Partimewages
Solar Addict
Yep, some like to be the smartest in the room!
GUIDE to properly Top-Balance and Charge a LFP Battery: Part 1
- Thread starter shvm
- Start date
If you ask me, leave it disabled. You're not running lab tests, you're using a production system. Stay within 3.0V and 3.5V per cell. Stop charging at 3.5V (no tail current, no absorption) and stop discharging at 3.0V per cell. Put float at 3.375V or below. Go enjoy the nice weather after that.
Daddy Tanuki
Solar Wizard
got a question for you... if you do not like what that person has to say on his posts... why do you go out of your way to look for them? is it a mentla sickness, do you need this arguing to feel special? do you need to feel like the white night charging in to save the day? or are you just a horrible person? you could put him on ignore if you dislike him that much instead of taking time to shitpost....... is that you, my @Solarcabin Channel friend?
This seems to be very interesting. It made me think of a few questions now. (which have probably been answered a million times before already)
Is 3.0V the minimum cutoff voltage for LFP?
What about 2.9V or 2.8V? What are the drawbacks of setting it to 2.8V or 2.9V?
Will it shorten the life of the battery?
Another is what if i just charge it to 3.45V instead of 3.5V? Will I lose alot of capacity or just a few?
In my situation,the charging amps is maximum 40A (usually 30A) for any given system. (either 12 or 24 or 48V)
Is 3.0V the minimum cutoff voltage for LFP?
What about 2.9V or 2.8V? What are the drawbacks of setting it to 2.8V or 2.9V?
Will it shorten the life of the battery?
Another is what if i just charge it to 3.45V instead of 3.5V? Will I lose alot of capacity or just a few?
In my situation,the charging amps is maximum 40A (usually 30A) for any given system. (either 12 or 24 or 48V)
ArthurEld
Solar Wizard
Since most batteries are top balanced, you will likely hit 2.5V with one of your cells if you try discharging to 2.8V
You won't lose much capacity charging to 3.45 instead of 3.5.
My settings keep my cells between 3.0V and 3.4V.
I'm sure you will hear from others with more experience than me.
A very safe cutoff voltage for LFP.
It is important to understand why datasheets use the 2.5 V 'number'.
For instance, here is the datasheet for my CALB cell.
It says, the cell was discharged at 1C constant current until the cell hits 2.5 V.
Because every cell has some internal resistance, when the 1C load is removed at 2.5 V, the cell voltage 'jumps back' to some higher voltage.
To find the same for a battery with multiple cells in series, discharge with rated constant current, until one of the Cell hits 2.5 V. Then note the voltage of that cell after recovery. That in theory, represents the absolute minimum cut-off voltage for LFP.
I don't have the money and equipment to test it with factory new cells, but I suppose it is somewhere around the ~2.8V mark.
sunshine_eggo
Happy Breffast!
Please cite a reference, or disclose that you have just made this up. Where has the manufacturer published discharge voltage vs. C rates? This "standard discharge model" is used to validate the capacity specification.
If you take two LFP Cells,
charge one of them to 3.45 V until current goes to 0 and the second to 3.5 V until current goes to 0,
you are going to be pulling roughly the same capacity. Although the latter will get charged far quicker due to higher charging rate available.
That is because of the peculiar way in which LFP charges.
You should just do those calculations regarding what equipment is available to you to minimize charging time utilizing maximum (solar) power available to you and maximize cell health.
Just give me your thought process and proper reasoning behind what you think is the 'ideal discharge cut-off voltage' and how I'm supposed to physically determine it for my hardware.
It is that simple.
sunshine_eggo
Happy Breffast!
As someone with an advanced technical degree, you understand this very basic requirement: You've made a claim. Now you must provide evidence to support it.
You don't get to make an unsubstantiated claim and then say, "prove me wrong" when challenged.
Put up or admit you're just making it up.
Exactly my point.
I'm not making any claims in the first place.
It's you who is acting like an authority on LFP charging without any scientific reference or properly done research to back it up.
The burden of proof is on you, not me.
You still don't realize that I'm the one using least amounts of assumptions directly from Cell datasheets. If you read understand Cell datasheets, you can easily test what I'm saying. I don't have to back anything unlike you.
Even highly advanced technical degree don't have a course on how to correctly identify people using the very same scientific jargon incorrectly. That is something you learn mostly by yourself.
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Partimewages
Solar Addict
We all know that's not going to happen!
Requesting mods to bless us with a 'facepalm' emoji. This is actually too funny.
Quattrohead
Solar Wizard
I don't have proof and couldn't care less but it feels right to me (3v min, 3.5v max cutoff).
I'm not flogging the shit out of my batteries.
I'm not flogging the shit out of my batteries.
?
Claims to be a facepalm but sure doesn't show up very well.
Not getting in this discussion just pointing out we do have one
My bad. I meant a facepalm reaction.?
Claims to be a facepalm but sure doesn't show up very well.
Not getting in this discussion just pointing out we do have one
Kenny_
Solar Addict
Thanks for that....certain discussions/posters should just be ignored cause they are only here to cause trouble. Some call them trolls.?
Claims to be a facepalm but sure doesn't show up very well.
Not getting in this discussion just pointing out we do have one
Kenny_
Solar Addict
I vote for #2!Something like this ?
or maybe this ?