Wiring Powmr into battery system

[Redbeardbeer]

Hi all.
I'm trying to wire in a Powmr MPPT 60A solar charge controller into a system with a battery and an inverter.
I am using a JK BMS.
The issue I have is, the Powmr charge controller won't turn on unless it see's the battery. So I have to turn the discharge function of the BMS on.
For the charge controller to feed into the battery (through the BMS) I have to have the BMS's discharge function on, which also then means the inverter (or any other load) is activated. Not a big deal but it's also not ideal....unless this is normal?

How else could I wire it? I could wire the charge controller direct to the battery, bypassing the BMS - but I like the functionality of being able to turn charging off via the BMS.

Attached is how I was thinking of wiring it....

Cheers!

 

[sunshine_eggo]

Hi all.
I'm trying to wire in a Powmr MPPT 60A solar charge controller into a system with a battery and an inverter.
I am using a JK BMS.
The issue I have is, the Powmr charge controller won't turn on unless it see's the battery. So I have to turn the discharge function of the BMS on.
For the charge controller to feed into the battery (through the BMS) I have to have the BMS's discharge function on, which also then means the inverter (or any other load) is activated. Not a big deal but it's also not ideal....unless this is normal?

How else could I wire it? I could wire the charge controller direct to the battery, bypassing the BMS - but I like the functionality of being able to turn charging off via the BMS.

Attached is how I was thinking of wiring it....

Cheers!

Your sketch appears correct.

Bypassing the BMS could be disastrous. Never do that.

I don't understand your initial issue. Why is the BMS discharge "off"? It shouldn't be unless there's been a problem.

 

[Redbeardbeer]

Your sketch appears correct.

Bypassing the BMS could be disastrous. Never do that.

I don't understand your initial issue. Why is the BMS discharge "off"? It shouldn't be unless there's been a problem.

Yeah don't want to bypass BMS. I just thought it might be nice to have the solar run the inverter without the battery but I guess the charge controller needs to detect the battery so it can work out what voltage it is. Also would be nice to have the solar charge the battery without the battery being discharged.

*edit:

At the moment during the testing/proof of concept phase, I have a 1s14p pack of 18650 cells to simulate a 48V battery so I can test the setup. But I don't want to draw from it at the moment - would prefer to draw from solar only.

Also there would no way for the charge controller to charge the battery, without the inverter being in the loop, and therefore unless I turn the inverter off, no way to charge the battery by itself. If (for example) there is a 200watt load on the inverter and I have 250watt solar coming in, then (assuming the battery is not fully charged) there is 50w going into the battery. But what if I want to put that 250w into the battery? I can't turn off the 'discharge' function as this cuts the battery from the charge controller.

Or am I understanding the BMS wrong? If I have charge on and discharge off, will it allow current to go in via the P- and out via the B- but not the other way around? Is it able to control the flow?

 

[sunshine_eggo]

Yeah don't want to bypass BMS. I just thought it might be nice to have the solar run the inverter without the battery but I guess the charge controller needs to detect the battery so it can work out what voltage it is.

This is generally not possible on most off-grid inverters.

Also would be nice to have the solar charge the battery without the battery being discharged.

Not sure what you mean by this. In a properly configured system, solar charges battery and powers loads as any surplus allows.

If you've failed to specify a float voltage, then that's likely the issue.

*edit:

At the moment during the testing/proof of concept phase, I have a 1s14p pack of 18650 cells to simulate a 48V battery so I can test the setup. But I don't want to draw from it at the moment - would prefer to draw from solar only.

It sounds like you've failed to specify a float voltage, or it's too low. Assuming Li-NCA chemistry (4.2V peak), your float needs to be 0.1V below your absorption. Li-NCA chemistry has crap cycle life. For improved life, charge only to 4.0V/cell, or 56.0V absorption, 55.9V float.

Also there would no way for the charge controller to charge the battery, without the inverter being in the loop, and therefore unless I turn the inverter off, no way to charge the battery by itself. If (for example) there is a 200watt load on the inverter and I have 250watt solar coming in, then (assuming the battery is not fully charged) there is 50w going into the battery. But what if I want to put that 250w into the battery? I can't turn off the 'discharge' function as this cuts the battery from the charge controller.

You've just plain lost me here. If you want to put that 250W into the battery, how are you still going to power the 200W load?

Or am I understanding the BMS wrong? If I have charge on and discharge off, will it allow current to go in via the P- and out via the B- but not the other way around? Is it able to control the flow?

I think your understanding is lacking, and/or your thinking is flawed.

