Ran genset, now seeing 19+ volts from solar

[Snowman9000]

My MH has been sitting in the driveway for several weeks with the solar panels keeping it charged. NO shore power. Today I went in to run the genset.

The voltage meter read 13.6v before I did anything. The battery switch was On. No appliances or systems were turned on, it was on minimal life support.

I started the genset. After a minute or so I started the AC. After another minute or two the genset shut down. It was blinking 29, which means battery voltage over 19v. Which I thought was silly. I tried to restart it a couple of times but it shut down immediately and blinked 29. I putzed around and scratched my head for a bit.
Note: While the genset was running, I thought there was a relay chattering at the genset. That has been a recurring random issue.

Then I glanced over at the voltmeter and it was reading 19.6! I immediately tripped the circuit breaker coming from the solar panels into the Morningstar SS-20 controller, and the voltmeter went blank, telling me there was no longer ANY voltage in the house.

I checked my 100A fuse at the positive post of the battery bank and sure enough, it was blown. The battery bank read 13.2v at that moment, with the house cables disconnected. That's where things stand now. Let's set aside questions of what collateral damage there might be to boards and stuff.

It sure seems to me that the controller was letting the 19.6v go right through it. Or am I jumping the gun on that? How could running the genset (and therefore the converter) have damaged the controller?

What would blow the 100A fuse? It does serve the genset starter cable as well as the house. The genset cranking amps are 70-something. The fuse is a good one, a MRBF like this:



Put it another way, is there anything other than cranking the genset which could have blown the fuse?

My plan to start troubleshooting will be to disconnect everything from the batteries except the controller, then reconnect the panels and see what kind of voltage there is. And go on from there.

Thoughts?

Here is how I've got it wired. Obviously this is not a professional schematic. 🙂

[westend]

I think you're jumping the gun on the controller being the cause of 19.6V reading. I understand the diagram but where is the voltage meter connected in all of this? Is it the device that has the solar, the charger, and the genset all on post 'A"?

My first WAG is that the genset is back feeding the circuit and sending DC to the meter. The battery fuse will only open with more than 100 amps of current, not due to high voltage. Some controllers don't do well when they are disconnected from the battery and not the modules. That's why connecting solar charging directly to the battery is a good idea.

My other WAG is that something drew over 100 A of current from the battery.

[jrnymn7]

Did you happen to make any changes to the solar controller's settings, without first disconnecting it from the solar array and battery bank?

[YC_1]

Ok, calm down. That high voltage was because the panels were not seeing a load so put that worry aside. The fuse blowing is an issue by itself but fuses often die just because they are an electrical device and they can have bad connections inside.

So, clean all connections you can find and tighten and clean the battery terminals. Replace the fuse then. Test again.

There are a lot of sneak paths in these complex devices and even with a schematic not all things can be completely explained. Forty years of sorting through difficult issues has always led me back to the basics. Fix the obvious. The obvious is the blown fuse. Then recheck after doing the things I suggested in the beginning.

[2oldman]

Snowman9000 wrote:
Then I glanced over at the voltmeter and it was reading 19.6!

It's a little tough to see exactly where your voltage is reading from, but, 19.6 sounds like Voc of your panels. Is that possible?