Help with proper MPPT settings for these LiFePO4

Hiesenfig

New Member
I just got these batteries from Amazon (NINTHCIT Grade A 4PCS 3.2V 120Ah LiFePO4). They did not come with a datasheet. :( All 4 tested to be 3.28vdc out of the box (getting new meter so i can read mV). I'm assuming I still need to top balance though. I ordered a 30v-10a CC/CV benchtop charger for that. (I'm using this guide for top balance.

I have an Overkill BMS that came pre-programmed for LiFePO4 (see below). But I'm trying to figure out what settings to use on the MPPT. There seems to be varying opinions about recommended settings for LiFePO4.

Code:
Overkill BMS 4S 120A settings (came preset for LiFePO4 with these settings)

                         Trigger / Release / Delay
Cell over voltage         3650mv   3500mv     2s
Cell under voltage        2500mv   3000mv     2s
Battery over voltage     14600mv  14000mv     2s
Battery under voltage    10000mv  12000mv     2s
Charge over current     130000mA     32s     10s
Discharge over current  130000mA     32s     10s
Charge over temp            65C      55C      2s
Charge under temp           -1C       5C      2s
Discharge over temp         75C      70C      2s
Discharge under temp       -10C       0C      2s

I tried to match up these MPPT settings with similar settings from BMS.
Code:
EPEver Tracer4215BN Settings (Must use user mode)
Over Voltage Disconnect Voltage            14.6
Charging Limit Voltage                     14.2
Over Voltage Reconnect Voltage             14.0
Equalize Charging Voltage                  13.8 (diabled by the duration setting
Boost Charging Voltage                     14.2
Float Charging Voltage                     13.6
Boost Reconnect Charging Voltage           13.3
Low Voltage Warning Reconnect Voltage      12.0
Under Voltage Warning Reconnect Voltage    12.0
Under Volt. Warning Volt.                  10.5
Low Volt Disconnect Volt.                  10.0
Discharging Limit Voltage                  10.5
Equalize Duration (min.)                    0
Boost Duration (min.)                     120

Do these settings look sound?
 

Hiesenfig

New Member
hmm.. i had understood that setting the Eq Duration to 0 would disable Eq, but now i'm not sure that's right. Maybe it means to disable the Eq duration only (meaning always on)? I'm not sure yet, i haven't attempted to power it own since I still have to balance the batteries first. Can it be set out of range, so that it just doesn't take affect? I'm not sure exactly what Eq does.
 

mikefitz

Solar Addict
Setting the equalization duration to zero time should prevent the charger operating in this mode, to be sure set the equalization volts to the same value as float.
Epever use the term Boost for Bulk/Absorption stage , once the Boost target volts is reached it holds the voltage constant for a time, the Boost duration.
The settings look acceptable but you may wish to make slight modifications.
Change float charging voltage to an even lower value, say 13.3 or 13.4, with boost reconnect slightly lower. Depending on solar input and loads you may have to adjust these values for optimum performance. Reduce the boost time to a shorter period, perhaps even zero. You can evaluate this when the system is complete and you are monitoring charging current. Where the charge current is constant and high, some absorption time may be needed, but for low currents a short or no absorption time is optimum.
Depending on the cells, cell balancing may be needed whilst charging and the absorption time may have to be selected to give enough time for the balancing to be effective. Again this can be determined once the system is in use.
The low voltage settings for the Epever load outputs could be higher, there is no point in taking power from the battery below 12.0 volts.
epever.jpg
Mike
 
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Hiesenfig

New Member
Thanks, Mike. Bewtween this and escpecially the other thread where you posted definitions of the parameters, It all makes much more sense to me. I came up with these Adjustments. I re-organsized them to make better sense of them. The prefix# is just their original order.

Code:
EPEver Tracer4215BN Settings (Must use user mode)
CHARGE
02.Charging Limit Voltage                     14.2
04.Equalize(Absorption) Charging Voltage      13.4 (duration set to zero below)
05.Boost(Bulk) Charging Voltage               14.2
06.Float Charging Voltage                     13.3
07.Boost Reconnect Charging Voltage           13.2
13.Equalize Duration (min.)                    0
14.Boost Duration (min.)                      60 for now.  Will adjust later.
LOAD
01.Over Voltage Disconnect Voltage            14.6
03.Over Voltage Reconnect Voltage             14.2
11.Low Volt Disconnect Voltage                11.5
08.Low Voltage Reconnect Voltage              12.0
12.Discharging Limit Voltage                  11.0
MISC
09.Under Voltage Warning Reconnect Voltage    11.6
10.Under Voltage Warning Voltage              11.5

My CV/CD charger should arrive today, so I'll be doing the balancing this weekend.
 

