Have you noticed this?

I've noticed this before, and apparently USATracy had, too.

When you have a bunch of cells in a string, the ones nearest to the + lead wear out a little faster. You might have noticed that if you switch the batteries around in a dead remote, it starts working again.

USATracy noticed that on both of his XMs, the batteries conditions got worse the further along the string they were.

For me, the most recent and noticeable of this is my lithium battery pack. I've been charging up each cell one at a time with some Voltphreaks chargers. The ones nearest the - side of the string charged up way faster than those nearest the + side. Hours of difference.

It seems weird that they do this, since current has to go through the whole string, but it happens. What is the deal? :?

Almost. My new 8 amp LiPO4 charger has sixteen digital lights which come on at the completion of the charge cycle. These are indications the BMS is balancing the pack and the lights come on seemingly at random over a period of a minute or so. If the brightness of the bulbs is any indication then cells one and sixteen aren't as strong as the rest. A voltmeter however reads each cell the same.

Disconnecting the charger and reconnecting it starts the cycle again but since the batteries are charged it only takes the charger a moment to figure this out and it goes into the balancing act again. This time the lights go on quicker and the lights for one and sixteen are possbily brighter. Do it again and while the charger fan comes on but the charge light merely glows orange but the BMS will cycle with the same results.

Thus far, and I don't check often as it requires a bit of dissasembly of my battery cover, each cell is balanced when using a voltmeter to test them. The pack is about 8 months old, the charger only a couple. (Aten Energy 48 volt 20 AH)

Mike

mvadventure said:

Almost. My new 8 amp LiPO4 charger has sixteen digital lights which come on at the completion of the charge cycle. These are indications the BMS is balancing the pack and the lights come on seemingly at random over a period of a minute or so. If the brightness of the bulbs is any indication then cells one and sixteen aren't as strong as the rest. A voltmeter however reads each cell the same.
Mike

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Mike, assuming your DVM is accurate, there are a couple of factors that can influence your finding.
I'm not aware of your charger type, but I'll assume for this reply that it integrates a voltage clamp to shunt energy for each parallel cell group.

(1) The simplest and most common answer would be that the threshold knee voltage for the vclamps differ by a small amount. Meaning the activation voltage may differ between the sixteen vclamps by 5-10mv, and results in what appears to be a "weak cell". Careful calibration can resolve this problem.

(2) Depending on the wire gauge, the run length of wiring between the pack and charger /vclamp circuit, connectors etc, the resistance between the tapped cells and the clamp will vary. Also, with higher charge current there could be a considerable voltage offset if the clamp circuits for #1 and #16 are shared with the main power connectors. Effectively #16 would be overcharged and #1 would be undercharged, depending on the polarity. It gives the same result as in #1 above.

Taking either of these scenarios into account, I doubt you are suffering weak cells in a particular group. It is a charger/clamp design issue.

Regards, Jeff

I also noticed that on all my new DIY 3x 25V 23Ah packs.

The first and the last cell ( parallel group no 1 and 6) of each of the 3 pack seems differents. When i want to plus my hyperion 6s balancer on them to PERFECTLY balance them even though they dont need balancing, the first and last balancing led blinnk first.

Also, THAT'S the reason why i can get alot of makita 18V 3Ah deffective packs!! cause their problem is always the first or the last cell that is completly dead!!!.

The questions that come are:

-does cells like to be close together???

-does the cell tab that have the positive or negative drain their heat better than the cell in the middle because it flow thru the wire that is more massive than the strip between the cells?

-does these cells have a different temperature becasue theu are ofteh in the edge of the packs... ? I would say yes.. so they are sumbited to different conditions and their discharge rate is affected...

Doc

.

Different chemistry, but, with NIMH packs we have long noticed that the cells connected to the + and - power output wires are soldered rather than welded for their connection, and excessive heat possibly used to make the connection to the cell.
These end cells are very often the first or only problem with a bad NIMH pack.

