60A Charge Controller Limiting to 20 A

[msra20]

I have an installation job for a medium size off grid setup:

4 parallel strings of 4 x 150Wp 12V panels in series (8A Impp) , total 2400Wp
1 unit of EPSOLAR VS4548BN 45A solar charge controller
2 parallel strings of 8 units of 6V 237Ah ENERSYS Forklift Batteries (total 474Ah at 48V)

recently the owner wanted to add more panels and a larger charge controller to suit, so i added another string of 150Wp panels (making it 5 parallel strings of 4 x 150 Wp and a total of 3000 Wp) and upgraded the charge controller to the next size up (60A 48V PWM).

Now the problem i am having is that the new charge controller, with the added panels, should be giving out around 40 A at midday full sun, this is NOT happening, i've watched it from the morning and PV output seems to hover around 20A constantly. The strange thing is the kWh totals for the day , seen at 11 pm was already 6 kWh, much higher than before the additional panels and new charge controller install, which seems to suggest the energy is coming in. Still, I have never seen the amps-in above 20 A. We are in Central Java so the sun is very strong, we sometimes get 10A from 8A rated solar panels.

Strange thing is when I turned the PV breaker off and then on again, I see the PV-IN amps go to 40 A, then slowly go down to around 19.4 A, PV Voltage coming in is 66.5V

What could be making the charge controller reduce the amps coming in? The batteries are not fully charged and do not reach float (stays in boost mode constantly). Thanks for any help!

[sensij]

With a PWM controller, PV voltage equals battery voltage + rise from transmission losses. 66.5 V sounds way too high, and if that number is bad, others might be as well.

[Mike90250]

at night, switch off the breaker for the PV cells, Wait till nearly noon, when the sun is well oriented on the panels, and then turn the panels on, The batteries will be low from overnight and the sun strong, so you should see max amps at that time,

What I believe is currently happening, is at sunrise, the panels start to produce power, and by noon, the batteries are nearly fully charged.

[msra20]

at night, switch off the breaker for the PV cells, Wait till nearly noon, when the sun is well oriented on the panels, and then turn the panels on, The batteries will be low from overnight and the sun strong, so you should see max amps at that time,

What I believe is currently happening, is at sunrise, the panels start to produce power, and by noon, the batteries are nearly fully charged.

I hope this is what's happening, will try that tomorrow. As for the batteries getting fully charged, I am still waiting for it to happen, from BOOST to FLOAT, target voltage is 57.6 V.

[Sunking]

I have an installation job for a medium size off grid setup:

4 parallel strings of 4 x 150Wp 12V panels in series (8A Impp) , total 2400Wp
1 unit of EPSOLAR VS4548BN 45A solar charge controller
2 parallel strings of 8 units of 6V 237Ah ENERSYS Forklift Batteries (total 474Ah at 48V)

So what is the problem other than you really screwed up using a PWM controller and battery panels? With a PWM controller Output Current = Input Current

In ideal conditions for a few minutes around noon if the batteries were discharged you might see 25 to 30 amps at best. With the added string 35 to 36 amps.

Now if you would have bought a good reputable MPPT controller, you would see around 50 amps, and with the added Panels 60 amps.

With a voltage of 66 volts at the input tells you instantly the controller is in Absorb or Float mode. In Boost the voltage would be roughly 1 volt higher than the batteries. Sounds like you just do not know how batteries charge. Try reading this. What you are describing is perfectly normal operation of a battery that is nearly charged up.

I also agree with Mike, the easy way to tell what is going on is disconnect the panels at night, next day let system run without panels until about noon so you discharge the batteries, then reconnect the panels. Bet you see the current you are looking for, then as the batteries charge the current will taper off.

Another thing you can do is at noon when you see the low current, turn every thing on that you can to draw as much current from the system you can. Up around 3000 to 4000 watts of load. You should see the panel current shoot up to maximum smoke.

Bottom line, I don't think you understand what you are doing and how to interpret results. If you did, you would have never used a PWM controller or battery panels to begin with. Example it takes a 3000 watt PWM system with battery panels to equal 2000 watt MPPT system. Not only that but a lot less expensive using high voltage Grid Tied Panels.

