EG4 Charges All Day Never dropping to Float?

[ddxv]

We have a 12000XP and 700AH of 48v Flooded Lead Acid batteries. We are completely off grid (ie no grid connection available).

The screenshot is from a sunny day. You can see the Incoming Watts rise over the morning, spiking to 3k for an hour or so then as the batteries reach their set charge of 59v the incoming Solar watts drops.

What we are worried about is the system never seems to settle and move to float, possibly over charging the batteries? I've been making sure to keep up with watering the batteries, but not sure if this is damaging them long term.

A couple questions:

1) Do other people using EG4 see a profile like this? How do you get your batteries to drop into float? When I talked to EG4 they said it was because there was likely some power draw (which yes, there is constantly some power draw + small usage spikes).

2) Am I right that this could harm the FLA batteries?

Let me know if you need more info.

 

[sunshine_eggo]

Charge termination depends on attaining absorption voltage and holding it for a given time period or until a tail current is reached. Your data suggests you have inconsistent PV that can't maintain the absorption voltage.

1) are you experiencing clear skies with no intermittent clouds? Your power/voltage curves strongly suggest that you have intermittent PV.

2) If it truly held at peak absorption, yes. Given that yours is oscillating quite a bit, I'd be less concerned.

Unfortunately, the manual doesn't show or describe the charge behavior. A somewhat common charge profile is as follows:



time = the time to reach a little less than absorption voltage. Then absorption time is 10X that time, min 1hr, max 12hr

It could be following this criteria, or your PV isn't consistent enough.

@EG4TechSolutionsTeam thoughts?

 

[ddxv]

Charge termination depends on attaining absorption voltage and holding it for a given time period or until a tail current is reached. Your data suggests you have inconsistent PV that can't maintain the absorption voltage.

1) are you experiencing clear skies with no intermittent clouds? Your power/voltage curves strongly suggest that you have intermittent PV.

2) If it truly held at peak absorption, yes. Given that yours is oscillating quite a bit, I'd be less concerned.

Unfortunately, the manual doesn't show or describe the charge behavior. A somewhat common charge profile is as follows:

View attachment 292807

time = the time to reach a little less than absorption voltage. Then absorption time is 10X that time, min 1hr, max 12hr

It could be following this criteria, or your PV isn't consistent enough.

@EG4TechSolutionsTeam thoughts?

Re: intermittent PV, this is on a clear day. There is a shadow around 10 to 10:30 but nothing after that. Full sun and should be getting around 5k watts if there was enough pull.

 

[sunshine_eggo]

Re: intermittent PV, this is on a clear day. There is a shadow around 10 to 10:30 but nothing after that. Full sun and should be getting around 5k watts if there was enough pull.

I can't fathom why the voltage is that erratic. Admittedly, I don't have much load variation (fridge turning on and off). Here was yesterday's battery voltage/current:



I cycled about 2800W of loads on/off over a few minutes, and it looked like this:



As you can see, there were very little changes in voltage even with a 2800W increase/decrease in loads:



I would expect similar performance from any quality system whether on lead acid or lithium.

Given that it does appear to register attaining absorption voltage, it still remains to be seen if the charge algorithm is akin to the one I listed where long absorption times are the norm.

@EG4TechSolutionsTeam might be able to shed some light...

 

[ddxv]

I can't fathom why the voltage is that erratic. Admittedly, I don't have much load variation (fridge turning on and off). Here was yesterday's battery voltage/current:

View attachment 292898

I cycled about 2800W of loads on/off over a few minutes, and it looked like this:

View attachment 292915

As you can see, there were very little changes in voltage even with a 2800W increase/decrease in loads:

View attachment 292916

I would expect similar performance from any quality system whether on lead acid or lithium.

Given that it does appear to register attaining absorption voltage, it still remains to be seen if the charge algorithm is akin to the one I listed where long absorption times are the norm.

@EG4TechSolutionsTeam might be able to shed some light...

Thank you for sharing that, just to be clear, are you also using EG4?

I am thinking now the issue might be a DC load which is connected to the batteries directly, bypassing the inverter. Maybe this draw is what is messing with it.

 

[Brett V]

Thank you for sharing that, just to be clear, are you also using EG4?

I am thinking now the issue might be a DC load which is connected to the batteries directly, bypassing the inverter. Maybe this draw is what is messing with it.

How big is this load?

 

[ddxv]

How big is this load?

It is 12v lights in the house, which may or may not be left on during the day, so I would think around 100-200w from that. Additionally an electric water pressure pump which turns on occasionally. In total I would think it is less than 500w ever and theoretically should be 0 at times assuming lights are all turned off during the day.

All the 12v comes from a 48V to 12v DC-DC step down converter attached to the lead acid batteries. So maybe the EG4 inverter just sees this as a dip in voltage and attempts to bring the charge back up to absorb.

I see that a AC 110v - DC 12v converter is quite cheap, so I will try that to remove any noise that the 12v lights might be causing.

 

[sunshine_eggo]

Thank you for sharing that, just to be clear, are you also using EG4?

No. Victron, but all systems should operate with relatively consistent absorption voltage if sufficient PV is available to maintain it and power any loads.

I am thinking now the issue might be a DC load which is connected to the batteries directly, bypassing the inverter. Maybe this draw is what is messing with it.

I have a steady 200W of DC loads, so that shouldn't influence it.