The BMS should do NOTHING most of the time. It should only activate (terminate charge or discharge) when cell limits are exceeded (cell voltage too high or too low or temperature too low/too high). You shouldn't be turning it on and off for any reason. It's there as a safety system, not a management system.

If you have 200W load and 250W solar coming in, you can't force 250W to go to the battery and still power the 200W load. If you want 250W to go to the battery, you remove the load or turn off the inverter.

Note also that your inverter consumes power even if it's not powering loads.

 

[Redbeardbeer]

This is generally not possible on most off-grid inverters.



Not sure what you mean by this. In a properly configured system, solar charges battery and powers loads as any surplus allows.

If you've failed to specify a float voltage, then that's likely the issue.



It sounds like you've failed to specify a float voltage, or it's too low. Assuming Li-NCA chemistry (4.2V peak), your float needs to be 0.1V below your absorption. Li-NCA chemistry has crap cycle life. For improved life, charge only to 4.0V/cell, or 56.0V absorption, 55.9V float.



You've just plain lost me here. If you want to put that 250W into the battery, how are you still going to power the 200W load?



I think your understanding is lacking, and/or your thinking is flawed.

The BMS should do NOTHING most of the time. It should only activate (terminate charge or discharge) when cell limits are exceeded (cell voltage too high or too low or temperature too low/too high). You shouldn't be turning it on and off for any reason. It's there as a safety system, not a management system.

If you have 200W load and 250W solar coming in, you can't force 250W to go to the battery and still power the 200W load. If you want 250W to go to the battery, you remove the load or turn off the inverter.

Note also that your inverter consumes power even if it's not powering loads.

The inverter is a grid-tie inverter - so was wondering if I could use the solar to charge the battery, without providing power to the inverter (even if there is a load on the inverter/house) but perhaps not. Bu that's ok, I can just shut the inverter down in this case.

 

[sunshine_eggo]

The inverter is a grid-tie inverter - so was wondering if I could use the solar to charge the battery, without providing power to the inverter (even if there is a load on the inverter/house) but perhaps not. Bu that's ok, I can just shut the inverter down in this case.

Since you haven't disclosed your actual hardware, it's impossible to provide additional assistance.

 

[Redbeardbeer]

Since you haven't disclosed your actual hardware, it's impossible to provide additional assistance.

Powmr 60a MPPT solar charge controller
2x 200 watt panels
SUN-1000GTIL2 inverter - grid-tie.
Currently using a 14s1p 18650 li-ion pack to test the setup as a proof of concept until I finish building the 14s32p battery.

 

[sunshine_eggo]

Why don't you have the solar connected to the GT inverter?

 

[Redbeardbeer]

It is - sorry should mention that the two leads for P- and B- coming out of the BMS are joined to the same bus bar inside the BMS - they are effectively one on each side.

 

[sunshine_eggo]

The GT inverter is designed to work without a battery. The panels should be directly connected to the DC in. You have not installed it correctly. You are powering it with batteries rather than solar.

 

[Redbeardbeer]

The GT inverter is designed to work without a battery. The panels should be directly connected to the DC in. You have not installed it correctly. You are powering it with batteries rather than solar.

Can you suggest a resolution? Or is a grid tie system just not able to work with a battery?

 

[sunshine_eggo]

Can you suggest a resolution? Or is a grid tie system just not able to work with a battery?

I don't even know why you're trying to use a battery. What's the point of a battery on a grid tie system? If grid goes down, you can't provide AC power with a battery or solar as its AC output shuts down.

Why do you want to use a battery?

The GT inverter you purchased has its own MPPT controller on the DC input. It is designed to take 45-90VDC from panels and inverter it to 120/230VAC and feed it to the grid/loads.

It CAN run with a battery in the voltage range, but there's hardly a good reason to do so. Essentially, your battery is taking the place of the solar panels, but they are at a "fixed" voltage defeating the inverter's MPPT function.

 

[Redbeardbeer]

I want to use a battery so that I can supplement some usage when needed. For example if my idle/unoccupied load is only around 200 watt during the day, but I'm generating 350watt (for example), then the remainder can go into the batteries and they can be used later on.

This is more of a proof of concept for scaling up both the PV array and battery in the future - and for a bit of fun!

From what the sticker on the side of the inverter says, the DV input voltage range is only 22-65VDC - which is outside my PV range as I have 2 panels series together making over 70V.

I think this is an earlier model as I don't know it even supports MPPT solar control - either way, I cannot use it.

