Over wattage input on the Kid

[ZoNiE]

I'm looking at using my three 173 W panels in parallel with a kid. Using the sizing tool, it tells me I will have excessive wattage, but I really don't think I will actually get the full 519W, more like 80% of that best case. In the event that I do get the perfect output, or something high enough to overpower the Kid,  instead of the Kid shutting off, could it control a relay to shunt one of the panels out of the parallel circuit instead?

Sure, I could probably design and build a monitor ckt that would do this, but it might be a simple software change on the kid to close contact on an added relay or output DCV to a pin one could connect a relay to? I'm sure I could void my warranty and mod it myself, but a user selectable feature would be kinda cool. Same algorithm turns on a relay output instead of crow-baring the whole system sort of thing...

Instead of going into standby and waiting for some clouds, doing zero charging, opening circuit on one panel would reduce the array output by 1/3 instead and then the system would still produce.

85% output on all three panels will be excessive.

Have you guys considered something like this? (I'd be willing to be the test subject)

I have the panels, I have the room, I want the max output...

[dgd]

In the event that I do get the perfect output, or something high enough to overpower the Kid,  instead of the Kid shutting off, could it control a relay to shunt one of the panels out of the parallel circuit instead?

Doesn't work like that, you can't 'overpower' the KID.
The KID will only take the input power it needs until a maximum of 30Amps is output to the battery bank.
And the KID will not 'shut off' because there is excess power available.
It will shut off if the input voltage is too high but thats not what you will see with three parallel connected panels.

dgd

[Mario]

The kid will limit the current out to 30 amps it doesn't care if there is more power available. So if you try to over power it it will limit you to the 30 amp spec.... it will not completely turn off if there is more power than what it is design to handle.

Thanks,
Mario

[ZoNiE]

OK, that is what I thought, but then why does the sizing tool say "excessive" If the wattage is too high? I realize It will go into standby over 150V, (Which I will probably never see) and will limit the output to 30A, (which is ok with me) but then why should the sizing tool care? Is it just trying to tell me that I'm wasting photons with this config?

I plan to use all three panels in Parallel, and If the Kid limits output to 30A, then I'm ok with that.

[Westbranch]

why should the sizing tool care?

Well you are wasting money if nothing else, so try another design, configuration or panel size or...

[bennyspoon]

 so provided the string voltage is low enough, if there was more than 30 amps coming from the array through one cable, and if more than one kid was connected, would they share the load equally or would one be dealing with 30 amps and the other the remainder?

[ZoNiE]

why should the sizing tool care?

Well you are wasting money if nothing else, so try another design, configuration or panel size or...

already have the panels. got them basically for free.

[dgd]

OK, that is what I thought, but then why does the sizing tool say "excessive" If the wattage is too high? I realize It will go into standby over 150V, (Which I will probably never see) and will limit the output to 30A, (which is ok with me) but then why should the sizing tool care? Is it just trying to tell me that I'm wasting photons with this config?

I plan to use all three panels in Parallel, and If the Kid limits output to 30A, then I'm ok with that.

Are you sure you have used the string sizing tool correctly?  Your sig shows you have a 2200watt 24 volt inverter so it looks like you will be using a 24 volt battery bank,
This would mean an array up to 750 watts would be ok on 24volt battery.
How did you figure just over 500watts was excessive?  Did you tell the sizing tool you were using a 12 volt battery?

dgd

[ZoNiE]

Yes 12V battery (gonna use 4XGC2's, actually)

I don't plan on using that inverter in this application. (Sig also says nothing connected to anything.) sorry if that's confusing.

This will be a pure 12V system for the trailer.

The inverter will probably be sold or traded for something else I can use or saved for the future. The thing has not even been used...

[lowerlevel]

Doesn't work like that, you can't 'overpower' the KID.
The KID will only take the input power it needs until a maximum of 30Amps is output to the battery bank.
And the KID will not 'shut off' because there is excess power available.
It will shut off if the input voltage is too high but thats not what you will see with three parallel connected panels.

dgd

I am pretty sure I overpowered the KID with 1440 watts of panels (4pair of 2*180 suntech).
It would attempt to charge, showing somewhere between 9 or 11 watts, and then just show 0 amps.
This was when turning on all the panels at once in full sun.  If I turned one string on at a time the KID seemed to be able to keep up...  but I was too nervous to leave the whole array connected for more than a few minutes.
At 720 watts it works fine.  I have let it run all day in full sun without a problem... yet.

[tecnodave]

Lowerlevel,

Maybe you have something else going on as well.  The OVR light will light up when you hit the 30 amp limit but will also light up when over temp. When running at 30 amps continous the kid will get hotter. You may see current limiting cut in and see a thermal overload which will cause the kid to wait and cool down.  I'm currently running 1020 watts in and see temps rise in full sun. I keep an eye on my kids when doing this and turn down current limiting (found in battery menu) to 22-25 amps when FET temp approaches 50 deg.

I need that much panel as I have thick fog at this time of year.

td

[lowerlevel]

Hmmm.  I checked my LED menu to ensure they were turned on and working.  All looks good. But the OVR light has never come on.

EDIT-  firmware updated and OVR LED working fine now.  will retest with full array tomorrow.

[Vic]

Just to add one fairly obvious but fairly important note on Over PVing  a Charge Controller;

When there is abundant sun available to an over-PVed MPPT CC,  and the CC is clipping the excess output current in excess of its capability,  the PV modules are not fully-loaded.   This lighter load causes the PV voltage to rise.  The higher Vin to the CC will cause the CC to run somewhat hotter than it would,  where the PV input power is well-matched to the CC  (causing the PV string to be at the lower Max Power Point voltage).

Some here,  like perhaps technodave,  and dgd (?),  may be diverting some the excess power to heat water,  etc.   This diversion CAN help load the PVs more fully,  reducing some/all of the excess available power of the array,  and therefore reduce the PV input to the CC.  These diversions will help alleviate some of this added heating,  especially to the extent that this diversion can occur during Bulk and Absorb stages.

FWIW,  my opinions.     Vic

[tecnodave]

bennyspoon,

so provided the string voltage is low enough, if there was more than 30 amps coming from the array through one cable, and if more than one kid was connected, would they share the load equally or would one be dealing with 30 amps and the other the remainder?

I am setting up to exactly that.......parallel the inputs and outputs with a pair of kids......my understanding is that in bully mode the kids will split the load equally

I have 6 Sharp 170 watt 72 cell poly panels I plan to run in strings of two for a Vmp of 68 volts  which will be the primary panel set for this configuration. I may add a set of Toppoint 72 cell 190 watt panels to this configuration

I will also be trying follow me mode as I may try having panels with different alignment.

I will be posting results as soon as I get everything reconfigured.

td

[ZoNiE]

Thats a good idea.