Can panels overpower charge controller?

[Craig]

I'm curious now what would happen if I connected for example 10kW of panels to the charge controller(for the sake of argument).
If the panels are connected in parallel at 24V nominal. Would the CC just make use of 1400 watts and not allow any more energy to pass?
Or would the transformer inside the MPPT just act like a short circuit and all 10kW would burn through it and set it on fire?

I think that the amps would fry the controller. Maybe not a fire but destroy whatever limits the current.

I think if you maxed out the theoretical input of 60 amps at 100v. You would also heat the unit up. What I think my main takeaway from this thread is that the quality SCC such as the Victron are worth the extra cost in some instances. My makeSkyBkue controller clearly states to not feed it more watts than it uses to charge batteries. The Victron in our off grid low sunlight scenario is well worth it due to the fact that you can add extra panels

 

[electric]

Panels don't create current, they create potential for current to flow (voltage), but it's controller's job to regulate amount of current, based on it's design limits, temperature, etc. You can connect bazillion jigawatts , but as long as you don't exceed controller's voltage rating, nothing bad is going to happen. Think of it as water flowing in pipes and faucets controlling the flow. There is potential amount of water to flood your whole house, but it won't happen if faucet is closed, or open as needed. But if there is too much pressure ( voltage ) then pipe bursts open and floods the house as fast as possible.
Using water, pipes, pressure is the best analogy for understanding how electricity works. People can imagine water behavior because we can see it and been around it for 1000s of years, but electricity is invisible and still mysterious to a lot of us.
Bottom line, shitty controller is like a shitty faucet, it might work for a while, but one day you come home and it's flooded. Good controller like a good faucet will keep your home dry.

 

[gnubie]

I know there are cheapie controllers out there that will self destruct because they don't current limit because I performance tested quite a few CCs as candidates for power in remote areas. One of the units that couldn't even maintain keep the load voltage stable was a UEIUA CPY-2420, and it didn't current regulate at all. It would unhappily output as much current as the input / load allowed. I didn't take it to smoke escaping, but it would have if I had taken it far enough.

 

[mrevesz]

Ok so no all charge controllers are designed using the same basic electric circuit then. Good to know. I suppose to Victron is safe to have current regulation. That really is how(in my opinion) these things ought to be built. Every other appliance that we use daily works like this. You don't worry about how much current a wall socket can supply before you plug in your device. The device determines how much current will flow. The charge controller should work in the same way, as long as voltage is not exceeded.

That would make it handy in application where you want a few extra panels to give boost in winter and on cloudy days but don't want to fork over big bucks for high amp rated controller/cable/batteries/BMS/etc. Just overbuild your panel installation and you will have consistent power all year.

Thanks for all these responses and insights everyone!

 

[electric]

I know there are cheapie controllers out there that will self destruct because they don't current limit because I performance tested quite a few CCs as candidates for power in remote areas. One of the units that couldn't even maintain keep the load voltage stable was a UEIUA CPY-2420, and it didn't current regulate at all. It would unhappily output as much current as the input / load allowed. I didn't take it to smoke escaping, but it would have if I had taken it far enough.

Regulating current is literally the main function of a charge controller. So, to say you had a controller which didn't do that is to realize that you did not have a controller at all. You just had a box with wires attached to it and you paid money for it.
Analogy with faucets is to have a faucet that doesn't close, basically it's just a piece of pipe.

 

[gnubie]

Sure, but that's not the only part of the equation. The controllers do actually do MPPT to optimise power from the PV, even if it means they blow up in the process.

 

[electric]

Sure, but that's not the only part of the equation. The controllers do actually do MPPT to optimise power from the PV, even if it means they blow up in the process.

MPPT works by regulating current while monitoring voltage in order to maximize both values, which creates maximum power. So, technically MPPT is also about regulating current.
Pretty much any electrical power conversion is all about regulating current in various ways.

 

[gnubie]

Not really, MPPT attempts to maximise the power from the array. It doesn't regulate, ie target, a specific current flow.

 

[electric]

Not really, MPPT attempts to maximise the power from the array. It doesn't regulate, ie target, a specific current flow.

"Maximize the power" are just words describing end goal, but how do you think it actually works in electrical circuit? Electrical circuits can measure voltage and current and then influence change in the circuit to achieve desired result in most efficient way possible. Power conversion devices work by influencing flow of the current ( i.e. current regulation ). MPPT is a type of power conversion circuit and it works by the same principles.
In general there are buck circuits and boost circuits, or a combo of buck/boost used in MPPT designs. Basic principle of these circuits is to regulate flow of current by switching it on/off at high frequency ( PWM ) and pass the current thru inductors and/or transformers to achieve the desired change in voltage/current relationship, which means control of power.

 

[gnubie]

I know precisely how it works. The MPPT will, and we'll assume the load can absorb anything the controller produces for simplicity, sweep the current it draws from the array whilst monitoring the voltage and performing simple maths to determine the optimum current draw for the array. Once that point is located the controller will hold the current at that point so that it can stay on the MPP. Of course the output of the panels will vary as conditions change so the MPPT will have to periodically sweep to determine the correct point at that given time.

Of itself MPPT does not seek a specific current flow, only the flow that yields the optimum performance of the array.

A charge controller that implements MPPT does not need to control the current to the battery, assuming the well being of the battery is not taken into consideration, nor does it specifically need to control it's input current aside from obtaining the MPP. CCs that do not limit the current that they will pass will destroy themselves if they are presented with a configuration that will permit them to pass current beyond their components ability.

 

[offgriddle]

My my my, all of this incredibly wonderful deliberation when the answer was, is, and always will be simply: "STAY WITHin the manufacturer's specifications of your equipment". You're welcome. Have a nice day.

 

[mrevesz]

I imagine if you crack one of these MPPTs open you've got a transformer with half a dozen or so leads sticking out of it. The controller decides which lead to pull the current from depending on voltage etc. and open and closes mosfets to allow that to happen. So long as you don't exceed the breakdown voltage of any of the mosfets the controller should be able to open all the mosfets and break the current flow.
Hopefully also some overtemp control in their to avoid cooking the mosfets.

This would be my guess.... kinda wanna buy a cheap MPPT now just to break it apart and take a look.

 

[offgriddle]

I purchased an MPPT controller that was totally encased in a heavy, metal, heat sink housing with radiation fins and I mounted the unit on spacers to allow air flow all around it. I will not exceed the specified maxium voltage or the maximum wattage input. ~ I picture in my puny noggin, instead of the charge controller dumping the excess of un-needed input current to a humungo load resistor to waste the excess power as heat like perhaps in the days of old, the controller simply opens the charge path to the battery when the charge is complete. ~ On one hand, if you don't exceed the charge controller's input maximum, even if the demand for output to the batteries and/or load terminals exceeds the maxmim specs., I'm guessing that while the controller would heat up quite a bit perhaps to the point of premature failure eventually under long term excessive demand, the unit would not burn up simply because it is not able to output more than specifications because it's input is within specifications. ~ https://tops-stars.com/schematic/mppt-charge-controller-schematic-diagram/

 

[offgriddle]

With that being said, if you have 100 amps of reserve capacity and your charge controller is limited to 60 amps output and a demand in exces of 60 amps is placed upon the controller, either a fuse or circuit breaker will trip or some other current limiting circuit in the controller will activate quickly enough to prevent damage or, the controller will fry. The rule of thumb is, "stay with the mob", I mean, "stay within specs.". Have a nice day.