li batteries--a good primer

Pianotuna here is a link for folks that might want a little more info than what was provided at the OP link. They have 10+ years of experience and tons of information from charging/ discharging, cold weather and other testing done. Searching within the blog will produce tons of real life experience not just white paper parroting.

Thought you might like it or others that like to do research.

https://www.ev-power.eu/blog/

GordonThree wrote:

pianotuna wrote:
Hi all,

This is a good explanation of what to expect from LIfePo4.

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

Here is their summation:

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

That's a lot of restrictions for a battery that costs at least 10x what a lead acid costs. Operating temp 30C?! horse hockey! Charge current 0.2 to 0.5C, that's terrible.

I agree completely, Gordon!

Too narrow a usage temperature range and too many $$$ -> just to reduce RV battery weight per useable amp hour of capacity.

Also, when not on the road we like to keep our RV in the back yard with continuous power applied ... including not having to remember to ... either turn OFF the solenoid to the AGM house batteries or turn OFF the built-in converter, so as to not float the batteries too much.

One thing that I think is misunderstood that the lfp can be charged at a higher C rate but the manufactures recommend a lower amount for longevity or warranty reasons.
If I needed or wanted to go higher, GBS has a max 3C charging rate or a max 3C continous discharging rate/ 10C pulse.

Homework needs to be done for what fits end users wants/ needs. One brand might not fit all. If you actually look Battleborn, Lifeblue, Relion and other dropins they do vary slightly but they're trying to fill the void of the "dropin" ease.

The killer for me is still cold weather. As I'm no longer full time my existing system will happily meet my needs. About the only upgrade I need to make is a way to charge the generator battery so the remote start feature doesn't kill it. I'll possibly add a 2nd trik-l-start.

I can charge my pack at 1.0 C, not that I have that much charging power.

GordonThree wrote:

pianotuna wrote:
Hi all,

This is a good explanation of what to expect from LIfePo4.

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

Here is their summation:

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

That's a lot of restrictions for a battery that costs at least 10x what a lead acid costs. Operating temp 30C?! horse hockey! Charge current 0.2 to 0.5C, that's terrible.

The "restrictions" should be covered by the bms which is protecting the battery or specifically the multiple cells that make up the battery.

LFP has operating temps ranges from -20c/ -4f to 140-158f/ 60-70c depending on manufacturer. As suggested by manufacturers cooler temps are better but it not like oh-no it's a 100f the batteries are going to die.

Charge current of 0.2-0.5C how is that possible bad? 20-50a on a 100ah battery. It will take it all right to the full capacity, unlike lead where you have to charge till the sun goes down and occasionally hook a generator up or hurry home and scury for your plug in charger to get long life out of them. Or the couple current threads going on right now of having the perfect x amount of charge for x amount of time to get the life quoted by the manufacturer after it's already been being charged by solar. That is crazy in this day and age but if it makes a person feel good more power to you.

After living off my system for 37 months now while I fulltime travel and solar being the main charger for my 500ah lfp bank it will max out 80a but for the sake of argument 60-65a will be the norm while there is always some draw on the batteries. From late spring till fall with these lfp batteries I don't worry about "having" to turn our everyday comforts off so the batteries can hurry up and get charged it's normal to have 15-45ah draws and the balance of 15-25a still get the batteries to full be the end of the day and if they don't so what. Or just this evening use the microwave 15 minutes straight other to flip a veggie bag and replace with another that needed cooking, watch tv, charge a couple phones (inverting 12.8v, -145a draw/ lfp batteries showing 13.16v at 97% SoC) now as I type this 92% SoC 13.34v, inverting 13.2v -10a draw. Solar added 10ah or 2% back into the batteries after cooking.

I hope that dropin style batteries work out as good as prismatic cells built batteries perform.

pianotuna wrote:
Why that particular formula?

The performance is similar to the "dangerous" Lithium Cobalt formula but much more forgiving.

10C discharge is common

They're more suited to electromotive applications I believe.

Why that particular formula?

pianotuna wrote:
GordonThree,

I could live with slower charging (after all lead acid is poor that way) but not with discharge rates that low.

That is remarkably low discharge current... I wonder if that's per parallel string inside the battery? so if you have a 4S4P configuration of cells inside the battery, it's actualy 0.5 * 4 or 2C charge/discharge?

I plan to buy another round of AGM in the next year or two when my batts hit 7 years. When they're done, I hope Li Nickel Manganese Cobalt (NMC) batteries have reached the mainstream.

GordonThree,

I could live with slower charging (after all lead acid is poor that way) but not with discharge rates that low.