Got some cells from EZealco and I’m wondering…

[PipHelix]

I bought 4 100ah cells from EZealco for making a small auxiliary battery to use in my camper. When I received the cells a week ago, they were all at 3.29V with no bulging or anything out of the ordinary. I finally got my Overkill BMS hooked up today and found that a week later this is the voltage situation of the 4 cells. I took this pic about a minute after hooking up the BMS. Somehow after a week of sitting, one of the cells went from 3.29V up to 3.886V and another went down to 2.695V.

Did I get some bad cells? I’m wondering if I should even bother trying to top balance of if I should just reach out to EZealco for a return/exchange. Bummer because I thought EZealco was supposed to be one of the good vendors.

 

[42OhmsPA]

Double check you sense wires and all of your connections. I'm betting you have one flip flopped.
Did you verify the reported voltages with your meter?

 

[PipHelix]

Double check you sense wires and all of your connections. I'm betting you have one flip flopped.
Did you verify the reported voltages with your meter?

Ha! Can you tell I’m new to this? LOL. My Fluke DVOM says they’re all at 3.29V. Here’s my wiring though. Not sure what might be flip flopped. You see anything weird?

 

[42OhmsPA]

Ha! Can you tell I’m new to this? LOL. My Fluke DVOM says they’re all at 3.29V. Here’s my wiring though. Not sure what might be flip flopped. You see anything weird?

View attachment 201020

I'd double check the wiring diagram, it's been a while since I wired my 4s.
Can you post the diagram?

You can also meter the connector, voltage should step up incrementally.

 

[PipHelix]

I'd double check the wiring diagram, it's been a while since I wired my 4s.
Can you post the diagram?

You can also meter the connector, voltage should step up incrementally.

I had all 3 of the BMS leads on the positive terminals so I connected them to the negative terminals. That did the trick and now my cells read as expected. I’ve seen people with the BMS leads soldered to the bus bars so I’m not sure how it matters what post the lead is connected to but apparently it does. Why so?

Overkill shows 3 different ways of connecting the leads. First with the leads on BC1 +, BC3 - and BC2 +. Then on the bus bars which suggests it doesn’t matter which post you use. Then using all the positives as I did earlier when I got an inaccurate reading. My experience suggests it does matter where you put the leads, but why show 3 different ways?





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[SparkyJJO]

As long as you're consistent across them all it shouldn't matter. What it tells me is one was just not making proper contact, and redoing it corrected that.

 

[PipHelix]

As long as you're consistent across them all it shouldn't matter. What it tells me is one was just not making proper contact, and redoing it corrected that.

Thanks! That makes sense. I’ll use my inch/lb torque wrench next time to make sure all is well.

 

[42OhmsPA]

I had all 3 of the BMS leads on the positive terminals so I connected them to the negative terminals. That did the trick and now my cells read as expected. I’ve seen people with the BMS leads soldered to the bus bars so I’m not sure how it matters what post the lead is connected to but apparently it does. Why so?

Overkill shows 3 different ways of connecting the leads. First with the leads on BC1 +, BC3 - and BC2 +. Then on the bus bars which suggests it doesn’t matter which post you use. Then using all the positives as I did earlier when I got an inaccurate reading. My experience suggests it does matter where you put the leads, but why show 3 different ways?

View attachment 201135

View attachment 201134

'View attachment 201133

I'm guessing it's because you didn't have one on the main negative to start.
Glad to hear that you got it working now.

 

[42OhmsPA]

Looking at your photo again I'd recommend adding an insulator between the cells when you get to final assembly.

 

[PipHelix]

Looking at your photo again I'd recommend adding an insulator between the cells when you get to final assembly.

Yes! I’ve got these sheets and I’ll cut them to size

https://a.co/d/g33PqIc

 

[Quattrohead]

Top white spade terminal looks burned, double check it.

 

[PipHelix]

Top white spade terminal looks burned, double check it.

I used a lighter on the heat shrink. Got too close. Then I found my heat gun, which is why all the other ones look okay.