Top Balancing "How to"

Gazoo

Dumb Dumb
So it sounds like you don’t know of any reason repeated top-off cycles to 3.65V are anything to be worried about
I am trying to understand why anyone would want to. Is it because of the BMS balancing at the top? As you know most everyone uses there cells between the knees so why use repeated top off cycles? I admit I wandered into this thread and haven't read everything.

There has been a graph posted that shows capacity loss in relation to SOC over a period of time. Even if the cell is fully charged and then settles to it's resting voltage, it is still considered to have a full SOC.
 

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Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Well, you can't count cell voltage to pack voltage simply. Your battery assembly is an aggregate of the combined cells within. To say I will charge my battery to 3.65 per cell (29.2 for 8S for example) and actually get all these cells to 3.65 is dreaming. There will always be a cell what will force HVD. Unless you had expensive Matched, Batched & Binned Winstons or Calbs or "new" EV cells (not what is bought on eli* ebay/amazon etc).

Just happens that I finished topping off Cell-4 yesterday morning, let it sit an hour and then put it in parallel with the other 3 topped cells. Applied charge for 4 hours to the set, of which 2.5 hrs was just sitting at 1.9A. Just checked right now, settled to 3.55V, which is exactly where the cells settled into independently.

With regards to my "Topping" the cells in this manner. It's partly because I am testing / evaluating these particular cells and for my own curiosity before I put the actual pack into service. An opportunity, you might say.

There is really No Point taking these cells to 3.65 on a regular basis, 3.55 is what they settle to. 3.450 +/-.050 to 3.100 +/- is where the power is.

EDIT:
I thought I should add, that while this is difficult to accomplish getting cells as full as possible with a single "battery", when you have multiple batteries in a battery bank, well it gets even more hard to manage. The "batteries" themselves, even if in perfect parallel will wander in the amount of voltage & amperage they will take in at any given moment, it all floats around a bit. So really you are having to work with a set of "Best Compromises" to maximize what you get.

If someone was selling the 272's or 280 packed up in "PreBuilt" packs as 12V/250AH or 24V/250AH with a semi-smart BMS that kept the cells within 3.45 & 3.00 for these prices, would anyone balk ?
 
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fafrd

Solar Addict
Well, you can't count cell voltage to pack voltage simply. Your battery assembly is an aggregate of the combined cells within. To say I will charge my battery to 3.65 per cell (29.2 for 8S for example) and actually get all these cells to 3.65 is dreaming. There will always be a cell what will force HVD. Unless you had expensive Matched, Batched & Binned Winstons or Calbs or "new" EV cells (not what is bought on eli* ebay/amazon etc).

Understand (which is why I was asking about floating only a single cell or parallel-connected set of cells).
Just happens that I finished topping off Cell-4 yesterday morning, let it sit an hour and then put it in parallel with the other 3 topped cells. Applied charge for 4 hours to the set, of which 2.5 hrs was just sitting at 1.9A. Just checked right now, settled to 3.55V, which is exactly where the cells settled into independently.

With regards to my "Topping" the cells in this manner. It's partly because I am testing / evaluating these particular cells and for my own curiosity before I put the actual pack into service. An opportunity, you might say.

There is really No Point taking these cells to 3.65 on a regular basis, 3.55 is what they settle to. 3.450 +/-.050 to 3.100 +/- is where the power is.
Yes, I am not planning to take my cells to 3.65V on a regular basis. Only while characterizing / testing cells (I’m in the same phase as you).

I was mostly asking because I wanted to be sure that ‘overcharging’ a cell by repeatedly tipping off to 3.65V will not cause damage or premature degradation/aging.

If I get my cells well-balanced, my 8S charger will cut-off when the cells reach 3.575V (28.6V for 8S).
EDIT:
I thought I should add, that while this is difficult to accomplish getting cells as full as possible with a single "battery", when you have multiple batteries in a battery bank, well it gets even more hard to manage. The "batteries" themselves, even if in perfect parallel will wander in the amount of voltage & amperage they will take in at any given moment, it all floats around a bit. So really you are having to work with a set of "Best Compromises" to maximize what you get.

If someone was selling the 272's or 280 packed up in "PreBuilt" packs as 12V/250AH or 24V/250AH with a semi-smart BMS that kept the cells within 3.45 & 3.00 for these prices, would anyone balk ?
Off-topic, but how do you access the EDIT function? I’ve bungled a few posts I wanted to edit but could not find any way to do so in this Forum...
 