[Raul]

Ep solar 4548 it is a mppt controller for sure but not the most efficient. The other think is, have you got big enough wires to handle the 45a that cc is capable to charge ? If the conductor is to small the cc will not push full smoke.

[Sunking]

Ep solar 4548 it is a mppt controller for sure but not the most efficient. The other think is, have you got big enough wires to handle the 45a that cc is capable to charge ? If the conductor is to small the cc will not push full smoke.

No it is not MPRT. Clearly states PWM. EPSOLAR VS4548BN 45A

[Sunking]

The other think is, have you got big enough wires to handle the 45a that cc is capable to charge ? If the conductor is to small the cc will not push full smoke.

Incorrect answer. It will push the current, it will just loose voltage along the length of the wire and possibly over heat the wire if it is too small. It is a power loss from voltage, bu tnot current.

[Sunking]

After reading the manual a couple of times I am certain there is really nothing wrong. Only possible thing that might be wrong is one or more of the parallel strings might be open. The Controller is a very inexpensive PWM controller with only 2-Stages, and the operator is misinterpetting what is happening.

The controller only has what they call BOOST and FLOAT. The BOOST is actually Constant Current and Constant Voltage charging, aka Bulk and Absorb on a 3-Stage Controller. What the OP is seeing is the CV stage aka Absorb stage.

Real easy to figure out by a couple of different methods.

1. At noon on a bright sunny day when the current seems low, just turn everything on you possible can that exceeds the panel wattage rating. Example if before the test you only see 20 amps of charge current turn on enough load to draw 50 or more amps. If you see th epanel current come up to maximum, all is well. The idea here is to draw more power than the panels can generate to force the batteries to take maximum panel current by forcing the controller to FULL ON 100% modulation. Essentially it connects the panels directly to the batteries.At that point panel input voltage will roughly equal battery voltage.

2. For a a lazy person, just disconnect the panels for a day and let the user run off batteries for a day. Try this as the sun sets, then over night and up to about noon next day, draw the batteries down with normal use. Then at noon reconnect the panels and you will see maximum power. Again Maximum power is when Battery Voltage roughly equal Panel Input Voltage.

3. For a Novice Amatuer who knows a little about batteries and chargers can tell what is going on with nothing more than a volt meter and 30 seconds. Just measure the battery voltage and panel input voltage will tell you everything you need to know. When the controller is calling for maximum power. Panel Voltage will roughly equal Battery Voltage. The panel voltage will be about 1-volt higher than the battery at Max Smoke. In addition the battery voltage will be lower than the set point voltage. Example you might see 52 volts at the battery, and 53 volts on the panel Input with maximum current. When you see this you know the Controller is in Constant Current Mode, or stated correctly for solar Constant Power.

As the battery charges, the battery voltage will begin to rise. At around 80 to 90% SOC the battery voltage will reach the set point. When that happens the controller switches to Constant Voltage to hold the Set Point Voltage. Charge current will begin to taper to 0 amps, until the CHARGER reaches 0% Modulation or open circuit. In Absorb or CV mode the battery voltage will be whatever the set point is, and the panel voltage will begin to rise until it reaches Voc of the panels. Example the battery voltage is 58 volts, and panel input voltage will be anywhere from 60 to 72 volts.

[sensij]

As the battery charges, the battery voltage will begin to rise. At around 80 to 90% SOC the battery voltage will reach the set point. When that happens the controller switches to Constant Voltage to hold the Set Point Voltage. Charge current will begin to taper to 0 amps, until the CHARGER reaches 0% Modulation or open circuit. In Absorb or CV mode the battery voltage will be whatever the set point is, and the panel voltage will begin to rise until it reaches Voc of the panels. Example the battery voltage is 58 volts, and panel input voltage will be anywhere from 60 to 72 volts.

Ok.. so the panel input voltage readout is averaged across the entire PWM duty cycle. Makes sense. The high voltage reported suggests the duty cycle was low. The 20 A charge current reported might actually be an average current then, with higher instantaneous current during the ON portion of the PWM cycle?

