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Discussion Starter #1
I recently got a new charger for the 26 batteries that power my 2002 Chevy
S-10.

I'm concerned that the installed charging curve is not appropriate for these
6v flooded lead acid batteries.

During charging, the pack voltage never goes beyond 180v.

This got my attention because USB recommends a build-up to 7.75v per batt,
which would finish out at 201.5v for all 26. Even if I were shooting for
7.5v per, that would end up as a total of 195v.

Unfortunately, the charger never makes it all the way through its cycle.
While the pack voltage stays at 180v, the batteries start to heat up.

Finally, after six hours or so, the center-most battery gets up to 120
degrees F, and the charger shuts down in error mode.

And if that's not strange enough, here's some additional info...

There are 3 stickers on the device, and all 3 say "144v". Only the rear
sticker has a piece of tape on it, where someone has written "156v".
Furthermore, the product itself came in a box that clearly said 144v.

So now I don't know if I have a 156v charger with the wrong profile, or a
144v device that has been improperly modified.

Or maybe there's some other explanation.

My pack is 2 years old. Somehow, I don't think it will survive much longer
if the individual batts are consistently undercharged and overheated.

Names of the manufacturer and dealer have not been mentioned because I want
to get my understanding straight before pressing forward on this issue.

Any insights you might have would be appreciated.


Steve Kobb
http://www.myelectrictruck.com
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Discussion Starter #2
Hello Steve,

Contact the dealer and say you sent me the wrong charger. It will not
charge a 156 volt pack batteries as per USB specifications to 7.75 volt per
battery at a battery temperature of 80F.

You won't be able to do any temperature compensation which would add 0.028
volts per cell for every 10 degrees drop of temperature below 80F.

Now if you charger is temperature compensated, then it should drop the
charger voltage 0.028 volts for every 10 degrees above 80F. The charger
should be in the same ambient temperature of the batteries it should have a
remote temperature sensor from the charger to the battery compartment.

It could be that the charger temperature compensation control is not
adjusted right or does not have one.

If you batteries get to 120 F during charging, that 120 -80 = 40. 40 / 10 =
4. 4 x 0.028 volts per cell = .112 volt drop per cell or .336 volts per
battery. The 7.75V charge at 80F now becomes 7.75-.336 = 7.414 volts.

The total pack charge now becomes 7.414 x 26 = 192.764 volts which is still
higher than your maximum 180 volt charger.

My average temperature of my batteries are at 70 F. which are in a 20
R-factor plus compartment which would require 7.75 + 0.028 = 7.83 volts or
26 x 7.83 = 203.58 volts for 26 batteries.

I am using a PFC-50B charger where I am charging 30 each USB 6 volt
batteries to 7.83 volts per battery at a battery temperature of 65 F. which
was setting for about a hour in ambient temperature of 5 below It only
takes about 4 minutes per mile to charge these batteries which will may
increase the battery temperature to 70 to 75 F degrees.

Roland


----- Original Message -----
From: "Steve Kobb" <[email protected]>
To: <[email protected]>
Sent: Sunday, December 05, 2010 8:40 AM
Subject: [EVDL] New charger: Wrong profile?


>
> I recently got a new charger for the 26 batteries that power my 2002 Chevy
> S-10.
>
> I'm concerned that the installed charging curve is not appropriate for
> these
> 6v flooded lead acid batteries.
>
> During charging, the pack voltage never goes beyond 180v.
>
> This got my attention because USB recommends a build-up to 7.75v per batt,
> which would finish out at 201.5v for all 26. Even if I were shooting for
> 7.5v per, that would end up as a total of 195v.
>
> Unfortunately, the charger never makes it all the way through its cycle.
> While the pack voltage stays at 180v, the batteries start to heat up.
>
> Finally, after six hours or so, the center-most battery gets up to 120
> degrees F, and the charger shuts down in error mode.
>
> And if that's not strange enough, here's some additional info...
>
> There are 3 stickers on the device, and all 3 say "144v". Only the rear
> sticker has a piece of tape on it, where someone has written "156v".
> Furthermore, the product itself came in a box that clearly said 144v.
>
> So now I don't know if I have a 156v charger with the wrong profile, or a
> 144v device that has been improperly modified.
>
> Or maybe there's some other explanation.
>
> My pack is 2 years old. Somehow, I don't think it will survive much longer
> if the individual batts are consistently undercharged and overheated.
>
> Names of the manufacturer and dealer have not been mentioned because I
> want
> to get my understanding straight before pressing forward on this issue.
>
> Any insights you might have would be appreciated.
>
>
> Steve Kobb
> http://www.myelectrictruck.com
> --
> View this message in context:
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/New-charger-Wrong-profile-tp3073401p3073401.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
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Discussion Starter #3
Some random thoughts.

