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70 Posts
Discussion Starter · #1 ·
My truck has been acting weirdly. Voltage sagging way
more than it should. Usualy the voltage would return
almsot instantly when letting off the accelerator, but
last night, with only about 15 amp-hours out of the
pack, I noticed it was taking 10s of seconds to
recover. This is not good... As soon as I got home, I
checked each voltage, but by that time the pack
voltage had returned pretty much to normal. I fixed
my heater (bad ground on the relay that controls the
contactor to the heater), turned on headlamps, power
steering, fan full blast, and heater on high, and
while drawing about 15 amps off the pack, checked
voltages again, but still all pretty close to each
other. Darn... so I bumped up the voltage a bit on
the PFC-30 and started charging, planning on wattering
after a full charge. Near the end of charge, I was
inspired to check voltages again, and most were at
about 8.1V (a bit high), 6 batteries, interestingly
enough, all in the same battery box, and they were the
dirtiest of them all (maybe significantly higher
leakage currents discharging them? Hard to imagine it
could be significant...) were reading more like 7.5V.
So I'm goiing to try to indiviually charge these 6
T125s.

I've got a 7.5V, 70A adjustable voltage/current power
supply, that I think goes up a bit higher in voltage.
If so, I'll equalize each of those 6 batteries
individually. If not, I've got some other options,
like a 50V 20A sorensen power supply. Another option
might be, bring down the entire pack, use the 7.5V
power supply to bring up these 6 batteries as much as
possible, then charge the entire pack.

I was not able to find much in the way of technical
information on the Trojan web site. What little I did
find was a chart that says to equalize at 7.8V per 6V
battery, adding 0.028 volts per cell for every 10 deg.
F below 80 deg. F (It was about 70 deg. F last night).
So I plan on charging at about 7.9V (assuming it's 70
degs again) until the current tapers to about 4 amps
so so. Is this the correct way to do it? I imagine
it would be "best" to keep charging until the specific
gravity of each cell is the same, but for some reason,
I'm not very good at getting consistant results from
my (temperature compensated) refractometer. I'll try
taking readings, at least before, middle and after,
but I can't really count on being able to do this
often enough. Someday I'd like to try rigging a
digital camera, or small b&w video camera to this
thing, so I don't have to squint as much, and
hopefully can get more consistant readings.

Does the above sound good? Any other suggestions?

Thanks for your time,

Steven Ciciora




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Discussion Starter · #3 ·
Sounds like along the lines of what I was thinking.
To help bring up the low ones, I think you can, before
your next full charge of the pack, use your 6V charger
on the low ones, then charge the pack as a whole.

I would be very interested in seeing your serial data
from the pac-traker, even if it's raw data. I myself
built a serial data logger for my e-meter, that logs
_everything_ to a secure digital data card. Someday
(sigh...) I need to find some time to modify the
software to only record interesting data (not data of
the car just sitting there), and to figure out an
easier way to set the clock on the arm processor.

- Steven Ciciora

--- Deanne Mott <[email protected]> wrote:

> I don't know if this is the right thing to do or
> not, but it's what I
> did and I was able to improve the performance of my
> pack.
>
> I have T-125's too, and let them get out of balance.
> At the
> suggestion of a local EV'er, I measured the voltage
> of all the
> batteries, while they were charging, at the end of
> the charge cycle.
> I had voltages ranging from 7.0V to about 7.6V. I
> took my Soneil
> 604CC 6V charger to the worst 4, the ones that were
> less than 7.3V
> (since the Soneil documentation said it charges up
> to 7.3V.) I left
> the Soneil's on for a long time, at least 12 hrs
> each battery. None of
> them ever got above 7.1V with the Soneil on them so
> I was a bit
> disappointed.
>
> However, while I know these batteries are not back
> up to snuff, the
> pack as a whole is alot better. My range,
> acceleration, and sagging is
> almost what I used to have months ago. I installed
> a Paktrakr this
> weekend and once I get the serial link working I'll
> have lots of data
> to decide if I need to replace a few batteries or
> not.
>
> On 8/29/07, Steven Ciciora
> <[email protected]> wrote:
> > My truck has been acting weirdly. Voltage sagging
> way
> > more than it should.
> >
> > Does the above sound good? Any other suggestions?
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>



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Discussion Starter · #4 ·
Hello Steven,

Could be several things, the first one is the defusing time that the battery
takes to recover the acid deep inside the negative plates after you quickly
pull the surface charge off the grids.

