Lithium Battery goes to resting instead of Float

[ClassicCrazy]

I have 16 Calb 100Ah cells in series for 48v system.
I am doing bottom balancing so drained each cell out carefully to 2.5v  .
I set Absorb voltage to 56v , float to 54v , ending amps to 5 .

Last night I ran a small load and SOC went to 94%  , today the Classic started charging in Bulk - charged to 100% where voltage had climbed to 55.5 last report on MyMidnite . but instead of it going to Absorb or Float  or maybe it did it really quickly and didn't show up on MyMidnite - it went to Resting 38 ( unknown ) . It has done this for a few days I have been watching it.

Any ideas ?

Larry

[Westbranch]

Larry is that a double peak in the WBjr line?  and why does the power (in?) drop so precipitously (Sun down?)?

All connections nice 'n tight?

can't think of much more.... do you use the LApp?  If so have you tried Grahams Android version...  the Live Chart is every 2 seconds... not  delayed... might help

[Vic]

Hi Larry,

Have never used Lithiums in an RE system.

Normally,  Li batteries do not use Temp Compensation,  as I read it,  so this should not be a factor ...

Regarding RFR 38,  am sure that you have seen this,  Reply #5:
http://kb1uas.com/mnsforum/index.php?topic=2880.msg27522#msg27522

Forget the FW version that you are running in the CC ...

Dunno,    Vic

[ClassicCrazy]

Larry is that a double peak in the WBjr line?  and why does the power (in?) drop so precipitously (Sun down?)?

All connections nice 'n tight?

can't think of much more.... do you use the LApp?  If so have you tried Grahams Android version...  the Live Chart is every 2 seconds... not  delayed... might help

No it wasn't sundown  - it was morning when that did that. Yeah I should watch it on Grahams Android app and see what it does there.

Larry

[ClassicCrazy]

Hi Larry,

Have never used Lithiums in an RE system.

Normally,  Li batteries do not use Temp Compensation,  as I read it,  so this should not be a factor ...

Regarding RFR 38,  am sure that you have seen this,  Reply #5:
http://kb1uas.com/mnsforum/index.php?topic=2880.msg27522#msg27522

Forget the FW version that you are running in the CC ...

Dunno,    Vic

Thanks Vic for that link. I missed that in the past.
I will take a look at the reason for resting according to that method right away next time it does this.
I got this small lithium pack just to get familiar with it . It is different compared to lead acid in that the voltage doesn't really sag - lots of energy available .

One of the weird things is that at the end of the day it then goes into float.

I have 2079 in it - guess I didn't update to 2096 yet . I did on my other Classic controller but then went back to 2079 because I was getting all the dropouts on MyMidnite.

Yes now that I read up in the other post about reason for resting 38 maybe it is because the lithium voltage goes too high since I don't have any loads on it.

Larry

[australsolarier]

the classic midnite,  lifepo4 batteries and no load seems to be the weak and unpredictable area of the midnite software.
i have this small 12v system with 300ah lifepo4. when i am at work the charger correctly charges up to the absorb settings, then drops into float.  but the float point is way down from what i set it. in my case it is set to 13.4v. the midnite starts to think it has to go to 13.1v for some reason.  (for a lifepo4 battery that is way down in soc)    at the other hand when i am at home and the computer and other things are connected to it, after float it correctly tries to remain 13.4v
a bit like an unruly teenager:  the mice play up when the cat is not at home.

there is a light load connected maybe so between 50 and 100w when it does not want to go into proper float mode

when at work i remotely "force absorb". it will go to absorption voltage again, then drop below float again. until i am back at home and turn on a load. in the southern summer it was not a problem, as the fridge and freezer chest was connected to this system. however they are plugged in to another power source now. due the way my solar panels are oriented, there is not much sun hitting them in the winter here.

so, i suppose i just have to wait until such times as the midnite blokes come out with a software that also solves this problem.

[ClassicCrazy]

I will have to put a load on mine and see how it reacts.

What do  you think Midnite could do to make it better for lithium batteries ?

Larry

[Priusron]

I also have lifepo4 batteries. They do not like to float. I was concerned because the charging curve was different from my lead acid batteries. I am used to it now. I have the float voltage set below the absorb voltage with a end amps of 10 I believe. I have a 12 volt 600ah system. I do not want them at 100% soc. If you limit it to 95% your cells will last significantly longer.

I checked your numbers and they are right on. Send your absorb time to 3 hrs. It will only be a few minutes but that is just in case it ever needs it. Your end amps will trip it off. I have watched mine on the android app and it moves from bulk to absorb, float, resting very fast. The app does show that it hit float. I quit worrying about it because it is working great.

Basically with your settings, from my research, it is performing as it should for lithium batteries.

[australsolarier]

Larry, did you ask me?

for one thing the lifepo4 batteries have very "stiff" voltages. so 1/10th of a voltage makes a big difference to them particularly with a 12volt system. for example on my 12v system float is set to 13.4v. however it keeps float reading on the status panel at 13.5v. (for practical purposes, the real voltage at the battery terminals are close enough at 13.4v for me not to worry about)
as contrary to the to the 48v system. there absorb is set to 56.0v, but the midnite reckons it should be 59.9v. (does it compensate??? hehe).
with led acid batteries those discrepancies are no big deal. but it can be a problem with a 12v lifepo4 system. (voltage loss through breakers and cables are an added problem)

then we have my problem with the 12v system the midnite deciding float should be at 13.1v or there abouts when programmed to 13.4v when there is a light load applied, like between 50 and 100w. is the load larger it will go to float at the programmed voltage and keep it there.
this looks to me like soft ware programming things. i do not know what the problem is, i have absolute no insight how the midnites are programmed
another problem i noticed the "pumping". on a sunny day with no clouds and absolutely no shading on the panels. the midnite does the absorb thing and then gradually reduces power until it reports "shading" or something like that. to start then again with the cycle. (this was solved from changing the setting from "solar to legacy p&o)
on the 12v system when set to "solar" half way to 100 SOC the software decides, well, mppt voltage should not be 31v but 35v with the result that charging is reduced 80% or there abouts. (and way short of absorption voltage) again legacy p&o solved that particular probem.

maybe i have too much time on my hands to notice those irregularities.

at the other hand maybe midnite classice engineers should hook up lifepo4 batteries and see what they are doing.
having all said that, the next solar charger will be a midnite classic again.
greetings urs

[ClassicCrazy]

Thanks for the tips - now I know what my system is doing is more typical with other LiFePo4 batteries.

I am moving my lithium system to a different location and took the battery pack apart so checked the voltages. A few of the cells were high or low so I think I will bottom balance the all again just to be sure . But with the bottom balance from what I have read is that is why if some of them are off then they are still not too close to the critical over voltage range.

Main reason for moving my system is so that I don't have to listen to the inverter and charge controller various sounds , high pitched squeals, hums,  and fans - had them in the camper and much quieter having them outside !

Larry