New lithium installation - float always on?

[qwerty_steve]

I've finally got my lithium system up and running and need a little help finalising the programming on the KID. I should state up front that I have a 100ah lithium system with a House Power BMS for monitoring cell voltages.

After the initial setup, the KID performs a bulk charge cycle, then switches to float mode and basically stays there. Is this normal? The only way I can figure out to get the KID to switch to bulk mode is to do a factory reset. It will then charge to whatever I have set for the absorb, then switch to float indefinitely. I'm guessing this has something to do with lithium's flat voltage discharge curve (but can't say for sure).

My settings FYI:

Absorb: 13.8V, time: 0
Float: 13.2V

I have tested the output of the KID in float mode and (after a factory reset) bulk mode... both seem to be about the same output. I was under the impression that bulk mode takes advantage of MPPT, while float is more akin to PWM. With the output almost identical in both bulk and float, I'm not sure if this is the case.

It looks like everything is working ok, I'm not sure. Can anyone offer any guidance on this?

[ClassicCrazy]

There is a lot of info on charging lithium batteries in this thread .
I think some of your setpoints depends on if you are top or bottom balancing them.
Take a look here
http://kb1uas.com/mnsforum/index.php?topic=962.0

Larry

[jamesb]

I know this is a really old post.  I'm having the same trouble did you ever resolve this issue?

Thanks,
James

[ClassicCrazy]

What qwety steve  described is pretty much how my Classic behaves with my calb lithium batteries.

Begins the day in Bulk and when it hits the setpoint of absorb voltage and then ending amps it changes very quickly from Bulk to Float.

It is going to stay in Float the rest of the day unless it goes below rebulk  which it probably won't .

Any loads while in Float the charge controller will give all the available PV current to the loads but still say in Float .

Steve did not say if he had an ending amps setting .

And since this was two years old I hope he has done a firmware update by now since there were some issues that were fixed for some things.

Larry

[jamesb]

I guess I misunderstood his problem.  I would be perfectly happy with what you describe, but what I see is that it starts the day in float and stays in float, so my system is rarely reaching a full charge.  Battery is reading 13.2 with the solar off, and by my ammeter I'm down about 40ah so I would expect it to be in bulk for sure.

Absorb 14.0 time 1 min
Float 13.8
EndAmps 8
Rebulk 13.1

I have played with every combination I can think of and can't get it to start the day in bulk.  The problem is that it's my rv in the woods so I generally only get to play on the weekends.

Any thoughts would be appreciated.

James

[mike90045]

might this have something to do with the Li voltage curve being much "flatter" than lead acid, and there is only a small difference in voltage if you are wanting to cycle 20%-80% without hitting the "knees" at either end ?

[jamesb]

I thought it would bulk until it hit the absorb voltage.  It couldn't have hit the absorb voltage with my batteries down the way they are.  Please correct me if I'm wrong.

James

[ClassicCrazy]

I guess I misunderstood his problem.  I would be perfectly happy with what you describe, but what I see is that it starts the day in float and stays in float, so my system is rarely reaching a full charge.  Battery is reading 13.2 with the solar off, and by my ammeter I'm down about 40ah so I would expect it to be in bulk for sure.

Absorb 14.0 time 1 min
Float 13.8
EndAmps 8
Rebulk 13.1

I have played with every combination I can think of and can't get it to start the day in bulk.  The problem is that it's my rv in the woods so I generally only get to play on the weekends.

Any thoughts would be appreciated.

James

Why do you have Absorb Time at only one minute ?
I am wondering if it climbs to Absorb voltage really fast and then with one minute on timer you just don't notice it changing over ?
With only one minute Absorb time it may never use the 8 amp ending amps point.

Are you using the Whizbang SOC to determine that you are -40 amps ?
If so what do you have setup for the capacity and efficiency of the Battery SOC setup ?

Have you tried forcing it into Absorb and watch closely what happens ?

Larry

[jamesb]

I felt that once it reaches absorb voltage it's essentially full, but that seems like fine tuning.  If I reached absorb voltage then my voltage would be at least 13.4, since I have very little load 1.5 A in the morning.  Plus, the float would really ensure it was full, but I'm seeing the voltage at 13.2 and the ammeter indicates it's still down.  I don't have a wizbang jr, I have a shunt and an ammeter that has been working well for a couple of years.  I bought the new controller because my cheap controller was tripping my BMS.

How would I force it into absorb mode?