When a pb acid battery is new, the grid paste is more tighter and it takes
time for the acid to go deep inside the plates and remove while charging,
that is why we recommended a 100 cycle break in period to open up more
passage ways, so the plates now have more surface area, thus more AH
capacity.

If you discharge at a high rate of ampere at first, you could blow a lot of
the surface off the batteries at this time.

Now as these negative plates age more, there may be some sulfate the block
or covers some of the plate area of these plates. What happens when you do
a quick charge, you may do only a surface charge on the battery and not deep
enough charge, so when you discharge, you are removing the surface charge
and it taking more time for the batter to defuse or releasing the acid from
deep into the plates.

One time I tested this out with a new set of 90 each 2-volt cobalt 300 AH
cells. To see how far I could drive the car, which was estimated to be 78
miles, I drove around a loop around the city until I was starting to slow
too much, so I let it coast to a stop about 1500 feet from my home.

I let the batteries set at rest for about 15 minutes, to allow for the
batteries to defuse the acid deep inside the grids to the surface of the
grids. I was able to drive the rest of the way home.

Another cause of a battery not recovering, might be cause by a highly
conductive battery top surface that may be shunting some of the current
across that battery. Take a voltmeter and put one lead on one post and the
other on the battery top next to that post and then slide that lead across
the battery and will should see a voltage that is on the surface of the
battery.

First clean the batteries and do a very slow equalization charge after you
do a normal charge. The equalization charge ampere may have to be as low as
2 to 4 amps for about 2 weeks!

There could be sulfate build up in the bottom of the cell which may be
touching or covering the grids. Sometimes you can clear these faults by
applying a vibration to the battery and do a long slow charge.

A long time ago, I met a battery maintenance man, who job was to go and
shake or vibrate the batteries. This method also mixes the electrolyte on
the bottom of the battery that has a high SG than on top, because H2SO4 is
heavier then H2O, making the top SG reading lower than it is at the bottom.

My roads are very rough, so my batteries have plenty of shaking.

I have seen stationary batteries with its grid all eaten out on the bottom
surface of the plates because of the higher SG at the bottom. Also I have
seen the tops portion of the battery grids completely missing all of its
pasting compound, which is cause by high discharge of this surface that is
closer to the top inter ties.

A good battery will have grid ties at the bottom and at the top and a plate
design with less lead on top and more at the bottom to prevent this unequal
charging or discharging.

Roland




----- Original Message -----
From: "Steven Ciciora" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Wednesday, August 29, 2007 7:12 AM
Subject: [EVDL] How to equalize charge Trojan T-125s?