Also noticed on some large NIMH packs, the interior cells go bad at a faster rate than the exterior cells -- posibly due to less surface area to disipate heat and more cells sending heat via contact area. Especially bad in packs that run hot for numerous reasons.
These packs seem to go unbalanced more easily especially with large square/cube 36v and 48v arrays. They like the poorman's NIMH balancing act... ~c/30 overnite after full charge. Keep the big packs ventilated when charging.

The Long stick arrays with just 2 rows of cells are the best for equal heat dissipation--- easiest to swap bad cells too.

Not many folks left dealing with NIMH repair. Soon the various LITH chemistries will be available for upgrades for most.

anyway, back to the thread topic.

d

Can't be heat/damage from soldering. Otherwise, how do you explain why it does it in TV remotes and the like? Or Tracy's scooters in which there are no soldered connections on the batteries?

Isn't it the way the cells are connected in parallel / series?
When cells are paralleled, does it matter where the power wires are positioned? Below, does the pack on the left discharges the cells and wears them out evenly than on the right?
And in connecting the parallel packs in series, each cell in the parallel pack are connected to each corresponding series cell - like the Killacycle battery pack below.

So wouldn't than mean that in a cluster of three the optimium wiring arrangment would be like this?

Yes, and yes, but that still doesn't explain how it happens in a 1p string. :?

At my niece's place in the States (SC) now til Sept. No kimchi for now.

Link: First everyone might mention the type of charger they are using. I'm using the Soneil (2 terminal type) and noticed the same effect on my LiFePo4 pack (12 series). First batteries near the + pole get up to 4.10V which goes down dramatically after the 4th-5th cell (3.65).

I thought I had a poor connection between two cells and troubleshot the h out of it, checking for ohms, then any V drop.

For my flintstone charger it has the individual line to each cell, so it doesn't do it.

Ahhh - barbeque pork, fried squash, fried okra :lol:

its been 15 years, but my professor gave us this as a problem for a project. Only it was resistors in series.

Take 10 resistors in series, and apply 10 volts through them. by Ohm's law, they should each drop 1 volt, but they don't. Not quite.

I have forgotten the answer as to why that works out, but I remember the key point was that we had to calculate up from each resistor individualy, and the measurements we took on it before we could understand what was happening.

I have never noticed this "USATracy effect" myself. (USAtracy being an uncannily similar character to "Safe" in this forum)

In the three Pb-acid packs I've used up so far, the batteries that fail first have been random with respect to their position in the string, but there is tendency for the batteries subjected to the most shaking (the rear battery box over the rear wheel in my case) to fail first.

Link,

The remote control effect you are experiencing is probably just your swapping the cells around caused the cells to make better contact - bad contact being the primary cause of the remote not working. Even if the cell in a certain position failed first, how would moving the low cell to a different position in the pack change the performance?

Link said:

When you have a bunch of cells in a string, the ones nearest to the + lead wear out a little faster

Click to expand...

I notice it all the time with my 36V (30-cell) 5AH NiMH packs. It bothers me and I have no viable explanation.
'Thermal Balancing' seems to negate this effect. But 'time will tell' on individual NiMH cell longevity.

I like my cheapo NiMH packs to stay "Toasty" and not ... "Frosty". (Oh the Hell I will pay for this statement).

.

Even if it is reestablishing contact, I've tested the voltages from a 4S string from a remote before. The +most ones showed slightly lower voltage than the -most ones.

I think DS may be on to something, though. If the cells nearest the negative side see more resistance, then they'll maybe won't discharge as fast? But current still has to flow through the whole string. Grah! What gives? :|

PJD said:

(USAtracy being an uncannily similar character to "Safe" in this forum)

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A tad arrogant, perhaps, but he actually did useful work.

"A tad arrogant, perhaps, but he actually did useful work."

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Yes, he eventually did provide some useful information on keeping those crappy XM 2000 scooters running - by sheer full-time effort - he clearly does not have to work for a living aside from an occasional call to his investment manger.

But he probably still can't as much as use Ohm's law...

LOL

PJD is right, I AM an arrogant fool who is clueless...

Byt the way, I have created a single cell BMS for TS cells that is working out great.

It sits on top of the cells and does not add to the height.

It can remove up to 10 amps but I limit it to 2 amps due to heat concerns but if your application is not sealed in tight it can do 10 amps.

