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Another Top Balance Screwup

I was going by the description (Cable Conductor Wire Size: 0.15mm Copper Wire, 18AWG, super flexible;)

I did notice the alligators look heftier than others. I still believe it's best to recommend ring terminals and at least 12awg cable especially if someone is complaining their supply isn't putting out the rated amps.

Voltage drop is much less at 12 volts (.16 volts or 1.34%) than 3.65 volts (.26 volts or 7%) using 2 feet of 18awg wire. What is the length of the cable that comes with that power supply?
I just measured 31 inches from the tip to the tip. I think they are 14awg, but aren't labeled and sometimes they make the insulation thicker to fool you.

Edit to add that ring terminals are much better and will keep your supply in constant current longer.
 
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A lot of folks have reported higher current and lower voltage drop when they make heavy duty leads with ring terminals:

My guess (without any data to back it up): The bulk of the improvement is from replacing the alligator clips with ring terminals. The improvements from heavy wire and replacing the banana plugs is probably small in comparison.

My reasoning is this:
* At 30" even 18AWG has very little resistance.
* The banana plugs will have 4 reasonable points of contact with the power supply post
* The teeth of the aligator clips will have between 2 and 4 tiny points of contact with the cell terminal post.
 
18 awg, 6.39 mOhm/foot, 5' round trip, 10A, 0.32V IR drop

with 3.65V setting on supply, above 3.33V cell, current starts to taper off below 10A.
 
18 awg, 6.39 mOhm/foot, 5' round trip, 10A, 0.32V IR drop

with 3.65V setting on supply, above 3.33V cell, current starts to taper off below 10A.
Looks like the 10 gauge would make it start tapering higher. That would help with the impatient.

I am getting like .05 running that calculation with 10 gauge, is that right? That would mean tapering at 3.6? Sounds high to me.
 
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I think the concern is from warnings from @toms who hates the way top balancing is done by most people.

To clarify, i commented that continuing to charge at low currents when a cell is full causes damage.

I would rather people look into the chemistry of the lithiation process and maje their own judgment if they wish to incur this damage or not.

Keep in mind that 20% loss of lifespan still may not be noticed for a decade or so..


edit: i liken this to buying a new car, then running the engine right at the redline for a few hours when it is new. You won’t find conclusive studies showing exactly the lifespan you have lost from your engine.
If it is not necessary, would you do it?
Parallel top balancing is not necessary, there are many other ways to ensure all cells in your pack will reach top charge voltage together. Why chose one that causes damage, even if the extent of the damage is unknown?

Also it is certainly incorrect to say most people parallel top balance their cells. A very small percentage of cells are balanced in this way by DIY enthusiasts.
All manufacturers that i know of have an initial charge regime that forms the SEI layer, and establishes the capacity and IR of the cell. The vast majority of cells are then discharged from exactly the same SOC to a safe for storage charge level and assembled by their customers into packs.
 
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The vast majority of cells are then discharged from exactly the same SOC to a safe for storage charge level and assembled by their customers into packs.
If that were the case wouldn't the cells be effectively top balanced?
It was my understanding that the process was more or less like this

Frankenstein charge to form the SEI layer
cells are full at the end​
effectively top balanced​
takes days​
IR and capacity test
takes ~2 hours​
cells are empty at the end​
cells are effectively bottom balanced​
"storage" charge to ~3.3 volts
cells are still effectively bottom balanced​
self-discharge test
takes about a month​
only done on cells that passed the IR and capacity test​
If I'm wrong please set me straight.
 
If that were the case wouldn't the cells be effectively top balanced?
It was my understanding that the process was more or less like this

Frankenstein charge to form the SEI layer
cells are full at the end​
effectively top balanced​
takes days​
IR and capacity test
takes ~2 hours​
cells are empty at the end​
cells are effectively bottom balanced​
"storage" charge to ~3.3 volts
cells are still effectively bottom balanced​
self-discharge test
takes about a month​
only done on cells that passed the IR and capacity test​
If I'm wrong please set me straight.
I'm not sure about this.
4 out of 16 cells I purchased arrived between 5 and 10 amp hours from 3.65v.
I am not sure at which stage they would have failed testing and been sold to me if your testing time-line is accurate.