1. The notion that you have a 144v nominal charger, not 156v, is not out of
line. Your finish voltage of 180v would make sense for a 144v pack.

2. However, for a 156v pack 180v close to float voltage, so I wouldn't
expect your batteries to heat up drastically at that voltage - certainly not
to 120 deg F.

3. What kind of charger is this? Is it a dumb boat anchor transformer and
rectifier charger, a regulated taper charger, microprocessor controlled 3-
stage, or ? (Your saying that it throws an error suggests the last.)

4. Measure the voltage across each battery in the pack when the charger has
been operating for several hours. What are the individual voltages?

5. Have you checked the specific gravity of the electrolyte in each cell?
What are the values? How much do they differ from cell to cell?

6. Is this an Elcon or Zivan charger? Is the dealer Electric Conversions?
Just curious.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Discussion Starter #4
>> Now if your charger is temperature compensated...

It is.


>> it should have a remote temperature sensor from the charger to the
>> battery compartment.

It does.


>> It could be that the charger temperature compensation control is not
>> adjusted right or does not have one.

That's an interesting idea. There is no way for me to adjust it, but it may
indeed be out of whack.


>> The total pack charge now becomes 7.414 x 26 = 192.764 volts which is
>> still higher than your maximum 180 volt charger.

Right. So even with temperature compensation, the achieved voltage peak is
still way too low.


Thanks, Roland. As per usual, your comments were very helpful.


Steve




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Discussion Starter #5
>>1. The notion that you have a 144v nominal charger, not 156v, is not out of
line. Your finish voltage of 180v would make sense for a 144v pack.


Thanks. That's a point of confirmation that I've wanted to get from someone
else.



>> 2. However, for a 156v pack 180v close to float voltage, so I wouldn't
expect your batteries to heat up drastically at that voltage - certainly not
to 120 deg F.


A few nights ago, I started charging late. When I checked the situation at
6AM, the charger was in error mode, and the center-most battery had cooled
DOWN to 115 degrees.

YIKES!



>> 3. What kind of charger is this?

microprocessor controlled 3- stage



>> 4. Measure the voltage across each battery in the pack when the charger
>> has
been operating for several hours. What are the individual voltages?

They vary between 6.83 and 7.1... with one exception: The 26th or most
negative battery. That one routinely goes way high -- 7.8v and up.

Yet, when the charger is turned off and everything settles down, it returns
to 6.3v.

Zener regs are on my to-do list for this problem child.

Which raises a question for me: Are the most negative batteries in a serial
pack usually higher than the rest of them in the string?

In other words, should I expect the most negative batt to be at least
somewhat higher?... or in a well-balanced pack, should the most negative be
no higher than any other battery?




>> 5. Have you checked the specific gravity of the electrolyte in each cell?
What are the values? How much do they differ from cell to cell?

Yes, I check SGs with a Misco Refractometer, and try to keep values in line
with the 1.275 recommendation.

Prior to charging, some cells are closer than others to that ideal, but none
of them are below 1.23.




>> 6. Is this an Elcon or Zivan charger? Is the dealer Electric
>> Conversions? Just curious.

I can understand your curiosity, and would like to answer your questions,
but I should probably keep a zipped lip at this point... if you know what I
mean.

Anyway, thanks for raising these points.


Steve
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Discussion Starter #6
Steve Kobb <[email protected]> wrote:

>
> I recently got a new charger for the 26 batteries that power my 2002 Chevy
> S-10.
>
> I'm concerned that the installed charging curve is not appropriate for
> these
> 6v flooded lead acid batteries.
>
> During charging, the pack voltage never goes beyond 180v.
>

I've recently noticed that my 6v floodies now require a lower charge voltage
in their old age. The voltage would not rise to the voltage set point and
the charger would keep pumping current into the pack in order to try to get
the voltage up. Previously, the pack would get to 183V and current would
drop in a matter of minutes down to 5 amps. Now, it'll never reach the
voltage set point and the current is maintained at 15 amps (and the
batteries would get very warm - fortunately there's a timer shutdown).