It provides low and high cell protection (cuts off charger or bike) and turns charger back on when voltage is brought back into tolerance from the voltage clamp device.

I have two units testing on two cells, I have a proto unit for my bike underway so road testing will commence in a few weeks, I will be looking for things I know nothing about like interence to the circuitry from motor noise etc...

And I will also be evaluating how the circuits I designed and built actually function when placed in daily use, I expect the worst, I only leanred electronics in about 10 days from self taught methods, but so far, it has met and exceeded all my design goals.

It is infinitely expandable, you buy only for the cells you need, a single wire plugs them all in together in a chain which goes to a master control unit to interface to charger and controller for low and high voltage shut down.

It is truly infinite because even if you reach the limit for how many cells the MCU can monitor (I dont know how many that is yet, surely more than 50 but some weird thing called impedance will limit it but in that case, you just add another MCU and ties the MCU's together.

The entire unit is a PCB just slightly smaller than the top of the cells, and has a bushing soldered in the temrinal areas so you can torque the temrinals down on the board without risk of breaking it, of course, the board is powered by bolting it to the cell.

Necessity is the mother of invention, and sometimes it takes and idiot to invent the solution for the need, I just may be that idiot

PS PJD, you really should remove that unsubstantiated posting on this system where you claim Elite Power Solutions may be the source for counterfiet TS cells, since they are the international distributor for TS cells, and since you have NOTHING to back up your absurd assertion, it is really not a warranted attack. I know you have posted I am a thief, and Nova Scooters bikes are all crap, don't care about that, but I don't get this constant intent you have to attack baselessy the vendors of this (hobby?) (interest?) while also railing there aren't anough non-chinese connections for the industry.

I have also brought your posting up to EPS, who also posts on this system. I believe, by the way, that your entire basis on the subject of countefiet cells came from MY testing and reports of the counterfiet cells in my possession, and as such, have no idea where you came up with dragging EPS into this as I have NEVER stated WHERE the TS countefeit cells were source from, not publicly, at his been revealed to TS N and TS S and others in the industry in China, Taiwan, New Zealand, Australia, Germany, California and other countries that are involved in our network, but none of those communications are ever posted on the net or revealed to non-members, and I know you are not one, so not sure where you got the info the EPS is the source of the bad cells, assuming you even have a source for the posting to begin with.

But what do I know, I am and idiot and probably a shyster

When you have a bunch of cells in a string, the ones nearest to the + end of string wear out a little faster

This is absolutely positively TRUE.

I was convinced it was true, I let the experts convince me it was not true, then, after MANY MANY bikes moved and batteries tested, I am convinced it is true and I think I even have finally come up with the explanation for WHY it is true, and why it will NOT happen on a 48 volt bike but WILL happen on a 60 volt

And I am keeping it to myself until I can get some expert opinion on what I have seen and what I think is the cause, I DO believe that roatating the batteries will eleviate the problem, but that is a pain in the ass, would have to be done probably every 30 days to get any gain, and you are better off just going to lithium at this point in time. It is cheaper in the long run IF you have a BMS solution.

I may, but not yet available.

I am NOT finding this issue to be catastrophic, meaning, if you have quality batteries that have EQ in place and are operated properly, they are not as effected by this as lower quality batteries pr those with no EQ. We have NOT seen this breakdown on new fresh GreenSaver SP27-12 bats, we HAVE seen it on other lower qaulity silicone and sealed lead acid.


I will say this, we have fielded SEVERAL 60 volt bikes that have EQ and are being operated PERFECTLY and cycled DAILY, in the ones that have experienced an early onset range problem it has ALWAYS been one battery and it is bat 5 the pos end of string.

We have fielded a few 48 volt bikes, exactly the same bike but 48 instead of 60, they do not have this issue.

usatracy said:

When you have a bunch of cells in a string, the ones nearest to the + end of string wear out a little faster
This is absolutely positively TRUE.
I was convinced it was true, I let the experts convince me it was not true, then, after MANY MANY bikes moved and batteries tested, I am convinced it is true...

Click to expand...

