What’s the best inverter?

[ShaneT]

Also….here is the current status of my BMS….idk if it helps or not…

 

[John Frum]

Also….here is the current status of my BMS….idk if it helps or not…

Turn off the charger immediately you are killing those cells!
Then discharge with a moderate load until the highest cell is under 3.4 volts.

 

[John Frum]

but I recently upgraded my freezer to an 18.5 cu. ft.

As @Supervstech allready mentioned we need to know the locked rotor amp rating on the freezer?

 

[sunshine_eggo]

@ShaneT

Given that you have been operating your battery without a BMS (the black cable bypasses it and makes it as though the BMS isn't even present), there is a very real possibility that you have damaged your cells.

You have just shown that your BMS is desperately trying to protect the battery.

Recommend you do as @smoothJoey says and then REMOVE all charge sources from the system until you get this figured out.

 

[Roswell Bob]

Hi all,
I have a fairly small system, running 8 3.2V LifePo4 280amp hour batteries. I’m only running a few lights a refrigerator and a freezer. Everything has been working great, but I recently upgraded my freezer to an 18.5 cu. ft. My inverter is 3000 watt. I have the freezer on a timer to shut off at night and save batteries. But in the morning when it try’s to kick on the inverter alarms.
Is it possible that I have an inverter with enough watts butt the surge is to much for it on the start up?

We havfilling ue 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.

Can you start the freezer later in the day when the sun is higher in the sky? I assume that freezer is full and any left over space is filled with bottles of water or liquid sodium. I'm curious if you have done an analysis to determine state of charge of cells when the inverter powers up in the morning. What are you using for charge controller? Do you know for sure that charger is filling up cells during the day? I would think cells would be quite a bit above 25v for full charge.

 

[sunshine_eggo]

1. Did you top balance your battery per the guide before you deployed it?
2. How long has it been in service.

 

[John Frum]

@ShaneT my priorities just got adjusted.
I suggest you follow the excellent advice of @sunshine_eggo and the other helpful folks in this thread.
Best of luck.

 

[ShaneT]

1. Did you top balance your battery per the guide before you deployed it?
2. How long has it been in service.

When I bough the cells they were brand new and already balanced. I checked each one individually and they were all 3.3
This set up has been in service now for a couple months. The change with the freezer has been about 2 weeks.

 

[ShaneT]

@ShaneT

Given that you have been operating your battery without a BMS (the black cable bypasses it and makes it as though the BMS isn't even present), there is a very real possibility that you have damaged your cells.

You have just shown that your BMS is desperately trying to protect the battery.

Recommend you do as @smoothJoey says and then REMOVE all charge sources from the system until you get this figured out.

I am completely off grid….this is my ONLY source of power….can you please help me figure out how to fix it?

 

[sunshine_eggo]

When I bough the cells they were brand new and already balanced.

You were lied to.

I checked each one individually and they were all 3.3

That tells you absolutely nothing about the state of cell balance.

This set up has been in service now for a couple months. The change with the freezer has been about 2 weeks.

You have had your BMS bypassed for a couple months. Had you NOT had it bypassed, you would have been at this website two months ago asking why your BMS kept tripping your system.

Refer to Overkill diagram:




You added the black wire indicated by the red arrow completely taking the BMS out of the loop. It has probably tried to take the battery out of the circuit one or more times for every day you charged it.

Pray that you haven't destroyed your investment.

Have you followed @smoothJoey's advice and mine yet?

If not, do it now.

I dont' care if this is your only source of power. If you continue to abuse it, it likely won't be for long.

 

[circus]

Unplug the fridge while the freezer starts. If your lucky the fridge will start while the freezer's running. Then all you'll need is another timer insuring the fridge is off while the freezer starts.

 

[sunshine_eggo]

Unplug the fridge while the freezer starts. If your lucky the fridge will start while the freezer's running. Then all you'll need is another timer insuring the fridge is off while the freezer starts.

Dude. Catch up. He's bypassed his BMS and is running cells as high as 3.9V. The fridge/freezer is no longer on the radar.

 

[sunshine_eggo]

Emergency (that's what this is) procedures.

1. disconnect or at least power off all charging sources (open the breaker on the Rover).
2. load the inverter with ANYTHING to get all cell voltages below 3.65V
3. completely power down the system and remove the black cable from the (-) battery and bus bar. Set it aside. Never use it again.
4. remove plexiglass cover. Check that all 16 terminal nuts are secure. Ideally 6-7 N-m of torque. "wrist tight" with a 10mm socket/1/4" drive ratchet is fine for now. DO NOT OVERTIGHTEN
5. Replace plexiglass cover.
6. confirm that ALL connections are at least "wrist tight." DO NOT OVERTIGHTEN.
7. Reconnect inverter.
8. Reconnect charger.
9. Adjust charger to a maximum charge voltage of 27.6V, float of 27.2V.
10. Change BMS to balance ONLY during charge, only above 3380mV and only when the difference is 20mV
11. Resume normal operation.
12. Prepare to be frustrated by BMS issues for days/weeks.

WTF is "wrist tight"?

Hold it like this and don't honk on it:

 

[ShaneT]

Dude. Catch up. He's bypassed his BMS and is running cells as high as 3.9V. The fridge/freezer is no longer on the radar.

Okay, I have everything turned off. No charging sources. So I need to remove haha big black wire all together?
The (blue) BMS wires should be the only ones going to the negative terminal? Then the black wires from the BMS go up to the negative busbar?

 

[sunshine_eggo]

Okay, I have everything turned off. No charging sources. So I need to remove haha big black wire all together?

Yes. It's what may have destroyed your battery.

The (blue) BMS wires should be the only ones going to the negative terminal? Then the black wires from the BMS go up to the negative busbar?

Yes.

 

[sunshine_eggo]

Please check the emergency procedures. I updated them.

 

[Jred]

I am amazed at the level of help you can get from strangers on a forum. Awesome!

 

[sunshine_eggo]

Shane and I spent about an hour on the phone. Many of the battery terminal and bus bar connections needed to be tightened. Proper torqueing still needs to occur, but at least things are good and "snug." Given the sheer number of connections that were tightened, I suspect that will address the issue with the freezer.

"Bypass" cable removed!

Charge controller has been set to a 27.6/27.2V absorp/float to lessen the impact of cell imbalance and hopefully lengthen the period where cells can balance. He's likely going to get lots of BMS OVP triggers, but hopefully over time, the cell delta will lessen.

Also have a plan to have him use resistors to bleed down individual cells if the BMS can't eventually bring things in line.

 

[Cdkipp]

Shane and I spent about an hour on the phone. Many of the battery terminal and bus bar connections needed to be tightened. Proper torqueing still needs to occur, but at least things are good and "snug." Given the sheer number of connections that were tightened, I suspect that will address the issue with the freezer.

Charge controller has been set to a 27.6/27.2V absorp/float to lessen the impact of cell imbalance and hopefully lengthen the period where cells can balance. He's likely going to get lots of BMS OVP triggers, but hopefully over time, the cell delta will lessen.

Also have a plan to have him use resistors to bleed down individual cells if the BMS can't eventually bring things in line.

So nice of you to help. I was thinking one of those Heltec active balancers could help him in the short run but that stuff takes a while to get.

 

[upnorthandpersonal]

Might want to make sure those cells aren't bloating now...