 

[sunshine_eggo]

I want to use a battery so that I can supplement some usage when needed. For example if my idle/unoccupied load is only around 200 watt during the day, but I'm generating 350watt (for example), then the remainder can go into the batteries and they can be used later on.

That makes sense, but you're shoe-horning this hardware to meet your needs.

You're storing excess solar in the battery and using that energy outside solar hours. Perfectly valid.

Unfortunately, you're stuck with the limitations of the setup. Loads determine what gets pulled from the battery and charge is determined by surplus solar. The setup doesn't allow you to choose otherwise.

This is more of a proof of concept for scaling up both the PV array and battery in the future - and for a bit of fun!

From what the sticker on the side of the inverter says, the DV input voltage range is only 22-65VDC - which is outside my PV range as I have 2 panels series together making over 70V.

I think this is an earlier model as I don't know it even supports MPPT solar control - either way, I cannot use it.

Yep. The next gen was the 45-90VDC. Your model is designed to handle parallel panels. Both have MPPT capabilities within that range.

 

[Redbeardbeer]

That makes sense, but you're shoe-horning this hardware to meet your needs.

You're storing excess solar in the battery and using that energy outside solar hours. Perfectly valid.

Unfortunately, you're stuck with the limitations of the setup. Loads determine what gets pulled from the battery and charge is determined by surplus solar. The setup doesn't allow you to choose otherwise.



Yep. The next gen was the 45-90VDC. Your model is designed to handle parallel panels. Both have MPPT capabilities within that range.

I can set the inverter to only draw XX watts or XX amps from the DC side - which would mean anything over that from solar would go into the battery to charge it, or it would not be used. Problem is working out what to set that to as if I set it too low, then could 'waste' some of the power, and set it too high, and there would be a draw on the battery to top it up.

Of course while I'm testing this - there's heavy cloud today!

 

[Redbeardbeer]

Ok I have wired up a test setup as per my drawing (thanks MSPaint haha) but I have an odd issue/observation.

After 'some time' with the BMS discharge off and charge on, the inverter draws too much from the solar that the voltage drops below the Powmr's low voltage cut off and as there is no continuity between the P- and B- so the Powmr no longer 'see's' the battery and turns off.

I assume what's happening is without discharge enabled on the BMS (I have it turned off as the test setup I have is only a 14s1p so limited to a few amp draw from battery - it's mostly there to simulate what it would be like when I've finished my 14s32p one) the voltage from the solar drops too low during heavy cloud cover and the inverter draws too much from the MPPT controller then is the solar charge controller hits the low voltage cut off (set to 40v) and shuts down. It won't turn back on again until it sees a battery (which is only when I enable discharge setting on the BMS).

Guess I could set the low voltage cut off on the Powmr to lower (think it can go to 9 (which it multiplies depending on battery size, so that would be 36V)).

 

[sunshine_eggo]

Ok I have wired up a test setup as per my drawing (thanks MSPaint haha) but I have an odd issue/observation.

After 'some time' with the BMS discharge off and charge on, the inverter draws too much from the solar that the voltage drops below the Powmr's low voltage cut off and as there is no continuity between the P- and B- so the Powmr no longer 'see's' the battery and turns off.

Symptom of the setup. Normally, the GT inverter works with direct panel voltage and conducts its own MPPT operation to find the max power available from the panels. The GT MPPT can't function properly with the Powmr in between.

I assume what's happening is without discharge enabled on the BMS (I have it turned off as the test setup I have is only a 14s1p so limited to a few amp draw from battery - it's mostly there to simulate what it would be like when I've finished my 14s32p one) the voltage from the solar drops too low during heavy cloud cover and the inverter draws too much from the MPPT controller then is the solar charge controller hits the low voltage cut off (set to 40v) and shuts down. It won't turn back on again until it sees a battery (which is only when I enable discharge setting on the BMS).

Yep.

Guess I could set the low voltage cut off on the Powmr to lower (think it can go to 9 (which it multiplies depending on battery size, so that would be 36V)).

This is all experimental. I would set it to the 22V min allowed by the GT MPPT.

 

[Redbeardbeer]

Symptom of the setup. Normally, the GT inverter works with direct panel voltage and conducts its own MPPT operation to find the max power available from the panels. The GT MPPT can't function properly with the Powmr in between.



Yep.



This is all experimental. I would set it to the 22V min allowed by the GT MPPT.

Cheers - yeah - just playing around for now with this setup. Enjoying learning as I go (and generating 'free' electricity is a bonus haha).

I'll see how low the min the Powmr will allow me to go. I think it only allows me to go to 36V but will see.