What Am I Missing...

[LDVV]

I have two 12V 120Ah AGM batteries.

The attached image shows the arrangement.

#1 - positive and negative to the Inverter.

#2 - positive and negative to the charge controller.

The Battery icon (on controller display) shows the battery as being full. In certain situations the battery level drops pretty rapidly. E.G, the only load was the Inverter, which was plugged into a stereo, which was on standby (~24w). It was cloudy, but I had around 30w coming in.

Why does the battery level still drop, and so fast? What have I messed up or overlooked here?

 

[LDVV]

These pictures were taken about five minutes apart.

Again - Inverter on, but only a stereo (on standby) connected. Cloudy, but more watts coming in, than being used.

As quickly as it can drain, it can replenish, and the battery is full again.

I'm either in the Twilight Zone, or the Stupid Zone.

?

 

[Bud Martin]

These pictures were taken about five minutes apart.

Again - Inverter on, but only a stereo (on standby) connected. Cloudy, but more watts coming in, than being used.

As quickly as it can drain, it can replenish, and the battery is full again.

I'm either in the Twilight Zone, or the Stupid Zone.

?

Is it showing 21.A/2.2A of current being drawn from the panels or it is the charging current to the battery?
If the load is drawing 24W of power on the AC output of the inveter, but due to inverter efficiency, 85% is typical, the power being drawn from the the battery will be about 24W/0.85 = 28W, at 12V then the current draw from the battery will be 28W/12V = 2.33A.
So if that reading is showing 2.1A/2.2A of charger output that means the load is using all the incoming power to run your inverter and nothing will be going to your batteries.

 

[LDVV]

Is it showing 21.A/2.2A of current being drawn from the panels or it is the charging current to the battery?
If the load is drawing 24W of power on the AC output of the inveter, but due to inverter efficiency, 85% is typical, the power being drawn from the the battery will be about 24W/0.85 = 28W, at 12V then the current draw from the battery will be 28W/12V = 2.33A.
So if that reading is showing 2.1A/2.2A of charger output that means the load is using all the incoming power to run your inverter and nothing will be going to your batteries.

It is showing the current drawn from the battery.

Allegedly (from the inverter advert) - *this model No-load current is very low, only o.4a, that is very important for DC system(most other brand is 2.0a)*

...not that I necessarily believe it.

Regardless, the stereo was showing as 24w. I unplug the stereo, while Inverter on, and it goes down to 0w (on Inverter display). So, I do feel that all the load was from the stereo (not saying that the Inverter won't still be consuming some power itself obviously).

More important than this drain of power, is how quickly my battery level drops.

I thought for sure that I could be consuming ten times that amount of power, and not see this amount of battery capacity depleted.

According to the manual:

Two bars of battery icon: 36-61%

Three bars: 62-86%

Keeping in mind that the battery had been showing as Full all day, and no Inverter was on, or any device connected, to the battery.

So in the space of five minutes, after turning on the Inverter (connected to a stereo on standby) the level seemingly dropped to <61%, in five minutes.

A few nights earlier I did have a string of LED lights (creates a ~2A draw), powered straight from the battery, on for about an hour. That hardly made a dent in the battery level.

I'm unsure what is so different now. The atmospheric temperature would not have been too different...if that has much relevance.

 

[Mattb4]

Displays of SOC are based on voltage and are not accurate indication of battery health. I have a 3 year old AGM that indicates full charge but if placed under load drops the voltage quickly. No capacity left.

 

[LDVV]

Displays of SOC are based on voltage and are not accurate indication of battery health. I have a 3 year old AGM that indicates full charge but if placed under load drops the voltage quickly. No capacity left.

Thanks for the explanation.

So how do I watch my usage and make sure that I don't drain them too far? Ideally I shouldn't go under 50% (for AGM), right?

I'd like to do something a bit more accurate than calculations based on appliance ratings etc l, there are just too many variables for me to rely on that.

