Effect of no absorption on LiFePo4?

[Ramblin__Ralph]

I bought a low end 100Ah LiFePo4 a couple of years ago. The manufacturer only listed charge and float voltages on their spec sheet. Later I asked them about absorption and they told me 14.4v. They also said it wasn't on the spec sheet because "it's not that frequently ask by our customer". 🙂 I never got around to setting my solar controller for absorption. For 2 summers of extended summer travel the battery has performed very well and is only charged by my 225w solar system.

So what is the effect on the battery to not have absorption?

Thanks,
Ralph

[bdosborn]

10-4, thanks for the clarification....
Bruce

[3_tons]

bdosborn wrote:
It seems like you're confusing my post with Don's, I didn't say anything about a "calendar-scheduled approach…".

The Battery Management System (BMS) in all LiFePO4 batteries has a cell balancer built into it and it works every time the battery is charged completely. Some batteries (like Battleborn) need an absorption stage to give the balancer more time to work; they typically only balance at 500mA so it can take awhile. Its transparent to most battery owners unless they have a BMS that displays battery cell voltages.

Its all in the specs of the battery you buy, if it doesn't say anything about an absorption stage then you….

Bruce

Not intended, I was merely speaking to the broader audience, primarily revisiting the so-called every 30 day approach which Don had mentioned (Don has once before stated “every 7 days” applies…(FWIW, I disagree)…Yep, the balancing phase (at 14.x volts, whatever phase one opts to call it…) is relatively transparent - this is why I always recommend a Smart-Shunt so one can observe the occurrence and completion of re-balancing…Depending on the several previous variables I’d mentioned, this can take from several minutes to say roughly 20 min or so, often depending on battery capacity…

3 tons

[bdosborn]

It seems like you're confusing my post with Don's, I didn't say anything about a "calendar-scheduled approach…".

The Battery Management System (BMS) in all LiFePO4 batteries has a cell balancer built into it and it works every time the battery is charged completely. Some batteries (like Battleborn) need an absorption stage to give the balancer more time to work; they typically only balance at 500mA so it can take awhile. Its transparent to most battery owners unless they have a BMS that displays battery cell voltages.

Its all in the specs of the battery you buy, if it doesn't say anything about an absorption stage then you don't need one.

Bruce

[3_tons]

bdosborn wrote:
Some LiFePo4 batteries recommend an absorption stage, it gives the BMS cell balancer time to work. The voltage region that most BMS balancers work in is so high on the charge curve that actual balancing might only last a minute or two. Here's what Battleborn recommends:
https://battlebornbatteries.com/programming-a-victron-smartsolar-charge-controller/
Bruce

Be advised, we are not talking rocket science here (except to those few FWC die-hards who snub a different approach).

Note that many charge controllers (as is Victron’s) are user configurable for a LiFePo4 battery format, and this configurability feature is why the moniker of ‘Absorption’ is used…Whether one cares to call it absorption or bulk (no matter…), a voltage somewhere in the high 13 teen’s to the mid 14 teen’s, not to exceed 14.6v (constant voltage, constant current) is all that’s really needed (higher voltage = faster charge)… And, cell balancing need only be done periodically…How so?? From my own observed experience, the need for rebalancing is a function of say number of ‘less than FULL charge/discharge’ cycles, and % of ‘depth of discharges’…From my perspective, and in the added interest of longevity, this is a far more cogent approach than some thoughtless ‘one size fits all’ (made-up…) calendar-scheduled approach…

3 tons

[bdosborn]

Ramblin' Ralph wrote:

So what is the effect on the battery to not have absorption?