If your batteries are aging and you can measure the current into the pack,
you may be able to determine if your in a similar situation. If the current
is still high at end of the charge cycle (which I suspect is true since
they're getting warm), the charger is trying to get the voltage up, but the
batteries are just old. They'll require a lower voltage set point.

Joe
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Discussion Starter #7
Hello!
Did I read this all correct. You are concerned that your charge voltage is
to low but you are concerned because your battery temp is so high? The two
don't mix.

Sincerely,
Mark Grasser


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Steve Kobb
Sent: Sunday, December 05, 2010 6:57 PM
To: [email protected]
Subject: Re: [EVDL] New charger: Wrong profile?


>>1. The notion that you have a 144v nominal charger, not 156v, is not out
of
line. Your finish voltage of 180v would make sense for a 144v pack.


Thanks. That's a point of confirmation that I've wanted to get from someone
else.



>> 2. However, for a 156v pack 180v close to float voltage, so I wouldn't
expect your batteries to heat up drastically at that voltage - certainly not

to 120 deg F.


A few nights ago, I started charging late. When I checked the situation at
6AM, the charger was in error mode, and the center-most battery had cooled
DOWN to 115 degrees.

YIKES!



>> 3. What kind of charger is this?

microprocessor controlled 3- stage



>> 4. Measure the voltage across each battery in the pack when the charger
>> has
been operating for several hours. What are the individual voltages?

They vary between 6.83 and 7.1... with one exception: The 26th or most
negative battery. That one routinely goes way high -- 7.8v and up.

Yet, when the charger is turned off and everything settles down, it returns
to 6.3v.

Zener regs are on my to-do list for this problem child.

Which raises a question for me: Are the most negative batteries in a serial
pack usually higher than the rest of them in the string?

In other words, should I expect the most negative batt to be at least
somewhat higher?... or in a well-balanced pack, should the most negative be
no higher than any other battery?




>> 5. Have you checked the specific gravity of the electrolyte in each cell?

What are the values? How much do they differ from cell to cell?

Yes, I check SGs with a Misco Refractometer, and try to keep values in line
with the 1.275 recommendation.

Prior to charging, some cells are closer than others to that ideal, but none
of them are below 1.23.




>> 6. Is this an Elcon or Zivan charger? Is the dealer Electric
>> Conversions? Just curious.

I can understand your curiosity, and would like to answer your questions,
but I should probably keep a zipped lip at this point... if you know what I
mean.

Anyway, thanks for raising these points.


Steve
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Discussion Starter #8
165 to 166 volts resting for a fully charged pack for a 156 nominal voltage
pack. End resting voltage should be about 6.37 and an SG reading of about
1.27 at around 80 Degrees. So a resting voltage of 6.3 is not out of range
and sounds like your charger may be working properly after all.

Pete :)

-----
If you don't understand, be patient, you will. Now I understand. :)
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Discussion Starter #9
A little charger theory,

7.75 volts per 6 volt battery, translated to 12 volt battery term is 15.5
volts. You want to charge to his voltage every time you charge the
batteries? Kiss them good-by. This is an equalization charge. You should do
this once every three months, "maybe" an big MAYBE more often. An absorption
voltage, your daily charge voltage, would be more like 7.4 volts and I would
recommend 7.3. That would equate to 189.8 to 192 volts. Let's discuss how a
3 step charger works. During fast charge the charger will be at full current
while it increases the voltage of the bank up to the absorption voltage.
Let's say it is a 10 amp charger and you have removed 100 amps. This means
to make it to the 90% point it will take 10 hours. It is at this point it
will reach the absorption voltage. At this point a timer should start and
put the charger into a 4 hour absorption phase. This is theory, however
theory is not typically followed. Due to the fear of the charger not making
it to absorption voltage, due to a shorted cell etc, many manufacturers will
start the absorption timer early. I have seen timers that start at as low as
14.0 volts (i2 volt battery theory) this equates to 182 volts.

