Surpassing a controller max amp.

Fabian

I have a epever tracer 3210A mppt controller rated at 24v 30A 750watt.
Is it possible for me to draw 40amp from it constantly by adding some cooling fans on the heatsink keeping the temp at room temperature all the time without causing any damage or charging  issue to the controller?
My aim is to be able to can attach (4) 250watt panels to it and get the max 1000watt from it even though it is rated at 24v 30A 750watt.

If it cannot work that way suppose I change out the built in fets for some larger current type will it be able to pull the 40amp constantly or even more without causing any damage or charging issue to the controller with or without fans attach to the heatsink?

The reason why I ask is due to the fact that in the past I had a 30amp pwm cc and I was able to pull about 50amp from it without causing any issues because I install a bigger size heatsink and also added a cooling fan.

littleharbor2

You can add more wattage but you wont ever get more than 30 amps output, that's just the way MPPT controllers work. The plus side is you will get full power in less than ideal lighting, temperatures and earlier as well as later in the day.


 

mike95490

Sure, try it.  No guarantees though, it bight just blow after 3 minutes, or it might work fine.  The Buck coil may be the limiting factor, once it saturates, you get no more.
 Changing FETS might be tougher, you would have to find ones with higher rating, but use the same drive current.

Estragon

There may also be software/firmware limitation which may reduce output based on temp, but not go beyond rated current at cooler temps.

Fabian

If I connect (2) 24V 8a 250watt panels rated at 38V each in series bringing the total to 76v at 8a then connect that in parallel with (1) 250watt 24v panel rated at 38v would the mppt function still operated smoothly giving me close to 750watt and operating close to the 76v even thou the voltage is mismatch with the series parallel connection?

BB.

What voltage is your battery bank? 12 or 24 volt?

And, with three panels of ~240 Watts @ 38 Vmp--No, there is no way of wiring them to one single MPPT epever controller...

If you have a 12 volt battery bank, as long as Vmp>~18 volts, you can connect 2x panels to one controller and 1x panel to a second controller (both controllers MPPT type).

If you had a single higher end MPPT controller (MorningStar, Schneider, Outback, Midnite, etc.) controller with Vpanel>~140 VDC max input, you should be able to put all three panels in series for Vmp-array~114 VDC STD conditions.

I think you are on Jamaca (nice warm island)? If so, then that high of Vmp-array should not be an issue (never approaches freezing weather at your place, if my guesses are correct).

But, the cost of a new MPPT high end controller (something like $500-$600 USD for high end solar MPPT chargers+shipping+taxes) would probably cost more than 1x more epever MPPT and 1x more 240 Watt @ ~380 Watt panel (2x matched panels on 2x MPPT controllers) and give you more power.

-Bill

Photowhit

Fabian said:

If I connect (2) 24V 8a 250watt panels rated at 38V each in series bringing the total to 76v at 8a then connect that in parallel with (1) 250watt 24v panel rated at 38v would the mppt function still operated smoothly giving me close to 750watt and operating close to the 76v even thou the voltage is mismatch with the series parallel connection?

Why? I think if you read the chart @littleharbor2 has provided, You can safely connect up to "2340W/24V" So there is no reason NOT to connect the 4 panels in 2 strings of 2 panels. I can only assume it is a language barrier. 

What they are saying in the chart, is you can have a maximum array power of 2340 watts at 24 volts.

In addition there are 2 other factors to consider, your 1000 watts of panels will normally only produce 750 watts! This will be very close to their Normal Operating Cell Temperature value (NOCT value) 

The charging voltage of a 24 volt battery bank will only be 24 volts if your batteries are nearly dead. Normal charging will be around 29 volts  if you are discharging your battery bank 20-30%. So if you could produce 1000 watts you could use 30 of the available 34.5 amps. (1000/29=34.5)

Estragon

If I'm reading this right, the solution is to add a 4th panel (wired 2p2s) to roughly max out a 30a @24v nominal mppt controller. You likely can't get 40a out of it, but that's the best way to get 30a.

Fabian

If I connect all 3 panels in parallel giving me a total of 38v at 24A would the mppt operate effectively with just 38v input instead of 76v and stI'll be able to give me close to 750watt/30A total in output?

Or.what if I connect all 3 panels in parallel then feed that to a dc step up converter which  step it up to say for example 60v ot 76v then feed that back to the epever so that it has a higher volrage input would that be able to let me get close to the 30A 750 watt output from it?

Photowhit

Fabian said:

I'll be able to give me close to 750watt/30A total in output?

OTHER THAN COLD DAYS IN WINTER 750 WATTS OF SOLAR PANELS WILL NEVER GIVE YOU 750 WATTS OF POWER!

Normal operating temperatures will make the output about 75% of the panel rating!

If you will give me the brand and model of the panels I can try to track down the NOCT figures if they publish them, Until then you might read about the difference between STC and NOCT.

Here is a chart that the manufacturer SIlfab uses for their 350 watt panel, showing it is likely to produce 264 watts under NOCT, or about 75% of the STC 350 watts.


If you want 750 watts of output put up at least 1000 watts of panels.

mike95490

Fabian said:

If I connect all 3 panels in parallel giving me a total of 38v at 24A would the mppt operate effectively with just 38v input instead of 76v and stI'll be able to give me close to 750watt/30A total in output?

Or.what if I connect all 3 panels in parallel then feed that to a dc step up converter which  step it up to say for example 60v ot 76v then feed that back to the epever so that it has a higher volrage input would that be able to let me get close to the 30A 750 watt output from it?

All 3 in parallel, might (or might not) work with that controller.

Adding a DC step-up gizmo will most likely (>95% failure) NOT work, as it would need to have a MPPT circuit and likely will not.

Obtaining another panel, to create an array 2S, 2P is the best bet.  2nd best is to try all 3 in parallel, and see if the controller will still function.

Photowhit

Link to your manual;

https://img.banggood.com/file/products/20161022015720TracerASeriesManual.pdf

From page 9 of your manual on string sizing;


So it appears that parallel if preferable to strings of 2 for 72 cell panels. I do find this odd, but I guess since it has a low max it stresses the charge controller to have 2 in a string.

littleharbor2

I need to ask the OP, Are these 72 cell panels?  You mention 38 volt output but is this, in fact, the Vmp or is it Voc.?  250 watt panels these days are typically 60 cell panels. 250 watts divided by 8 amps +31.5 volts, not 38 volts. Also 38 volts x 8 amps = 304 watts. This is very important to clarify when wiring up your array.  60 cell panels are NOT 24 volt nominal panels. If you parallel wire 60 cell panels and try to charge a 24 volt battery bank, especially with an MPPT controller, your results will be less than optimal.

Fabian

38v is the O.C. the panels are 60cells.

littleharbor2

Yep, either 2 panels in series or 4 panels 2s2p. Parallel wiring wont give you high enough voltage to properly maintain a 24 volt bank or allow your MPPT controller to function as designed.