Latest Philosopy on Classic Settings / Firmware for LFP Batteries

[5 Minutes 2 Midnite]

Greetings. Have been putting together the parts for an off-grid system for about two years. Actually just now putting it all together. Feeling pretty comfortable with all aspects of the install... except configuring the Classic 150. Still a wee bit hazy. Note, I have not powered up the classic it. It was purchased in DEC 2015 and was still boxed up until last week. Hoping to nail down how the unit should be configured for when I power it up.

In perusing a countless number of threads on other forums for general LFP charging knowledge, and then recently this forum for specifics, it seems an important feature that has been added to the classic is the ability to taper the charge current. Yes? Here is all I have on the requirements for my recently purchased cells:


SUGGESTED CHARGING CURVE
Constant Amperage to 3.65V,
Constant Voltage,
Decrease Amperage,
Stop at 1A Charge

http://www.electriccarpartscompany.com/New-Energy-72Ah-Aluminum-Encased-Battery

I won't know what FW is in my Classic until I power it up. But if anyone has a recommend on the minimum FW to best charge LFP cells it would be helpful. Also helpful would be a suggested initial profile for the Classic to charge the pack (16 cells in 48V array).

thank you.

[Westbranch]

grab the latest... Rev 2126 is on the MidNite site

[ClassicCrazy]

You don't even need to wait until you put the whole system together to update the Classic - you can just hook up 12v from any power supply to the battery input and use  the update cable to do the updates. Also that would give you a chance to poke through the menus , set up the parameters, hook up the Local Status App , etc.  before you put it online for real.

As Westbranch said - get the latest firmware from the Midnite site and follow instructions there to do the update.

Larry

[5 Minutes 2 Midnite]

Thank you. It's always a good bet to update FW, and doing so now. Was just curious about any LFP specific features. Saw the sticky detailing FW updates and will check there.

If anyone could offer some initial parameters for an LFP array as described above it would be appreciated.
jim

[dgd]

Just noticed your SIG info and that sure looks like a very tiny battery bank considering the inverter capability and that 3500+ watts of PV into the Classic.
Are you sure this bank can supply enough power between PV charge cycles?
dgd

[TomW]

You don't even need to wait until you put the whole system together to update the Classic - you can just hook up 12v from any power supply to the battery input and use  the update cable to do the updates. Also that would give you a chance to poke through the menus , set up the parameters, hook up the Local Status App , etc.  before you put it online for real.

As Westbranch said - get the latest firmware from the Midnite site and follow instructions there to do the update.

Larry

I have updated Classics in the past using a common 9V battery. Its enough to fire it up and update / poke about  in the menus, do initial configuration (if  needed), etc.

Tom

[ClassicCrazy]

Thank you. It's always a good bet to update FW, and doing so now. Was just curious about any LFP specific features. Saw the sticky detailing FW updates and will check there.

If anyone could offer some initial parameters for an LFP array as described above it would be appreciated.
jim

Well you want to make sure you don't go under voltage on your battery pack. I have a small 100 ah lithium pack that I got to experiment around with . And I thought I could rely on bottom balancing alone - but found out stuff goes wrong and the minimum I should have had was something to cut off batteries when voltage was too low. I had one time when the Classic itself drained the batteries too low when I had turned off the PV .

So if you have BMS protection of some kind you will just have to observe your high voltage setpoint which is petty easy to do. When I was doing the bottom balancing I set the ending amps to take it out of Absorb into Float. I was following advice of Cinemand on this group who had a similar setup . If you search bottom balancing on this group you will find lots of discussions on all kinds of lithium battery charging strategies .

I was hoping Midnite would add the option to shut off PV charging when battery temperature got below certain point since my lithium are out in the cold and not recommended to charge below freezing . But they haven't added that feature yet so I shut them off for the winter.