Once the charger reaches absorption voltage, should be 190 to 192 volts for
a 156 volt bank, it should stay there for about 4 hours, maybe more. At the
end of absorption, when the charge current drops to 2 to 3 amps, the charger
should go to float. On a 156 volt bank this should be 172 to 175.5 volts. It
should stay there until you switch off the charger to get in and use the
car.

What you need to do is put a volt meter on the pack and track the voltage
every 15 minutes to see what it does. Measuring the current is also a good
idea, this will tell you if it is completing the charge. A medium quality
clamp on would do fine for this.
Nothing short of this amount of data is even worth discussing. IMHO

Mark Grasser

PS. Note in your data when the LEDs change from Fast charge to Absorption
charge to Float charge, this will also tell you what the charger is doing vs
what the batteries are doing.



I recently got a new charger for the 26 batteries that power my 2002 Chevy
S-10.

I'm concerned that the installed charging curve is not appropriate for these
6v flooded lead acid batteries.

During charging, the pack voltage never goes beyond 180v.

This got my attention because USB recommends a build-up to 7.75v per batt,
which would finish out at 201.5v for all 26. Even if I were shooting for
7.5v per, that would end up as a total of 195v.

Unfortunately, the charger never makes it all the way through its cycle.
While the pack voltage stays at 180v, the batteries start to heat up.

Finally, after six hours or so, the center-most battery gets up to 120
degrees F, and the charger shuts down in error mode.

And if that's not strange enough, here's some additional info...

There are 3 stickers on the device, and all 3 say "144v". Only the rear
sticker has a piece of tape on it, where someone has written "156v".
Furthermore, the product itself came in a box that clearly said 144v.

So now I don't know if I have a 156v charger with the wrong profile, or a
144v device that has been improperly modified.

Or maybe there's some other explanation.

My pack is 2 years old. Somehow, I don't think it will survive much longer
if the individual batts are consistently undercharged and overheated.

Names of the manufacturer and dealer have not been mentioned because I want
to get my understanding straight before pressing forward on this issue.

Any insights you might have would be appreciated.


Steve Kobb
http://www.myelectrictruck.com
--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/New-charger-Wro
ng-profile-tp3073401p3073401.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

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Discussion Starter #10
It may be useful to read Lee Hart's battery charging basics :

http://www.evdl.org/pages/hartcharge.html

David Roden - Akron, Ohio, USA
EVDL Administrator

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Discussion Starter #11
I will just point out that while it is contrary to what most on the list recommend, the original poster is following the manufactures instructions.

Some say they make that recommendation so you have to replace your batteries more often, but I for one believe Nawez, a VP at US Battery that monitors the list and occasionally posts, when he says they recommend the high voltage charge every day for technical reasons.

Also note USB recommends charging at C/10. A few years ago there was a thread indicating damage could occur from never charging at high currents.

6,200 miles and counting.

John


"Mark Grasser" <[email protected]> wrote:
> want to charge to his voltage every time you charge the
> batteries? Kiss them good-by. This is an equalization charge. You should do
> this once every three months, "maybe" an big MAYBE more often.
>


> original poster
>
> This got my attention because USB recommends a build-up to 7.75v per batt,
> which would finish out at 201.5v for all 26. Even if I were shooting for
> 7.5v per, that would end up as a total of 195v.
>
>

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Discussion Starter #12
I believe some batteries are constructed slightly different than others
and besides it may be true that cool batteries at high current can
charge
to unbelievably high voltage.
When I take the two (17 year old!) Hawker SBS30 batteries that I still
use
for battery backup and put them on a 1-Amp unlimited voltage charge
then they will soon climb to 16V, if I maintain this voltage for a
little
while then the battery starts warming up and the voltage starts falling.
While I do not believe that batteries need to be charged so high every
day,
I recognise that charging at higher (C/10) current and "unlimited"
voltage
for a certain period towards the end of the charging can be beneficial
to cause some gassing (preferably NO venting on AGMs! That is why
current
must be reduced and time must be very limited for AGMs) which stirs up
any electrolyte that has stratified.
I also recognise the complaint that old (flooded) batteries have lower
charging voltage, so some charger profiles have trouble meeting their
pre-programmed thresholds.
Use an Ah counter such as Emeter to keep an eye on current in/out
and you have a pretty good idea when the charger should be about done.
No point in keeping the charger as a battery heater all night!

