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Rooster

New member
Joined
May 17, 2022
Messages
1
This site looks absolutely awesome, I want to build a 24 volt lithium pack, as I’m waiting for a few leads to source secondhand hopefully free battery’s.
I will need to fully understand more about low and high voltage limits using a load testing device hopefully with the original BMS still attached. In other words a non invasive test and battery cell balance.
I really enjoy learning about lithium battery science at the same time will admit I have many hours required to get up to speed regarding lithium battery safety
I found this site via a YouTube video
View: https://youtu.be/IEi99Xkb6uY
HB power wall this Australian guy is extremely helpful and very knowledgeable.
Really appreciate this site
 

OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
2,218
Welcome to the site!

If you plan to test using the existing/working BMS, then you typically charge to the max and then discharge till the BMS cuts off.
Having said that,

Lithium-ion voltage ranges are 4.2v/cell max and 2.5-3.0v/cell low kind of thing. The high is critical but the low 3.3v -> 2.5v not so much because there's very little power... you just don't want to go so low as to damage the cells which is why I put it at 2.5v low.

LifePo4 voltage ranges are much flatter. I'm lithium-ion so I don't have hands-on experience but its 3.65v hi and 2.5v low kind of thing. The key is that the batteries sit at a constant voltage for most of their charge/discharge cycle (check the specs of your cells) - very flat voltage curve so you can't estimate the SoC by voltage like you can with lithium-ion.

In either case, you'll want to figure out how many cells are in series in your 24v battery - lithium-ion is often 7s and lifepo4 is 8s. Then you can divide the overall battery voltage by 7 or 8 or X to get the individual cell voltage. It could be the BMS has bluetooth of some way to report the cell voltages + if you can access the battery you can measure them with a voltmeter. :)

Have fun and let us know how it goes. Pics are always fun!
 
Last edited:

cak

Member
Joined
Mar 14, 2021
Messages
148
Welcome!

There are lots of good YouTube channels to learn from and make sure to check out the FAQ section of this forum which will give you a good foundation of knowledge.
 

hbpowerwall

Administrator
Joined
Oct 7, 2016
Messages
2,117
Boss, Erummm I guess..... Maybe the owner but Kori is probably the boss lol

Welcome aboard.
 

Korishan

Moderator
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Jan 7, 2017
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