HaldorEE

Photon Sorcerer
Understand (which is why I was asking about floating only a single cell or parallel-connected set of cells).

Yes, I am not planning to take my cells to 3.65V on a regular basis. Only while characterizing / testing cells (I’m in the same phase as you).

I was mostly asking because I wanted to be sure that ‘overcharging’ a cell by repeatedly tipping off to 3.65V will not cause damage or premature degradation/aging.

If I get my cells well-balanced, my 8S charger will cut-off when the cells reach 3.575V (28.6V for 8S).

Off-topic, but how do you access the EDIT function? I’ve bungled a few posts I wanted to edit but could not find any way to do so in this Forum...
Got to work fast. After about an hour, the edit function on a post is removed. I guess so we can't hide the evidence of our stupidity after we get called on it.
 

fafrd

Solar Addict
Got to work fast. After about an hour, the edit function on a post is removed. I guess so we can't hide the evidence of our stupidity after we get called on it.
Didn’t realize it disappeared after an hour (which may explain why it took me over a month to find it).

I’ve got a bunch of posts out there with stupid typos on them! Never proofread because I got spoiled on other Forums which make editing much easier...
 

HaldorEE

Photon Sorcerer
Didn’t realize it disappeared after an hour (which may explain why it took me over a month to find it).

I’ve got a bunch of posts out there with stupid typos on them! Never proofread because I got spoiled on other Forums which make editing much easier...
If you notice, almost 100% of my posts have been edited. I immediately go back and reread them. I don't know why typos only show up after I click the Post Reply button. I think it is the site software. Yah, that's my story.
 

carbon60

Solar Enthusiast
Is there a known-good bench power supply currently available to purchase? Seems like every time one is mentioned as being acceptable, it goes out of stock.

Also, is it worth investing in a capacity testing rig? I have 16 Lichen 272s on order, to build an 8S pack and an 4S2P pack for two different applications.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Yes, BUT there's a GOTCHA LOL.
If you buy from Amazon.CA CDN$ 484.30 & FREE Shipping
TekPower TP1540E DC Adjustable Switching Power Supply 15V 40A Digital Display: Amazon.ca: Electronics

If you buy from Amazon.COM $189.99
+ $51.44 Shipping & Import Fees Deposit to Canada Details IN USD
Amazon.com: TekPower TP1540E DC Adjustable Switching Power Supply 15V 40A Digital Display

I bought it from AMAZON USA for OBVIOUS reasons. Fricken Markup is Horse SH******************* and )*(&^E(*&^)(#*7_!@73-`907u
 

Just John

Photon Sorcerer
Yes, BUT there's a GOTCHA LOL.
If you buy from Amazon.CA CDN$ 484.30 & FREE Shipping
TekPower TP1540E DC Adjustable Switching Power Supply 15V 40A Digital Display: Amazon.ca: Electronics

If you buy from Amazon.COM $189.99
+ $51.44 Shipping & Import Fees Deposit to Canada Details IN USD
Amazon.com: TekPower TP1540E DC Adjustable Switching Power Supply 15V 40A Digital Display

I bought it from AMAZON USA for OBVIOUS reasons. Fricken Markup is Horse SH******************* and )*(&^E(*&^)(#*7_!@73-`907u
Wow, quite the difference. Crossing borders (even if they mostly exist as a line on a map) makes a big difference! Based on your experience (thank you, BTW) I purchased one myself (and only paid the $189.99 plus tax, which is about 9% here). It works well, and is better quality than I expected for the price and capacity. I would second your recommendation for the supply, but can't comment on the price due to location.

I do remember in the 1990s, we once shipped a nice Sun 21 inch monochrome monitor to our office in Toronto. No problems getting into Canada (the monitor is stamped "made in USA"). After six months use, they shipped it back, but it was held up in USA customs for nearly 9 months while lawyers and customs argued paying import duties. Go figure.

Working on some military contracts, it was a REALLY BIG DEAL when IBM changed their fulfillment site from US based to Ireland based. Ordering CDs with software releases means all sorts of hoops to jump through and months of delays because they didn't originate from inside the USA.

I won't go into the problems on military contracts when IBM moved support to China and Canada. Months of Chinese engineers asking us to please send them a copy of the database giving a problem. It was only tracking and data relay information for 800+ satellites operated by the US Air Force, sure, we'd be glad to send it to China (NOT).
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
I was an IT Core Engineer for DND / NATO before I retired. Still under 30 Year non-disclosure rules. BUT I know exactly what you are talking about and much more... a total freakshow circus and IBM is one company that should NOT be in business... the shyte I saw them pull to fluff contracts and push off deliverables and worse... non-disclosure, can't say more... but maybe before I kick the bucket I'll drop a few bombshells to the media. Let them try and persecute a corpse.
 