Regards,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of John
Sent: Monday, December 06, 2010 9:05 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] New charger: Wrong profile?

I will just point out that while it is contrary to what most on the list
recommend, the original poster is following the manufactures
instructions.

Some say they make that recommendation so you have to replace your
batteries more often, but I for one believe Nawez, a VP at US Battery
that monitors the list and occasionally posts, when he says they
recommend the high voltage charge every day for technical reasons.

Also note USB recommends charging at C/10. A few years ago there was a
thread indicating damage could occur from never charging at high
currents.

6,200 miles and counting.

John


On Dec 5, 2010, at 9:38 PM, "Mark Grasser" <[email protected]>
wrote:
> want to charge to his voltage every time you charge the batteries?
> Kiss them good-by. This is an equalization charge. You should do this
> once every three months, "maybe" an big MAYBE more often.
>


> original poster
>
> This got my attention because USB recommends a build-up to 7.75v per
> batt, which would finish out at 201.5v for all 26. Even if I were
> shooting for 7.5v per, that would end up as a total of 195v.
>
>

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Discussion Starter #13
)
From: Steve Kobb



>During charging, the pack voltage never goes beyond 180v

Is the charger still putting out amps at this point . Maybe the output
is no hi enough to push to batteries to there charged voltage and they
are sitting at this lower voltage and cooking . New batteries will
only need a few amps at the end of the charge to bring up there
voltage but old ones can take as much as 10 amp . Once they start
getting hot and in thermal runaway there voltage will even go down.


>This got my attention because USB recommends a build-up to 7.75v per batt,
which would finish out at 201.5v for all 26. Even if I were shooting for
7.5v per, that would end up as a total of 195v>

There are lots of factors here ,, If you have the amperage up high
enough you can get a batteries voltage up but that doesn't mean much ,
What the amperage is tells a big part of the story . Old batteries are
going to take more amperage to bring them up and the older the battery
the more of a chance of thermal runaway.

>Unfortunately, the charger never makes it all the way through its cycle.
While the pack voltage stays at 180v, the batteries start to heat up.
Finally, after six hours or so, the center-most battery gets up to 120
degrees F, and the charger shuts down in error mode.

And if that's not strange enough, here's some additional info..>>

This sounds good , dose the charger have a heat sensor , or maybe its
doing it by time ,,, What kind of ah are you able to pull form the
batteries ? Have they lost any capacity? Do you have a amp hour meter
?


>>There are 3 stickers on the device, and all 3 say "144v". Only the rear
sticker has a piece of tape on it, where someone has written "156v".
Furthermore, the product itself came in a box that clearly said 144v>>

180 v would be about right for 144v but as the charger is not going to
its end of charge cycle it may well be a 156v charger. .

>>>>My pack is 2 years old. Somehow, I don't think it will survive much lon=
ger
if the individual batts are consistently undercharged and overheated.>>>>>>

Under charging and overheating don't go together this kind of sounds
like slow cooking over charging you may be able to put a timer to
shut down the charge for now , then when you get your new batteries
the charger will work fine.as the new batteries will charge right . 2
years of use is about when things go wrong , this often happens after
there daily rue teen has changed like running them down to far. . I
would on the next charge watch the voltage and write it down every 15
min once it gets 2/3 charged . Keep track of amps and volts going in
,, At the point where volts stop going up after 1/2 hour unplug and
let the batteries cool for 4 hours then plug in again and see if you
get a higher Finnish charge voltage . Are you putting a lot of water
in them? Are all the batteries about the same voltage
Another thing you could do to see that the charger is working right is
to put 2 12v batteries in line after the pack is 2/3 charged and see
where the chargers cut off voltage is ,, and dose it cut back on the
amps .
We need more info on your set up to help .
Steve Clunn

v

--
Tomorrows Ride TODAY !
Visit our shop web page at: www.Greenshedconversions.com

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Discussion Starter #14
Steve Kobb wrote:

> I recently got a new charger for the 26 batteries that power
> my 2002 Chevy S-10.
>
> I'm concerned that the installed charging curve is not
> appropriate for these 6v flooded lead acid batteries.
>
> During charging, the pack voltage never goes beyond 180v.

[...]

> Finally, after six hours or so, the center-most battery gets
> up to 120 degrees F, and the charger shuts down in error mode.

