BMS flipping into charge protection rapidly.

[ppzzus]

I have been charging my 24v system 8 cell system via a generator as my charge controller went out. I have a power supply plugged into the generator and the power supply ground lead hooked into where the BMS ground would go into the charge controller. Positive going to the main positive on the battery pack.

Now when I was charging these at home using the same method it all went very smoothly, no power cuts or anything. Now when I'm using the generator (predator 1100) I can see the BMS going into charge protection every few seconds. Since the load changes it changes the revs of the generator. I can see the volts/amps/watts on the power supply drop to almost zero, then the charge protect kicks off for maybe ten seconds then repeats itself forever. I know I changed some of my BMS settings so I'm wondering if I did something incorrectly? The generator should have more than enough power to run the power supply. Power supply only has a max of 10-11 amps.

 

[John Frum]

Now when I was charging these at home using the same method it all went very smoothly, no power cuts or anything.

What is different?

 

[ppzzus]

What is different?

The BMS is flipping into charge protection and cutting the current to the batteries. It's doing this like every ten seconds.

 

[John Frum]

The BMS is flipping into charge protection and cutting the current to the batteries. It's doing this like every ten seconds.

Do you know why it is tripping?
Possible reasons are...
high cell voltage
high pack voltage
overcurrent
under temperature
over temperature
probably more that I'm not pulling to mind.
Is you BMS smart?

 

[John Frum]

I know I changed some of my BMS settings so I'm wondering if I did something incorrectly?

Ok that is another change.
Please detail the changes you made.

 

[ppzzus]

It is a current connected BMS and I'm told it's similar to an overkill BMS. I believe I enabled charge protection but I'm not sure. That period is pretty foggy. I included some screen shots just so we can be on the same page about it. Does anything stand out to you?

 

[John Frum]

Its tripping on high cell voltage.
Independently verify that the bms is seeing correct voltage with your dvom.
Since its so grossly over and settles so low I would verify all the joinery is clean and torqued.

 

[ppzzus]

Ah that does make sense. I drove 2200 miles over 3 days with these in the back. I've been very ginger with the bolts as threaded aluminum scares me. I've had some issues with them vibrating loose.

 

[Rocketman]

Get your DMM (digital multimeter) out and verify each cell voltage. (I don’t have that brand of bms) but your last screen I think it is saying you have cells at 3.973v! That is way too high!

 

[ppzzus]

Get your DMM (digital multimeter) out and verify each cell voltage. (I don’t have that brand of bms) but your last screen I think it is saying you have cells at 3.973v! That is way too high!

Yeah they definitely aren't getting that high lol makes a lot of sense. Appears I have some loose nuts caused by the road vibrations.

 

[Rocketman]

Change your nuts out to lock nuts - so they don’t vibrate lose.(nylon insert lock nuts)

 

[ppzzus]

Change your nuts out to lock nuts - so they don’t vibrate lose.

I do half lock washers on there currently. They don't seem to be doing the job. It's probably my fault... I am terrified of tightening these too much and stripping the threads.

 

[chrisski]

These were recommended to me instrad of lock washers:

https://www.amazon.com/dp/B07R59HPCF

I have not started the battery build but I have them. My cells also came with serrated lock nuts. Not as sharp as the serrated washers in that link. I plan on using Red Loctite also.

 

[Bvillebob]

If by "half lock washers" you mean split ring, the kind that are a circle with a slit in them and slightly twisted, don't use them. They are completely worthless at doing what you think they're supposed to do, lots of studies proving that, even look on Youtube for some good videos documenting that. In addition, they almost completely remove contact between the nut and the bus bar due to their small size, terrible for electrical connections. For vibration resistance, Nylok nuts, or similar with the nylon insert in the center are best, but for electrical purposed the serrated nuts or or the serrated washers linked above are good.

 

[ppzzus]

If by "half lock washers" you mean split ring, the kind that are a circle with a slit in them and slightly twisted, don't use them. They are completely worthless at doing what you think they're supposed to do, lots of studies proving that, even look on Youtube for some good videos documenting that. In addition, they almost completely remove contact between the nut and the bus bar due to their small size, terrible for electrical connections. For vibration resistance, Nylok nuts, or similar with the nylon insert in the center are best, but for electrical purposed the serrated nuts or or the serrated washers linked above are good.

That makes a lot of sense.

 

[ppzzus]

Thanks for all the help. Went out to the far side of town again to run the generator. Followed the event log to chase the loose connections in real time. Got it charging now without any clipping. I'm waiting to install the new nuts etc until I get my new charge controller on Monday.

Then maybe I can get the setup nice and clean so it doesn't look like such a hodgepodge of junk ?