Beta Kid is blowing batt fuse

[philb]

First, let me explain a little about this PV system.

I have an old concrete slab that used to have a equipment barn on top. It flew away three years ago. I was considering PV panel temporary locations and this looked the best. No mowing, can put panels on the slab and use concrete blocks to get the approx. angle for summer sun.

The batteries, controllers and inverters went to the center of the slab. There is an 2285 watt east array (pointing south) controlled by Classic East, a 2285 south array (pointing south) controller by Classic south and a west 855W array (pointing west with 70 degree incline that's controlled by the KID. As in the last post, the two classics has a fau of their own blowing up through the bottom holes and the Kid gets the residual, as does the VFX3524 at the top of the box. Here's the boxes beginnings: http://ecorenovator.org/forum/solar-power/3516-temporary-pv-solar-hookup.html I'll try to get a photo of it now to post.

I knew I would have shading problems on the east array from about 2 pm. That's when the KID would come on stage to make up some of the difference.  At about 5 pm, part of the south array would also have shading and the KID's array would be about dead on to make up for more power.Volts are close to the KIDs specs and Amps are within 30 amps too. Classics are on follow me and the Kid is on its own right now. There are appropriate midnite din breakers on the in and output of each unit.

The south, east and west panels are all in absorb, the Kid blows a battery fuse. If the south and west panels are in EQ and the Kid doesn't start its own, it will blow its fuse again.

If there is a possibility the fuse could be blowing by trying to match or catch up with the absorb and EQ of the classics? Any ideas?  Voltages are within a tenth of a volt each on all three.

I can check it out Saturday. Thanks!

[Halfcrazy]

Yeah thats a tough one. I have Pinged Mario to jump in here. 855 watts could exceed 30 amps but the Kid is very good at regulating. Maybe you can get a Clamp meter on the kid.

One thing that does come to Mind is did you keep the PV negative line isolated all the way to the Kid? If the negatives are not isolated the Kid will read the Current low and allow it to go over 30 and blow the fuse.

Ryan

[philb]

Thanks Ryan
The positive and negative PV go directly into its own separate breakers. The only common point is after the output breakers into the +- of the battery.
I have an old clamp meter. I'll see if it will work this afternoon.

I also thought about putting a diode on the battery outputs. I would not think it could backfeed, but I don't know. Of course, I don't have the schematics so it's hard to say. Anyway, when it blows again, I'll try that.

[Vic]

Hi philb;

OK,  BUT,  just to make sure,  Halfcrazy Ryan is saying the the PV negative is separate from the battery negative all of the way to the KID's PV Negative terminal.   The PV Negatives will be connected together before running to the KID's PV Neg,  but there should be NO other connections from the PV Neg at the combiner and the KID.  The KID has its own connection between the PV Neg and the battery Neg.

Rev B KID wiring diagram:
http://www.midnitesolar.com/pdfs/Kid_24V_4p_Series+Par_REV_B.pdf

As I read your post,  there is a circuit breaker in the PV Neg (?).

From Ryan's post,  the KID measures currents in the negative leads,  and these must be separate for the KID to know the current.

Good Luck,   Vic

[philb]

Ok,
I should have said the pv positives are on breakers. The negative WAS connected to a common pv negative as shown in the diagram with other pv negatives. My mistake. I have two 20 amp breakers tied together on the pv positive input. They were both tripped this evening.

There were lots of clouds this afternoon and I wasn't able to make any significant measurements. I'll try again tomorrow.

Thanks Ryan and Vic.

[Resthome]

Ok,
I should have said the pv positives are on breakers. The negative WAS connected to a common pv negative as shown in the diagram with other pv negatives. I have two 20 amp tied together on the pv positive input. They were both tripped this evening.

There were lots of clouds this afternoon and I wasn't able to make any significant measurements. I'll try again tomorrow.

Thanks Ryan and Vic.

Make sure your PV Neg do not connect to the Battery Neg before connecting to the Kid. They need to have separate negatives going into the Kid.

Not sure I understand your comment "two 20 amp tied together on the PV positive input."

[philb]

Resthome-
I didn't have a larger dc breaker than 20 amp at the time so I used two coupled together. I got my parts order in yesterday and changed out those breakers for a one larger one.

The kid was alive and well this morning. It won''t generate much power until about 2 pm this afternoon. I'll check it then and see if my clamp meter will get meaningful readings. There are big storms coming in later today so the meter is iffy at best.

I also have to find a battery for  one of my classics. Every time it is turned off, the time needs to be reset. I have made sure there is no paper or other obstructions, just a bad battery. It's serial is CL4171.

[Halfcrazy]

So is the PV negative for the Kid isolated and not common to any other negative in the system?

[philb]

That's correct Ryan.
I just checked the kid. It's still running.

[boB]

The negative WAS connected to a common pv negative as shown in the diagram with other pv negatives.

Was it connected this way when the fuse blew ?   This would probably do it.
Unless I'm reading that sentence wrong, it sounds like all of the negatives were tied to a common negative.

[philb]

Your correct boB. All pv negatives were tied in together when the kid fuse blew. I understand now the kid can't be tied with the negatives of the two classics, if I'm reading Ryan's post correctly.

The two classics are still tied with the pv negative together. Is that not correct? The panels are all from the same lot and box. They seem to be working fine until I put the kid in the circuit. The voltage and amps vary panel to panel maybe .001 volt IIRC.


None of the PV or battery connections are tied to ground, except through one classic.
Now all three controllers seem to be happy. If I'm wiring this up wrong, please let me know.

[boB]

OK, so now I am not so sure I understood what you originally said and what I responded to.

The PV negatives can certainly be tied together, even with the Kid...   Just not the PV  negatives
AND battery negatives...

But, on the Classic, you CAN tie the PV negatives to the battery negatives because it measures current on the
positive legs.

boB

[philb]

boB-
The original system had all the PV negative connections from all the panels going into one bus bar. From there, one was routed to each charge controller on the PV negative terminal.

Ryan said to disconnect the kid's pv negative and put it directly into the kid. When I did that, so far, I have not blown any more fuses. At noon today, they are all doing their job.

Thanks for all the help.