Hiesenfig

New Member
Preping for Top Balance. Have the batteries hooked up in series with the BMS to get them nearly full, then will switch to parallel to do the top balance. The values shown in the BMS dashboard match what I see with a meter.
 

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Hiesenfig

New Member
A couple of screenshots of the BMS dashboard.
 

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Hiesenfig

New Member
It's strange.. as it's charging, the AH remaining is increasing (up to 70.00AH now and steadily climbing), but the individual voltages are not. They fluctuate up and down very slightly and one has dropped slightly.. they are like this now compared to the screenshot above. 1: 3.333, 2: 3.336, 3.337, 4: 3.338

I assume it's still going fine.. lol

Edit: the individual cells voltages are starting to slowly increase.
 
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Hiesenfig

New Member
Update on my progress. With a couple of questions at the end.

The Balancing went well. I charged all batteries in Series with the BMS connected until one battery reached the limit and the BMS cut off the charging. Since it was late, I unhooked everything and waited until the next morning to continue. This morning I connected the batteries in parallel and charged at 3.65v. It took about 4 hours before they all got to 3.65 and current dropped to zero. I had my DMV connected to the battery to watch the real voltage at the terminals. After getting everything unhooked, all the cells showed at 3.648 +/- a few millivolts.

I then continued putting everything toghether. I put the BMS under the batteries, but now I don't have a way to turn the BPM off. I'll need to add an on/off toggle somewhere that's reachable. The plug on the opposite side from the MPPT is a port to plug in solar panels.

QUESTIONS
1. Is it normal that the Overkill BMS dashboard reports negative amps during discharge? I'm assuming so, since it was showing positive amps during charging.

2. When I first hooked up the BMS for the initial charge yesterday, it asked the total amp hours and cycle amp ours and I put in 120 and 96. During charging, it showed amp hours remaining (increasing as it charged) and battery SoC percentage. Today, when I turned the whole thing on, the BMS was showing 100ah total and 80ah cycle, like the default, so I updated them back to 120 and 96. The battery state screen says 0ah remaining and Soc 0%. But the cell levels show fine (see screenshots). Any idea why it's like that? It also shows there was 1 counter of cell undervoltage. Which I know is not possible. But everything seems to be working, other those stats. I ran my cooler on it for about 10 minutes drawing at about 5 amps.

3. Can I use my new CV/CC Charger and connect to the MPPT Panel port and provide it say 24v at about 8amps to charge the battery? (but not at the same time as the panel) Does the MPPT care where the power is coming from? Or say if I used a 19v - 90w laptop charger and connect it to the Panel port in lieu of the panels? Would that work?
 

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Hiesenfig

New Member
QUESTIONS
1. Is it normal that the Overkill BMS dashboard reports negative amps during discharge? I'm assuming so, since it was showing positive amps during charging.

2. When I first hooked up the BMS for the initial charge yesterday, it asked the total amp hours and cycle amp ours and I put in 120 and 96. During charging, it showed amp hours remaining (increasing as it charged) and battery SoC percentage. Today, when I turned the whole thing on, the BMS was showing 100ah total and 80ah cycle, like the default, so I updated them back to 120 and 96. The battery state screen says 0ah remaining and Soc 0%. But the cell levels show fine (see screenshots). Any idea why it's like that? It also shows there was 1 counter of cell undervoltage. Which I know is not possible. But everything seems to be working, other those stats. I ran my cooler on it for about 10 minutes drawing at about 5 amps.

3. Can I use my new CV/CC Charger and connect to the MPPT Panel port and provide it say 24v at about 8amps to charge the battery? (but not at the same time as the panel) Does the MPPT care where the power is coming from? Or say if I used a 19v - 90w laptop charger and connect it to the Panel port in lieu of the panels? Would that work?
For question 2 above, I determined my issue was that the balance plug was already connected to the BMS when I connected the balance wires to the battery. So the BMS actually powered up before the last battery was connected, so it saw it as 0% SoC. It triggered cell undervolt again as I disconnected everything in the opposite order. tl;dr: I've moved the BMS to the back (instead of under) the batteries, so I can actually reach the plug for connecting disconnecting. After hooking up the balance wires THEN plugging it in, it showed me AH remainging and % remaining, though it kept forgetting that it's a 120ah battery, going back to 100ah everything i disconnected and reconnected. I think I just wasn't setting it in the right spot. After changing it on the parameter setting page (instead of the parameters view page), it seems to remember it now. I did notice the SoC has dropped to about 50% already and I've hardly used it since it was top balanced. I'm assuming it's because it didn't stay in "Absorption" long enough at full charge. I'll try to throw it back on the charger for a little while at 14.2 and let it sit in absorption for a while once it's charged back up and see how that does.

