98% wall

[Deleted member 1888]

I have 2 EPever 100a 200v CC and they cant seem to get my bank over 98%. Right now there is still good sun but the controllers are only pulling in a total of 50w. I have a 24v LifPo4 bank and over 1200 amp hours. The controllers have an MT50 to set the charge levels. What settings can I change to get the banks to full each day?

 

[snoobler]

Where is the 98% coming from?

 

[Deleted member 1888]

My victron smart shunt

 

[Luthj]

Which model of Victron battery monitor are you using, and what are your 100% full settings? What is the charge efficiency factor (if set)?

What is the absorb voltage of the charge controller? What duration?

LFP batteries have zero need to be fully charged, and typically last longer charging only to the high 90s SOC. They are considered full when the terminal voltage reaches 3.65Vpc, but 3.45-3.5Vpc is typically over 95% SOC.

 

[snoobler]

Which model of Victron battery monitor are you using, and what are your 100% full settings?

What is the absorb voltage of the charge controller? What duration?

LFP batteries have zero need to be fully charged, and typically last longer charging to the high 90s SOC. They are considered full when the terminal voltage reaches 3.65Vpc, but 3.45-3.5Vpc is typically over 95% SOC.

This.

98% may not mean much. You need to have your BMV or smartshunt setup to match the charge termination criteria of your charging system.

Confirm your charger absorption and float voltages make sense. Check your absorption time.

Set shunt to terminate 0.2V below absorption voltage and your tail current to 5%.

 

[Deleted member 1888]

What is the absorption setting in the MT50 it only have normal charge, boost charge and float charge settings. Once the batteries hit 28.8 the controllers drop the power way down. I now the batters max voltage is 29.2 but I cant get it to that with the charge controllers.

 

[snoobler]

What is the absorption setting in the MT50 it only have normal charge, boost charge and float charge settings. Once the batteries hit 28.8 the controllers drop the power way down. I now the batters max voltage is 29.2 but I cant get it to that with the charge controllers.

boost = bulk = absorption

Tell your normal, boost and float values?

 

[Q-Dog]

On the Victon monitor, set the "charged voltage" setting to just below the charge controller cutoff, so try 28.7 for your controller's 28.8 cutoff. Also, set the "charged detection time" to something like 2 minutes so the battery has to sit at 28.7 for at least 2 minutes before the monitor will register it as fully charged.

 

[snoobler]

On the Victon monitor, set the "charged voltage" setting to just below the charge controller cutoff, so try 28.7 for your controller's 28.8 cutoff. Also, set the "charged detection time" to something like 2 minutes so the battery has to sit at 28.7 for at least 2 minutes before the monitor will register it as fully charged.

3 criteria:

charged voltage
tail current
time that BOTH are met.

Victron specifically recommends 0.2V below absorption.

Most LFP tail current is 0.05C.

Hence my recommendations above.

 

[Q-Dog]

Copy that. I just looked at my settings. I made some adjustments when I lowered my upper charge limits and must have missed that. Was set at 4%. Working fine.

 

[snoobler]

Copy that. I just looked at my settings. I made some adjustments when I lowered my upper charge limits and must have missed that. Was set at 4%. Working fine.

Yah. It just depends on your system. I've constantly fiddled with mine. I always seemed to have a jump where it reset a little prematurely. I finally have it tweaked to where jumps are pretty rare.

 

[Q-Dog]

I rely on the BMV battery monitor because the multiplus built in monitor only counts what it sends out and not what the charge controller puts in. I guess a Cerbo is in my future.

 

[snoobler]

I rely on the BMV battery monitor because the multiplus built in monitor only counts what it sends out and not what the charge controller puts in. I guess a Cerbo is in my future.

Get it now. It's just too awesome, and I just have the measly CCGX. VRM is amazing.

VRM Portal - Victron Energy

vrm.victronenergy.com

 

[Deleted member 1888]

I have tried setting the float to 29v and the boost to 29.2v, the sun is going down so I will not know ifit worked until tomorrow.

 

[Q-Dog]

No, you do not want to float LiFePo4 that high. 27.4 - 27.6 volts. Really, you don't need float at all. I set mine at 27.0v

 

[Dzl]

I have tried setting the float to 29v and the boost to 29.2v, the sun is going down so I will not know ifit worked until tomorrow.

You should not do this, 29V = 3.625 Volts per cell = too high for float voltage.
Ideally float should be less than or equal to 3.40Vpc (most reputable brands I've looked at use by default or recommend 3.375 or 3.4 as a default, one or two may use 3.45)

I suggest checking out this resource for a fuller understanding.

As a general point, pushing to get that extra 2% capacity might well result in a much greater than 2% loss of cycle life. There is nothing objectively wrong with charging to 3.65Vpc, but its also not strictly necessary and not optimal from a cycle life perspective. Many people feel the juice is not worth the squeeze (unless its a scenario where getting every last amp hour takes priority over battery longevity--but even then, the gains between say 3.55 or 3.60 and 3.65 are pretty modest).

 

[snoobler]

Using Battleborn's guidelines, 27.2V max.

Take LFP much above 3.4V/cell, and you can overcharge it with low current over long durations.

PsychoticEpisode

Please provide your:

normal voltage
boost voltage
float voltage (before you changed it)

And the circled values from the smartshunt:

 

[Deleted member 1888]

Ok so you all recommend this
Float 27.2V
Boost 29v?

I use Valance(12v batteries in pairs)batteries and the supplier gave me the voltages
29.2v max
28.8v min (90%)
28.4v (70%)
Ill take pics of all my settings and post them and you guys can tell me what to change.

 

[Dzl]

Ok so you all recommend this
Float 27.2V
Boost 29v?
...
Ill take pics of all my settings and post them and you guys can tell me what to change.

I still think its important you read the explainer linked to above (or any other explainer) rather than going only on the advice of others without understanding the 'why,' at a basic level.

With that caveat out of the way, the numbers above sound about right for float and absorption (at least in terms of vanilla lifepo4--more on that below)


However these numbers:

I use Valance(12v batteries in pairs)batteries and the supplier gave me the voltages
29.2v max
28.8v min (90%)
28.4v (70%)

Are not normal for vanilla lifepo4. Maybe the slightly different chemistry of the Valence batteries means the voltage curve is different or maybe the supplier was incorrect (when you say supplier, was this an established battery retailer that you would trust or like an ebay reseller?). I don't know much about Valence batteries, I know there are others who have these Valence batteries, maybe they can confirm or clarify the voltage/SOC values you were given by the supplier.

 

[Deleted member 1888]

Over Volt Disc 29.3v
Charge limit 29.2v
Over Volt Rec 29v
Equal Charge 29.2v
Boost Charge 29.2v
Float Charge 27.2v
Boost Rec 26.4v
Low Volt Rect 25.2v
Under volt rect 24.4v
Under Volt warn 24v
low volt disc 22.2v
Discharge limit 21.2v

Let me know how bad my settings are and how I can fix them.