> My truck has been acting weirdly. Voltage sagging way
> more than it should. Usualy the voltage would return
> almsot instantly when letting off the accelerator, but
> last night, with only about 15 amp-hours out of the
> pack, I noticed it was taking 10s of seconds to
> recover. This is not good... As soon as I got home, I
> checked each voltage, but by that time the pack
> voltage had returned pretty much to normal. I fixed
> my heater (bad ground on the relay that controls the
> contactor to the heater), turned on headlamps, power
> steering, fan full blast, and heater on high, and
> while drawing about 15 amps off the pack, checked
> voltages again, but still all pretty close to each
> other. Darn... so I bumped up the voltage a bit on
> the PFC-30 and started charging, planning on wattering
> after a full charge. Near the end of charge, I was
> inspired to check voltages again, and most were at
> about 8.1V (a bit high), 6 batteries, interestingly
> enough, all in the same battery box, and they were the
> dirtiest of them all (maybe significantly higher
> leakage currents discharging them? Hard to imagine it
> could be significant...) were reading more like 7.5V.
> So I'm goiing to try to indiviually charge these 6
> T125s.
>
> I've got a 7.5V, 70A adjustable voltage/current power
> supply, that I think goes up a bit higher in voltage.
> If so, I'll equalize each of those 6 batteries
> individually. If not, I've got some other options,
> like a 50V 20A sorensen power supply. Another option
> might be, bring down the entire pack, use the 7.5V
> power supply to bring up these 6 batteries as much as
> possible, then charge the entire pack.
>
> I was not able to find much in the way of technical
> information on the Trojan web site. What little I did
> find was a chart that says to equalize at 7.8V per 6V
> battery, adding 0.028 volts per cell for every 10 deg.
> F below 80 deg. F (It was about 70 deg. F last night).
> So I plan on charging at about 7.9V (assuming it's 70
> degs again) until the current tapers to about 4 amps
> so so. Is this the correct way to do it? I imagine
> it would be "best" to keep charging until the specific
> gravity of each cell is the same, but for some reason,
> I'm not very good at getting consistant results from
> my (temperature compensated) refractometer. I'll try
> taking readings, at least before, middle and after,
> but I can't really count on being able to do this
> often enough. Someday I'd like to try rigging a
> digital camera, or small b&w video camera to this
> thing, so I don't have to squint as much, and
> hopefully can get more consistant readings.
>
> Does the above sound good? Any other suggestions?
>
> Thanks for your time,
>
> Steven Ciciora
>
>
>
>
> ____________________________________________________________________________________Ready
> for the edge of your seat?
> Check out tonight's top picks on Yahoo! TV.
> http://tv.yahoo.com/
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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70 Posts
Discussion Starter · #6 ·
Hi Steven, Deanne and all,

Be careful when charging lower batteries first, before charging the rest of
the pack. I've done it with my Orbitals in the past -- granted they are
sealed batteries -- but if the suspect batteries are essentially fully
charged and then you charge the whole pack, you can cook the questionable
ones while the rest of the pack slowly comes up. I usually play a balancing
act of trying to partially charge the questionable ones first, and then
charge them as a whole. It allows me to use a higher 35 Amp charge at the
beginning with one battery at a time, then I can rely on the regulators (or
gassing in your case with floodies) during the finishing stage.

On the subject of the PakTrakr, I've been working on an application to
analyze this serial battery data. One feature is the straightforward
presentation of battery voltages in either a strip chart or bar chart. But
the more interesting thing to me is to plot an individual battery's voltage
versus the current in order to generate a polarization curve. By using a
best fit to determine the slope of this curve you can get a very good
indication of the relative health of each battery in your pack. You can see
two screen shots at:

http://www.jouleinjected.com/PakTrakr_Bar.jpg

and

http://www.jouleinjected.com/PakTrakr_Strip.jpg

Steven, if you want to see the data from the PakTrakr, which also includes
the current from the optional sensor, I can send you a CSV file.

Matt

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Steven Ciciora
Sent: Wednesday, August 29, 2007 10:07 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] How to equalize charge Trojan T-125s?

Sounds like along the lines of what I was thinking.
To help bring up the low ones, I think you can, before
your next full charge of the pack, use your 6V charger
on the low ones, then charge the pack as a whole.

I would be very interested in seeing your serial data
from the pac-traker, even if it's raw data. I myself
built a serial data logger for my e-meter, that logs
_everything_ to a secure digital data card. Someday
(sigh...) I need to find some time to modify the
software to only record interesting data (not data of
the car just sitting there), and to figure out an
easier way to set the clock on the arm processor.

- Steven Ciciora

--- Deanne Mott <[email protected]> wrote:

> I don't know if this is the right thing to do or
> not, but it's what I
> did and I was able to improve the performance of my
> pack.
>
> I have T-125's too, and let them get out of balance.
> At the
> suggestion of a local EV'er, I measured the voltage
> of all the
> batteries, while they were charging, at the end of
> the charge cycle.
> I had voltages ranging from 7.0V to about 7.6V. I
> took my Soneil
> 604CC 6V charger to the worst 4, the ones that were
> less than 7.3V
> (since the Soneil documentation said it charges up
> to 7.3V.) I left
> the Soneil's on for a long time, at least 12 hrs
> each battery. None of
> them ever got above 7.1V with the Soneil on them so
> I was a bit
> disappointed.
>
> However, while I know these batteries are not back
> up to snuff, the
> pack as a whole is alot better. My range,
> acceleration, and sagging is
> almost what I used to have months ago. I installed
> a Paktrakr this
> weekend and once I get the serial link working I'll
> have lots of data
> to decide if I need to replace a few batteries or
> not.
>
> On 8/29/07, Steven Ciciora
> <[email protected]> wrote:
> > My truck has been acting weirdly. Voltage sagging
> way
> > more than it should.
> >
> > Does the above sound good? Any other suggestions?
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>




