Mixing Panels

[Offgrid]

Nice and simple explanation.I understand now.What I did today was disconnect my array from my charge controller ( x1 50watt panel and x1 100watt panel in parallel) and measured amps and volts. This is what I got V=18 and I=8. So 18v x 8a = 144watts instead of 150watts.I am very happy with this result! Going back to the SOC topic,in future I will leave battery to rest unloaded for 5 hours,take a voltage reading and then place a small load like a car 12v bulb for 30 minutes ( is this long enough) or so,disconnect the bulb and let the battery rest for another 30 minutes (once again is this long enough) and read the voltage then.This should be a ball park SOC.Thanks for your patience and helping me try understand the correct SOC method for a sealed deep cycle.

[Sunking]

Nice and simple explanation.I understand now.What I did today was disconnect my array from my charge controller ( x1 50watt panel and x1 100watt panel in parallel) and measured amps and volts. This is what I got V=18 and I=8. So 18v x 8a = 144watts instead of 150watts..

Care to explain just how you measured this? Where did you find a MPPT tracking load to make the measurement. They can cost up around $200,000 or more, and not portable.

My guess is you measured Voc and Isc. If that statement is true does not mean your system produces 144 watts. Only a MPPT tracking load box can measure Vmp and Imp. Vmp and Imp is roughly 80% of Voc and Isc so 14.4 volts x 6.4 amps = 92 watts at the panel terminals. Throw in PWM CC losses of 33% and you are probable looking at 60 watts to the battery.

[Offgrid]

Makes sense as my whatsup meter between my controller and battery was measuring way way less.I only did the exercise to see if there was a simple jump in power to know if I should take down the DIY panels.The 100 watt alone gave me slightly over 100w with the 50w panel in parallel I got 144.So not matter how bad the ration from losses etc,it would still be better with the DIY panels.If I took your above calculations on the 100w,I would be even worse off.

[Offgrid]

Oh to answer your 1st question,I measured on the terminals of the panels with a multimeter and then the amps of both panels in parallel.Couldn't measure the amps for too long as my fluke would of hated me if you know what I mean lol

[Sunking]

Oh to answer your 1st question,I measured on the terminals of the panels with a multimeter and then the amps of both panels in parallel.Couldn't measure the amps for too long as my fluke would of hated me if you know what I mean lol

How did you measure the voltage and current?

Did you measure the voltage with the panels disconnected, and just measured the voltage? If so that is Voc. VOC on the factory panel should be up around 22 volts. My guess is 18 is the Voc from the DIY panel pulling down the factory panel that is in parallel with the DIY panel.

As for current how did you measure it? Short the leads with your meter? That is Isc

The factory 100 watt panel should have a Vmp of 18 volts, and Imp of 5.5 amps. Voc should be around 22 volts and Isc around 7 to 8 amps.

If you are going to do this you need to test each panel separately at noon on a very bright day with the panels facing directly into the sun.

[Offgrid]

Yeah I shorted with a multimeter. The panel sticker says Voc is about 20v and amps is about 6 and Vmp of 19 and amps of 5.12. Is that right for a panel? Going to catch some sleep,thanks for helping out.

[Sunking]

Yeah I shorted with a multimeter. The panel sticker says Voc is about 20v and amps is about 6 and Vmp of 19 and amps of 5.12. Is that right for a panel? Going to catch some sleep,thanks for helping out.

Yeah that sounds about right for a commercial 12 volt panel.

Sure would like to know what the Vmp of your DIY panel is. If for example it is down around 14 volts means you turned your 100 watt panel into a 70 watt panel

[Offgrid]

Yeah could be, just not worth going DIY you know.Always have a eery feeling about those panels. Just a quick question, my charge controller is rated 10 amps, I read on the forum that's a 10amp max to the batteries.My whatsapp meter is not reading even close to that, more like 4 amps max from the CC to the battery.Does that mean I can add another panel? Because max watts = 12v x 10amps and that's 120 max watts and 2x 100watt panels is 200 watts.You agree I need to get a new controller?

[Sunking]

What kind of charge controller?

If it is PWM, then the input current = output current. So what that means is the controller current rating should be equal to or greater than the panel current.

If it is MPPT the maximum panel wattage if the amp rating of the controller times the battery voltage.

