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diy solar

Spark/fusion issue

JRA

New Member
Joined
Sep 26, 2024
Messages
13
Location
Colorado
I have a 4s2p 24v set up. I have Mc4 cables coming from opposing pos/neg that plug into Mc4 connectors on the charge controller.
The voltage at the set from the battery bank read 26.5 on my meter.
I connect the positive together but when I go to connect the negative terminals the terminals fuse themselves together and the charge controller does not turn on.
I have verified that connections are good. I have rewired the mc4 connectors 3 times with the same result. I have also tried making the connections without the plastic housing of the mc4 to verify that the connection is solid and get a very large spark as soon as I touch metal to metal on the negative. This spark fuses connectors together, making the connectors not reusable.
I have this same set on multiple other 12v battery banks with no issues. The charge controller is 24v compatible.
Like I said, the cables from the batteries test 26.5v at the mc4 terminals. Any ideas of what can be happening?
 
You need to detail every bit of wiring that you have (or give us a photo and and describe what each cable is). What you have happening indicates you probably have significant wiring issue/mistake.
 
what charge controller do you have? What size is it?

Do you have the charge controller connected to the battery first?

Or are you noting the MC4 connections have a large spark when connecting the battery to the SCC? It is not common to have MC4 connectors from the SCC to the Battery.

After the battery is connected to the SCC Do you then connect the PV to the charge controller?
 
what charge controller do you have? What size is it?

Do you have the charge controller connected to the battery first?

Or are you noting the MC4 connections have a large spark when connecting the battery to the SCC? It is not common to have MC4 connectors from the SCC to the Battery.

After the battery is connected to the SCC Do you then connect the PV to the charge controller?
Sorry I didn’t get to respond sooner, out of range.
It’s a BougeRv 40a Sunflow charger.
When this happens the PV is not connected. It is when I am connecting the battery bank to the controller.
I have multiple battery banks. The controller will not power on with any of them, however I guess it could be fried.
The 4s2p bank, which is the battery bank I first tried connecting will power on my other solar controller which is a BougeRv 60a.
I am using 4 balancers for the for the 4s2p. I have checked that my wiring is correct, if not pretty.
 
what charge controller do you have? What size is it?

Do you have the charge controller connected to the battery first?

Or are you noting the MC4 connections have a large spark when connecting the battery to the SCC? It is not common to have MC4 connectors from the SCC to the Battery.

After the battery is connected to the SCC Do you then connect the PV to the charge controller?
Sorry I was unable to reply sooner.
Yes the spark happens when I connect the battery bank to the SCC. I connect the positive then when I connect the negative is when the spark occurs. The same battery bank will power my other SCC which is a BougeRv Sunflow 60A.
The fact that the battery bank will power my other controller makes me think that the wiring is fine but I do have a lot of wiring going on with the battery balancers.
I will try and post some pictures later but my van is in the shop today.
The voltage test correct at the battery terminals as well as the Mc4 connections coming from the battery that connect to the SCC.
The first Sunflow 60A charger I got from BougeRv came unable to charge. Had power all the way to the terminals on the SCC but had 0A of charging.
Could the SCC be the issue? I have 3 battery banks and all will power on the Sunflow 60. The common denominator seems to be the Sunflow 40 but I do t understand what might be allowing the charger to do that.
 
You need to detail every bit of wiring that you have (or give us a photo and and describe what each cable is). What you have happening indicates you probably have significant wiring issue/mistake.
I will try and post some pics later today or tomorrow morning. Van is in the shop today.
As far as the wiring, I checked everything and even mocked up everything before installation but didn’t connect the SCC. The 4s2p battery bank, which is the one that I first tried, will power on my other SCC. (BougeRv Sunflow 60A) so I think the wiring is correct but can’t be ruled out.
I’ve had issues with BougeRv SCC in the past. A google search of the issue mentioned it could be a faulty controller but why the spark. This was also just an AI diagnosis.
 

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