____________________________________________________________________________
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http://autos.yahoo.com/green_center/

_______________________________________________
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70 Posts
Discussion Starter · #11 ·
Steven Ciciora wrote:

> My truck has been acting weirdly. Voltage sagging way
> more than it should.
[...]
> while drawing about 15 amps off the pack, checked
> voltages again, but still all pretty close to each
> other.

I think you may need to monitor the module voltages while under more
significant load to find the suspect modules/cells. Unless you've got
something homebrewed, the PakTrakr is a readily available,
reasonably-priced plug and play system that will do the job. It's main
limitations are the 0.1V resolution (a bit low for 12V modules, but not
too bad for your 6Vers), and that even when equipped with the optional
current sensor it does not track Ah (so don't get rid of your E-meter
yet! ;^).

> Near the end of charge, I was
> inspired to check voltages again, and most were at
> about 8.1V (a bit high),

8.1V = 2.7V/cell this is a normal finish voltage. What current were you
running into the pack at this point?

> 6 batteries, interestingly enough, all in the same
> battery box, [...] were reading more like 7.5V.

7.5V = 2.5V/cell, a bit low for a finish voltage.

Could this box of batteries be at a different temp than the others? If
there were a bad cell that heated significantly during driving and
warmed its neighbours, or if this box is under the hood and subject to
different cooling/heating than the batteries in back of the truck you
might see voltage and/or behaviour differences.

> So I'm goiing to try to indiviually charge these 6
> T125s.
>
> I've got a 7.5V, 70A adjustable voltage/current power
> supply, that I think goes up a bit higher in voltage.
> If so, I'll equalize each of those 6 batteries
> individually. If not, I've got some other options,
> like a 50V 20A sorensen power supply.

You've got a PFCxx charger, fer Pete's sakes! You could just wind the
voltage down to that for a 36V pack and charge this box individually
after charging the entire string.

I would not charge these six individually and then charge the entire
string, as that will significantly overcharge these six and possibly
undercharge the rest.

My suggestion is to charge normally, then set your PFCxx for 5-10A and
perhaps 2.8V/cell (or just wind the voltage up nearer 3V/cell so it
doesn't limit) and let the entire pack continue charging for another
couple of hours. Ideally, you want to keep checking the pack voltage
(better still, check each module voltage) at 30min or 60min intervals
and keep charging until the voltages remain essentially steady over 2-3
consecutive observations.

> I imagine it would be "best" to keep charging until
> the specific gravity of each cell is the same,

In a perfect world, perhaps, but in the real world you aren't ever going
to get every cell in your pack to exactly the same SG. If you wanted to
charge based on SG, what you want to do is continue charging until the
SG quite rising; that is, each cell has charged as fully as it is going
to. Problem is that SG lags voltage during charge, so you might be able
to use this approach for the equalise, but it would be difficult to use
as a means of terminating the normal charge cycle.

> but for some reason, I'm not very good at getting
> consistant results from my (temperature compensated)
> refractometer.

What device are you using? Unless the SGs really are still changing
(i.e. the batteries are on charge), you should be getting consistent
results from one observation to the next. Consistency of the readings
is one of the reasons I much prefer my refractometers over either float
or bulb type hydrometers.

Something to bear in mind is that some of the temperature compensated
refractometers assume that the electrolyte sample is at the same temp as
the refractometer; they don't actually measure the sample temp. If the
sample is small and you allow time for it to warm/cool to the
refractometer temp, and the refractometer is already about the temp of
the electrolyte, then it works pretty well. If you bring the
refractometer outside from an airconditioned or otherwise cool ambient
and start measuring warm electrolyte (or vice versa) you could get
varying readings as the refractometer and electrolyte temperatures get
nearer. I try to keep the refractometer near the batteries so that
their temps are as similar as possible when I start taking readings.

