Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

Top Balancing LiFePo4 Cells using a low cost benchtop power supply. 2021-05-30

This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low cost bench top power supply. To get the tutorial, click on the orange "Download" button.

Reviews for accuracy, completeness and clarity are requested.

Notes:
* I understand that this is a highly debated topic. I am just trying to share what works for me.

* This procedure is in line with the @Will Prowse Top Balancing video:

Video included for reference. Overview only. See PDF for important details and step-by-step instructions.

The following are edits I have made since I published the original document.
  • Appendix E: Edits from original version.
    (Most recent change listed first)
    • Throughout: Minor formatting and typo updates.
    • Section 4: Added Link to @Will Prowse’s top balance Video
    • Section 3: Added and then updated note about starting with cells that have significantly different SOC.
    • Section 5: Added the “Other Opinions” section.
    • Section 4: Added note about voltage drift after top balancing.
    • Section 1: Added link to @Will Prowse’s tools page for his power supply recommendation.
    • Section 5: Added reviewers concern about letting the current go to zero at the end of top balancing.
    • Added appendix that notes some people top balance by charging individual cells.
    • Section 2: Added comment that if you assemble new cells and a capacity test indicates full capacity, the cells probably came balanced and further balancing may not be necessary.
    • Section 3: Added note about getting cells close in voltage before putting them in parallel.
    • Appendix D: Added appendix about DIY power supply leads.
    • Section 4: Added image and text about hooking up the power supply to diagonal posts on the cells.
    • Introduction: Added warning to be careful of cell terminal threads.
    • 5/29/21: Appendix D: Added comments about wire size and type.
    • 5/29/21: Section 2: Added note about target top-balance voltages.
    • 5/29/21: Section 1: Added note about Power Supply Amps
    • 5/29/21: Section 1: Added note that a higher voltage supply would be needed for pre-charging cells for 48V systems.
    • 5/30/21 - Section 2: Added note about being patient with the process and about leaving the cells unattended.
    • 5/30/21 – Section 3: Added note about power supplies for pre-charging.
Author
FilterGuy
Downloads
4,595
Views
11,965
First release
Last update
Rating
5.00 star(s) 18 ratings

More resources from FilterGuy

Latest reviews

Thank you for compiling sir!
Great tutorial, thank you. This is exactly the way I do it and advise people to do. I wrote a similar tutorial in french and was asked to translate it in English - no need anymore, I just point to yours.
Excellent, this is very -very helpful! I love Will's videos, they're what got me here. In addition, I need this kind of methodical step by step tutorial to really help it sink in. Also, this gives me something that I can easily follow when I get my cells and assemble my battery. Many thanks.
Excellent how to for beginners. You can't go wrong if you follow the directions to the letter.
HOLY CRAP!!! This is AWESOME! I could not have found this at a better time as I am looking for help on doing exactly what you describe here. I am now going to order my variable DC power supply right now. I'll look at the power supply you recommend and compare it to what I am considering.

By the way, I like the Alfred E. Neuman avatar.
... THANKS .... :)
Great information! I will be using this tutorial when top balancing my batteries.
Thanks
OUtstanding!
Thank you for taking the time to teach us yet again! This makes sense to me!
Very nice! Only one appreciation, maybe is my fault, but when precharging the cells (wired in series) the first cell with the positive connected to the source is getting 3,65 pretty before the others (the others are at 3,40), when the power source is of, all the cells are at 3,40. I'm doing something wrong?!
FilterGuy
FilterGuy
No..... You are not doing anything wrong. We know the cells are not ballance and one will hit 'full' first. It just means that cell is further out of balance than the others. It also means that once you put them in parallel, it will take longer for them to get up to 3.65 because the other cells are not as well pre-charged.

Some folks will say that .25 volt difference is too great to put them in parallel.
Personally, I would not worry about it. However, if you are concerned, start top balancing the other cells till they get up to 3.5 or so and then add the last cell in.
Top