bypass epever mppt charge controller max current capability

[fabieville]

The Epever Tracer series MPPT comes with various max current handling. I have one that is rated for 40A. Is it possible to increase the max 40A rating without damaging the controller by implementing additional cooling?

What i would want to know is how does the controller know that it has reach the 40A max? Is it that the controller monitors the temperature so once the heatsink or mosfets reach a certain temperature then the current limiting capability kicks in so therefore the temperature/current does not pass that level so therefore if you have additional cooling on it to keep the mosfets/heatsink cool at all times you can trick the controller to produce more current output than the rated 40amp?

Or is it that the current limiting  features kicks in base upon some I.C or circuit/sensor to know when you reach 40A max so in essence there is no way to bypass that feature?

Reason for my question is due to the fact that my epever tracer is rated at 12/24v 40A 1040Watt. I have (4) 320watt panels which total is 1280watt so that surpass the max wattage by 240watt and i would like to be able to can draw close to the 1280watt which would be that i would be pulling more than max 40amp from the controller so I would like to hear your comments on this regard.

if i connect (3) of the 24v 320watt panels  in parallel to charge my 24v battery bank will the charge controller operate in mppt mode seeing that the input voltage is not 1.5 times or 2 times my battery voltage?
The input voltage will be close to my battery voltage. I will have about 33-35volts coming in while my battery is going to be around 25 or 26V.
So with this in mind will i be able to can pull close to my 960watt total in optimum conditions?

[fabieville]

Suppose I use (2) 24v 320 watt in series along with (2) 24v 200 watt in series then parallel the 2 set of strings giving me a total of 1040watt which is the max wattage rating of the controller would I be able to can pull the max 40amp in mppt mode giving the fact that the 320watt vmp is slightly just a few volts different from the 200 watt vmp?

[DamonHD]

I think you'd have to be unlucky for a few volts in Vmp to lose you an enormous amount of power, though I guess you'll lose some.  I'm guessing, given the shape of a typical knee, that you'll end up sitting a little above the lower Vmp.

Rgds

Damon

[Scruff]

I reckon it'd involve fooling the current transformer/shunt.

I don't think it'll end well.

[Artful Bodger]

I'd think there is some current limiting in there, else everyone would just keep loading her up, and she'd pop around 50A.  If you crack it open, you might find a fat wire link.  That's the shunt. Put another piece of wire in parallel,  but as Scruff has said, it won't end well.

[Scruff]

Quite possibly a better solution is recline the array more. You'll get less kW and more kWh.

Shallow angle..more horizontal. Extended exposure hours.

[Rob Beckers]

Hi Fabieville,

I know those EPEver Tracers well... Sold and installed them by the hundreds! For the money they are excellent charge controllers.

As with all MPPT charge controllers, it actively controls the output current by moving the power-point to either get maximum output from the panels, or limit its current to 40A by moving the power-point for the panels at a higher Voltage then where the maximum would occur. The limit is baked into the firmware, and while there is a current sensing device somewhere (probably small resistor) that you could fool, as others noted it won't end well. While better than average for product from that country, it's still Chinese, and I'm sure they are walking the fine line between meeting specs while cutting every corner they can.

As with any MPPT charge controller you are free to oversize the solar array with respect to that maximum output current. We've had people put 150% of rated on these, all that does is cause the output to clip at 40A if there's enough sun. On the cloudy and winter days you get the benefit of the extra solar Watts though! The specs and manual just list how much solar will result in maximum output under certain conditions, it is not the limit of the charge controller. Also keep in mind that a 24V battery bank charges closer to 28V most of the time, and solar panels rarely produce rated output, so 40A x 28V = 1120 Watt; with your 1280 Watt that's only a 114% oversize, it wouldn't clip very often!

Now, having said that, there is a limit to oversizing the array before things "get interesting" (as in, 'the magic smoke comes out'). There comes a point where the processor just isn't fast enough to move the power-point of the controller to limit the current to less than self-destruct values (when a cloud moves away from the sun, and output spikes very quickly for example). The more expensive charge controllers (Morningstar, Outback, MidNite) are made there you can pretty much throw anything on the input, but EP-Solar/EPEver isn't quite in that class. I'd limit things to about 150% for this one to be on the safe side.

-RoB-