Cheers,

Roger.

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Discussion Starter · #12 ·
Hey Roger, thanks for commenting! I was hoping you
would, being a charger-algorithm-developer :)

<snip>
> I think you may need to monitor the module voltages
> while under more
> significant load to find the suspect modules/cells.
> Unless you've got
> something homebrewed,

<snip>

If only I had a little more time, to finish some of
the many projects I've started...
<snip>

> > Near the end of charge, I was
> > inspired to check voltages again, and most were at
> > about 8.1V (a bit high),
>
> 8.1V = 2.7V/cell this is a normal finish voltage.
> What current were you
> running into the pack at this point?

Really? Going off what little I could find on the
Trojan web site

http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/Charging.aspx

they say equalize at 7.8V, increasing 0.028 volts per
cell for every 10 dg. F decrease below 80 deg. F.
Maybe I've been undercharging? Do you know of any
more technical info on the Trojan web site?

I think the current was around 10A and 5A the two
times I measured 8.1-ish... if I remember correctly,
most of the batteries under the hood were in the range
of 8.17 and 8.18V... The ones under the bed were
closer to 8.1, so that's why I rounded to just saying
8.1V.

>
> > 6 batteries, interestingly enough, all in the same
> > battery box, [...] were reading more like 7.5V.
>
> 7.5V = 2.5V/cell, a bit low for a finish voltage.
>
> Could this box of batteries be at a different temp
> than the others?

Well, they are _all_ different temperatures, it's just
a matter of what's significant. 16 of them are under
the bed. There are 3 behind the rear axel, seven in
front of the rear axel (these 6 I'm refering to, and a
"spacer" battery, waiting for me to replace it. It
was D.O.A.), then about 8" for a cross member, and
then two groups of 3, 3 on each side of the drive
shaft. The ones in front of these 6 and behind these
6 are a lot closer to each other in voltage, and
similar to the 8 under the hood. If the strange
batteries were all under the hood, for example, then
I'd be more likely to believe it's a temperature
issue. But given the layout, I'm not so sure...

If
> there were a bad cell that heated significantly
> during driving and
> warmed its neighbours,

That's a good thought... but on occasion, I've felt
all the battery terminals (for hot ones), and never
noticed any difference. Doesn't mean there wasn't
one...

or if this box is under the
> hood and subject to
> different cooling/heating than the batteries in back
> of the truck you
> might see voltage and/or behaviour differences.
>
> > So I'm goiing to try to indiviually charge these 6
> > T125s.
> >
> > I've got a 7.5V, 70A adjustable voltage/current
> power
> > supply, that I think goes up a bit higher in
> voltage.
> > If so, I'll equalize each of those 6 batteries
> > individually. If not, I've got some other
> options,
> > like a 50V 20A sorensen power supply.
>
> You've got a PFCxx charger, fer Pete's sakes! You
> could just wind the
> voltage down to that for a 36V pack and charge this
> box individually
> after charging the entire string.

Ahh, but it's _such_ a pain to change the voltage, and
know what it's been changed to... I have a 10 turn pot
and a 10 turns counter just _waiting_ go to into the
PFC... then I can have a table taped to the charger
and I can just dial in the finish voltage I want.
Just like Bill Dube' has on his charger...

>
> I would not charge these six individually and then
> charge the entire
> string, as that will significantly overcharge these
> six and possibly
> undercharge the rest.

Yup, that's a risk, but I'm thinking it will do less
damage than the cronic under-charging I think I've
been doing, and it would be a one-time thing to get
them back in ballance.

>
> My suggestion is to charge normally, then set your
> PFCxx for 5-10A and
> perhaps 2.8V/cell (or just wind the voltage up
> nearer 3V/cell so it
> doesn't limit) and let the entire pack continue
> charging for another
> couple of hours. Ideally, you want to keep checking
> the pack voltage
> (better still, check each module voltage) at 30min
> or 60min intervals
> and keep charging until the voltages remain
> essentially steady over 2-3
> consecutive observations.

