Help keeping my cells healthy

[Matty-Lee]

Q. Should I change some of the solar charger settings to get a longer life from my battery and what would your suggestions be?

Details below...

I've watched this video which explains how you can get more life out of your battery if you don't allow it to run down or charge up fully.

I think I'd quite like to do this as I have 12v 200ah battery that is pretty much feeding some LED lights and USB sockets so there should be lots of capacity but I'm a newbie so would like some advice to get it right.

The batteries are from https://www.aliexpress.com/item/1005001270537853.html and the spec says:

Nominal capacity: 200Ah
Minimum capacity: 200Ah
Internal impedance: 0.1 ~ 0.3mΩ
Nominal voltage: 3.2v size (length * width * height): 173 * 55 * 210mm
Weight: 3.9 ± 0.2kg
Recommended constant current: 200a (1c)
Discharge termination voltage: 2.5v
Recommended constant current: 200a (1c)
Charging voltage: 3.65v
Maximum continuous discharge current: 200a (1c)
Life cycle (80% dod): 4000 times
Cycle loading temperature: -5 60 60 ° c
Discharge temperature: -30 60 60 ° c
Production date: February 2020
Battery lithium iron lithium phosphate


The solar charger is EPEVER and I have it set up for LiFePO4 with these settings as recommended by the manufacturer:




Thanks,

Matt

 

[Goombah111]

I suggest following what Will is saying. Charge slowly, discharge slowly, keep in optimal temperatures, don't overcharge, don't overdischarge. Set voltage lower to get more cycles but lower capacity, do what works for you. He is speaking truth in that video.

He provides an interesting chart and says light blue is his sweet spot, might save this for myself.

 

[mikefitz]

Hi Matt, the settings you have in the Epever are general settings for fast charging. For hobby use If you want a less aggressive charge regime, the boost charge and float charge values need to be reduced. I cannot see boost duration on the chart you posted but this should be a short period.

Any charge voltage over 13.6 v will charge the battery to full, and voltage 13.4 volts will charge to around 90%. However for realistic charge times higher voltages are used, for example 13.8 volts or 14 .0 volts. Any float voltage should be lower than 13.4 volts.
Because of calibration differences in equipment together with the fact that the voltage characteristic of the lithium battery shows little change over the 75% to 25% SOC range, using voltage alone to indicate state of charge is a poor guide. Perhaps using a voltage of less than 13 volts as a indicator 'needs a charge' and a voltage of over 13.3 as ' getting full' is an option.

Mike

 

[Supervstech]

What wattage total are your lights and usb loads?

how much solar do you have on the battery? 200Ah is a huge battery for what sounds like a light load setup like you have. I doubt the battery dips below 80% in a day...
my 160Ah used cell setup runs all day charging my tools, and radio, and doesn’t ever dip below 13V...

 

[Matty-Lee]

Hi Matt, the settings you have in the Epever are general settings for fast charging. For hobby use If you want a less aggressive charge regime, the boost charge and float charge values need to be reduced. I cannot see boost duration on the chart you posted but this should be a short period.

Hi Mike, the chart shows a Boost Charging Voltage and a Float Charging Voltage. Should I lower those to something?

 

[Matty-Lee]

I'm still a bit confused about which settings to change.
If I want to charge the battery to only 85% like Will says which settings should I alter and to what?

Thanks,

Matt

 

[Supervstech]

You want boost and float to be 13.6 if it won’t let you make them the same, have boost be 13.8 and float be 13.6

 

[mikefitz]

If I want to charge the battery to only 85% like Will says which settings should I alter and to what?

Without additional equipment that accurately monitors monitors battery capacity its not practical. It also may detrimental to battery performance due to memory effect and cell balancing, if the battery is consistently charged to a partial state.
The best you can do practically is to charge to 13.8 volts ( boost volts), have a short boost duration, and set the float value lower than 13.4v and a re boost at 13.2v. This would still charge to almost full every day.

If the battery is for hobby use with a few led lights and no significant load, charge it up and turn the charger off. Recharge when the voltage falls to 13.0 volts.

Mike

 

[Supervstech]

What most do not take into consideration on altering the charge parameters is, the TOTAL KWh of the battery won’t be altered drastically by changing the parameters.
if the battery is rated to 2000 cycles at an 80% DOD, it works out to be only marginally better as 1000 cycles at 100% DOD...
or 6000 cycles at 50% DOD...
A 100Ah battery cycled 1000 times to 100% uses 1.28MWh
100Ah cycled 80% and only charged to 80% full 2000 times is 1.5MWh
100Ah cycled 50% 5000 times is 1.92MWh
To do 100Ah of work each day, you need 1 battery in the 100% dod
You need 1.2 batteries in the 80% DOD
And you need 2 batteries in the 50% DOD...
so... the amount earned on lifespan improvements is eaten up in additional battery purchases needed to perform the same tasks, and the batteries need to be purchased up front... instead of years later, when batteries have fallen in cost...

 

[Gazoo]

if the battery is rated to 2000 cycles at an 80% DOD, it works out to be only marginally better as 1000 cycles at 100% DOD...

A LFE cell rated at 2000 cycles means the cell will have 80% capacity left after fully charging and discharging the cell 2000 times. As you are pointing out, cycle life can be dramatically increased by keeping the cell between the knees at lower SOC's.

The spec sheet for the newer EVE 280ah cells is interesting. EVE claims a greater then 6000 cycle life with an ambient temp of 25C using the standard .5C charge and discharge rates and properly clamped cells.

If the ambient temp is 45C then cycle life is reduced to greater than 2500 cycles using the standard .5C charge and discharge rates and properly clamped cells. This is good IMO for those subjecting the cells to high temps. But again this is all with properly clamped cells. I think most will find their cells aging before the cells cycle life is complete.