Help! What went wrong?!

[Wandererrr]

Posting for a friend
We have 2 100w 12v solar panels, 3 12v 100ah lifepo4 batteries, a 3000w inverter, 30a charge controller.
We recently finished our solar set up and at first everything seemed fine. We could use a vacuum, and charge a drill, and a couple other things, and not much of the batteries which were fully charged were used. But the second or third time we used the power, just for a little 1500w space heater, the batteries reached 0%.
Now, while it's dark out, as I use the heater, the battery dies down really fast (like from 82-68 in a split second and then 2% every 5sec), but once I turn it back off, the battery goes back up.
But it also only goes back up to 82-86%. Which I think is the max it went to when the sun was out.
So,.. please tell me the batteries aren't ruined.
What changed, why are they dying so fast? How are they supposedly going back up in charge?

 

[sunshine_eggo]

If you start with your batteries fully charged, you can power the 1500W space heater for:

3 * 12.8V * 100Ah = 3840Wh

3840Wh / 1500W = 2.6 hours.

sound about right?

With your 200W of solar, you can produce MAYBE 1000Wh in PERFECT conditions (no shade, full sun, panels perfectly tilted and oriented to the sun, etc.), which could run the space heater for about 40 minutes.

This does not count the power that any other devices use, or the inverter's power use (yes, they consume electricity just to provide it).

The % readout is completely and totally useless. It is reporting % charge based on the RESTING voltage of lead-acid batteries, i.e., batteries that have sat for about 24 hours with no charging or discharging.

Until your batteries reach 14.4V measured AT the battery terminals and held there for 30 minutes, your batteries aren't fully charged.

The batteries aren't ruined. The system is poorly designed without a basic knowledge of how to meet needs.

Recommend your friend check out links #1 and #5 in my signature. Turn phone sideways and/or enable signatures in your user profile.

 

[Brett V]

A “little” 1500 watt space heater is a very significant power hog. A pair of 100 watt panels doesn’t stand a chance.

 

[sunshine_eggo]

Umm... "for a friend?"

Sure sounds like your system:

Is this a good setup?

We recently purchased a partially converted skoolie that came with 2 100w 12v Renogy solar panels, a 30a Renogy solar charge controller, and a 1500w pure sine inverter. We bought 3 100ah 12v Renogy LiFePO4 batteries, #10 wires to go from the charge controller to the batteries, #2 wires to...

diysolarforum.com

did you not notice @MichaelK 's comments? You've added a 1500W space heater to that list, and you think it should work?

 

[Supervstech]

As you have been told repeatedly, you don't have anywhere near enough solar to keep the batteries charged, or get them recharged.
1500W is 125A out of the battery by itself...
#2 wires are far too small feeding the inverter.
30A charge controller far too small to funnel the amount of solar needed to keep up...