RyanNicholas

New Member
Hey everyone... I'm a beginner here, and I hope someone can help me. I'm trying to top balance these 4 cells using the method Will shows in the video. (didn't have 6 busbars, so I had to use these other big things..) But they've been connected like this for over 3 hours and the amperage has hardly gone down at all. Am I doing something wrong? Or can this take way longer than the 'few hours' the video says?

Also, I just checked each cell with my multimeter. They all started out at 3.28. Currently the one in front has 3.32, and the other three still read at 3.28. It doesn't seem like there's a lot of 'balancing' happening here. Can someone please help me understand this? 20210127_164719.jpg
 

MisterSandals

Participation Medalist
Your "bus bars" look fine. You need to charge from the ends of the cell groups: negative on cell 1, positive on cell 4.
This will help all cells get charged equally (its not perfect but works well).

If you start your own thread, we can help you with all your issues (opportunities?) in one place.
 

FilterGuy

What, me worry?
You are seeing voltage drops due to resistance across various connections. Be patient..... as the higher voltage cells reach full charge the current will go down and the voltage drops will go down. Eventually they will all be at the same voltage.

DO NOT try to raise the voltage at the power supply to compensate for the drops.
 
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Just John

Photon Sorcerer
Hey everyone... I'm a beginner here, and I hope someone can help me. I'm trying to top balance these 4 cells using the method Will shows in the video. (didn't have 6 busbars, so I had to use these other big things..) But they've been connected like this for over 3 hours and the amperage has hardly gone down at all. Am I doing something wrong? Or can this take way longer than the 'few hours' the video says?

Also, I just checked each cell with my multimeter. They all started out at 3.28. Currently the one in front has 3.32, and the other three still read at 3.28. It doesn't seem like there's a lot of 'balancing' happening here. Can someone please help me understand this? View attachment 34836
Looks like you have voltage set at 3.6 volts, and currently your supply is putting out 3.314 amps. You have 4 cells at 280 amp hours each, for a total (theoretical) capacity of 1,120 amp hours. Cells should be shipped between 20 and 50% state of charge, so being generous you should have over 500 amp hours to put into the cells. Ballpark guess, 150 hours. It could be a lot less, or it could be a lot more. I had two cells shipped to me that took all of 5 amp hours to get full, others were more like 200 amp hours. Please start a separate thread, there are lots of people to help, but first and foremost, BE PATIENT.
 

RyanNicholas

New Member
Looks like you have voltage set at 3.6 volts, and currently your supply is putting out 3.314 amps. You have 4 cells at 280 amp hours each, for a total (theoretical) capacity of 1,120 amp hours. Cells should be shipped between 20 and 50% state of charge, so being generous you should have over 500 amp hours to put into the cells. Ballpark guess, 150 hours. It could be a lot less, or it could be a lot more. I had two cells shipped to me that took all of 5 amp hours to get full, others were more like 200 amp hours. Please start a separate thread, there are lots of people to help, but first and foremost, BE PATIENT.
Oh wow, OK... Will's video pretty clearly suggested this would only take a few hours. I actually don't have 150 hours to spare - only a few days before I hit the road. Will the cells charge any faster individually?

I can start another thread also...
 

Dzl

Perpetual Newbie & Unofficial Forum Librarian
Staff member
Moderator
Oh wow, OK... Will's video pretty clearly suggested this would only take a few hours. I actually don't have 150 hours to spare - only a few days before I hit the road. Will the cells charge any faster individually?

I can start another thread also...
The only way to efficiently speed up the process that I am aware of is to rewire the cells in series (including hooking up your BMS) charging in series until the first cell hits the high voltage disconnect, then remove BMS, rewire in parallel, and complete the top balance as normal. There are explanations of it elsewhere that go into more detail (check out the link @FilterGuy posted above).
 

RyanNicholas

New Member
Your "bus bars" look fine. You need to charge from the ends of the cell groups: negative on cell 1, positive on cell 4.
This will help all cells get charged equally (its not perfect but works well).

If you start your own thread, we can help you with all your issues (opportunities?) in one place.
I'll copy my post to a new thread... But for the record I'm doing it the way Will shows in his video (+ and - on cell 1).
I actually decided it might be better to charge them individually, which I'm doing now...
 
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