Please, need recommendation for Charge controller (12V LifePo4 Bank)

gingerboy

New Member
Joined
Aug 13, 2020
Messages
17
This is my small project, got 8 pcs used CALB cell (100Ah, test them got 70-80Ah), make the 12V banks for 12V pump to fix underground water problem.
So, the 12v bank has about 150Ah capacity, I can put on 100W x 3 panels in serials for it. However, seems like the controller will not pull out full juice from the panels into the battery.
I have cheap MPPT controllers, MakeSkyBlue and ESmart3. with setting:
Absorb voltage: 14.4
Float voltage: 14.4
Equalize: 0 (MakeSkyBlue has only option for Li, which I believe for Lithium ion, it just Absorb = Float. ESmart3 has little more option)
The max watts was around 125W, the only way I can pull out more is by increase charge Voltage, 14.6,14.8,.... but of cause it will be too high for LifePo4.
Both controllers work well with my 48V battery bank. But, Seems like they are not so friendly for 12V large capacity bank.
I searched for more information, those RV battery bank (12V system) seems all with Victron or MidNight. On youtube shows charging 12V banks in high Amp. And the MakeSkyBlue and ESmart3 are all with 24 or 48 volt banks.
In my project, I was looking for charge capable around 20A.

So, Which charge controller shall I looking for? or which controller can charge high Amp for 12V large capacity banks? Epever? Victron and Midnight just too expensive.

Thanks
 

snoobler

Solar Honey Badger
Joined
Jul 10, 2020
Messages
8,430
Location
HBR, AZ
This is my small project, got 8 pcs used CALB cell (100Ah, test them got 70-80Ah), make the 12V banks for 12V pump to fix underground water problem.
So, the 12v bank has about 150Ah capacity, I can put on 100W x 3 panels in serials for it. However, seems like the controller will not pull out full juice from the panels into the battery.
I have cheap MPPT controllers, MakeSkyBlue and ESmart3. with setting:
Absorb voltage: 14.4
Float voltage: 14.4
Equalize: 0 (MakeSkyBlue has only option for Li, which I believe for Lithium ion, it just Absorb = Float. ESmart3 has little more option)

Float should be 13.6. 14.4 float will shorten their lives substantially.

14.4 will get the batteries to an extremely high state of charge PROVIDED you have good connections. If you are using thin wires and/or low quality connections, you will have voltage drop between the charger and the battery and you may fall well short of fully charged.

The max watts was around 125W, the only way I can pull out more is by increase charge Voltage

This makes no sense to me unless your charge controllers are only 10A. Increasing the voltage shouldn't do anything about allowing more amps.

What MAY make sense is that your connections are poor, or your wires are too thin causing the aforementioned voltage drop.

You need to measure voltage AT the SCC terminals and at the battery. The difference should be VERY small.

Note also that once absorption voltage is hit, 14.4V, no more current can go to the battery because it can't accept it.

Both controllers work well with my 48V battery bank. But, Seems like they are not so friendly for 12V large capacity bank.

This is likely a configuration/connection issue.

I searched for more information, those RV battery bank (12V system) seems all with Victron or MidNight. On youtube shows charging 12V banks in high Amp. And the MakeSkyBlue and ESmart3 are all with 24 or 48 volt banks.
In my project, I was looking for charge capable around 20A.

So, Which charge controller shall I looking for? or which controller can charge high Amp for 12V large capacity banks? Epever? Victron and Midnight just too expensive.

You need to get to the bottom of why your SCC are not working as they should. Refer to the bold italicized portion above.
 

gingerboy

New Member
Joined
Aug 13, 2020
Messages
17
Float should be 13.6. 14.4 float will shorten their lives substantially.

14.4 will get the batteries to an extremely high state of charge PROVIDED you have good connections. If you are using thin wires and/or low quality connections, you will have voltage drop between the charger and the battery and you may fall well short of fully charged.



This makes no sense to me unless your charge controllers are only 10A. Increasing the voltage shouldn't do anything about allowing more amps.

What MAY make sense is that your connections are poor, or your wires are too thin causing the aforementioned voltage drop.

You need to measure voltage AT the SCC terminals and at the battery. The difference should be VERY small.

Note also that once absorption voltage is hit, 14.4V, no more current can go to the battery because it can't accept it.



This is likely a configuration/connection issue.



You need to get to the bottom of why your SCC are not working as they should. Refer to the bold italicized portion above.
Thank you so much for such detail reply.
And yes, It was so simple, bad connection. Don't know how but when I look closly, one of the calb cell post seems to be remade or some sore of repair. I reconfigure and test them in 4 pcs group, identified the One cell cause the problem.
 

Napalm

New Member
Joined
May 20, 2021
Messages
33
Correct. 14.4 is the absorb , 13.6v for float

Also switch off Equalize to 0

Gel or normal Lead-acids or AGM's need equalize, lithium doesn't need that as they don't lose power as quick.


Absorb or Bulk kicks in only once voltage drops below a certain amount (known as Boost Reconnect 13.4 V)
So if many devices are pulling little voltage and during the daytime battery is still around the 14.2 down to 13.6 (float will apply)

Once a bigger draw or current is pulling during daytime and it drops below 13.4 then the boost applies and charges it up fully again. Keeping battery on 90-100% before evening hits.

Obviously once the sun sets, then any draw will just pull power till next morning. Next morning on sunrise it will charge up again if it dropped below float.


(i have found that i can run 2 or 3 x 5watt or 10watt USB LED lights during the night, say 6pm to 6am next morning. It still stays above float during night time on my 200ah Lithium Mecer Lifepo4)
 
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