[ClassicCrazy]

I felt that once it reaches absorb voltage it's essentially full, but that seems like fine tuning.  If I reached absorb voltage then my voltage would be at least 13.4, since I have very little load 1.5 A in the morning.  Plus, the float would really ensure it was full, but I'm seeing the voltage at 13.2 and the ammeter indicates it's still down.  I don't have a wizbang jr, I have a shunt and an ammeter that has been working well for a couple of years.  I bought the new controller because my cheap controller was tripping my BMS.

How would I force it into absorb mode?

No on your idea of  Absorb. It reaches Absorb setpoint and then stays there until it either reaches Absorb Time or Ending amps whichever is first.  Then it goes to Float.

I think your Absorb Voltage is more like the point it is at 80% to 90 % full for Calb batteries. That is what I use for the top of my bottom balancing which is not a 100%  full battery .

I guess I was thinking of the Classic which you can force into Absorb.  I don't  believe you can do that with the Kid. 

What amp meter are you using ? You would have to have one that counts amp hours from full t know what your batteries use. It would use an external shunt that has only one connection from the battery negative to shunt and all other negatives go to the other side of the shunt.  Without using a Whizbang which knows exactly what is going into the battery and what is going into loads it is not very easy to use an Ending Amps setting unless you know exactly what your load is and compensate for that .

A Whizbang is a very good and relatively inexpensive investment in knowing exactly what your battery state of charge is.

Look at the charts for your Calb batteries here
http://evwest.com/support/CALB-CA100Ah.pdf

I don't remember exactly how many cells you had and how you had them configured - I think it was in your other post where you said what you had. 

Larry

[jamesb]

Okay, based on your statement about absorb, I'm confused, how does the kid know when to do bulk and when to do absorb? You described when it goes to float.

Your description of the shunt installation is correct
Ammeter: http://www.electriccarpartscompany.com/ECPC404-Ammeter-and-Voltmeter-Intelligent-Digital-EV-Battery-Pack-Monitor
Shunt: http://www.electriccarpartscompany.com/400A-75MV-Shunt_p_608.html

I have 12 100 ah cells configured for 12 v @ 300 ah.

[jamesb]

I looked at the WhizBang Jr and see that my shunt won't work, not a huge deal, but it does say, ". To use the Whizbang Jr (MNWBjr) with any of the Classic Lites, you will either need the local app or an MNGP."  I don't know if the KID is included in that classic lite group or not, do you?  The KID doesn't have a local app but it does have a graphics panel.

[Westbranch]

YES, the Kid and WBjr are fully compatible...  if you go through the menu pages on the Kid graphics panel, you will see a WBjr Yes or No tick box IIRC ... 

They are highly recommended for any battery type if you truly want a full charge, without one it is a guessing game,....

[ClassicCrazy]

Okay, based on your statement about absorb, I'm confused, how does the kid know when to do bulk and when to do absorb? You described when it goes to float.

Your description of the shunt installation is correct
Ammeter: http://www.electriccarpartscompany.com/ECPC404-Ammeter-and-Voltmeter-Intelligent-Digital-EV-Battery-Pack-Monitor
Shunt: http://www.electriccarpartscompany.com/400A-75MV-Shunt_p_608.html

I have 12 100 ah cells configured for 12 v @ 300 ah.

Oh - too bad they use that shunt for your amp meter. If it was 500 amp 50mv shunt like Midnite uses you could have hooked up the Whizbang on it and also still used your existing meter both at same time.
https://www.solar-electric.com/mkb-500-50.html

As Westbranch said - you just enable Whizbang on the Kid and set it up on the screen and it will display all the data there.

Yes I do believe it should be in Bulk at the beginning of day if the voltage is lower than your Absorb Setpoint and up until it gets to the Absorb setpoint. Not sure why yours may not be doing that.  You may want to run some big loads for awhile - and watch the voltage so you don't go below the critical 10v point ( your BMS should cut off the batteries before that happens) . Anyway run the batteries down some night and see what happens in the morning when the solar starts charging again.  You will also be load testing your batteries . You should check each cell to make sure they are pretty close in balance too.

Larry

[jamesb]

I think I can likely use my ammeter with the MN shunt with some programming changes.  I'll consider getting a whizbang jr if I can ever get this working.

The batteries are well balanced, I had the pack apart over the winter to balance them.  My batteries were down weeks ago and it made no difference, they still sat in float. I'm really at a loss where to go from here.

Thanks,

James