LiFePo4 battery users

[Ticklebelly]

i guess the only time you really need to fully charge lithium is when you need their full capacity for that next discharge.

My supplier of LiFePo4 discrete cells does EV conversions as about half his business as an Auto Electrician.   I have had discussions with him, lots, about what a top charge voltage number should be aimed for.    Battery life is never mentioned when we talk.   My supplier has his first conversion in the shop for demo and to use as the shop vehicle.   The battery pack in the vehicle is on charge when ever it is not being used; 3.65 per cell.   The underlying rational is that the range of this vehicle is not that great and when it leaves the shop, he wants as much reserve as possible.

I typically rotate my two batteries every second day.   Rough figures, my batteries would be below 90% SOC for about 30 hours out of every 48.

[RoamingKat]

Popeye....no lithium does not like being full. It is not like lead acid technology (agm or other)

No...keeping lithium full will shorten the life. But, I only ask by how much

As for all the comments about charging and discharging...yeah, already knew that, already have it covered.

You never worry about keep lead acid full....it is a worry with lithium.

I think I am going to see if I can cut off at 80%. This cannot be done based on voltage...since lithium will sit at 13.1 at every point between 80% full and about 30%. I’ll just watch the battery monitor and try to cut off charging. According to the info from manufacturer, long term storage should be at 70%. So maybe on a daily cycle I will try to keep to a top of 80%.

[rvpopeye]

Hmmmmmmmm the cycle def seems to still apply though , maybe using different full/empty numbers...

I think I may have found a couple of future experts on those batteries right here on the forums.
Looks like Ticklebelly is our only member using them currently (or at least posting about it) and soon you !

There are so many developing batt formulations coming up ...so this is probably gonna happen a lot more too.

Best keep all info gathered here on this thread (that forum linked sounds like a good source for more on this type at least) and maybe a separate thread for each type of battery.
Here on the solar forum???

[rvpopeye]

Oh yeah , one of those batteries is actually a super capacitor.

[Ticklebelly]

This cannot be done based on voltage...

I suggest you investigate a device known in the RC world as an IMAX B6.   My cells came as nominal 50AH.   Factory test data before release came with the cells I have and all the individual cells factory tested at least a couple of AH above the 50AH.   I played around using the B6 device to establish a usable capacity of 43AH by setting and varying voltage levels top and bottom. 

To aim for a no more than 80% as a goal to get a maximum life out of a battery first requires some decision of what 100% is.    Max life?   what is that?    I will need about 20 years a couple of times before I can report what life I got out of mine.   How will I ever know if I could have got longer life by charging to a lower and upper voltage level?   Three mostly rhetorical questions there.   I am mostly concerned about what usable capacity I have available to run my campervan use.   My EV building friend in mostly concerned with leaving the shop with the batteries as full as electrically possible.   People who have a major focus on battery bank life will need to work out what upper and lower levels to work between. 

I am going to a workshop this weekend to share ideas on good ways to upcycle electrical equipment.   I am building a Li Ion pack to power an electric conversion Quad.   The relevance is that several of the workshop presenters are upcycling lap top battery packs and broken down PowerWall 16850 cells.   Seriously time consuming, but these people are testing individual cells using the B6 to establish either good or bad on the to , be upcycled 18650 cells.   As testing happens, records of the capacity of each cell under test are kept.   Most of the testing relies on looking at the capacity written on the cell then testing the cell to see if the cell gets close to that baseline.

[RoamingKat]

Tickle....exactly. I have put this question to another fellow who run LiFePo4....he doesn’t have the answer..but would like to know.

I have a victron BM. I have run the inverter/charger on shore power till it reads 14.0. With everything off over night, the battery “rests” at 13.3 in the morning. But, that does not mean it is not full?

Then, I set it to 100%.

Yes, I know there is constant drift and it needs to be recalibrated from time to time, but it is the only thing I have.

I guess we are all learning. I have had mine for almost 3 years now. But daily living/using it for about 2.

[rvpopeye]

That B6 unit sounds like a good tool for testing standard Li Ion but it also tests your batts too ? COOL , there is hope !

The life cycle length seems to be a bad thing and a good thing at the same time.......

TB is on the case.........arrrrrrrrrrrrrrrrr ye thinkin' of developin' an electric ship ??????
If soooooooooo , I'll be lookin' to appropriate it as soon as I can get some crew what ain't crows...........

[tx2sturgis]

As lithium batteries age (age = number of charge cycles) they take less and less time to charge to 'full', and return less and less energy on discharge.

This is a slow decline, and depends on a lot of factors, of course. 

It happens with smartphones, e-bikes, drones, cordless power tools, RC airplanes, and anything else using lithium batteries. 

They keep working, but they deplete faster than they used to, and take noticeably less time to recharge.

Nature of the beast.

[Ticklebelly]

It happens with smartphones, e-bikes, drones, cordless power tools, RC airplanes, and anything else using lithium batteries. 

They keep working, but they deplete faster than they used to, and take noticeably less time to recharge.

Smart phones, most RC devices, and cordless tools use Li Ion.   My main interest is LiFePo4 for house battery duties.   Does your assertion about degradation apply to the LiFePo4 technology?

Ageing characteristics are quite different depending on technology used in the battery.   Ni Cad batteries used in Air Force emergency radios are replaced after a period that starts from date of manufacture.   Manganese based batteries degrade in capacity about 10% each year from date of manufacture.   Manganese batteries can have the degradation slowed by storing them in a freezer.   Carrying your batteries around in a freezer does away with any weight advantage from using that kind of battery.

[Ticklebelly]

With everything off over night, the battery “rests” at 13.3 in the morning.   But, that does not mean it is not full?    

Then, I set it to 100%.    

The issue I have with declaring a rested battery terminal voltage as "full" is that the discharge curve of a LiFePo4 battery is so flat.   in my case, I charge to 14.1 then set the rested terminal voltage as full.   From your description, you are doing the same procedure but with a final active charge voltage of 14.

My supplier charges the battery in his EV conversion to 14.6 ( actually 3.65 per cell) and leaves it on charge until he wants to drive the vehicle. He has not given me any info what his cells might rest at, voltage wise.

Most understand that many AGM chargers put out 14.6/7 then float at 13.8.    The charge voltage is set as a way of charging more quickly.   People who want to do a drop in can use these chargers if the battery they want to drop in have a BMS that will handle the charger applying the high voltage.

The latest LiFePo4 chargers I am looking at, charge to either 14.1 or 14.4 then shut off, that is, no floating.   My attempt at reverse engineering the thinking of the charger manufacturers is that they have made some decision that 14.1 or 14.4 leads to a "full" battery.   I have gone for a safety margin by charging to 14.1, for the time being.