Larry

[5 Minutes 2 Midnite]

Well you want to make sure you don't go under voltage on your battery pack. I have a small 100 ah lithium pack that I got to experiment around with . And I thought I could rely on bottom balancing alone - but found out stuff goes wrong and the minimum I should have had was something to cut off batteries when voltage was too low. I had one time when the Classic itself drained the batteries too low when I had turned off the PV .

Interesting.

I have taken an extra precaution regarding low voltage threshold. In addition to bottom balancing, and In addition to the low voltage cutoff on the inverter, my BMS has an option for an LVD.. a relay that disconnects the array on a settable low voltage condition.

For now I am going to set the disconnect a bit high (conservative) in the case one cell dips too low. But I just realized something in replying to your point. All the research I've done on BMS systems I have failed to look for what I just realized should be a straightforward feature. Individual cell voltage monitoring, and a disconnect facility when any one cell goes too high.

I do understand that BMS systems monitor individual cells and [supposedly] bleed off charging current when one cell gets too high. But in looking at BMS systems I don't recall seeing one that actually forces a disconnect if voltage rises beyond a certain threshold as a sort of Plan B to keep from ruining a cell (or more). Again, my BMS does that on the low side, but not the high side. (as best I know. I have not implemented it yet, and this is my first system. So for all I know there may be many BMSs that cut off the entire array on a high voltage condition. I just hadn't noticed one.) ;>

So if you have BMS protection of some kind you will just have to observe your high voltage setpoint which is petty easy to do. When I was doing the bottom balancing I set the ending amps to take it out of Absorb into Float. I was following advice of Cinemand on this group who had a similar setup . If you search bottom balancing on this group you will find lots of discussions on all kinds of lithium battery charging strategies .

"high voltage setpoint". Again maybe mine or any BMS can disconnect if unable to bleed off enough current to keep voltage within tolerance. I am still learning.

Good advice on the search term "bottom balancing".

[5 Minutes 2 Midnite]

Are you sure this bank can supply enough power between PV charge cycles?

No.


:>

[5 Minutes 2 Midnite]

SUGGESTED CHARGING CURVE
Constant Amperage to 3.65V,
Constant Voltage,
Decrease Amperage,
Stop at 1A Charge

Just an update. I updated the FW on my classic. Also, I went a couple of rounds with support and got some helpful information on tapering current. In perusing some old threads here (2012-2014) I saw some requests to provide such a feature, and I think a note from boB that it had been implemented. Support explained the setting and that it required a wizbang jr and shunt. Had not heard of the wbj but it makes sense. The controller has to know how much current is passing to moderate it.

Shunt-wise, I have a Magnum MMP with a builtin 500a 50mv shunt. Exactly what support told me the wbj wants. Except a different brand. And my BMS wants a 500a 75mv shunt. So now I get to figure out if the BMS will get along with a 50mv shunt (I would think not), and if so can it share the shunt in the MMP panel with the wbj, and if so, will the wbj even mount to the MMP shunt. Fun.


Any other thoughts on Classic + LifePO4 I'm all ears. (I'm tempted to look for an emoticon with big floppy ears... but, no).

[RossW]

But I just realized something in replying to your point. All the research I've done on BMS systems I have failed to look for what I just realized should be a straightforward feature. Individual cell voltage monitoring, and a disconnect facility when any one cell goes too high.

I do understand that BMS systems monitor individual cells and [supposedly] bleed off charging current when one cell gets too high. But in looking at BMS systems I don't recall seeing one that actually forces a disconnect if voltage rises beyond a certain threshold as a sort of Plan B to keep from ruining a cell (or more).

The BMS (Battery Monitoring System) I built some years ago (and have supplied to several of the forum members here) constantly outputs the voltage of each cell, and has a user-programmable threshold (window) for a delta. Any cell gets that far (or more) from the average of the entire pack, and it sends up a flare. (Well, flags it in the data stream, and a LED on the board). It'd be easy enough to make it be a beeper, or to operate a relay, or whatever.

So, they are out there. They may just not be so common.