If the batteries are getting hot at 180V, then you aren't going to be able to charge them to a higher voltage.

You say this is a new charger; what voltage did the original charger take these to before you swapped it out?

Did the old charger die and were the batteries left sitting for some time (possibly at a low state of charge) until the new charger arrived?

Is the new charger higher or lower current than the original?

180V on a 156V pack is 2.30-2.31V/cell, which is on the low side for an absorption voltage. One possibility is that your new charger is lower current than the original, and is unable to push your aging batteries up to the target voltage, so it just keeps charging at its full current until it finally faults out.

> Yes, I check SGs with a Misco Refractometer, and try to keep
> values in line with the 1.275 recommendation.

So, what are the SGs looking like after charging with this new charger?

Do you do anything besides charging to try to keep the SGs near 1.275 fully charged?

Cheers,

Roger.

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Discussion Starter #15
Mark Grasser wrote:

> Let's discuss how a 3 step charger works.

Bear in mind that "3-step charger" is largely a marketing term and the *only* thing you can infer from such a description is that the charger proceeds through 3 different steps on its way from start of charge to finish.

Exactly what each of those steps are and what logic the charger uses to determine when to switch from one to another will vary from charger to charger.

Cheers,

Roger.

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Discussion Starter #16
Roger,
That would be why I described the steps. As I think they should be.


Sincerely,
Mark Grasser


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Roger Stockton
Sent: Monday, December 06, 2010 1:03 PM
To: 'Electric Vehicle Discussion List'
Subject: Re: [EVDL] New charger: Wrong profile?

Mark Grasser wrote:

> Let's discuss how a 3 step charger works.

Bear in mind that "3-step charger" is largely a marketing term and the
*only* thing you can infer from such a description is that the charger
proceeds through 3 different steps on its way from start of charge to
finish.

Exactly what each of those steps are and what logic the charger uses to
determine when to switch from one to another will vary from charger to
charger.

Cheers,

Roger.

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Discussion Starter #17
Mark Grasser wrote:

> That would be why I described the steps. As I think they should be.

Understood. Someone reading your post might have misunderstood and assumed that all 3-stage chargers behave this way rather than that it is one person's opinion of what a 3-stage charger should do. Now they know ;^>

Cheers,

Roger.

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Discussion Starter #18
There is no need to provide a so called three stage charge profile for
flooded GC batteries with the third stage being a float stage.

In fact floating the batteries will decrease the battery life and is
highly not recommended. Float is for stationary, stand by battery power.

My opinion of three stage charging is:

1) First Stage is constant current until,
2) Second Stage takes over when the battery voltage rises to the preset
level and holds that voltage as the current continues to decrease, then
3) Third stage is a preset timed low constant current, sort of like the
first stage, but at a much lower current for, say, one hour, then shut
off.

This is typical of AGM battery charging requirements, such as Optima,
which require a three stage charge each time. Not so important or even
necessary with flooded batteries.

Russ Kaufmann

RUSSCO Engineering

http://russcoev.com

The Other PFC Charger.


> Roger,
> That would be why I described the steps. As I think they should be.
>
>
> Sincerely,
> Mark Grasser
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf
> Of Roger Stockton
> Sent: Monday, December 06, 2010 1:03 PM
> To: 'Electric Vehicle Discussion List'
> Subject: Re: [EVDL] New charger: Wrong profile?
>
> Mark Grasser wrote:
>
>> Let's discuss how a 3 step charger works.
>
> Bear in mind that "3-step charger" is largely a marketing term and the
> *only* thing you can infer from such a description is that the charger
> proceeds through 3 different steps on its way from start of charge to
> finish.
>
> Exactly what each of those steps are and what logic the charger uses to
> determine when to switch from one to another will vary from charger to
> charger.
>
> Cheers,
>
> Roger.
>
> _______________________________________________
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Discussion Starter #19
>> You say this is a new charger; what voltage did the original charger take
these to before you swapped it out?

I'm embarrassed to say that I didn't take a reading of the entire pack right
before I disconnected the previous charger and pulled it out of the truck.

However -- wow, I'm getting a serious flash of insight now -- the measured
output had declined to about 6 amps... and I attributed that decline to the
charger; i.e., I assumed that the batteries could take more but that this
particular charger was no longer up to the task.


>> Did the old charger die?

