Strange electrical phenomena with batteries and solar

[Whempy]

Hi!

We have a 2022 Keystone Outback with Solarflex 200i, a 200W solar panel, Victron 75/15 charger, 50 amp service and two 12V batteries.

A few weeks ago, my husband cleaned and sealed the roof. The next day, we left for a 4 day camping trip, plugged in to shore power at the campground and all worked fine. We brought the camper home and later that night I noticed the fridge was way above temp. As we had to leave town the next day, in the car, we turned off everything and emptied the fridge. We returned after 1 week and the batteries appeared to be drained (multimeter test on each battery showed ~ 4 V). At the same time, Victron controller light was blinking blue.

Today, the batteries tested at ~2 V each, no lights working on the battery/fresh/black/grey display inside the coach. Thinking the roof cleaning and sealing may have dislodged a solar contact, hubby got back on the roof and used electric spray cleaner on the contact attached to the roof, which showed some type of green corrosion. Plugged it back in and the Victron controller light was solid blue. Suddenly, the batteries tested at 12.05 and 12.20 V and the interior coach display was lit up normally! We are not plugged in to shore power. Obviously, the batteries did not suddenly charge in 30 seconds?!

We are hoping the batteries will be fully charged by noon tomorrow, after the sun has shined on the panel tomorrow morning.

Questions:

1) Why would the corroded solar plug have anything to do with the obviously false readings we got on the 12V batteries?

2) If our solar panel ever broke or was removed, does that mean the 12V batteries would show no charge? (Not logical to me but...)

3) Is there anything we should be concerned about regarding this odd battery behavior?

Thanks

 

[stephd203]

OOhh! I would be interested too--in an effort to revive a semi-old thread.
Although, it has been my experience while working on auto electronics, that green corrosion is almost always the cause of sensor misreadings, failing grounds, and bad fuses or bulbs. Moisture can and will get into little connectors. Wire brushing or cleaning with electrical contact cleaner can often help to get the connection fixed again. Since the solar system is inherently a 12 volt system, I would expect the green corrosion to negatively affect that as well. Other threads have recommended checking the inputs and outputs of the wiring with a multimeter, and comparing them to original specifications. This would give you solid evidence of failure. If the solar panel(s) are connected together in series, then you would have to isolate each one for measuring, all in the same orientation to the sun.

 

[NH_Bulldog]

The issue for the OP was that whatever was used to clean the roof caused a chemical reaction that led to the corrosion. This prevented the batteries from charging and they died since they were not connected to shore power. Parasitic loads will deplete a battery fairly quick unless on shore power, a battery maintainer or solar. The same thing would have happened if they had plugged into shore power.

Once the contacts were cleaned on the roof, the readings at the battery that seemingly made them look charged was nothing more than the voltage from the panel that was once again charging the battery.

Similar to jump-starting a car, you are not charging the dead battery when you connect the jumper cables, you are using a good power source to supplement the bad. If you measured the dead battery at that moment it might show normal voltage, but you would just be reading the voltage from the good battery, or in this case the solar panel.

Nothing really weird, odd or unusual in what the OP reported, just a lack of understanding.

 

[St. Michael]

Solar MC4 connections are probably one of the most overlooked components of an RV. Most people don’t really understand how they work and they’re supposed to be waterproof right! Wrong! Plenty of YouTube videos on how they work. MC4 kits are cheap and readily available on Amazon. They’re pretty simple. Check them regularly just like anything else.