Now with that said if you are seeing 4 amps from the controller could mean a lot of things.

1. is your panels are not producing full rated power.

2. As the battery approaches full charge the current tapers off until it goes to almost ZERO.

[Offgrid]

If it is PWM, then the input current = output current. So what that means is the controller current rating should be equal to or greater than the panel current.

My qoute thing doesn't want to work but to answer your question,I think it's PWM,some cheap ass Chinese make which I can't even find a website for but still better than that 30amp clicking on off controller that had minimal parts inside which I had connected originally.

I think my amp reading on the wattsup meter connected like this... Panels -> CC -> wattsup meter -> battery. Is showing such low amp flow is because the battery's are getting full.When I turn a AC load on the amps go up on the Wattsup meter but to give you a clearer picture,like we discussed Isc on all the panels is measured with multimeter is about 8amps and I see on the wattsapp meter only about 3 max unless battery's are not very full. Kinda thought I was loosing a crap load,never seen more than about 40watts on the meter.

[Offgrid]

Oh if my controller is PWM 10a then I will need a new panel as 2 100w panels are 5,12amps each and I'm sure pushing that little cc's limits.The question is now.Buy a decent PWM like Stecca now or go straight for MPPT.

[Sunking]

When I turn a AC load on the amps go up on the Wattsup meter but to give you a clearer picture

That is normal and what you want to see.

like we discussed Isc on all the panels is measured with multimeter is about 8amps and I see on the wattsapp meter only about 3 max unless battery's are not very full.

OK again how are you measuring the Isc current? If you have 8 amps from the panels going into the charge controller, and only see 3 amps out going to the batteries and load, you have a problem, a big problem.

So try this with the system connected normally measure the current going into and out of the charge controller. With a PWM they should be roughly the same minus what the controller needs for it to do its work. If the output is lower than the input, you have a problem.

[Offgrid]

OK again how are you measuring the Isc current? If you have 8 amps from the panels going into the charge controller, and only see 3 amps out going to the batteries and load, you have a problem, a big problem.

Ok I was measuring the panels by putting the positive of the panels that are in parallel to the positive lead of the multimeter and the negative of the panels to the negative of the multimeter.In affect shorting it? I then took a voltage reading and then unplugged the positive lead out of the socket of the multimeter and put it in the multimeters 10amp max plug and took a reading of amps.

So try this with the system connected normally measure the current going into and out of the charge controller. With a PWM they should be roughly the same minus what the controller needs for it to do its work. If the output is lower than the input, you have a problem.

What I will do this time INSTEAD of shorting the panels to get a reading of current is put the multimeter INLINE with the panels positive so that it goes like this... Panel postive -> Multimeter positive -> Mulitimeter negative -> CC solar input connection. I will then take a reading of what current is flowing from panels before the CC.

I will then do the same AFTER the CC so that it goes like this... CC positive battery output -> Multimeter positive lead -> Multimeter negative lead -> Battery. I will then take a reading of what current is flowing from the CC to the battery.

I will compare the 2 and see if they roughly the same.Is this the correct method to test and what you had in mind?

[Sunking]

Ok I was measuring the panels by putting the positive of the panels that are in parallel to the positive lead of the multimeter and the negative of the panels to the negative of the multimeter.In affect shorting it? I then took a voltage reading and then unplugged the positive lead out of the socket of the multimeter and put it in the multimeters 10amp max plug and took a reading of amps.

Ok that is Voc and Isc, standard test procedure that confirms the panel array is working, but has nothing to to with the rest of it.

What I will do this time INSTEAD of shorting the panels to get a reading of current is put the multimeter INLINE with the panels positive so that it goes like this... Panel postive -> Multimeter positive -> Mulitimeter negative -> CC solar input connection. I will then take a reading of what current is flowing from panels before the CC.

I will then do the same AFTER the CC so that it goes like this... CC positive battery output -> Multimeter positive lead -> Multimeter negative lead -> Battery. I will then take a reading of what current is flowing from the CC to the battery.

I will compare the 2 and see if they roughly the same.Is this the correct method to test and what you had in mind?

OK now you are on the right track.

[Offgrid]

I only get a chance to test this at night, I don't suppose I could run the test with a small AC charger hooked up to the CC panel input and measure? I see some have done this in other applications, my AC charger produces about 3 amps at 14.5v.