Lifepo4 float setting?

pianotuna wrote:
Stir find me an Li battery that provide 9C for 5 seconds, 4C continuous, and be charged at -40. You may find that is unobtainable.

As to size, I have room for 7 Group 31, so that is not an issue.

Fair enough (from the SiO2 Camp…), though you fail to mention SiO2’s discharge voltage plateau or usable DOD, please show me the RV person (i.e. not in SiO2’s typical utility or industrial application…) who needs that high of discharge rate??…This is where the rubber meets the road - Enquiring minds really want to know…

3 tons

Come to think about it, if the ongoing ‘stealth confusion’ campaign (conducted by the two SiO2 promoters…) could be extracted from the LFP battery enquiries, I suspect the page count might drop by at least 50% or MORE !! - lol :) - JMHO

Either way, note that in the end, the disinfectant of Sunlight seems to always works it’s magic…

3 tons

Stir find me an Li battery that provide 9C for 5 seconds, 4C continuous, and be charged at -40. You may find that is unobtainable.

As to size, I have room for 7 Group 31, so that is not an issue, nor is the weight.

otrfun wrote:
What are you striving for? Absolute max cell longevity? Max usability/ah capacity? Or, somewhere in-between?

If you want absolute max cell longevity float a 12v lifepo4 at ~13.15V (~50% SOC). Downside, minimal usability/ah capacity.

If you want max usability/ah capacity, float the battery between 13.6 - 14.4v (~99 SOC). Downside, some reduction in cycle life. More so as you approach 14.4v. Floating at 14.6v is not recommended.

Can't have your cake and eat it, too. Pick your poison.

Well put...Something in the middle I guess realizing I can change the settings if need be for certain scenarios..So other than the occasional cell balancing,what bulk charge voltage should be set at if your battery settles at 13.3/13.35 after a 14.4 charge.

pianotuna wrote:


You might want to mention the advantage of weight. It is the only area where LiFePo4 clearly wins over SiO2.



Li banks are wonderful where it doesn't get cold, or if one is full time so the bank is in a temperature controlled area.

you also forgot size, cold weather capacity and so on. yes I said cold. at -20 degrees C SiO2 only have 60% of there capacity when fully charge, where LFP have 80 to 85% so if you take a 200AH SiO2 and you use it to get maximum lige (so they recomend a 50% depth of discharge max for maximum life) so you have a 100AH battery but due to the cold can you use all 100AH and stay with in your 50% DOD? probably more realisticaly 60 to 80AH available. a 200AH LFP you would have 160 to 170AH you can use at that temp. remember its only charging that is a no no. even then once your using the batteries they are making there own internal heat and if you have them insulated it can be enough to bring them above 0 degrees. I know mine with just a wrap around them at -6 were well above 0 degrees and thats in a uninsulated outside cabnet. when I move them inside they will be in a heated space so who cares how cold it is.


then you forget the speed of charging. if I have a 45 to 50Amp charger it has to be limited to 25amps for that SiO2, but I can pound the full 45 to 50amps into the LFP which works out to over twice the charging speed more likly 3 to 4 x as there is no taper above 80% with the LFP. and yes I charge all my batteries to 100% I don't play games and try skew numbers by staying in a spicific range an never fully charge.. GC, or LFP the aim is to be at 100% before I go to bed each day with enough reserve that I can go 5 to 10 days with out sun depending on battery type.

I do not envy the people down south that have to include AC use in there builds, that would drive the price up quite a bit.

I also don't think it is sour grapes I just think its a lack of understanding of the actual use of the LFP battery. we can read resellers websites all we want and take there word on some stuff , which is what causes have the confusion on here. I wish some of these resellers would just stop trying to put out information about LiFePO4 batteries as they are putting out half truths and in some cases outright BS and then certian people take it as gospel and spout off on the internet.

anyways I digress .....

otrfun wrote:

jaycocreek wrote:
I'm still confused about float with LFP batteries..Is it better to be in float or bulk the majority of the time?

