What’s the best inverter?

[Cdkipp]

We have one string of 3 of 280w panels, they reach around 25 volts, showing 100% on the charge controller soon after the sun is up. No issues running things as long as there is sun. But the startup in the morning of the freezer on the timer is when we have the issue.

Taking into consideration the accurate responses above let me share with you that I have a Magnum 4024 inverter/charger in my RV that can handle both a fridge and AC at the same time. The wiring suggested by Magnum is 2/0. In your position, you may have to replace three things, the inverter, BMS and wiring. I would start with the wring and switch to 2/0 with your inverter and battery as close together as possible. If that doesn't work, or even if it does work, your next weak link is going to be the BMS. I bypass the BMS problem by connecting my BMS to a contactor/relay but there are also large BMS units available. If these two steps, (which you should take regardless) do not work then you know you have a problem with the inverter or possibly the freezer

 

[sunshine_eggo]

How do I know the correct torque?

Possibly listed on the inverter or battery spec. If not, look up torque for the thread sizes (diameter of threads, NOT hex head) used and select something from the low end.

We have one string of 3 of 280w panels, they reach around 25 volts, showing 100% on the charge controller soon after the sun is up. No issues running things as long as there is sun. But the startup in the morning of the freezer on the timer is when we have the issue.

"100% on the charge controller" is meaningless. It's purely based on voltage, and it could read 100% even when your batteries are dramatically lower.

Voltage based SoC is WORTHLESS UNLESS the batteries have sat without any load or charge on them for 2+ hours.

I suspect that you have the following in play:

1. poor connections
2. 2awg wire
3. low battery

One or more of those is causing the voltage the inverter sees to drop below the disconnect voltage.

Or your 3000W inverter is a turd.

 

[ShaneT]

What does the red light signify?
It could be low voltage disconnect or it could be overload or it could be something else.

I just double checked, the right light and audible alarm signify that there is low voltage protection on the inverter.

 

[John Frum]

I just double checked, the right light and audible alarm signify that there is low voltage protection on the inverter.

Confirms my hypothesis.
Now lets see about a remedy.

Please post a picture of the entire wire path between the inverter and the battery.

 

[ShaneT]

Possibly listed on the inverter or battery spec. If not, look up torque for the thread sizes (diameter of threads, NOT hex head) used and select something from the low end.



"100% on the charge controller" is meaningless. It's purely based on voltage, and it could read 100% even when your batteries are dramatically lower.

Voltage based SoC is WORTHLESS UNLESS the batteries have sat without any load or charge on them for 2+ hours.

I suspect that you have the following in play:

1. poor connections
2. 2awg wire
3. low battery

One or more of those is causing the voltage the inverter sees to drop below the disconnect voltage.

Or your 3000W inverter is a turd.

Okay, I think I’ll try with the connections first….I don’t understand how to set the torque though…what kind of wrench do you use for that?? All I have are socket and end wrenches….

As far as the batteries are concerned, do I need to read the levels on the BMS when the error occurs to find out if it’s a low battery issue? All of my cells are at a healthy level right now and I have a balancer to manage them that I monitor through the app.

 

[ShaneT]

Confirms my hypothesis.
Now lets see about a remedy.

Please post a picture of the entire wire path between the inverter and the battery.

 

[Cdkipp]

Okay, I think I’ll try with the connections first….I don’t understand how to set the torque though…what kind of wrench do you use for that?? All I have are socket and end wrenches….

As far as the batteries are concerned, do I need to read the levels on the BMS when the error occurs to find out if it’s a low battery issue? All of my cells are at a healthy level right now and I have a balancer to manage them that I monitor through the app.

You can also feel for heat at the connections and/or check voltage at each connection to look for problems. I wouldn't worry about torque right now, I would just make sure everything is snug.

 

[John Frum]

I can't see the battery or its connections which could be an issue.
The shunt(which in the wrong place) has a ring terminal underneath the inverter lug.
Switch those so that the inverter lug is on the bottom and test again.

