Solar array voltage drop issue

[Selica]

Hi everyone, Ive been trying to figure out a problem with my solar array. Panels are 4 x 325w CS6U-325P wired two sets in series then paralleled. I'm only getting 46v reading at my cc from night into the day(11am). I will then disconnect both sets it will read 88v roughly with multimeter, reconnected and voltage will then be 70v+ at cc. Tracer 4215bn

This issue has started that Ive notice this spring was fine previous. Ive got two separate arrays 1300w and 1360w on separate cc

thanks for any suggestions or advice
Joseph

[jflorey2]

Hi everyone, Ive been trying to figure out a problem with my solar array. Panels are 4 x 325w CS6U-325P wired two sets in series then paralleled. I'm only getting 46v reading at my cc from night into the day(11am). I will then disconnect both sets it will read 88v roughly with multimeter, reconnected and voltage will then be 70v+ at cc.

That sounds about right. What current are you seeing into the battery when that happens?

[Selica]

Its been cloudy with sunny breaks but when I disconnect and reconnect panels about 20amps est. I'm hoping its sunny here tomorrow and I'll get a better idea, its just seems rather strange as voltage is very low

[foggysail]

CC a control center? Back to solar, solar panels are current sources, not voltage sources.

[jflorey2]

Its been cloudy with sunny breaks but when I disconnect and reconnect panels about 20amps est.

20 amps at 46 volts is 920 watts. That's pretty good for a 1300 watt system.

[Ampster]

.. I'm only getting 46v reading at my cc from night into the day(11am). I will then disconnect both sets it will read 88v roughly with multimeter, reconnected and voltage will then be 70v+ at cc.

That is probably the MPPT doing its thing to find the optimum power by tweaking current and voltage. As mentioned earlier 920 Watts from a 1300 Watt system is not bad. Without knowing the tilt angle and orientation to South it is hard to say whether that is optimum. Hopefully you were not expecting to get 1300 Watts?

[Selica]

Its a 24volt battery bank. Im seeing 20amp at 24v after cc has optimized power. Im starting to think my cc is acting up now its sunny today ill get a better idea of what is happening. Usually setup will max out cc at 40amps

[jflorey2]

Its a 24volt battery bank. Im seeing 20amp at 24v after cc has optimized power. Im starting to think my cc is acting up now its sunny today ill get a better idea of what is happening. Usually setup will max out cc at 40amps

Wait a minute! You are seeing 46 volts INTO your 24V batteries? Disconnect them immediately and don't use the CC again until you have this figured out. That will rapidly destroy your batteries.

[Ampster]

20 Amps at 24 volts is 480 Watts. Depending on chemistry the voltage of a 24 volt battery will not be exaxtly 24 volts. What chemistry are your batteries and what is the Constant Voltage (Absorb) setting? I presume that the 46 volts is at the solar panel input to charge controller?

[Selica]

I have come to the conclusion that the cc algorithm is causing this issue. I might rewire the panels all in parallel which will drop voltage to 40v instead of 80v seems the cc isnt allowing full potential until way later in the day (past noon). My other array doesnt act like this at all and its a 37v setup. Its been like this for a couple of years and has been ok I just notice the lower voltage this month when we lowered the panel angle. Im thinking a quicker bulk charge is beneficial since my battery bank is 1148ah and the arrays are alittle undersized.

[foggysail]

I have read your posts and not sure of what your problem is. CC = charge controller? Battery charging? As others have posted or alluded to, batteries have terminal voltages and are voltage sources. That means they try to keep the terminal voltage constant regardless of the load current provided by them. Yes, the terminal voltage will change slightly due to their internal resistance which increases as the available stored energy diminishes.

Solar panel output voltage... you should look at the panel's data sheet. Panels are current sources which means the output voltage will change to whatever is needed to keep the output current constant. There is little change in output current as when a panel is matched to its Vmp or a direct short on the output. The output voltage is going to change all over the place as a charge controller or MPPT device functions to maximize its designed output characteristics. You can forget all of the above if I have misread your problem as described.

[Selica]

Its the bulk charging at early day my arrays are right beside each other and the one wired at lower panel voltage is producing much higher current at early day. Ive conclude that my cc (charge controller) isnt allowing full potential of the higher voltage since I disconnect array from cc and reconnect it. Ill see a increase about 15-20 amps almost like its content to just make something instead of recalculate the potential.
I'm going to rewire and lower the voltage to see if it rectifies it

[Ampster]

I have come to the conclusion that the cc algorithm is causing this issue. .......... Im thinking a quicker bulk charge is beneficial since my battery bank is 1148ah and the arrays are alittle undersized.

What is your conclusion based on? Without any information about your battery chemistry or state of charge it would be difficult for me to reach a conclusion. I think that is what foggysail is saying as well. Have you considered that your batteries are full and the charge controller is ramping down the current to keep voltage constant. Since the output of the solar panels is limited by their capacity how are you going to make the Bulk (Constant Current) stage quicker? To make that stage of charging quicker you would have to increase current going to the batteries. That does not necessarily mean more current from the panels at lower voltage. That may depend on the specifics of the charge controller.

[Mike90250]

What are the specs for your charge controllers CC ?

[Selica]

In bulk charge the lower voltage array is producing much more current than the higher voltage array. I can than disconnect the high voltage array and reconnect it, it will then produce more roughly the same as the lower voltage array. My think is the programming of the cc isn't reevaluating quickly as the sun comes up. There's lots of different cc many behave very differently. these are far from the best but . Lowering panel voltage should see an increase base on what the other array is doing.
Anyways I'm pretty sure ill be buy some better charge controllers in the future, Id like to have alittle more control over absorption time and end amps