Epever, confused, undercharging?

[DRD WOODWARD]

Hi
First off let me start by saying I'm not electrical expert. (ie be gentle .. lol )
I have a basic grounding but no more.
(Though I have watched a few of Wills videos)
I've been increasingly engaged with creating an off grid life style, or at least one that relies on the grid minimally.

My newest project is made up of :
4 X 250W 28.5Voc Solar Panels in parallel
An EPEVER TRACER 4210AN (40A)
1x LiFePO4 25.6v 200Ah 5120Wh Battery
A 3000w 24v/240v inverter. (uk)
All New

Where I live sunshine is not Californian in duration or intensity but as spring draws on I'm getting a few consecutive days of blue sky that register a good and constant 27v+ form the panels.
My issue is the battery charging level seems to have stalled at 25.2-3 v. ( noted over several weeks )
The battery icon on the LCD remote controller display shows the battery only about 5/8 full all be it with a smiley face ( I told you I was not expert )

Is this a case of adjusting the settings.
Or a more fundamental issue.

Below I've listed the default settings:

Type: Sealed ( options: Flooded, Gel, User )
Batt : 200AH
Temp Comp Coeff : -3mv/C/2v
Rated Voltage - Auto ( options: 12v/24v )
Over Volt Disc : 32.0v
Charge Limit : 30.0v
Over Volt Rec : 30.0v
Equal Charge : 29.2v
Boost Charge : 28.8v
Float Charge : 27.6v
Boost Rec : 26.4v
Low Volt Rect : 25.2v
Under Volt Rect : 24.4v
Under Volt Warn : 24.0v
Low Volt Disc : 22.2v
Discharge Limit : 21.2v
Equalize Time :120min
Boost Time :120min

Any advice would be much appreciated.
Regards
Duncan

 

[sunshine_eggo]

Your battery is at a VERY low state of charge - nearly empty.

The voltage curve of LFP batteries is very very flat, so there may be very little movement in the voltage for very long periods of time.

The battery "gauge" on the controller is completely worthless. Disregard it.

Does the controller show current flowing to the battery? If so, how much?

 

[MisterSandals]

I'm getting a few consecutive days of blue sky that register a good and constant 27v+ form the panels.

This is likely too low for your charger to charge a 24V battery (at 28V).

You should put your panels in 2S2P or possibly all in series (4S) config to get the array voltage up. The SCC needs roughly 5 volts "headroom" over charging voltage to work.

 

[sunshine_eggo]

This is likely too low for your charger to charge a 24V battery (at 28V).

You should put your panels in 2S2P or possibly all in series (4S) config to get the array voltage up. The SCC needs roughly 5 volts "headroom" over charging voltage to work.

This is totally it. I completely missed it.

Even if there's some head room to start charging, even the slightest draw of current will pull them down.

 

[DRD WOODWARD]

Thanks for the replies.
Still scratching my head.
Situation so far is:
I put the pv array into 2S2P ... and as you said that was enough to start recharging.
However after a while ( .5v) the current being drawn was negligible.
So I put all 4 panels in series
This made it climb up to 25.8v but as soon as the full sun comes out the pv volts out exceeds the chargers max input of 100v and disconnects charging.

I then disconnected 1 panel....

Currently pv-27.9v 0.6a >> bat-25.9v 0.6a
So it is creeping up ..

But what I don't understand is when I disconnect/reconnect the input to the charger from the panels ..
the readings initially are more like pv-50v+ 1.2a >> bat-25.9v 2.4a, but this rapidly drops down.
Demonstrating that the power is there but for some reason the charger drops it down ... ?

Is this a function of the settings... ?

In layspeak could you explain the settings
Boost Time (v) and Equalize Time (v) and if and how they can be adjusted to deliver max charge rate which is what I need.
Surely the way a charger should work is to start high and reduce as it nears capacity.
Confused.

Duncan

 

[mikefitz]

Hi Ducan, what battery are you using, a DIY or ready built ? Does the BMS report battery and cell status?

Don't exceed the maximum input volts of the Epever, 92 volts at 25 deg C, three in series for your panels is the maximum string. Hopefully your initial over voltage with a 4 panel string did not cause damage.

Your charger voltage settings may need adjusting. You don't need or want equalisation, set the volts the same as boost and equalisation time to zero.
To avoid overvolts due to cell imbalance that may occur as the battery reaches full, a lower boost voltage of 28.4 or lower at 28.0 volts may be needed, boost duration 30 minutes.
Float volts, 27.0 volts.
Your description of charge current falling to a low value at a battery voltage of 25.9 is strange, at this voltage the battery should be taking all the power the panels can deliver.
To determine where the problem exists each element of the system needs to have its performance evaluated.
Do you have an AC charger capable of charging the battery?
Testing the OC voltage and SC current of the panel string would be useful, ( disconnected from the Epever).
The issue could be as simple as a faulty interconnection.

