AC watts, DC watts, VoltAmps, Kwh, battery runtime, huh?! I've confused myself, newbie needs a math lesson please!!

[cyberfed]

Nice thank you @fnnwizard and again the rest of you as well!

Coming up on 3 hrs

Pack:
53.12V
-2.20 A

RSOC: 90%
Remain: 66.48 AH
FCC 74AH
Average volts 3.320
delta 6-7mA
Image through the computer connected to the BMS shows 90% available. Hey that matches RSOC I just noticed, so remaining SOC? maybe?
Power factor on killawatt - hovers around .88 to .90
total KWh: 0.334
1.1 A
hovering around 119watts



So all this because 1 battery wasn't at the same SOC as the others?! holy smokes! Mental note ensure, make DARN sure, you top balance your pack when you build it!

I just built the thing slapped it on a SCC with some solar panels and the appropriate protection mechanisms and called it a day. BIG Mistake I guess! oh its 3:17 thats 3 hours! woo woo!

 

[MrSparkle]

I have seen expression "the devil is in the details" on this forum, here and there..
This would be the best scenario, if it turns out the issue was due to absence of balance and/or inadequate settings in the BMS.

 

[sunshine_eggo]

Nice thank you @fnnwizard and again the rest of you as well!

Coming up on 3 hrs

Pack:
53.12V
-2.20 A

RSOC: 90%
Remain: 66.48 AH
FCC 74AH
Average volts 3.320
delta 6-7mA

mV

Image through the computer connected to the BMS shows 90% available. Hey that matches RSOC I just noticed, so remaining SOC? maybe?

Yes

Power factor on killawatt - hovers around .88 to .90
total KWh: 0.334
1.1 A
hovering around 119watts

So all this because 1 battery wasn't at the same SOC as the others?! holy smokes! Mental note ensure, make DARN sure, you top balance your pack when you build it!

If your pack was indeed imbalanced to that degree, yes, but I haven't seen data supporting that, and I've never heard of cells so wildly out of balance that it would limit you to a small fraction of the capacity. The worst I've seen is around 50%.

I just built the thing slapped it on a SCC with some solar panels and the appropriate protection mechanisms and called it a day. BIG Mistake I guess! oh its 3:17 thats 3 hours! woo woo!

Wait a minute... okay... I forgot about these cells specifically. Other forum members reported receiving cells at NOTABLY different states of charge with pretty big voltage differences. That could do it.

 

[cyberfed]

Yeah I'm going to check other builds I have to make sure they are good. I've heard too LEV60s were found at different SOCs.

4 hr mark, we are still good! 85% remaining and still at 53.1 volts
.507KWh consumed per Kill-a-watt
cells are at 3320mV
Delta is down to 4mV

When I call it a day (work) in 30 mins, the power usage is going to drop a lot (30-40W I believe is the max). So I'll check it in the morning to see if it survived the night and where things are at.

 

[cyberfed]

All good this moring gents!! .99KWhs consumed since we started yesterday. Battery was still at 53 volts and 3.25 per battery volts nice and balanced showing like 78% or something like that free. What a difference. Un real! Thank you all for your help!!!! I would buy you all a beer if you lived near me!

Thank you again. I'll be back with more dumb questions, you guys know me by now. I really want to build a 16x pack that uses some of these huge 300+AH batteries but I dont know if they are quality or not.

Is that what the DIY community uses for serious storage of energy? (ESS)? These EVE or CALB batteries? What's the most respectable place to get legit ones that work right? I've been using Jag35.com for the LEV60 fun but I'm done with those. Batteryhookup is another well recommended place but I dunno...I hear a lot of good things from OverkillSolar but they only carry 100ah batteries and I called them they have zero plans to carry any other type of batteries. I've heard they are really good quality.