For question 3 above, I've been reading and understand that the reason you can't use something like a laptop charger as a substitute for a solar panel is because the laptop charger won't limit the current drawn by the MPPT. The MPPT will try to draw as much current as is can. But wouldn't a CC/CV bench power supply limit the current? If I set it to CC 8amp and turn the voltage all the way up to 30v, the MPPT would not be able to pull more than 8amps, right? Then it would take that in at some v/a ratio and step it down to supply to the battery. Is this wrong?
 

Hiesenfig

New Member
I went ahead and tried plugging the CV/CC info the solar port and it worked just fine. It would start of at .01 amps and keep increasing until it got to the limit of the power supply. Then I dialed back the amp and volts just a bit. But the mppt display closely showed the same volts and amps as the supply. And the BMS showed the same amps going on. When the battery got back to full SoC, the amps dropped to practically 0.
 

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Hiesenfig

New Member
I get it now!!

I have my laptop connected via a inverter (off the controller load, since it's not much power being used) and my phone connected to the load. I let it go till about for about an hour so and was down to about 108ah left out of 120 (can't remember what the voltage was at the time.

Then connected my CC/CV as a mock solar panel. Set max voltage to 25v and max current to 8am. The controller scanned thru the amp range and settled in it at the max I set for both and started charging at about 200w. When it hit about 14.27, it switched to CV mode and dropped current to about 4amps to maintain the 14.2 volts for the hour duration I had set (60 minutes). At the end of the hour, it dropped the amps again to just enough to handle the load. At this point I turned off the load and amps dropped to 0. Turned the load back on and waited. When it hit 13.3, it started drawing just enough amps to maintain 13.3v (float mode).

I'm assuming it will stay in float mode indefinitely unless I use more power than it can maintain at CV 13.3 (or the current is limited by a cloud). So that when it drops to 13.2 (boost reconnect), it'll switch back to Bulk and start the whole cycle over.
 

late

New Member
Thanks for sharing your process and progress.

I also have 120AH cells that look identical to yours. I have gone through the process of top balancing in parallel, then constructing a battery in series and began to monitor via the same Overkill BMS. My construction, while functional, does not look nearly as clean as yours!

Would you mind sharing some additional details.?

What is the container? Looks like a plastic ammo box with the perfect width for those cells.
What products did you use for studs/washers/nuts, busbars on the terminals?
 

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Oscar Milian

New Member
I just got these batteries from Amazon (NINTHCIT Grade A 4PCS 3.2V 120Ah LiFePO4). They did not come with a datasheet. :( All 4 tested to be 3.28vdc out of the box (getting new meter so i can read mV). I'm assuming I still need to top balance though. I ordered a 30v-10a CC/CV benchtop charger for that. (I'm using this guide for top balance.

I have an Overkill BMS that came pre-programmed for LiFePO4 (see below). But I'm trying to figure out what settings to use on the MPPT. There seems to be varying opinions about recommended settings for LiFePO4.

Code:
Overkill BMS 4S 120A settings (came preset for LiFePO4 with these settings)

                         Trigger / Release / Delay
Cell over voltage         3650mv   3500mv     2s
Cell under voltage        2500mv   3000mv     2s
Battery over voltage     14600mv  14000mv     2s
Battery under voltage    10000mv  12000mv     2s
Charge over current     130000mA     32s     10s
Discharge over current  130000mA     32s     10s
Charge over temp            65C      55C      2s
Charge under temp           -1C       5C      2s
Discharge over temp         75C      70C      2s
Discharge under temp       -10C       0C      2s

I tried to match up these MPPT settings with similar settings from BMS.
Code:
EPEver Tracer4215BN Settings (Must use user mode)
Over Voltage Disconnect Voltage            14.6
Charging Limit Voltage                     14.2
Over Voltage Reconnect Voltage             14.0
Equalize Charging Voltage                  13.8 (diabled by the duration setting
Boost Charging Voltage                     14.2
Float Charging Voltage                     13.6
Boost Reconnect Charging Voltage           13.3
Low Voltage Warning Reconnect Voltage      12.0
Under Voltage Warning Reconnect Voltage    12.0
Under Volt. Warning Volt.                  10.5
Low Volt Disconnect Volt.                  10.0
Discharging Limit Voltage                  10.5
Equalize Duration (min.)                    0
Boost Duration (min.)                     120

Do these settings look sound?
How did it go with the NINTHCIT batteries are they any good?
 
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