 

[Mattb4]

Sadly many inverters do not have adjustable low voltage cut off. If yours does a discussion about what voltages should be for 50% discharge cycles can be read here: https://sunonbattery.com/agm-battery-voltage-capacity/

 

[Bud Martin]

What is the exact model of this EPEVER?
What charging current do you see on the display while the batteries are being charged while inverter is not on?
BTW, if the inverter is on it will still drawing power from batteries even if there is no AC load connected but the inverter, typical power draw is around 10W or more, you can easily test the current draw using the DC Clamp on Amp meter.
Can I also see the wiring diagram or the pictures of how the system is wired up? Is the inverter connected to the Load terminals of the EPEVER?

 

[LDVV]

What is the exact model of this EPEVER?
What charging current do you see on the display while the batteries are being charged while inverter is not on?
BTW, if the inverter is on it will still drawing power from batteries even if there is no AC load connected but the inverter, typical power draw is around 10W or more, you can easily test the current draw using the DC Clamp on Amp meter.
Can I also see the wiring diagram or the pictures of how the system is wired up? Is the inverter connected to the Load terminals of the EPEVER?

Thanks.

Model is DR3210N. Dual battery model. No second battery connected. No load terminals. Inverter is wired straight to the battery.

You should be able to see wiring method in the bottom half of the top picture.

 

[Bud Martin]

So what is the batteries charging current you see while charging? This is 30A charger. What are the panels Wattage?
It sounds like the batteries are not truly fully charged if the batteries drop down so fast.
This the user manual I found:

https://cdn.shopify.com/s/files/1/0092/3628/3447/files/Temank-DuoRacer-SMS-EL-V1.0.pdf?v=1598489845

BTW, it does not look like the EPVER can show how much current the load is pulling from the batteries since there is no current shunt on the battery for it to monitor, so the current reading as shown on the display must be the battery charging current.
Do you have DC Clamp on amp meter?

 

[LDVV]

So what is the batteries charging current you see while charging? This is 30A charger. What are the panels Wattage?
It sounds like the batteries are not truly fully charged if the batteries drop down so fast.
This the user manual I found:

https://cdn.shopify.com/s/files/1/0092/3628/3447/files/Temank-DuoRacer-SMS-EL-V1.0.pdf?v=1598489845

Sorry, forgot to answer that... I've seen up to ~8.5A coming in from the panel.

This is just an experimental set up, so I only connected one REC 260W panel for now.

Just for clarification; it's a 30A Controller. Does that mean it can handle up to 30A in? Or it can provide a 30A charge to batteries that are connected to it?

 

[LDVV]

BTW, it does not look like the EPVER can show how much current the load is pulling from the batteries since there is no current shunt on the battery for it to monitor, so the current reading as shown on the display must be the battery charging current.
Do you have DC Clamp on amp meter?

No DC Clamp. I could try investigate with Multimeter later.

From what I can see, it seems to coincide with devices being run from the Inverter... actually, that doesn't make (accurate) sense, as the Controller can't really "see" what appliances are being run. I think when the current draw occurs in the batter, the controller ups the supplied charging current appropriately?

 

[Bud Martin]

Sorry, forgot to answer that... I've seen up to ~8.5A coming in from the panel.

This is just an experimental set up, so I only connected one REC 260W panel for now.

Just for clarification; it's a 30A Controller. Does that mean it can handle up to 30A in? Or it can provide a 30A charge to batteries that are connected to it?

8.5A is the current being drawn from the panel, 30A rating is the battery charger current rating not the panel current.
The MPPT converts high Voltage low current from panel to charging battery Voltage and higher higher current.
For example (disregard conversion loos for now): the panel Voltage is 18V and 8A is being drawn by the charger controller, the charge controller will then convert 18V 8A (18V x 8A = 144W) to 14V 10.28A (144W) to charge the battery.
Your display shows only 2.2A of charging current which is really low and not enough to charge the battery and running the inverter at the same time.