More on LFP Charging

[BFL13]

Some "sales" statements here, but also some possibly good info of interest.

One thing is they found longest life (most cycles) was to charge at 14.4v but at lower amps at 0.3C.

Some LFP owners on here ISTR have taken to charging at lower voltages hoping for longer battery life. Perhaps it needs to be established which is correct--lower amps or lower voltage?

They say 14.4 vs 14.6 to reduce stress, and recommend their own charger (of course!) which is single stage 14.4--BUT they say shut charging down-disconnect- once the charger says the batt is full. (light comes on---what makes that light come on? oh well)

They are strongly against floating! see why.

Anyway, it covers some of what has come up on here lately.

https://dakotalithium.com/2021/09/22/how-to-charge-dakota-lithium-and-lifepo4-batteries/

[time2roll]

My issue with going to zero % is that there is a hard cut off and all goes dark. The 10%-20% buffer is for convenience of timing the next charge cycle if needed. Going to 100% discharge is not an issue as much as going 101% at a bad time to charge.

[jaycocreek]

I have been using lifepo4 for just a year using them daily running compressor refers and TC stuff,watching numbers out of bord-om and constantly reading about them..I find it interesting that there is no number or numbers agreed on by the mass of users..

You have Will Prowse saying charge them to 100% and use them down to 0% because calendar aging will get them before the cycle count does..Then the masses on his forum argue over the best numbers for the least stress on the cells..

I have picked out a few of the most intelligent opinions(IMHO) on LFP settings from mostly DIY solar forums and saved them by there names to my phone and Victron app library setting to try for my uses..A couple/few of them post here..Example in my library MikeF/Steve/Time2 etc..They all work great but I haven't came up with a final setting for my use yet..

Everyone knows each setup is different and each person has to find his golden numbers that work best for his style of use and charging..In my case with an older TC,I just bypassed the old converter and use 100% solar and a 20 amp LFP charger for gen time if needed with my two 100ah batteries in parallel..

Most people agree with this from solacity though(I think)

Solacity wrote:
To sum up, for long and happy LFP battery life, in order of importance, you should be mindful of the following:
Keep the battery temperature under 45 Centigrade (under 30C if possible) – This is by far the most important!!

Keep charge and discharge currents under 0.5C (0.2C preferred)

Keep battery temperature above 0 Centigrade when discharging if possible – This, and everything below, is nowhere near as important as the first two

Do not cycle below 10% – 15% SOC unless you really need to

Do not float the battery at 100% SOC if possible

Do not charge to 100% SOC if you do not need it

[3_tons]

time2roll wrote:

3 tons wrote:
I have a 100a pass-thru charger and a PD 9245 - the highest combined amperage I ever witnessed is 82a (usually a bit lower as it tapers down), this feeding into 400a/h of LFP (cylindrical cells = air gaps), mfg’s ‘C’ rate is 1.0, but I can’t even get close…With just the lowly PD, I can’t hardly imagine exceeding most other mfg’s C rate…

3 tons

Would seem like a charger issue or the wiring is inadequate more than a battery limitation.

I’m running 0004 / 3’ cabling with crimped, silver soldered lugs…I think it has to do with at what SOC point I begin the charge, but it’s pretty much inconsequential to me since I mostly use solar and ‘play’ somewheres in the 60-80 % SOC range…No doubt, internal resistance plays a role…

3 tons

[Itinerant1]

time2roll wrote:

3 tons wrote:
I have a 100a pass-thru charger and a PD 9245 - the highest combined amperage I ever witnessed is 82a (usually a bit lower as it tapers down), this feeding into 400a/h of LFP (cylindrical cells = air gaps), mfg’s ‘C’ rate is 1.0, but I can’t even get close…With just the lowly PD, I can’t hardly imagine exceeding most other mfg’s C rate…

3 tons

Would seem like a charger issue or the wiring is inadequate more than a battery limitation.

I agree.

I know if I had to combine my solar and Magnum charger it would max around 175a charging (with good sun) and have seen 165a when running the generator one time to see what it would do combined. Makes for some quick charging. 😉

As far as charging I can feed the batteries 100a (.2c) my with the eu2200i till 98% SOC when absorbs kicks in for 6 minutes and tapers to 99% SOC.

I mentioned this in previous post that I could just about put a stop watch to the minute for how long it takes to use the generator to charge batteries to full if need be.

[time2roll]

3 tons wrote:
I have a 100a pass-thru charger and a PD 9245 - the highest combined amperage I ever witnessed is 82a (usually a bit lower as it tapers down), this feeding into 400a/h of LFP (cylindrical cells = air gaps), mfg’s ‘C’ rate is 1.0, but I can’t even get close…With just the lowly PD, I can’t hardly imagine exceeding most other mfg’s C rate…

3 tons

Would seem like a charger issue or the wiring is inadequate more than a battery limitation.

