Lithium voltage range

[Camperklahowya]

I’m curious if my range is normal.
I have two 200ah dragonfly batteries on my trailer, charged with shore power up to 14.4.
Btw, all readings are done with a multimeter on the terminals in the panel.

I unplugged shore and have used the 200 watt solar panels installed by keystone for the past several days.
In the mornings I’m at 13.25, afternoons I’m 14.2.
There is nothing on, in fact I turned all the breakers off except the converter to verify there was no electrical drain.

Is this range normal?

[bobbecky]

Your actual battery voltage should be checked with nothing adding power to the batteries. If the batteries are fully charged, the lower voltage showing could be a maintenance charge, but with some power used by the batteries, the voltage may go back up to 14.4.

[chuckster57]

Batteries are 12VDC. Turning off all the breakers does nothing as that is all 120VAC and the converter charges.

Unless you remove all the FUSES, there will be a draw on the batteries from the radio presets, LP detector and any illuminated switch/USB charging port.

There is also little/no charge at night, so that reading may be the fully charged reading and not the “surface charge”.

At least that’s my thinking, unless somebody has a different explanation.

[Stircrazy]

generally when under charge 14.6 will be 100%, after resting off charge that will drop to 13.6 which is a 100% charge resting battery. you would be sitting at about 75% state of charge at 13.25V. have you ever fully charged it or is your converter capable of putting out a constant 14.6V? or are you running a normal converter that doesn't hav a Li setting. if so you may bever reach a full charge.

[Camperklahowya]

Originally Posted by Stircrazy

generally when under charge 14.6 will be 100%, after resting off charge that will drop to 13.6 which is a 100% charge resting battery. you would be sitting at about 75% state of charge at 13.25V. have you ever fully charged it or is your converter capable of putting out a constant 14.6V? or are you running a normal converter that doesn't hav a Li setting. if so you may bever reach a full charge.

Put in a new progressive dynamics converter, plugged in to shore and I got 14.6.
Then I unplugged and let solar do the work. fluctuating everyday between 14.2 and 13.2.

[Stircrazy]

Originally Posted by Camperklahowya

Put in a new progressive dynamics converter, plugged in to shore and I got 14.6.
Then I unplugged and let solar do the work. fluctuating everyday between 14.2 and 13.2.

do you know what kind of solar controller and panels they are? My question there is, did they set up the controller for Li mode when the batteries were installed if not you may not be getting a proper charge profile as the voltage won't be high enough or it isn't staying at full output long enough. if you have nothing using the power eventually, they should catch up but 200watts of panels is nothing spectacular, but it's also not bad for light power usage. depending where you are I would expect between 30 and 50 ah of charge a day realistically from 200watts depending on the controller

[xrated]

Originally Posted by Stircrazy

generally when under charge 14.6 will be 100%, after resting off charge that will drop to 13.6 which is a 100% charge resting battery. you would be sitting at about 75% state of charge at 13.25V. have you ever fully charged it or is your converter capable of putting out a constant 14.6V? or are you running a normal converter that doesn't hav a Li setting. if so you may bever reach a full charge.

A LFP battery cell is considered to be fully charge at 3.45V per cell or 13.8V for the entire 12V battery. Anything over 13.8V will simply charge the battery at a faster rate than if the maximum output of the charger were at say....13.8V or 14.0V And of course the 14.6V number is the maximum voltage that a LFP battery should ever get....or 3.65V per cell, without the risk of damage to a cell or cells.

[Stircrazy]

Originally Posted by xrated

A LFP battery cell is considered to be fully charge at 3.45V per cell or 13.8V for the entire 12V battery. Anything over 13.8V will simply charge the battery at a faster rate than if the maximum output of the charger were at say....13.8V or 14.0V And of course the 14.6V number is the maximum voltage that a LFP battery should ever get....or 3.65V per cell, without the risk of damage to a cell or cells.

kind of but not really. that voltage is resting voltage which works out to 13.6V like I mentioned.

3.65V is the maximum voltage you should subject the cell to, but it is also the correct voltage to charge to for 100% capacity and rated life.

This is right out of the EVE data sheet, who are the manufacturer of high quality Prismatic cells and the cells I bought to make the battery for my camper.

"4.2 Standard Charge
The standard charge means charging the cell with charge current 0.5CA and constant voltage 3.65V at (25±2)℃, 0.05C cut off"

Just like a regular battery, there is an adsorption phase for LFP. It's just shorter and done at the same voltage as bulk charging, so we can't tell when it is there by the changes in the charge. This is where the voltage of the group of cells are taken to 14.6V (3.65V/cell) and then after the charge is removed and it sits for 15 20 min the voltage will measure 13.6V. do we have to do this every time no, but most BMS inside these bought LFP batteries don't start doing there balancing until the battery its self is over 14V (quite a few have to be closer to 14.6V for the balancing to start ) so if your never getting up there or not staying up there for long enough, then you will never get a proper top balance on your cells.

when I am camping, I only charge to 13.4V which means the maximum charge I am ever going to get works out to 90% of my capacity and I set the cut out at 10% so that's my maximum working range I use, but every week I do a full charge so my BMS can ensure my top balance is good. I probably would be good with once every 2 weeks or once a month, but I just picked a week. I use my BMS to control this charging profile as I can adjust all m y cut offs and cut ins with my phone, so it makes it easy to say charge to 90% then turn the charge off and don't start charging again until the battery is at 78% capacity. My battery will last me 10 days in the early spring/late fall running the furnace at night, so I do shallow discharges to increase the cycle life.