Many others here have observed this and do think it's true (just read this thread), but have just not done any real scientific testing to prove what the real cause(s) are. As many here have said, the two obvious culprits are:
BMS using shared wires with the battery (meaning that most BMS's use at least one battery power lead for voltage sensing - bad);
Depending on battery design, the end cells may be at a different temperature than the rest of the cells (which changes the operation voltage of the cells quite a lot - colder cells have a lower nominal voltage than hotter cells).

...and I think I even have finally come up with the explanation for WHY it is true, and why it will NOT happen on a 48 volt bike but WILL happen on a 60 volt

Click to expand...

This is a forum, so why don't you share this idea with the community if you really have found the real problem? No use in just hinting at it repeatedly without really saying anything in the end...

And I am keeping it to myself until I can get some expert opinion on what I have seen and what I think is the cause, I DO believe that roatating the batteries will eleviate the problem, but that is a pain in the ass, would have to be done probably every 30 days to get any gain, and you are better off just going to lithium at this point in time. It is cheaper in the long run IF you have a BMS solution.
I may, but not yet available.

Click to expand...

Obviously rotating the cells regularly would fix the problem, but then you are just changing which cell is receiving the damage, so instead of just one pooping out ahead of the others, they'll all poop out together a little before they usually would if they weren't being damaged part time.
However, I don't understand the rest of your statement here; You seem to be saying that lithiums with BMS's never have this problem? That doesn't fit with other's observations here... but maybe I'm reading you wrong here.

I am NOT finding this issue to be catastrophic, meaning, if you have quality batteries that have EQ in place and are operated properly, they are not as effected by this as lower quality batteries pr those with no EQ. We have NOT seen this breakdown on new fresh GreenSaver SP27-12 bats, we HAVE seen it on other lower qaulity silicone and sealed lead acid.
I will say this, we have fielded SEVERAL 60 volt bikes that have EQ and are being operated PERFECTLY and cycled DAILY, in the ones that have experienced an early onset range problem it has ALWAYS been one battery and it is bat 5 the pos end of string.
We have fielded a few 48 volt bikes, exactly the same bike but 48 instead of 60, they do not have this issue.

Click to expand...

OK, ok, what's the secret already? You must be a fisherman to like dangling info like this without getting to the point... Even if you are not sure about your conclusions, just post them anyways as others have done with their musings in this thread. There are many knowledgeable people here that could give you feedback on your theory.

And I will also be evaluating how the circuits I designed and built actually function when placed in daily use, I expect the worst, I only leanred electronics in about 10 days from self taught methods, but so far, it has met and exceeded all my design goals.

Click to expand...

WOW! I thought it took more than 10 days to learn electronics AND micro-controller programming! You must have a brain the size of a watermellon paked with Einstein-like gray matter! Or maybe I'm just reallllllll slow? :lol:


Cheers!
Pat

For the amount of juice a remote needs it is usually the warming of the batts that makes the difference. Sitting on a remote for a few moments has the same effect without removing batteries (results of experiments conducted in my youth)

Doctorbass said:

I also noticed that on all my new DIY 3x 25V 23Ah packs.

The first and the last cell ( parallel group no 1 and 6) of each of the 3 pack seems differents. When i want to plus my hyperion 6s balancer on them to PERFECTLY balance them even though they dont need balancing, the first and last balancing led blinnk first.

Also, THAT'S the reason why i can get alot of makita 18V 3Ah deffective packs!! cause their problem is always the first or the last cell that is completly dead!!!.

The questions that come are:

-does cells like to be close together???

-does the cell tab that have the positive or negative drain their heat better than the cell in the middle because it flow thru the wire that is more massive than the strip between the cells?

-does these cells have a different temperature becasue theu are ofteh in the edge of the packs... ? I would say yes.. so they are sumbited to different conditions and their discharge rate is affected...

Doc

Click to expand...

Hi,

The Milwaukee packs (very similar chemistry don't have this problem).

Some possible reasons:
Wired differently.

No BMS for charging (even though the Konions self-balance they might do better if individually charged to something like 3.8).

Maybe the discharge rate should be limited to something like 4c or 5c.