Probably nothing, your cells might be a little out of balance but that would be about it. Here's a link to a guy that explains what LFP charge settings should be:

Andys Off-grid garage

Bruce

[bdosborn]

Some LiFePo4 batteries recommend an absorption stage, it gives the BMS cell balancer time to work. The voltage region that most BMS balancers work in is so high on the charge curve that actual balancing might only last a minute or two. Here's what Battleborn recommends:
https://battlebornbatteries.com/programming-a-victron-smartsolar-charge-controller/
Bruce

[time2roll]

pianotuna wrote:
Time2roll,

I have seen articles that suggest every 30 cycles or days that the bank be balanced.



https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

I scanned it. Not sure what you are reading that would indicate the 30 day cycle.

And the article is flat wrong about the battery will only be at 90% charged at 14.4 volts and zero absorption time.

[3_tons]

pianotuna wrote:
Time2roll,

I have seen articles that suggest every 30 cycles or days that the bank be balanced.

“I have seen articles”??

Don, this has been addressed here by ‘actual users’ (meaning, not by you) on post that I know you’ve even past authored…I hate to resort to this, but perhaps (once and for all) maybe consider avoiding the impulse at offering near endless LFP controversy or disinformation - as you’re well aware, this particular has already been clarified…

Very Respectfully,

3 tons

[pianotuna]

Time2roll,

I have seen articles that suggest every 30 cycles or days that the bank be balanced.



https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

[Grit_dog]

pianotuna wrote:
Ralph,

Quite the opposite. LiFePo4 do not want to be charged to 100%. They do want to be balanced charged once per month.

Correct but they’re not near as needy as described above.
Ralph, just when they are not in use, make sure they are not on a maintenance charge. If there is truly no draw. Ideal condition is NOT fully charged, however it’s only slightly less.
I don’t go out of my way to make sure my LFP batteries are drawn down some for storage nor do I maintenance charge them while not in use.
They probably end up fully charged. Like my MX bike. I’ve hooked up a little charger after it sitting for months 6-8 months even “just to see” and it literally takes 2 min or less to register full charge. (Small battery). Tells me it’s fully charged when I last shut the bike off.

[3_tons]

time2roll wrote:
Charging to 14.4 on any regular basis as described by the OP is sufficient to keep the cells balanced. There is no recommendation to periodically change the charging cycle for balancing. Yes if the battery is short charged to 13.6 or less it may or may not get any balancing from the BMS. Could go years like that without issue. The primary time balance can be a critical process is when the battery is first assembled to verify the cells are at the same level to start with.

X2….Mythology has it that LFP’s are in someway ‘fussy’ to charge when in fact (except for cold weather charge constraint) the opposite is true…

OP suggest he may have ‘damaged’ his batteries (how so??)…The basics are, don’t exceed 14.6v, don’t equalize, float at or below 13.6v (or not at all), don’t leave on charger for an extended period of time (say, once fully charged), no need for a full charge except for occasional cell re-balancing and (if applicable) SOC meter resynchronizations…

Applying this basic charge regime is a minor price to pay which negates conventional battery maintenance and achieve faster charge recovery times and a far deeper depth of discharge..

3 tons

[time2roll]

Charging to 14.4 on any regular basis as described by the OP is sufficient to keep the cells balanced. There is no recommendation to periodically change the charging cycle for balancing. Yes if the battery is short charged to 13.6 or less it may or may not get any balancing from the BMS. Could go years like that without issue. The primary time balance can be a critical process is when the battery is first assembled to verify the cells are at the same level to start with.

[pianotuna]

Hi,

My (limited) understanding is that there is a specific voltage needed to balance the cells. That is set by the battery management system. I don't know what that number is.

[bighatnohorse]

pianotuna wrote:
Ralph,

Quite the opposite. LiFePo4 do not want to be charged to 100%. They do want to be balanced charged once per month.

Isn't a "balance charge" a 100% charge?
As I recall, it is said that over time, individual component batteries can develop slightly different voltages. Thus, charging the entire battery to a full charge and holding it at full charge for a period of time will equalize the individual component batteries.
Can you clarify?

[pianotuna]

Ralph,

Quite the opposite. LiFePo4 do not want to be charged to 100%. They do want to be balanced charged once per month.