Say you were doing this project yourself what would you buy (please don't say a power wall I dont have 10K to drop on one). Looking for DIY. I've got a mountain of 400watt solar panels I DIY'd out in the yard, I need to have them doing something all the time. Right now I generate way more engergy than I use so packs remain topped off. I guess maybe I need to move to something like the fridge but I would want a battery that would survive overnight so its gotta have a lot of juice. Fridge is 966 watts on the sticker. Have not tested it yet w/Kill-a-watt I know due to the motors they have spikes in wattage.

I was kinda hoping to find some good batteries and wake up early on Black Friday or Cyber Monday nonsense and score some batteries. I'm ready to drop a few grand on batteries. Just dont know where/what! 48V of course that's what I'm setup for mostly with my inverters.

Cheers all!!

 

[MrSparkle]

Good to hear!
Though I am a little dubious about SOC estimation mid-test. (Especially considering LFP's characteristics.)
If I am correct, your discharge rate is ~0.03C? That is a very low rate. I have no idea about voltage-drop at that rate. So, hard to say what Resting Voltage would be if Voltage during discharge @0.03C is 2.25V.

I wonder how much cell voltage would rise IF you would stop the test and let the cells rise to their fully rested voltage? Do NOT stop the test though. I am merely highlighting the fact of difference between charging/discharging/rested states.

I am thinking it would be a good idea if you would start taking notes of individual cells' voltages at much more frequent intervals when you are starting approaching, dunno... 3.05V? Because the lower knee starts some where around 3.05V? Guys with more experience, chime in.

Also, I don't remember what end voltage did you choose and set in the BMS for this test.

So, when you closing in on 3.05V and lower, start taking notes on every cell-V and put them in a table together with Wh discharged that is reported within the BMS. Every 30 minutes? The Voltage-curve will start drop more and more sharply, for different cells. That is because the cells are not identical. The faster voltage starts to drop, the more frequent you take notes. 30m, 20m, 15m, 10m, etc, till your lowest cell finally reaches the set end voltage, aka LVD.

All ready now, you could make estimated time calculation, when the test could predictably reach 3.05 and lower. When you are asleep/work/home?

This way, you could get a quite good picture of how your cells behave and where their individual lower knees are (the part of curve that voltage starts to drop more and faster).

@sunshine_eggo
Did I miss something or made some flawed suggestion?

 

[sunshine_eggo]

All good this moring gents!! .99KWhs consumed since we started yesterday. Battery was still at 53 volts and 3.25 per battery volts nice and balanced showing like 78% or something like that free. What a difference. Un real! Thank you all for your help!!!! I would buy you all a beer if you lived near me!

3.25V under a light load is likely lower than 78%, but YMMV. Don't get too hopeful.

Under the low overnight load, the BMS may not have tracked the current accurately. Anything below 2A may be suspect.

Did you confirm all instruments agreed when load was reduced to the projected 30-40W?

Thank you again. I'll be back with more dumb questions, you guys know me by now. I really want to build a 16x pack that uses some of these huge 300+AH batteries but I dont know if they are quality or not.

Just follow the top balancing guide in the resources section, gross summary:
0) Fabricate quality leads for any power supply you use.
1) build battery and through through BMS until cut off.
2) breakdown and parallel cells.
3) Adjust power supply voltage only with leads disconnected
4) Charge in parallel to 3.45, then to 3.55, then to 3.65. Go by voltmeter on terminals, not that reported by power supply.

Details omitted, but that's the gist.

Is that what the DIY community uses for serious storage of energy? (ESS)? These EVE or CALB batteries? What's the most respectable place to get legit ones that work right? I've been using Jag35.com for the LEV60 fun but I'm done with those. Batteryhookup is another well recommended place but I dunno...I hear a lot of good things from OverkillSolar but they only carry 100ah batteries and I called them they have zero plans to carry any other type of batteries. I've heard they are really good quality.

EVE 280 seem to be the most popular. I've built two 8S batteries with them and did extensive single cell testing.

18650store is very popular.