I figured after the SEI layer was formed, they were discharged, then when charged with less than 280AH, they were rejected and sold on the grey market. (Just a guess on my part)
 
I'm not sure about this.
4 out of 16 cells I purchased arrived between 5 and 10 amp hours from 3.65v.

If the cells don't come at or near the 3.29 volts I would call that a red flag.
My cells came with a sticker on the side that described their voltage as 3.29 volts.

I am not sure at which stage they would have failed testing and been sold to me if your testing time-line is accurate.

I figured after the SEI layer was formed, they were discharged, then when charged with less than 280AH, they were rejected and sold on the grey market. (Just a guess on my part)
I suspect your cells underwent some jiggery pokery after the production process.
 
If the cells don't come at or near the 3.29 volts I would call that a red flag.
My cells came with a sticker on the side that described their voltage as 3.29 volts.

All were at nearly the same voltage. I will check my spreadsheet, but none were more than 3 or 4 millivolts different. The full ones were not even the lowest capacity.

I suspect your cells underwent some jiggery pokery after the production process.

I suspect they were rejected when they didn't get 280AH charged into them. Hard to get 280AH out when you can't put that much in, but that is just my guess. I think there isn't as much testing after the initial layer formation as you think. I suspect after layer formation, they are discharged, charged, and then discharged for capacity and IR testing, then charged to storage capacity and shipped.
 
I suspect they were rejected when they didn't get 280AH charged into them. Hard to get 280AH out when you can't put that much in, but that is just my guess. I think there isn't as much testing after the initial layer formation as you think. I suspect after layer formation, they are discharged, charged, and then discharged for capacity and IR testing, then charged to storage capacity and shipped.
I think the coloumbic efficiency isn't anywhere near 100% until after the SEI layer is formed. So I think they need to do a discharge capacity test post Frankenstein charge.
 
I think the coloumbic efficiency isn't anywhere near 100% until after the SEI layer is formed. So I think they need to do a discharge capacity test post Frankenstein charge.
Yes, I am guessing too. I think mine were discharged after SEI formation, and when they didn't accept 280AH charge were sold to me, no discharge, no charge to storage, etc.
 
Yes, I am guessing too. I think mine were discharged after SEI formation, and when they didn't accept 280AH charge were sold to me, no discharge, no charge to storage, etc.
I'm confused.
I think the capacity/ir test follows the Frankenstein charge.
Are you saying your cells were out of spec on the F charge and got diverted to the grey market without getting a capacity/ir test?
I would think batteries that got diverted before the capacity/ir test are likely to be pretty flakey.
It could happen but the vendors who sold them probably won't get much repeat business.
I also think that some cells that fail the discharge test get flogged to the low end of the grey market.
 
I'm confused.
I think the capacity/ir test follows the Frankenstein charge.
Are you saying your cells were out of spec on the F charge and got diverted to the grey market without getting a capacity/ir test?
I think part of the capacity test is charging them, if they don't accept at least 280AH, there really isn't any need to discharge them and check capacity. I wouldn't bother if I was capacity testing.
I also think that some cells that fail the discharge test get flogged to the low end of the grey market.
I think this would be the majority of the Eve cells, yes.
 
If that were the case wouldn't the cells be effectively top balanced?
It was my understanding that the process was more or less like this

Frankenstein charge to form the SEI layer
cells are full at the end​
effectively top balanced​
takes days​
IR and capacity test
takes ~2 hours​
cells are empty at the end​
cells are effectively bottom balanced​
"storage" charge to ~3.3 volts
cells are still effectively bottom balanced​
self-discharge test
takes about a month​
only done on cells that passed the IR and capacity test​
If I'm wrong please set me straight.