[3_tons]

This, from SolaCity:

Storing Lithium-Ion Batteries
The very low self-discharge rate makes it easy to store LFP batteries, even for longer periods. It is no problem to put a lithium-ion battery away for a year, just make sure there is some charge in it before placing it in storage. Something between 50% – 60% is ideal, that will give the battery a very long time before self-discharge brings the Voltage close to the danger point.

3 tons

[3_tons]

I have a 100a pass-thru charger and a PD 9245 - the highest combined amperage I ever witnessed is 82a (usually a bit lower as it tapers down), this feeding into 400a/h of LFP (cylindrical cells = air gaps), mfg’s ‘C’ rate is 1.0, but I can’t even get close…With just the lowly PD, I can’t hardly imagine exceeding most other mfg’s C rate…

3 tons

[StirCrazy]

BFL13 wrote:
Some "sales" statements here, but also some possibly good info of interest.

One thing is they found longest life (most cycles) was to charge at 14.4v but at lower amps at 0.3C.

Some LFP owners on here ISTR have taken to charging at lower voltages hoping for longer battery life. Perhaps it needs to be established which is correct--lower amps or lower voltage?

They say 14.4 vs 14.6 to reduce stress, and recommend their own charger (of course!) which is single stage 14.4--BUT they say shut charging down-disconnect- once the charger says the batt is full. (light comes on---what makes that light come on? oh well)

They are strongly against floating! see why.

Anyway, it covers some of what has come up on here lately.

https://dakotalithium.com/2021/09/22/how-to-charge-dakota-lithium-and-lifepo4-batteries/

I am not sure of most intentionaly chose a converter that charges at 0.3C or less. I think its a matter for most (myself included) the converter in my camper is a 45amp and I put in a 310AH LFP battery so I chagre at 0.15C from that and my solar will put out 23Amp at peak so the fastest I can charge is 0.22C even if I had a 90Amp converter that would still be less than 0.3C. so its more of an issue of how expensive of a converter/charger do you want to buy and if you only use 100AM over night is it worth the extra money to replace that in one hour as aposed to a few hours? so in a way just comon sence is limiting the charge rate. the thing is in the space a person can put a 200AH 6V set up, I could easily put two, maybe three, 310AH batteries but I would still have that same charging setup except Li compatable. and I do run mine at 14.6 charge and it holds for 90 min after reaching full charge then drops to 13.5. this is all set up on my solar as my converter is just a single stage for now so it only gets used if I need a quicker deeper charge, but for the most part the solar has me charged up before noon if I run the furnice over night.

Steve

[StirCrazy]

pianotuna wrote:
At 0.3 C the "rapid charging" feature disappears compared to my favorite chemistry.


.

kinda, but not realy. if you put 0.3 amps into your favorite chemistry and into LFP and both are at say 20% SOC the LFP will get to 100% long before the other one. even the bulk phase will be faster, due to the lower internal resistane of the LFP less of the energy sent to recharge it will be converted to heat and hence more is availble for actual charging. I am not saying this phase is a houge advantage but it is noticable. and when we hit the top part of the charge the LFP charging speed does run away from other types as there is no drop off untill just before the finished line.

Steve

[wa8yxm]

BFL13 wrote:
.
Some LFP owners on here ISTR have taken to charging at lower voltages hoping for longer battery life. Perhaps it needs to be established which is correct--lower amps or lower voltage?

Lower amps or lower voltage.. Well..

First I've heard claims (not comment) suggesting some oh wait. ot LFP so I won't even finish that thought.

Now. Every battery has what is called "internal resistance" And of course the wires connecting it to the converter/charger have resistance.

Current = Voltage divided by resistance.

So when bulk charging lower voltage = lower amperage.

now one you get to absorption phase. Well that still applies..

The FLOAT voltage is the only time where changing voltage actually changes the battery voltage.

In order to push more amps into the battery you inrease the charging voltage..

NOW: the danger.. Pushing too much voltage for too long a period.. That damages the battery.

Li type batteries, according to some should be STORED at about 50% charge or so at least one source tells me. I have not the means to verify.

[pianotuna]

time2roll,

I have twin battery banks. My biggest charging source is a Magnum 3000 watt inverter/charger. It maxes out at 127 amps. The recommended maximum charging rate for the existing telecom jars is 107 amps, or about 19%. If I did go to LiFePo4, I'd still not be able to charge them significantly faster without getting a larger inverter/charger.

My personal choice for replacements would charge at 0.25 C and do not taper. Assuming 400 amp-hours charging would be 100 amps. LiFeP04, again assuming 400 amps would be 120 amps. That would mean 20 minutes less charging time on Li. But Li don't even enjoy being charged to 100%--so in real terms there may be zero difference in charging time.

There is a savings in cost especially if you "roll your own" Li. But as I do use my RV at -37 c (-34 f), Li are pretty much not going to happen. As to having them in the heated area of the RV There would have to be major modifications to make them fit in the heated space. If I were still full time it could work. However, I'm personally not comfortable with ANY house bank inside the living quarters.

