li batteries--a good primer

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.