Your questions.

Boost voltage is the 'target ' voltage for the charge process, the battery will have received nearly all of its charge by the time this voltage is reached. Once this voltage is reached the voltage is held conatant for the boost duration. Unless there are cell balance issues, this duration can be short. Once boost duration is completed the charger drops to float volts.
Equalisation is only needed for acid lead flooded batteries , since with the Epever this cannot be deleted set the volts to the same as boost and duration to zero.

Mike

 

[DRD WOODWARD]

Mike thanks for your reply.

The story so far...

The battery is a brand new ready built LiFePO4 25.6v 200Ah 5120Wh Battery
Rated at 25.6v
Max charge v 29.2v
Cut off v 20v
STD charge current 20A
Max continuous discharge 100A
Peak discharge current (5sec) 200A
According to the spec it has a BMS but as the unit is sealed I have no access to it.


Regarding the four PV panels each is:
max power 250W
current at Pmax (Imp) 10.64A
voltage at Pmax (Vmp) 23.5v
open circuit volts (Voc) 28.5v
max system voltage 1000v

The panels are situated in a temporary location and not optimally, being 5-8% masked.
On testing each open circuit ... they each registered 27volts


Question:
Given the charge controller input limitation of 100 volts
such that only three panels in series can be used, what would be the comparative performance
of two in parallel then connected in series with the remaining two. If indeed that's allowable
and poses no risk of damage to the panels.

I did have an incident shortly after installation and testing at the end of 2022 where there had
been a deep overnight discharge down to 2volts! Possibly a device had been left on or the inverter in idle
consumed the charge? Not sure.
According to everything I've read this should not be an issue ... that said Im no expert.

My fear is that the battery has been irreversibly damaged. I can replace the other components
but the battery which took a long time to save up for is another matter.

I got to thinking, and again bare with me being a non techie, but might it just be an incompatibility
issue between the charger and battery. My thinking is, if the chargers programmed/electronic
charging profile is designed to operate on a battery whose rated voltage is 24 volts would it not
have problems with one rated at 25.6v, or am i clutching at straws.

Currently no matter what tweaks I do to the charge controller settings .. 25.8-9v is as high as
the battery charge goes.

What I find odd is whether the PV input voltage is showing 27v or up to 40+v and the battery showing 27v
the current being drawn by the battery rarely goes above 1.5A.
When the battery arrived it was charged to 26.4v.
I have another project with 6 x 100A lead acid 24volt leisure batteries that happily sit charged at 27volts,
from 1 x 250 watt panel with a cheap 10A MPPT.
My head is hurting.

I have ordered a 60A MPPT just to see if that gives any clues.
Also I asking about for a mains/battery 24v charger to test the batteries condition.

Hopefully one day someone will make all this 'plug & play'

 

[mikefitz]

Running the battery low to BMS shutoff will need a 'jump start' to release the BMS protection. The solar controller may/ won't, do this.
Apply a power supply , 26 volts with a few amps capability to the battery to wake it up. You could use your lead acid array.

There is also the charge limit of 20 amps for the battery, 1000 watts of solar will produce well in excess of this.

For solar chargers and AC battery chargers and invertets , I only install and recommend Victron Products.

Your battery, Cyclenpo 24 volt 200 Ah, is something I have not encountered in the UK. Its unusual having such a low charge current for the capacity, who was the supplier ? If the situation cannot be resolved you may need to make a warranty claim.
See how you get on with the 'jump start '.

Mike

 

[Browneye]

Subscribed. I'm curious to see how/if this gets resolved.

The "24V" battery is a nominal value, it actually sits at 3.45Vpc at full charge, so 27.6. If your boost/charge voltage on the controller is set for 28.8 volts then conceivably your cells may reach 3.6Vpc. Unless the cells are perfectly balanced, a bms will likely terminate charging for a cell over-volt. Hence the recommendation for a lower boost voltage of 28 to 28.4 volts, in an effort to get the whole battery to full charge without cells going over. Yes, lead-acid batteries settle to about 25.6 volts, or a bit higher if they just came off charge. Lead acid batteries cannot maintain a charge level of 27 volts - once allowed to settle they'll sit lower. Charts below.

I'm assuming there isn't a bms monitor for cell condition.

Lead-acid types:

Lifepo4 types:

 

[MisterSandals]

The panels are situated in a temporary location and not optimally, being 5-8% masked.
On testing each open circuit ... they each registered 27volts

This caught my eye. Is it possible that the panels simply aren't producing the amps that the OP expects?

5-8% masked can have a devastating effect for producing amps, even on a 3S array.

 

[Danbear]

Hey Duncan, Have you managed to solve the problem with the undercharging of your battery? I was looking for something else and got here. You said that your EPEVER charging settings were the default for Sealed bateries. Might not matter but tipically for LiFePO4 you should switch to User settings where you are more felxible with the different parameters. That made a difference to my system a while ago.