bad charger?

[johnfox]

I used my new epoch 36 volt charger for the first time yesterday and all is not well.
I have been charging with a nice slow 300w 5 amp solar system and it never charged the cells at max voltage.
yesterday when I hooked up the new charger everything started out looking normal 3.248 max voltage to 3.241 min voltage across all the cells a .007 differential, very good I think.
I watched for 10-15 minutes and it never recorded higher than 3.255 on the highest cell to 3.248 on the lowest.
very good I thought.
I went out to the garden for 15-20 minutes and when I came back the charge on the highest cell was now 3.305 volts, I panicked and pulled the plug.
being a Sunday I couldn't get customer support.
now the big question DID I HURT MY BATTERY?
the readings this morning after sitting are 3.229v on the highest cell and 3.214 on the lowest well within safe charge limits but still a 0.015 spread, higher than the 0.007 that was the normal spread.
is it normal to charge higher than 3.265v while charging then taper off to below 3.265v when fully charged? I wouldn't think so? but what do I know.
don't know if this has anything to do with it but the battery is at 56% of charge now.

 

[Steve_S]

Firstly LFP has a Very Flat voltage curve from 2.900-3.500 and due to that voltage increase is very slow as that is also the Working Range that delivers the actual Amphours. Depending on capacity, 5A will take forever ! Appreciate that a 280AH Cell can take 140A for 2 hours to charge from 0% to100% SOC. So 5A will indeed take forever.

LFP has an allowable voltage like all chemistries. That range is from 2.500-3.650. Within this range, no harm/damage occurs. Outside that voltage there is damage being done.
The working Range where the actual AH are delivered from is 3.000-3.400 with 3.200 Being Nominal (50% SOC).

You should Top Charge & Balance the cells to at least 3.600 Volts per cell. This is to ACTIVATE the electrolyte after storage & shipping.
Charge can stop at either the EndAmps point or even lower BUT NOT LOWER than 2A charge being taken.
EndAmps/Tail Current is calculated like this: 100AH X 0.05 = 5A or 280AH X 0.05 = 14A. This Value is also used in your SCC & Inverter/Charger to determine when to switch charge mode to FLOAT.

Absorb Bulk Charge to (3.450 Volts per cell). 13.8V / 27.6V / 55.2
Float Charge upon reaching EndAmps/TailCurrent: (3.425Vpc) 13.7V / 27.4 / 54.8V

Please download the following resources, they will answer most questions and more.

General LiFePO4 (LFP) Voltage to SOC charts/tables 12/24/48V

I've looked at several places for a simple, easy to read at a glance "chart document" for LFP. I could not find anything comprehensive. I discovered an XLS Worksheet in my stored file and took parts of that to create this chart, I did not...

diysolarforum.com

Luyuan Tech Basic Lifepo4 Guide

This document was posted to the forum by Amy from Shenzhen Luyuan and written by Steve S. It was meant to be posted as a resource. Below is her description of the resource: Dear all friends in the forum, This file in the attachment was...

diysolarforum.com

Also save the chart immediately below for reference.

 

[RCinFLA]

Example of an actual cell charge/discharge at 40 amps.

 

[johnfox]

O'boy I can come up with some real doozies.
look at something and see something all together different than what I'm looking at!
the charger is fine and dandy, completed charging cycle today with no problems,complete operator error.
but all the info & charts are welcome info,thanks guys.
by the way the EPOCH 36v charger seams to be a very good well made tool!