I can’t comment for all manufacturers, but the ones i have spoken to don’t fully discharge as part of their process, they discharge to stated capacity and then apply storage charge. The cells are effectively top balanced as they leave the factory.

I have capacity tested LifeTech, Winston, CALB, GBS, and Sinopoly as part of various builds, all cells were top balanced ex-factory. All had more than rated capacity.

Packs that i have rebuilt from older cells that were at different SOC’s i used to individually charge, now i add active balancing and balance in-situ.

I haven’t been in contact with EVE, i can’t see any reason they would fully discharge a cell though.

Perhaps the 272Ah cells are ones that hit LVD during the manufacturing process and were originally supposed to be 280Ah?

You would have to contact EVE or Lishen directly for their process.
 
I can’t comment for all manufacturers, but the ones i have spoken to don’t fully discharge as part of their process, they discharge to stated capacity and then apply storage charge. The cells are effectively top balanced as they leave the factory.

I have capacity tested LifeTech, Winston, CALB, GBS, and Sinopoly as part of various builds, all cells were top balanced ex-factory. All had more than rated capacity.

Packs that i have rebuilt from older cells that were at different SOC’s i used to individually charge, now i add active balancing and balance in-situ.

I haven’t been in contact with EVE, i can’t see any reason they would fully discharge a cell though.

Perhaps the 272Ah cells are ones that hit LVD during the manufacturing process and were originally supposed to be 280Ah?

You would have to contact EVE or Lishen directly for their process.
If the cells are effectively top balanced then @JoeHam is correct, we should just configure the cells into batteries and deal with any balance issues if/when they arise.
Honestly I don't think the grey market eve cells that are popular here come from the factory top balanced.
Mine weren't.
 
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The cells are effectively top balanced as they leave the factory.
Only if the self discharge rates are matched, but this is typically minor for storage times under 6 months.

As mentioned repeatedly ,commodity grey market cells are not always capacity matched, and thus can vary a bit. I had an order with cells only 1-2mv spread, and they were 10-12% from highest to lowest SOC.
 
I can’t comment for all manufacturers, but the ones i have spoken to don’t fully discharge as part of their process, they discharge to stated capacity and then apply storage charge. The cells are effectively top balanced as they leave the factory.

I have capacity tested LifeTech, Winston, CALB, GBS, and Sinopoly as part of various builds, all cells were top balanced ex-factory. All had more than rated capacity.

Packs that i have rebuilt from older cells that were at different SOC’s i used to individually charge, now i add active balancing and balance in-situ.

I haven’t been in contact with EVE, i can’t see any reason they would fully discharge a cell though.

Perhaps the 272Ah cells are ones that hit LVD during the manufacturing process and were originally supposed to be 280Ah?

You would have to contact EVE or Lishen directly for their process.

The EVE and Lishen cells we are getting here are not arriving with any form of balance. I've personally witnessed that. We're not buying from the factory, we're buying via Alibaba - so all bets are off.
 
The EVE and Lishen cells we are getting here are not arriving with any form of balance. I've personally witnessed that. We're not buying from the factory, we're buying via Alibaba - so all bets are off.


Exactly, so the folks who are quoting their experience with expensive factory direct cells, or with batched/matched cells as typicaly, are either being intentionally obtuse, or just downright malicious.

There is more than one way to top balance, and for those skilled/experienced its a non issue. These other methods are good, but they probably require an extensive writeup for the masses.

I would be curious what one of the US based sellers of BMS (Overkill etc) has to say about balancing issues. How many of their sales require after sales support for top balancing?
 
I would be curious what one of the US based sellers of BMS (Overkill etc) has to say about balancing issues. How many of their sales require after sales support for top balancing?

Section 2.3 of The Overkill manual discusses top balancing. 1 1/2 pages worth. Here's an excerpt

Before the battery pack is assembled, lithium battery cells must be top-balanced, if the factory or vendor did not do so before shipment [1] . This is an essential step, and should never be skipped. If you have been told differently, or don’t believe us, please read Appendix C, where we explain why.
 
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