

Yeah I made that mistake when I first got it. Battery was near fully charged and I could only get 2 amps out.

I did run a 165 amp load (Keurig coffee) while checking it and the battery (2 x 6v Costco golf cart batteries brand new) and I saw the amps jump to 11 input and watts were 138w. My panel voltage in is 16v and the kid says its in MPPT mode not absorb.

Should I be getting 17 amps at high noon on low batteries?

Whats the best panel on the market now (most bang for buck) if I have to return these and get a 24/36v panel? Also is there a local vendor (NO SHIP) close to Spokane/Coeur D Alene Idaho?

I plane on growing my system but wanted to learn before I buy!

Thanks for the help guys.....

I recently installed a single $238 Renogy 250W mono 24/36V (30.1V 8.32A optimum) panel since it was definitely the "most bang for buck" 250W 24/36V panel. I connected it to a Renogy Tracer 40A MPPT controller on our RV to feed our 2 x 6V series wired (232Ah @ 12V) Sam's Club Energizer GC2 Premium golf cart batteries in our 2011 Winnebago View 24K. The Tracer controller MeTer LCD shows this 250W panel inputting 34.7V into the controller and outputting 11.1A at 13.8V when the controller determines our batteries need a maximum recharge. This equates to approx. 161W from our 250W rated panel assuming a 5% controller / wiring loss (10' of AWG 10 from panel to controller + 10' of AWG 4 from controller to batteries + two Midnite Solar MNEPV 12VDC breakers on either side of the controller). This was also in 90ºF ambient temp... with our panel mounted completely flat (no tilt) on our RV roof which both factor into the actual power loss from the 250W optimum rating.

This system has been great to meet our needs since it allows us to recharge our 2 x 6V batteries while running our Fan-Tastic remote thermostat controlled fan (0.3 to 3.0 amps 12VDC) while recharging our personal electronics (two iPhones, one iPad), and recharge our thrifty overnight battery usage (LED lights). I'm hunting for a 345W X21 or 327W E20 SunPower panel (the only 325+W panels that fit our tight roof space) so I can add a 3.0A 12VDC TurboKool swamp cooler to run during the day and get more "spare" power from the sun.

Hopefully this info helps answer your question.

[Sunking]

I connected it to a Renogy Tracer 40A MPPT controller on our RV to feed our 2 x 6V series wired (232Ah @ 12V) Sam's Club Energizer GC2 Premium golf cart batteries in our 2011 Winnebago View 24K. The Tracer controller MeTer LCD shows this 250W panel inputting 34.7V into the controller and outputting 11.1A at 13.8V

Completely meaningless unless you know how much current is flowing into the controller. Based on output power of 155 watts th einput current had to be around 4.3 amps well below Maximum power point. The second clue is 13.8 volts which is a float voltage meaning your battery was substantially charged up already and not drawing full power from the panels. In other words your panel was only generating around 160 watts at the time you looked.

[BrokerDon]

Completely meaningless unless you know how much current is flowing into the controller. Based on output power of 155 watts th einput current had to be around 4.3 amps well below Maximum power point. The second clue is 13.8 volts which is a float voltage meaning your battery was substantially charged up already and not drawing full power from the panels. In other words your panel was only generating around 160 watts at the time you looked.

Good points. Unfortunately the Renogy Tracer MPPT controller MeTer doesn't show input amperage, just voltage. Lame, huh.

I bought a multimeter recently but haven't learned how to use it yet. Next time out RV is out of storage I'll see if I can find this info.

So much to learn Solar Grasshopper.

[Sunking]

Good points. Unfortunately the Renogy Tracer MPPT controller MeTer doesn't show input amperage, just voltage. Lame, huh.

Yeah kind of lame as voltage is the black part of a B&W picture. You need the current or power to complete the picture.

[paulcheung]

Good points. Unfortunately the Renogy Tracer MPPT controller MeTer doesn't show input amperage, just voltage. Lame, huh.

I bought a multimeter recently but haven't learned how to use it yet. Next time out RV is out of storage I'll see if I can find this info.

So much to learn Solar Grasshopper.

I hope the meter you bought has the DC ampere clamp feature, otherwise you need to get one DC clamp ampere meter.

[SunEagle]

I hope the meter you bought has the DC ampere clamp feature, otherwise you need to get one DC clamp ampere meter.

You can find a relatively low cost DC clamp on around $30. I use a Uni-T202 for my RC plane batteries. There are better ones out there like the Extech DC400 for about $80. It all depends on what you want to spend and how accurate the measurements need to be.

[BrokerDon]

I hope the meter you bought has the DC ampere clamp feature, otherwise you need to get one DC clamp ampere meter.

I have no idea but I sure hope so. The products we bought & installed are here:

40A MPPT Tracer charge controller: http://www.renogy-store.com/MPPT-Cha...trl-mppt40.htm

MeTer: https://www.renogy-store.com/product-p/trcrmtr-mt-5.htm

[boostinsteve]

The meter gives the basic info. Incoming voltage, and battery voltage and current. The part number for that charge controller is actually tracer 4010rn. It works, but has a very slow algorithm for tracking, so don't expect maximum watts at all times. If you have a nice sunny day, you can put a multimeter on the input, and watch it track every 7 mins or so.

As far as the original question, try wiring the panels in series, and see what happens. Just a suggestion to try.