[TUTORIAL] How to build your own LiFePO4 Replacement for a Group 24 Battery

dexter12353

https://youtu.be/TSRHDJhoQj0

The only thing missing is connecting up to an inverter, but we are working on making that tutorial/guide right now.

mcgivor

Explaining the importance of top ballancing the cells prior to assembly would be a useful addition to the tutorial, relying on the BMS to achieve ballance could take weeks or more, depending their individual SOC, this requires holding at maximum voltage for extended time.

Typically in offgrid applications the charge voltages are set below maximum cell thresholds to improve cycle life expectancy, so ballancing would never occur, I only bring this up because this is a solar forum, EV or other grid charging really doesn't apply, although not specifically mentioned.

Additionally accurate top ballancing is critical when assembling a large capacity prysmatic cells to create a cell block, this prevents potentially damaging cascading current to lower SOC cells, this is not applicable to series connected  single cells, but worth noting for the benifit of those who are considering building a large capacity parallel series prysmatic bank.

This comment  is intended to be constructive, not negative, please do not misconstrue the intent. 

wellbuilt

I’m headed in to my 3rd season with my golf cart battery’s and they still seam to be working 
 like new , except for one cell on one battery the sg seams to stay low 12.65 or so.
  If I’m charging them hard and giving them a lot of float time the one battery will keep up with the rest . 

  So I’ve been looking at the LiFe battery’s for my next set . 

 They sure seam expensive 
 but the video above makes it look like a regular guy could assemble a set of battery’s ? 

   Lucky for me I have a few years to figure all this out . 

 I’m in a very cold area my utility room dose stay above freezing I’ve seen some 31.5 temps 
  But in my battery box it stays warmer .
 When charging my lead acid battery’s every day they stay warm 45o 
   I have a friend looking to power up a travel trailer and he has perked my interest 
   Any thoughts

jtdiesel65

mcgivor said:

Typically in offgrid applications the charge voltages are set below maximum cell thresholds to improve cycle life expectancy, so ballancing would never occur, I only bring this up because this is a solar forum, EV or other grid charging really doesn't apply, although not specifically mentioned.

If I read this correctly, you are saying that absorb voltage will be less than the balance set point on the BMS and so the BMS will never enter balance mode? From what I read, some BMS allow you to adjust the voltage in which balance starts. But perhaps its that no significant balance can occur at the absorb voltages.

mcgivor

With the focus on top ballancing, regardless of where the trigger point for balancing is set to start, it would be impossible to achieve top ballance if the ultimate voltage is set below the aggregate of all cells combined 3.650V value, the result would be a ballance point somewhere other than top.

Generally speaking it's unnecessary to ballance on a regular basis, an initial ballancing before assembly is all that is required, this reduces the stress associated with doing so and results in extended life expectancy, this is explained in the manual for CALB cells.