(For my own installation, I'm living and working here all the time. The generator kicks in well before the inverter would shut down, and the inverter will shut down well before the batteries are low enough to be a problem, and the continuous cell balancers I have across each cell does its best to keep them all within about 10-15mV, charge, discharge or just sitting there quietly.)

[ClassicCrazy]

SUGGESTED CHARGING CURVE
Constant Amperage to 3.65V,
Constant Voltage,
Decrease Amperage,
Stop at 1A Charge

Just an update. I updated the FW on my classic. Also, I went a couple of rounds with support and got some helpful information on tapering current. In perusing some old threads here (2012-2014) I saw some requests to provide such a feature, and I think a note from boB that it had been implemented. Support explained the setting and that it required a wizbang jr and shunt. Had not heard of the wbj but it makes sense. The controller has to know how much current is passing to moderate it.

Shunt-wise, I have a Magnum MMP with a builtin 500a 50mv shunt. Exactly what support told me the wbj wants. Except a different brand. And my BMS wants a 500a 75mv shunt. So now I get to figure out if the BMS will get along with a 50mv shunt (I would think not), and if so can it share the shunt in the MMP panel with the wbj, and if so, will the wbj even mount to the MMP shunt. Fun.


Any other thoughts on Classic + LifePO4 I'm all ears. (I'm tempted to look for an emoticon with big floppy ears... but, no).

Yes you need the Whizbang to be able to use the ending amps feature which will take it out of Absorb to Float. You probably will have to get the right shunt for it - look on Northern Arizona Wind Sun - they have the right kind of shunt for $25 - a Deltec which is the same as the Midnite shunt. You can get the Whizbang from them too.  For my 100 AH Calb LiFePo4 I think it is 5 amps for the end amps stage when doing bottom balancing. You have to make sure if you do that  to drain every cell to the bottom voltage so they won't charge up to the top point where they need the BMS for balancing each cell. That is the theory anyway.  There are past discussions talking about these details. I wouldn't swear by them though - still evaluating my own setup but as I said before I need to put in some low voltage disconnect.

Larry

[5 Minutes 2 Midnite]

Yes you need the Whizbang to be able to use the ending amps feature which will take it out of Absorb to Float.

I'm glad you mentioned that, as in what the wiz bang actually triggers the controller to do. I've been hip deep in a couple of LifePO4 charging threads on a popular solar forum where a couple of the big dogs had to come to consensus that simply setting Bulk = Absorb = Float on the Classic is a workable strategy for charging such batteries.

One would assume then that setting all three charging stages to the same voltage might render the wiz bang function useless. ?

[Westbranch]

One would assume then that setting all three charging stages to the same voltage might render the wiz bang function useless. ?

I'm confused...What is your logic for this statement?

Bulk = Absorb = Float setting is in VOLTS and the WBjr reads only the AMPS going into the battery not the TOTAL Amps coming out of the Classic

[5 Minutes 2 Midnite]

One would assume then that setting all three charging stages to the same voltage might render the wiz bang function useless. ?

I'm confused...What is your logic for this statement?

Bulk = Absorb = Float setting is in VOLTS and the WBjr reads only the AMPS going into the battery not the TOTAL Amps coming out of the Classic

Well I may not have sound logic. I was keying on ClassicCrazy's statement "Yes you need the Whizbang to be able to use the ending amps feature which will take it out of Absorb to Float".

If (repeat, if) all the WBjr does is trigger the controller to go from absorb to float, then if one chooses to adapt the aforementioned strategy of absorb voltage and float voltage being set equal, then would any change in the charging profile occur when the End Amps setting is triggered by the WBjr.

I am making an assumption that ClassicCrazy's assertion is the whole story of what happens when End Amps is triggered. I'm further assuming that the setting of float voltage is what limits current flowing into the battery.

But I am really just a newb stumbling around in the dark looking for a way to satisfy the requirements of the cell maker, which again is:

SUGGESTED CHARGING CURVE
Constant Amperage to 3.65V,
Constant Voltage,
Decrease Amperage,
Stop at 1A Charge

Thank you for you interest!