Lifepo4 float setting?

time2roll wrote:

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.

Why would I need 9,000 amps, or even 4,000 for that matter??

If my battery actually drops to even -20 my energy and heating systems have failed to the point I am already rolling out. I mean propane does not even vaporize at -40. I would have to assume utility power is available at these temperatures(no battery required). Temps at -40 is an expedition vehicle and preparation is far beyond virtually all RVs. No reason to proclaim this as an ordinary criteria for an RV on this forum. Better suited to an expedition vehicle forum.

https://www.globalxvehicles.com/uxv-max.html

dont want to go there, I went there and searched SiO2 and here is a quote from the first post that came up .

"With the exception of cold weather charging, the specs on these are almost identical to any other flavor of lead acid battery. They are not really comparable to lithium with regard to cycle life, energy density, recharge rate etc. There do appear to be some folks shilling these on some RV themed sited that are making some very unrealistic claims about their performance. In the end, they are just extra jellied gel-cells.

The low temperature charging 'issue' with lithium is a bit overstate and fairly easy to address if it does apply."

Steve

3 tons wrote:
You didn’t mention your stats, but it’s entirely possible with my 400a/hr LFP and 660w of solar - with 400a/hr LFP concurrent with harvest, and 2/3rds duty cycle

835w solar, 100ah@48v li battery. If I ran air with that during the day I may not have much left over for evening use!

More ‘Friday funnies’ from the SiO2 battery camp:

BFL said, “ I got that from the Solacity guy.” (LOL on that, but what about actual LFP experience?) - while it seems PT can’t resist making the topic about SiO2’s vs LFP’s (huh?)…

Time2roll rightly states, “Best to start a new thread about low temps and the effect on batteries, etc”,

Agreed, but (with regards to SiO2’s…) this has been tried before, but as the old saying goes, “how do you start a party if nobody shows”?? - Just saying :)
3 tons

pianotuna wrote:
Time2roll,

It is true my rv is modified for cold use. That was the determining factor for the number of house batteries, so I could run a block heater for 3 hours at -40. I have boondocked at -37c (-34 f). Moving Sue and Photomike have me beat--they have both done -40.

One of my modifications is a magnetic block heater for the generator.

But -20 (-4 f) is quite common where I live.

Again Li are super batteries when full time, or no low temperatures.

And the thread is about float values of LFP.

Best to start a new thread about low temperatures and the effect on batteries etc.

StirCrazy said:

“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.”….

Maybe I’m misunderstanding here, but I sense that the info you seek has been offered here (dismissing usual confusion…), trust that it’s not even close to rocket science, and I believe all that remains is a well advised dose discernment (IMO…) and you should be good to go - from my non-theory sourced, hands-on experience, LFP charging is simpler than other types - but ironically, maybe it’s this level of uber simplicity is what leads to such confusion - lol :) JMO

3 tons

Time2roll,

It is true my rv is modified for cold use. That was the determining factor for the number of house batteries, so I could run a block heater for 3 hours at -40. I have boondocked at -37c (-34 f). Moving Sue and Photomike have me beat--they have both done -40.

One of my modifications is a magnetic block heater for the generator.

But -20 (-4 f) is quite common where I live.

Again Li are super batteries when full time, or no low temperatures.

time2roll wrote:

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

I respectfully disagree.

I got that from the Solacity guy.

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

"So what Voltage is enough to get those ions moving? A little experimenting shows that 13.6 Volt (3.4V per cell) is the cut-off point; below that very little happens, while above that the battery will get at least 95% full given enough time. At 14.0 Volt (3.5V per cell) the battery easily charges up to 95+ percent with a few hours absorb time and for all intents and purposes there is little difference in charging between 14.0 or higher Voltages, things just happen a little faster at 14.2 Volt and above."

He says longer "absorption time" which to me means after the battery reaches the set high voltage of the charger (controller for solar) so not sure that he means amps also taper for longer starting from a lower SOC like happens with fast charging a FLA.

On that, he has the LFP fast charging at 50% rate getting to 90% before amps taper, then says using the lower charging rate of 14 vs 14.6 means it gets to 95% before amps taper so that is kind of like FLA but not clear to me it is from the same battery chemistry internal whatever goings on.

EDIT--he had the 90 vs 95 when using the high charging rate as well as 14.6, so not clear that you do go higher in SOC before amps taper just from using a lower charging voltage (at what charging rate?)--but how can absorb time be longer and also get to a higher SOC before tapering Can't be both.

With a "few hours absorb time" I assume the usual notion that you only need ten or twenty minutes for LFPs does not apply at those lower than 14.6v charging rates.

With the longer absorb time I tacked on the idea in the Garage post earlier to keep Float at Bulk for longer too

ISTR Battle Born says voltage has to be 14.2 or so to even be able to balance their LFPs, but if you are not planning to do that, a lower charging voltage won't matter for I suppose.

time2roll always preferred slower charging for FLAs too

time2roll wrote:

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.

Why would I need 9,000 amps, or even 4,000 for that matter??

Agreed, but (as to LFP’s…) even though PT and I seldom agree, I do respect that he’s open and upfront about his battery of choice - rather than a steady stream of crafty spin, BFL would do good to just adopt PT’s straight-up, no subterfuge approach…JMHO

3 tons

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.

Why would I need 9,000 amps, or even 4,000 for that matter??

If my battery actually drops to even -20 my energy and heating systems have failed to the point I am already rolling out. I mean propane does not even vaporize at -40. I would have to assume utility power is available at these temperatures(no battery required). Temps at -40 is an expedition vehicle and preparation is far beyond virtually all RVs. No reason to proclaim this as an ordinary criteria for an RV on this forum. Better suited to an expedition vehicle forum.

https://www.globalxvehicles.com/uxv-max.html

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

I respectfully disagree.