Very good suggestion. The reason why I was thinking
about charging seperatly, is these 6 are way out of
wack from the rest of the pack, and I'm not shure how
out of wack they are from each other. One at a time
can bring them all up to the same state.

>
> > I imagine it would be "best" to keep charging
> until
> > the specific gravity of each cell is the same,
>
> In a perfect world, perhaps, but in the real world
> you aren't ever going
> to get every cell in your pack to exactly the same
> SG. If you wanted to
> charge based on SG, what you want to do is continue
> charging until the
> SG quite rising; that is, each cell has charged as
> fully as it is going
> to. Problem is that SG lags voltage during charge,
> so you might be able
> to use this approach for the equalise, but it would
> be difficult to use
> as a means of terminating the normal charge cycle.
>
> > but for some reason, I'm not very good at getting
> > consistant results from my (temperature
> compensated)
> > refractometer.
>
> What device are you using?

I've not seen a lot of different types, so it might be
hard to describe. It's a $35 e-bay special, brand new
chinese copy of some of the more expensive ones I've
seen. It's a tube you look through, and see a
graiting indicating the sg. On the other end, there
is sort of a prisim looking slat where you place a
drop of acid, put the lid down so capilary action
holds it in place. Depending on the index of
refraction of the liquid, it changes the level of
"blue" you see on the graiting. The inconsistant part
is depending on exactly how I hold it (what angle I
look into it), where the blue is changes... Like I
said, a cheap copy of probably a nice instrument.

Unless the SGs really
> are still changing
> (i.e. the batteries are on charge), you should be
> getting consistent
> results from one observation to the next.
> Consistency of the readings
> is one of the reasons I much prefer my
> refractometers over either float
> or bulb type hydrometers.
>
> Something to bear in mind is that some of the
> temperature compensated
> refractometers assume that the electrolyte sample is
> at the same temp as
> the refractometer; they don't actually measure the
> sample temp. If the
> sample is small and you allow time for it to
> warm/cool to the
> refractometer temp, and the refractometer is already
> about the temp of
> the electrolyte, then it works pretty well. If you
> bring the
> refractometer outside from an airconditioned or
> otherwise cool ambient
> and start measuring warm electrolyte (or vice versa)
> you could get
> varying readings as the refractometer and
> electrolyte temperatures get
> nearer. I try to keep the refractometer near the
> batteries so that
> their temps are as similar as possible when I start
> taking readings.
>

You are exactly correct. It doesn't measure the
temperature of the sample, but only one drop will
quickly change it's temperature to match the
instrument pretty close. Inside I believe there is
some sort of bi-metalic lever that moves the grating,
to compensate for temperature.

Thanks everyone for the comments. I've been using
Trojan's recomendation of 7.6V for everyday charge as
golden, since I would think they would know their
battery. But my mind can be changed, if presented
with a good reason...

> Cheers,
>
> Roger.
>
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Discussion Starter · #13 ·
Steven Ciciora wrote:
> Sounds like along the lines of what I was thinking.
> To help bring up the low ones, I think you can, before
> your next full charge of the pack, use your 6V charger
> on the low ones, then charge the pack as a whole.
>
> I would be very interested in seeing your serial data
> from the pac-traker, even if it's raw data. I myself
> built a serial data logger for my e-meter, that logs
> _everything_ to a secure digital data card. Someday
> (sigh...) I need to find some time to modify the
> software to only record interesting data (not data of
> the car just sitting there), and to figure out an
> easier way to set the clock on the arm processor.

Please keep in mind that voltage is only an *indirect* indication of
state of charge. You can very easily have two batteries with the same
voltage but at very different states of charge!

For instance, when a battery is under load, its internal resistance has
a bigger effect on voltage than SOC. They could be the same
open-circuit, and several tenths of a volt different under load.

Or while charging, the voltage of batteries nearly fully charged is
considerably different depending on their temperature and age. One
battery might shoot up past 2.6v/cell, while another at exactly the same
state of charge is only 2.4v.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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