Off-Grid Garage say's one should set float and bulk the same therefor it is in bulk mode charging when the sun is out vs floating or using battery capacity..

What are you striving for? Absolute max cell longevity? Max usability/ah capacity? Or, somewhere in-between?

If you want absolute max cell longevity float a 12v lifepo4 at ~13.15V (~50% SOC). Downside, minimal usability/ah capacity.

If you want max usability/ah capacity, float the battery between 13.6 - 14.4v (~99 SOC). Downside, some reduction in cycle life. More so as you approach 14.4v. Floating at 14.6v is not recommended.

Can't have your cake and eat it, too. Pick your poison.

Well said, thus based on preference, one might sense how truly forgiving LFP charge parameters can be…Theorist aside, in actual usage LFP charging parameters have proven quite flexible - JMO here, but (unlike spin-theory offered as fact…) based on real-world charging experience….

3 tons

BFL13 wrote:
You need 14.x to get those ions moving better. Once there you can lower the voltage

Lower charging voltage than 14.6 needs more time so keep
Float voltage same as Bulk longer too till desired SOC is reached

BFL, In the interest of discouraging added confusion, consider clarifying this statement as either ‘opinion’ or ‘fact’…If opinion (denoted by ‘IMO’ or ‘JMO’), feel free to state how you arrived at your conclusion…

3 tons

jaycocreek wrote:
I'm still confused about float with LFP batteries..Is it better to be in float or bulk the majority of the time?

Off-Grid Garage say's one should set float and bulk the same therefor it is in bulk mode charging when the sun is out vs floating or using battery capacity..

What are you striving for? Absolute max cell longevity? Max usability/ah capacity? Or, somewhere in-between?

If you want absolute max cell longevity float a 12v lifepo4 at ~13.15V (~50% SOC). Downside, minimal usability/ah capacity.

If you want max usability/ah capacity, float the battery between 13.6 - 14.4v (~99 SOC). Downside, some reduction in cycle life. More so as you approach 14.4v. Floating at 14.6v is not recommended.

Can't have your cake and eat it, too. Pick your poison.

You need 14.x to get those ions moving better. Once there you can lower the voltage

Lower charging voltage than 14.6 needs more time so keep
Float voltage same as Bulk longer too till desired SOC is reached

I agree with Time2roll…

IMO (Sad as it is…), Since earnest LiFePO4 post here have a tendency to get corrupted by ‘slight of hand’ theorist (SiO2 battery spin-masters busy at their crusade…), one need be wary of their long run at anti-LFP mischief - ‘Caution, extreme discernment required’, comes to mind!!…

Thus, I would recommend a solid information source, free of the imputed confusion - here’s what Solacity states - info here is uncorrupted and based in reality:

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

“Lithium-ion batteries are charged in two stages: First the current is kept constant, or with solar PV that generally means that we try and send as much current into the batteries as available from the sun. The Voltage will slowly rise during this time, until it reaches the ‘absorb’ Voltage, 14.6V in the graph above. Once absorb is reached the battery is about 90% full, and to fill it the rest of the way the Voltage is kept constant while the current slowly tapers off. Once the current drops to around 5% – 10% of the Ah rating of the battery it is at 100% State-Of-Charge.”

And then there’s BattleBorn (on charging):

https://battlebornbatteries.com/how-do-i-charge-my-rv-battery/

FWIW, In my case, using a single stage MPPT controller set at 13.x volts, and short of occasional cell-balancing, I seldom find a need for a higher voltage, this since LFP seldom require a 100% recharge, so this works well for me (Be advised, I have two parallel systems, another with a PMW controller set at 14.x volts )…Therefore, to some degree, individual preference, technique and charge equip all plays a roll - with a bit hands-on experience, I believe you’ll find your battery to be most forgiving and highly receptive to receiving a charge pretty much regardless of settings…Again, JM hands-on based opinion…

3 tons