Batteries really depleted overnight or is it a BMS problem?

[Mcstiggens]

The battery charger listed imho is totally insufficient for 400ah of battery. It would take forever to charge and probably be a loosing battle with any load while it’s charging

Yea, I'm aware. Just what I could swing at the time. Today I am accepting shipment of this one (below) just for good measure. This afternoon, when I receive the charger, I am going to take the batteries on a cart over to the barn and charge the shit out of them so that I know I'm starting with a full pair. As mentioned before, there is 110A/C on the property but it is way too far to tap into and I pledged to remain off-grid anyway.

Amazon.com

For lithium batteries, there are only two times a voltmeter is accurate, full and empty with no load. Anything in between is a guess and not worth considering. Only a good shunt type monitor can count remaining capacity and measure what’s going in or out of the battery.

Glad I know that now.

If you have a “three way” refrigerator, that could be the reason for a fast battery drain.

I have a brand new 12v only Furrion fridge, so it is as efficient as you can get.

 

[sunshine_eggo]

As far as I am aware, yes. They are wired in parallel, facing true south at around 38 degrees (i believe).
As you can see, the sun is just hitting them straight-on at 11:50am

As long as their Vmp values are within about 10%, it's fine. I was primarily concerned with the 50W.

Can the solar generator take more? At that angle, I'm guessing you could tilt some panels against the container and wire in parallel like in my first "ground mount" setup:



?

 

[Mcstiggens]

As long as their Vmp values are within about 10%, it's fine. I was primarily concerned with the 50W.

Can the solar generator take more? At that angle, I'm guessing you could tilt some panels against the container and wire in parallel like in my first "ground mount" setup:

View attachment 182005

?

Well, unfortunately, the real estate is all taken up behind my container with infrastructure and building materials, so it'll have to be a 2x4 job out in the field.

 

[Mcstiggens]

Status Report:

Yesterday I used a 40amp LifePO4 specific charger, direct from Li Time themselves and charged the batteries for around 6 hours until the charger indicated that they were at 100%. The voltage at this point was 13.7 volts, not the "14.2V to 14.6V that they are expected to be when full.
I then reset the shunt/monitor for 400AH and 100% capacity.

This morning when I checked them, they were alleged to be at 85% and 333AH remaining.
After running the furnace and fridge for 12 hours, I'd say that is pretty expected and reasonable readings.

I checked the charge controller stats which said the 165W panel on the roof (flat w/ no angle) was only putting out a measly 1.7 volts, BUT when I checked the panel directly, I said 20.1ish V so I don't know what is up with that major discrepancy

I then took one of my 185W 42V panels, propped it up around 38/40 degrees and took a reading which indeed was the rated 42-ish V. I then plugged it into the trailer and returned to the charge controller interface for stats, where it read 34.2-ish V. The monitor shows the batteries taking a good charge so I'll see what happens after the sun goes down today.

FWIW, since my 185W panels are older, they have the MC3 connectors and I only have one set of MC4 adapters. Otherwise, I would have set up two 185's in parallel just for a good start. Although I now think just starting with one of them to see how it preforms is a better idea anyway.

So that's where I'm at currently.

 

[Mcstiggens]

Can the solar generator take more?

I will report back on the specifics of the "little" solar generator when I get more time. Between my boondock life chores and dealing tedious, ultra slow and spotty internet, it is quite a challenge to keep up here.

 

[Tomthumb62]

I am definitely planning a quick and simple Mcguiver array with the panels. I like your idea but could you elaborate a bit on the concept of

"overpanelled" please.

For example, my Victron 100/30 MPPT says a max input of 440w for a 12v system. I have 600w connected. I never see the max production (highest so far is about 410W), so having that “extra” 160W of available potential power comes in handy on a daily basis. Come around this next summer solstice, I will probably see the MPPT maxing out at 30A output every day. But the rest of the year, it never reaches max potential.

 

[Tomthumb62]

The voltage at this point was 13.7 volts, not the "14.2V to 14.6V that they are expected to be when full.

Unless you caught the charger right during the absorption phase of the charge cycle, you’ll never see 14.2-14.6v. Within seconds or minutes of the charge cycle dropping from absorption to float mode, the voltage of the battery will settle to the RESTING VOLTAGE of 13.2 to 13.5v.
If you’re seeing 13.7v, then either the charger is still in float mode or it hasn’t yet settled to the resting voltage. 13.2-13.5 is considered 100% full, assuming the battery reached 13.8v or higher during the absorption phase.

 

[sunshine_eggo]

Status Report:

Yesterday I used a 40amp LifePO4 specific charger, direct from Li Time themselves and charged the batteries for around 6 hours until the charger indicated that they were at 100%. The voltage at this point was 13.7 volts, not the "14.2V to 14.6V that they are expected to be when full.
I then reset the shunt/monitor for 400AH and 100% capacity.

At 40A, you're charging at 0.1C, so the voltage spike to 14.4V happens very late and very fast. At 0.1C, getting nearly fully charged to 95%+ at 13.6-13.8V is readily achievable.

In retrospect at your prior 10A charge, 13.8V would have been a guarantee of "close enough to 100% not to matter."

 

[Mcstiggens]

In retrospect at your prior 10A charge, 13.8V would have been a guarantee of "close enough to 100% not to matter."

Well that being the case, I probably did start out at a decent baseline. It was just a matter of getting bogus readings due to
A: using a voltmeter at the inappropriate time and
B: not have the shunt/monitor properly formatted.

 

[Mcstiggens]

In retrospect.........

'Oh sure, it'll be great! Freedom from the system they said! Total autonomy, oneness with nature, you'll be in total control.....they said.


I kid.....I kid....there was no "They".
I was very aware of my uphill battles and hardships and the realization that it would be non-stop chores associated with the off-grid homesteading life; what with:
finding power/researching how your going to design a solar system
filling tanks
emptying tanks
prepping the coco coir
dumping your poopy buckets
filling your propane and switching bottles in the middle of the night cuz you forgot to check and ran out
researching how your going to get consistent internet, finding what type, how many redundancy's would be necessary etc.

and on and on and on it goes...

My only issue is that i was kinda thrown into this before I was ready.

My only saving grace is the great community and information you guys all provide. It's been a great help and I really appreciate ALL of you and your input.

All the best to you in these wild and ridiculous times folks.
Merry Christmas and stuff.

Lane

 

[sunshine_eggo]

Hang in there!!!!