Eve lfp280 w/ overkill + victron settings

So, I've been putting all of my research to work and have everything "together"

I'm using 4x280ah eve cells with an overkill bms. Until yesterday these were at shipping capacity and sitting around 3.2v. These came from DLET off Alibaba.

For this initial assembly I'm just running a single < 5amp load with a fuse straight off the bms-/battery+ I have 800w solar going to a victron 150/70-tr on a breaker going to the bms-/battery+ I'm in the pnw, with a steep solar angle, and I'm half under a tree. Yesterday was fine and the setup ran all day in bulk. It generated 2.3kw, and this morning the battery was near full.

So I'm trying to set my charge controller and bms to reasonable yet safe settings. I dont need 100% from the battery, and I dont need 5000 cycles, I need a reliable battery that isnt pushing its limits.

I had my bms set at:
3.64 / cell over v
14.5 pack over v

I had the victron set at:
14.4 absorption
13.5 float


This morning when the sun came up, I was seeing about 30a going into the battery at 13.7v and one of the cells tripped the over voltage protection. It was about 0.2 over the other cells. I disconnected the charger and bumped the bms up to 3.65/14.6 and bumped the victron down to 14.1v.

The cells evened out and the bms protection came off. The batteries were probably only a couple of ah from where the were, since I dont have much load. The pack was at about 13.7v

Hooked everything back up and the charger went in to absorption but it was still putting about 30a into the battery, and a different cell tripped the over voltage protection.

So i disconnected the charger again and let the pack drain and even out. I bumped the absorption down to 13.6v and knocked the cell settings down a smidge on the bms for comfort.

Hooked it back up, and the charger was in absorption for about 30 seconds and went to float. I feel like this is a safe setting, but no where near what I have seen recommended around here. All of my cells are now within .002v of each other and it was a different cell that tripped both times. I know there isnt much capacity at the top either.

Do cells normally charge this unevenly at the top? Can anyone else with the same setup compare settings?

Are these reasonable settings?

It sounds like your cells are poorly matched, or at least not balanced to each other. They should be top balanced. I recommend you stop discharging, keep charging while dialing back the current until the BMS can get them all top balanced at 3.65V at about 3A input. I don't know what the Overkill's balancing capability is, but this could be a tedious process.

You can also safely charge to higher voltages. LFP can safely go to 4.2V, but it's not beneficial to do so in a regular basis as it will shorten life. Upping your limit to 3.8 or 3.9V under low currents may help expedite top balancing.

54.2 is what I use, with no BMS (and therefore no protection). It gets them to about 93% pretty reliably. The achieved SOC varies a little bit depending on how much current is available to put in, temperature, and the phase of the moon.

54.4 sounds about right to me for a non-balanced pack.

Also, what @snoobler said.

Thanks, I'll keep running it like it is until I can top ballance.

Does the overkill bms have a current limit function? How can I do that without a bench top supply?

It's not weird that it's a different cell each time that jumps up?

You can set a lower max current in the Victron Connect app.

Thank you! I'll dial it down and try to get the pack v higher when I get a chance.

If I'm below 4v per cell is there any reason AI cant just let the bms keep cutting off as a specific cell hits 3.65v? Would that actually do anything?

I think that should be fine. Note that cells at 3.65-4.0V are all mostly fully charged. If the low current charging seems to be taking forever, you may find small discharges to about 80% can help normalize the top cells and help with balancing.

Given that you are dealing with very large cells, balancing may be a little tough depending on the Overkill's capability. You may find that light normal use near the upper end of the charge range may allow slow balancing over time.

bgflyguy said:

Thank you! I'll dial it down and try to get the pack v higher when I get a chance.

If I'm below 4v per cell is there any reason AI cant just let the bms keep cutting off as a specific cell hits 3.65v? Would that actually do anything?

Click to expand...

I'm in the process of setting up my batteries, using 240v battery charger set as power supply at 13.8v, charging stops at 13.816. I have a victron 150/60-tr and still playing. I setup the lithium profile and then reduced charging to 13.9v just to see how it worked. I do plan to drop it back to 13.8v when I get a day off work.

With a 35a charger and 400ah battery, voltage goes from 13.8 to 14.1 in minutes and then it only took seconds to reach 14.2v. I did this to get the cells to reach 3.55v to trigger 100% on Electrodacus bms. This was enough for me to determine I don't need to play around in the upper limits of maximum cell voltage. I am happy to set upper limits to 13.8v

Unless I missed it I saw no mention of the initial balance done to the cells before assembly ?

Also to answer your question about victron settings. I have a 560ah 12v setup of the same cells. My system is connected to the VRM and as such I have an immense amount of data so far on these cells over the last 3 months.

Your absorption settings are too high for the cells. See the attached graph of 13.9v absorption settings. As you will note the cell pack reached 100% and the voltages climbed FAST at the upper knees. There really is no need to go above 14v on a 12v setup as the addition ah's are so miniscule.

rbreding said:

Also to answer your question about victron settings. I have a 560ah 12v setup of the same cells. My system is connected to the VRM and as such I have an immense amount of data so far on these cells over the last 3 months.

Your absorption settings are too high for the cells. See the attached graph of 13.9v absorption settings. As you will note the cell pack reached 100% and the voltages climbed FAST at the upper knees. There really is no need to go above 14v on a 12v setup as the addition ah's are so miniscule.


View attachment 21203

Click to expand...

You're charging a massive battery with a tiny current. Not everyone's performance will be the same especially if they have a higher charge rate.

Your 560Ah battery is basically full at a 16A charge/absorption voltage. Yours spikes very rapidly over a short period of time due to the low current. Folks charging at higher than 0.03C (your example) will see the spike be less pronounced and over a longer period of time with a longer absorption time required.

The OP is charging at almost 4X the C rate you are, so his terminations will look different.

Oh I don't disagree that everyone's spike will look different, however the spike will be there as you hit the knees. If you have the ability to see that spike it makes it easier to dial in the settings.

I didn't have time to mess with this much. I limited the victron to 20amp and 13.8 absorption and it tripped a few times for a single cell being over voltage, but I didn't fuss with it any.

I'll pull it a part some time in the next couple of days and check individual cell performance as well as make sure there isn't any connection causing high resistance.

Thanks for the suggestions.

As an update, I was able to top balance and add my second set of 4 cells. I'm able to charge up to 14.1 volts or so without a single cell tripping the high voltage alarm.

Interesting enough, I think re torquing the connections and sanding the Bus bars helped as much as anything. At a high current discharge i noticed that a couple of the bolts were getting hot. Yikes.

Everything is much better now, and I have set the absorption back down as I'm barely using any capacity right now.