 

[ShaneT]

I can't see the battery or its connections which could be an issue.
The shunt(which in the wrong place) has a ring terminal underneath the inverter lug.
Switch those so that the inverter lug is on the bottom and test again.

 

[John Frum]

You have a double blue wire going to the negative terminal and a black wire.
Where does the black wire go?
I see the double blue wire goes to your bms.

 

[ShaneT]

I can't see the battery or its connections which could be an issue.
The shunt(which in the wrong place) has a ring terminal underneath the inverter lug.
Switch those so that the inverter lug is on the bottom and test again.

Is this the shunt? If I’m understanding correctly, it looks like the inverter lug is on the bottom. Or am I mistaken? Also, where does the shunt need to go to be in a better place?

 

[John Frum]

Is this the shunt? If I’m understanding correctly, it looks like the inverter lug is on the bottom. Or am I mistaken? Also, where does the shunt need to go to be in a better place?

Yes that is the shunt.
The shunt should be between the battery and everything else.
Before we change that we need to understand where that big black wire off the battery negative is going.

 

[ShaneT]

You have a double blue wire going to the negative terminal and a black wire.
Where does the black wire go?
I see the double blue wire goes to your bms.

The in the picture I am holding the black wire that goes to the negative terminal on the battery where the BMS is connected.

 

[John Frum]

The in the picture I am holding the black wire that goes to the negative terminal on the battery where the BMS is connected.

I think that wire is in parralel with our BMS effectively bypassing the protection your bms offers.
I wonder if someone put that in as hack to fix the inverter low voltage trip problem.
You system needs to be fixed.

 

[ShaneT]

I think that wire is in parralel with our BMS effectively bypassing the protection your bms offers.
I wonder if someone put that in as hack to fix the inverter low voltage trip problem.
You system needs to be fixed.

I am new at this stuff…..and did the install myself. The ways it’s connected isn’t a hack, it’s just the way I connected it….Is there any way you would be willing to help guide me to fix it?

 

[curiouscarbon]

is BMS C- connected to busbar negative?
is BMS B- connected to pack negative?
is mystery black cable connected to busbar negative?
is mystery black cable connected to pack negative?

it is hard to tell for me

ideally the BMS would be the only thing between Pack Negative (lowest voltage cell post) and Busbar Negative so it can fully disconnect power

the shunt will only monitor the inverter power use, sorry if this is inane to mention

 

[John Frum]

I am new at this stuff…..and did the install myself. The ways it’s connected isn’t a hack, it’s just the way I connected it….Is there any way you would be willing to help guide me to fix it?

The problem is that fixing that will make your system less able to cope with the inverter draw.
But yes I will help.
How about tomorrow?
I've got a busy afternoon.

 

[sunshine_eggo]

I am new at this stuff…..and did the install myself. The ways it’s connected isn’t a hack, it’s just the way I connected it….Is there any way you would be willing to help guide me to fix it?

The torque on all those 10mm nuts should be 6-7 Nm. If any of those are loose, problem. For the love of all that is holy, do NOT over-tighten them and destroy a terminal.

Harbor freight sells a workable 1/4" torque wrench that works in this range.

 

[ShaneT]

The problem is that fixing that will make your system less able to cope with the inverter draw.
But yes I will help.
How about tomorrow?
I've got a busy afternoon.

Okay, yes, tomorrow would be great if you have time.
So this wiring issue is not my only issue? You think I need a better inverter also? Something with more surge power? Possibly more volts?

 

[ShaneT]

is BMS C- connected to busbar negative?
is BMS B- connected to pack negative?
is mystery black cable connected to busbar negative?
is mystery black cable connected to pack negative?

it is hard to tell for me

ideally the BMS would be the only thing between Pack Negative (lowest voltage cell post) and Busbar Negative so it can fully disconnect power

the shunt will only monitor the inverter power use, sorry if this is inane to mention