[Sunking]

Ok.. so the panel input voltage readout is averaged across the entire PWM duty cycle. Makes sense.

Yes Sir

The high voltage reported suggests the duty cycle was low.

Right again

The 20 A charge current reported might actually be an average current then, with higher instantaneous current during the ON portion of the PWM cycle?

Right again, actually it should be the RMS equivilent

A PWM charge controller works exactly like a DC Series Wound Motor Controller. Where you control the speed or voltage by turning the Gate (switch) On/Off. At 100% modulation, you have essentially connected the panels directly to the battery like a Switch. The FET forward ON voltage is about 1 volt. Thus when fully ON the Panel voltage will be roughly 1 volt higher than the battery voltage. At that point the panels are pushing as much current as they can given the sun conditions or Imp.

Once the batteries reach the Set Point in the controller, say 54 volts, it starts Modulating the On/Off cycle just like a Switch would. When that happens, the panel voltage now rises to Voc at 0% modulation or an open circuit. You are correct with the right meter you wil see the AVERAGES of that Modulation.. Example let's say we have a 10 amp Imp at noon full sun. At 100% modulation you will see 10 amps. At 75% modulation 7.5 amps, @ 50% 5 amps, and at 0% is off/open or 0 amps. So if at 0% modulation you have open circuit and will read Voc of the panels. At 100% = battery voltage. Absorb and Float is 99% down to 0% modulation. 100% is Constant Current aka Full Smoke.

I do not know if this will help or not, but a Solar panel operates as a current source from Vmp down to Isc or Constant Current Source. That would be full smoke on a PWM controller. That same panel operates as a voltage source from Vmp to Voc. Once you wrap your head around that, everything starts to make sense.

Keep in mind a MPPT controller only operates like a voltage source from Vmp up to Voc. MPPT never operate from Vmp to Isc. On MPPT your panel voltage will never go below Vmp like PWM does unless it is malfunctioning.

[msra20]

Im learning a lot here , thank you very much for the education!

[Sunking]

Im learning a lot here , thank you very much for the education!

You are welcome. A DMM along with the Controller AMP Meter will tell you what you need to know.

First thing you need to know is what the Set Point Voltage in the Controller Boost Stage. With that Controller you only get 3 options.

1 Gel = 56.8
2 Sealed = 57.6
3. FLA = 59.2

All are a little high, but you gotta play the cards you are dealt.

1. So the every first thing is measure the battery voltage on the Output Terminals of the Controller since that is the voltage the Controller sees. This step alone tells you what to expect going forward. If the voltage is within 1/10 of a volt of set point, say 59.1 volts with a FLA setting, you already know the Controller is in a Constant Voltage Mode vs a Constant Current Mode.

2a.. Based on voltage in step 1, clues you in on what to expect to see at the Panel Input. Let's say you see 53 volts on the batteries, you know the controller should be e in Constant Current Mode, and you should see roughly 53 to 54 volts on the Panel Input side confirming the Controller is in Constant Current Mode aka Max Smoke. What current you will see depends on time of day, time of year, panel orientation, ect. I can tell you it will not be the panel Imp value for all the strings. 80 to 90% is good. Example if the total Imp adds up on paper to 45 amps, 36 to 40 is good to go and realistic assuming good bright noon day sun.

2b. If you see the battery voltage at the Controller Set Point, then Panel Input voltage is going to be at 1 volt or more higher than battery voltage. It can go as high as Voc of the panels and no current flowing. What voltage and Current? Beats me, it is what it is. Example let's say the panel Voc is 72 volts. You measure Battery Voltage = 59.2, Panel Voltage = 65, Charge Current = 5 amps is good to go. Another example Panel Voltage = 71 volts, Battery = 59.2, Current = 1 amp is good.

The only time the Panel Voltage = Battery Voltage is when the Controller is full ON or max smoke and that voltag ewill be LESS THAN SET POINT. That is Constant Current Mode. All other times the panels will be at least 1 volt or higher which tells you the Controller is in Constant Voltage mode and the batteries are nearing full charge. Duringg Constant Voltag ephase the batteries will be at SET POINT VOLTAGGE, panels will be higher.