Wiring question from controller to batteries and inverter

[alamow]

Hi everyone. I have a wiring question which might be really easy to answer but still I need to be sure I'm doing the right thing. Before continuing, this is my setup

6 panels (260W each) have 2 lines of 3 in series and then both series in parallel
Midnite Solar SL 150 MPPT controller
48V 400Ah AMG battery bank - never let it go lower than 55% charge
2 100A DC brakers - one before the controller and one between the controller and batteries
Pure Sine Wave grid tied inverter - this inverter works as a UPS, when grid power is present it charges the batteries, when not it runs from them.

So I'm moving off grid now, I have the panels setup. My question is, what is the correct way to wire the controller to the battery bank and the inverter?

This is my plan so far:
Positive from controller to DC braker
Positive from inverter and battery bank to DC braker
Negative from controller and batteries to negative of inverter

I intend to turn of the grid power from the inverter, activating its UPS mode and run from batteries. Then, on cloudy days when the PV is not enough, I can turn on the grid power for the inverter or connect the generator to it and charge the batteries. I do not now if by doing this it will damage the midnite controller. What I believe will happen is that it will sense an increased in power "charge" and assume the battery is charged then stop charging them or adjust its output as necessary.

Please share your knowledge. Sorry if this is in the wrong area but is the one I saw more related to it. And if this was asked somewhere else, sorry but I couldn't find that post.

[Sunking]

OK your first mistake is taking anything off-grid. You just gave yourself a 500 to 1000% rate increase. Why do you want to pay 5 to 10 times more for power?

OK with only two strings of panels, there is no need for any breakers or fuses between the panels and controller. Solar panels are Current Sources and a 260 watt panel Isc is less than 10 amps and with 2 strings if shorted out in bright noon sun is less than 20 amps. So as long as the wire is 12 AWG or larger there is no issue.

All the fuses or breakers on the DC get installed directly onto the Battery Term Post. There will be two of them on the Positive Term Post. One for the wire going to the controller, and other going to the load (Inverter). Although the sizes may not match your needs the schematic below is how to do this correctly. With 1500 watts of panels into a 48 volt battery, is only 30 amps so I have no clue where you came up with 100 amps for the controller wiring. The fuse between the battery and controller is sized to the controller rating. If you have a 40-amp Controller you would need a 40 amp fuse. Any larger and you risk fire and damage to the controller. The battery is the source of power, not the panels. The panels are not capable of burning up anything. It is the batteries that can vaporize wire.

Ignore the Isolator and battery vooltages in the schematics as the drawing is made for an RV using 12 volts.

[alamow]

Hi Sunking! Thank you for your answer. Well the reasons for going of grid are simple:
1) I live in Puerto Rico, since hurricane Maria I still have no power
2) before Maria, power was a constant issue, on and off
3) The local and ONLY power provided is broke, so don't expect good services, maintenance and improvements for years to come
4) On top of that they charge us probably 2-3 times what you pay for in the States.

As far as the 100Amp, I told the salesman I would be adding more panels in the future so he recommended the listed MPPT controller and brakers. Is done, I cannot reverse that so blame it to the savvy salesman and my lack of knowledge.

Thank you for the diagram and your help!

[alamow]

Hi everyone!. I have a 48V 400ah bank composed of 8 6V 400ah RELiON batteries part # REV-L16-400. Charging voltage is always between the 57-58V as per manufacturer. Been using them for about 4-5 months. Recently I noticed that after reaching the 100% charge and only float charge is being used, if the charger is disconnected the battery charge % drops from 100 to about 82 in less than 4 minutes. Load is on during that time, TVs, fans, lights, internet router, security cam, and sometimes a laptop.

First I tried doing EQ; did it 2-3 times but it didn't changed anything. Yesterday I decided to measure each single battery V to see if one was failing, all of them were between 6.3-6.5V. I took this reading while load was on them (same load mentioned above) and no charging whatsoever was being done. The batteries were cool, not cold because it never gets cold here, day temp was about 75F so maybe 80F close to the batteries and inverter.

When the charge drops to 82% then it takes maybe 10-12 hours to drop to 70-72%.

Why would this fast charge % drop happen?

[SunEagle]

I closed this post since it is a duplicate. Please refer to the one in sensij's post.

[sensij]

What actual voltages are you seeing? The charge percent displayed might not always be very accurate under some conditions.

What float voltage are you using? What time of day is it getting into float? It sounds like you need a longer absorb... How do you have that set right now?

EQ on AGM is generally not a good idea, and I don't see anything on the mfg data sheet that suggests it. What voltage did you use for that?

[alamow]

What actual voltages are you seeing? The charge percent displayed might not always be very accurate under some conditions.

What float voltage are you using? What time of day is it getting into float? It sounds like you need a longer absorb... How do you have that set right now?

EQ on AGM is generally not a good idea, and I don't see anything on the mfg data sheet that suggests it. What voltage did you use for that?

Wow, well I left the defaults in the controller, is a midnite solar sl 150. The voltages I saw using my multimeter match closely those displayed in the inverter. +-.5

I'm not aware of the float voltage as I was looking more at the amps being pushed to the batteries at that time. The amps were between 1.0-2.5.

my inverter can also charge the batteries using a generator, I noticed it was in float mode with the amps mentioned above during the morning when I turned off the generator. Had to run the generator as it was raining the day before and PV didn't push too much power.

The bulk and absorb time in the midnite is set to 1 hour. The inverter cannot be adjusted, the configuration is fixed and no options to make the adjustment are available.

The EQ was done with the midnite solar controller, however I left the default values and don't remember which one are those. I just selected "start eq"

I just got the batteries datasheet today, the person that installed them took everything away, I had to use my cell cammera to record a video of the top of the batteries to be able to see the part #; there is just enough space to connect wiring but not to read anything.

[Sunking]

Operator error. You just do not understand what is going on. There is nothing wrong with your batteries. Set Bulk/Absorb = 57.6, and Float to 54 volts. Absorb = 4 hours. NEVER EVER EQ your battery.

You cannot use voltage on a working system to determine State of Charge. 100% SOC is 51.2 volts. However in order to read that voltage would require you to disconnect the battery and let it rest over night before taking the reading.

[alamow]

Operator error. You just do not understand what is going on. There is nothing wrong with your batteries. Set Bulk/Absorb = 57.6, and Float to 54 volts. Absorb = 4 hours. NEVER EVER EQ your battery.

You cannot use voltage on a working system to determine State of Charge. 100% SOC is 51.2 volts. However in order to read that voltage would require you to disconnect the battery and let it rest over night before taking the reading.

Thank you! I wasn

[Sunking]

Thank you! I wasn

You are welcome. Not sure what got cut off.