In short, LiFePo4 are great where it is warm--but not too hot either. They simply do not meet my particular needs.

[time2roll]

pianotuna wrote:
At 0.3 C the "rapid charging" feature disappears compared to my favorite chemistry.

166 amps is too slow?

On a 100 amp Li it would be 30 amps yes? So where does 166 come from? (scratching my head)

Check your signature 😉

[pianotuna]

time2roll wrote:

pianotuna wrote:
At 0.3 C the "rapid charging" feature disappears compared to my favorite chemistry.

166 amps is too slow?

On a 100 amp Li it would be 30 amps yes? So where does 166 come from? (scratching my head)

[3_tons]

BLF said:

“How do you tell your BB "is charged" ? Also what do you mean by "is charged?

I see 3-tons also disconnects after his batt bank is full and if on shore power, he runs on LFP batt for 12v and shore power for 120v, even though he has a PD converter that can sit at 13.6 doing the 12 v while also floating the LFP at 13.6v”

****************

Close, but for added clarity, ‘IF on shore power’, I discontinue charging beyond an occasional cell-balancing, but never disconnect the battery (except for long term storage at about 50’ish % SOC…), I simply shut down the converter-charger…I would also add that you’ll know when it’s charged by watching on a LFP compatible SOC meter, the ‘to & fro’ dance of amps vs volts until end of cell-balancing when amps stops…

Here’s what I’d penned:

*****************
“Fair enough,

I’d only point out (unless I’m misunderstanding…) that this charging scenario seems to assume a practice of keeping a charged battery on an active converter-charger - but other than for ‘occasional’ cell-balancing (an activity requiring 100% SOC…) why do so with a LFP??

I would counter that this apparent consternation (possibly a FWC thingy?) mainly applies to ‘unattended set and forget’ shore power charging (as is typical with lead batts)…But even if using a ‘less that ideal’ charging device for LFP, one need ask how realistic of a scenario is this??

And, to arrive at the dreaded ‘the slide-out won’t work’ gottcha, it suggest that once ‘shore power’ charging has been completed (to whatever level?), for protection, an LFP battery needs to be sequestered….Why is this??

I’d counter that one can merely shutoff the onboard converter-charger (at it’s breaker…), at which time 12v power will come from the now charged, still active battery (minor loads only, and possibly with some solar assist?), while leaving shore power connected for 120v heavy appliances (e.g. air cond, etc)…

Regardless of the charging source (and, charged to whatever desired SOC?? - definitely NOT a lead acid thingy!!), one can simply opt to discontinue charging and just live for a considerable time off the battery’s deep reserves…This is exactly what I do, and with 400a/hr LFP and 660w of solar, seldom the need for shore or genny power - the last time I ran the genny was about 11 mos ago (and have since circumvented America…), and if in a park, ONLY use shore power where shading prevents harvest or when using air conditioner…In most other scenarios, the pass-thru inverter (concurrent with harvest) does the job…Just Saying”…

3 tons

[Microlite_Mike]

One needs to realize that while there are hundreds of manufacturers (if not hundreds, it certainly seems like it) there are really only two "Types" of LiFePo4 batteries widely used in RV's. One is based on "Prismatic" cells which are rectangular cells connected in series and "Cylindrical" cells which as their name implies, built from numerous cylindrical cells connected in series/parallel configuration.

C-Rate can be influenced greatly in the above types by their ability to dissipate heat during charging.

Battleborn uses Cylindrical cells, others use Prismatic. Instructions for one type may not be appropriate for another type.

Since I have Battleborn batteries (2x 100ah) I charge at the max output of my PD9160L Converter (57 amp avg) until charge current drops to <0.3 amp and shut off converter (I use the shutoff module PD sells for their 9100 series charger with TCMS "port"). Since most of the time I boondock and use my solar panels with Victron Smart MPPT controller, it charges to 14.4 volts then drops to 13.5 volts after an adaptive absorption charge (@14.4v). Controller decides how long the absorption charge needs to last based on DOD and it's calculated need for cell balance. Some absorption times can run up to an hour and some as little as 2 minutes, all depending on DOD.


I think that since LiFePo4 batteries are relatively new, and a total change from what we've all been used to with the 150 year old Lead/Acid tech, many think they're fragile and need to be babied. I think that in reality they're a lot more durable than people believe and the quality batteries have a quality BMS that takes most of the worry out of the equation. I charge mine then go camping. They get charged daily as needed (solar of generator) and when not camping I recharge when I get home then shut batteries off. Switch on charging while preparing for next trip and they charge from my Tow Vehicle via a DC-DC charger.

No more worry about corrosion, sulfation, low electrolyte levels, and since they're mounted inside they don't get cold when camping and needing recharging (no need to charge while in storage). Battleborn's are in their 4th season and I wouldn't be surprised to see them still going strong when my time on this planet is up.

I also own a Plug-In Hybrid (Volt) and it just stays plugged in when I'm not driving it. It's on it's 6th year and battery capacity shows no measurable loss of capacity yet.