No. But again, it got some pretty heavy use, and formerly put out more -- 8
amps max, but that was with a newer pack.

>> and were the batteries left sitting for some time (possibly at a low
>> state of charge) until the new charger arrived?

No.

>> Is the new charger higher or lower current than the original?

The new charger is rated at 11 amps, but -- maybe older batteries don't draw
that much. I wish I had a clamp-on ammeter, but I don't.

The previous device never put out over 8.


>> 180V on a 156V pack is 2.30-2.31V/cell, which is on the low side for an
>> absorption voltage. One possibility is that your new charger is lower
>> current than the original, and is unable to push your aging batteries up
>> to the target voltage, so it just keeps charging at its full current
>> until it finally faults out.


Possibly, but the new charger is a beefier device (4KW vs. 3KW, I believe).
Still, the red light stays on, blinks towards the end, and never gets to
yellow or green.



>> So, what are the SGs looking like after charging with this new charger?

Just checked this evening, after having charged the pack this morning, and
without driving the truck since then.

Total pack voltage is 163.8. This is more than a little interesting,
because... it indicates that I don't have a problem. In fact, 163.8 divided
by 26 = 6.3; i.e., right on the money.

So maybe I shouldn't worry about the peak charging voltage?

Well, anyway, I picked two batteries to test -- and of these two, one has
often seemed weaker (A), and one stronger (B).

Surprisingly, though, they both had an open-circuit voltage of 6.31.

Here are the specific gravity measurements:
(A) 1.270 1.270 1.272
(B) 1.276 1.282 1.275

So, the SGs look OK... to me, at least.


>> Do you do anything besides charging to try to keep the SGs near 1.275
>> fully charged?

Yes, and I'm sure that someone will wag a finger at me, and tell me to stop
doing this immediately, but...

I went to an industrial supply house and bought a gallon of lab-grade
sulfuric acid.

Armed with some good glassware, heavy-duty gloves, and my trusty MISCO
refractometer, I've done two "chemical refreshment" sessions for balancing
purposes. Yes, I know that it takes both acid AND lead to pump electrons,
but I found that weak sgs could be improved in a controlled manner -- not
for all cells, but for some that obviously needed some help.
--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/New-charger-Wrong-profile-tp3073401p3075741.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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Discussion Starter #20
On 6 Dec 2010 at 19:36, Steve Kobb wrote:

> >> Do you do anything besides charging to try to keep the SGs near 1.275
> >> fully charged?
>
> I ... bought a gallon of lab-grade sulfuric acid.

Here's the wagging finger, and a couple of reasons you might not want to do
this.

There are two reasons for some or all cells reading low specific gravity.
Either the battery is losing capacity, or some cells are undercharged and
need to be equalized.

First a little battery chemistry (disclaimer : I am not an electrochemist so
if someone with a degree corrects anything below, listen to him and not me).

When a battery discharges, some of its lead turns into lead sulfate. The
sulfate ions for this reaction come from the acid in the electrolyte
(another name for sulfuric acid is hydrogen sulfate, H2SO4).

When you charge the battery, the sulfate ions leave the lead and return to
the acid in the electrolyte.

This is why a hydrometer can tell you the battery's state of charge - it
measures how much H2SO4 is in the electrolyte.

But as a battery ages, gradually some of that lead sulfate doesn't quite
make it back into lead and sulfuric acid. It flakes off the plates and
sinks to the bottom of the cell instead. This is one reason (there are
others) that a battery's capacity declines with use.

For an old battery, "full" just isn't as full as it used to be. The plates
have lost some active material, and the electrolyte has lost some acid.

You can "fix" the latter by reconcentrating the electrolyte (adding more
acid). But you can't put the lead back into the plates so easily. Thus,
when you pour more acid into an old battery, you upset the battery
manufacturer's balance between plate capacity and acid capacity.

Now, when you run the battery flat, its plates will over-discharge. This
will make the battery wear out even faster.

That said, what you did here may also stem from a slightly different
problem. It may be that your SG differed from cell to cell because the
battery wasn't properly equalized.

The correct fix for this is an equalization charge. That's where you
overcharge the fully charged cells in a carefully controlled way, in order
to bring the lower cells up to a full charge. By adding acid, you hid the
problem rather than solving it.

David Roden - Akron, Ohio, USA
EVDL Administrator

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