That's how their connected is to three panels. And they stay charged as long as there is light and a little charge but they will shut down not long into the dark.
As others noted, the batteries are dead. And probably beyond repair. Some DIYers pry SLAs open and perform various incantations while adding water and baking soda and such. Lots of YouTubes on this if you have time to burn. Very low chance of success, IMHO.
When I have plugged it in to an electric source it throws codes and beeps and the fan goes and goes and goes.
Do you have manuals that explain what the codes and beeps mean? If not search online for any docs you can find.
The PerfectPower 1800 has an internal AC slow charger that's supposed to recharge the internal battery (and probably your two external ones as well). The unit can act as a UPS even without solar panels connected. It can just pass grid power through to whatever you plug into the outlets on front (and back?). And since it also keeps the battery charged, when you lose grid power it just switches over and powers those outlets using the battery and internal 1800W inverter.
Maybe it beeps when you plug it into grid power because it detects the dead internal battery. Or maybe it also has other problems.
I'd first try to get it working without the solar and without the other two battery boxes. I'd (carefully) take the PerfectPower 1800 apart, disconnect the internal battery then connect those wires to a good 12V battery (e.g. from my car) instead. Then plug a lamp or something into one of those 120V outlets on the front. If that works for a while, e.g. 30 minutes, the inverter should be OK.
Then turn off the lamp and plug the PP1800 into grid power. If that works without beeps, the internal AC charger is probably good (to really test it I'd drain the battery a while, measure the resting voltage, then make sure it actually recharges from grid power).
Then disconnect from grid power and run the same tests with a solar panel plugged in. Or maybe all three panels in parallel, if the wiring allows that. That will test your solar charge controller.
You can also test the DC outlets on the front panel, e.g. 12V "cigarette lighter" and USB plugs, although you may not really care about them.
If everything works with a good battery you can then decide how to proceed:
- Use witchcraft to revive the existing 80 Ah batteries?
- Buy new deep cycle lead-acid batteries?
- Buy new LiFePO4 batteries?
That really comes down to how you want to use it and how much you want to spend. But first you need to know which parts work.
