US125XC Battery Float Voltage Puzzler

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US125XC Battery Float Voltage Puzzler

Rob Trahms
Hi All -

1989 VW Cabby
16 x 6v US125XC batteries (96V)

I have read on this site and the US Battery FAQ that the resting open circuit voltage for these 6V batteries is 2.17Vpc / 6.51V per battery / ~104V for my pack.  Is this most people's experience?

I charge to an acceptance charge of no more than 7.75V per battery / 124V, but have never seen resting voltages above 101.5V for the pack.  Am I missing something?  Perhaps I am not leaving the batts at the acceptance charge long enough (1-2 hours after reaching the acceptance voltage).  The FAQ recommends 2-4 hours, but I wanted to check with other folks on their experience with US125XCs as well.

Thanks,
Rob
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Re: US125XC Battery Float Voltage Puzzler

Chuck Hursch-2
Well, to answer your question, Rob, it seems that at the EAA meetings I
went to in the past (mostly back in the '90s), people indicated that
new-ish batteries should be standing at 6.4-6.5V after several hours off
the charger.  Middle-aged batteries would be in the 6.30s.  (That's why
I've been wondering why mine, and yours, fairly new batteries are in the
high 6.30s.  I've also seen 6.30V specified as 100% charged.)  Maybe
6.20s for older batteries, although my experience has been that by the
time the batteries are resting in the 6.20s, they are more or less toast
for purposes of EV'ing and getting the car up the hill.

This morning, walked out to the car to unplug it, and the CanPulse light
was on, so over 103V about three hours after the timer shut off the
Zivan charger.  I am nearing the end of two weeks vacation, so the car
has been used sporadically.  The last charge before this one last night
was last Fri.  Little piddly trips:  Safeway on Sat (~6.9 mi), run to
the bank Mon or Tue (~2.7 mi, seems like 9.9 miles was on the trip
odometer), then take Mom to the doctor for her flu shot yesterday (ended
up with 12.3 miles on the trip odo).  Each trip had a run up the steep
hill to this apt (try to keep battery amps at 250 or less).  Per what
I've read on the EVDL (and here I'm primarily thinking of what of read
of Roland's), I hold off charging till 10 miles or over.  That's well
above 50% SOC, of course, but I do have a steep hill to worry about
bottoming cells with.  So I held off charging till last night.  I
decided to let it charge the full 7 hrs of my PG&E off-peak period at
8.5-9A.  I also felt that there were about 5 days of self-discharge, so
according to Lee, that's about 1%/day.  I saw 6.51kwh on the KillaWatt
meter.  (6.51/7=0.93, so average AC wattage is 0.93kw). As I said,
CanPulse light was on.  But I'll bet the sg readings are down 10-20 pts
right now.  On the road my voltages under load and standing according to
the expanded-scale SOC meter will be somewhat higher than in the
paragraph below.

When I'm doing the daily work commute, 12.6 miles round-trip, charge
every night, with the timer shutting off after six hours (I do an
informal guestimate of mileage / 2.5 at this charge rate - seems about
right), so timer dump at 6AM.  Will register usually 4.9 - 5.1 kwh on
the KillaWatt.  (5kwh/6h = 0.83kw tells me the charger ramped down
earlier here.)  CanPulse light will be off.  Sg readings will almost
certainly be normal, 1260-1285 (after letting the batteries rest at
least several hours).

What can I say...  I'll believe the sg readings more than anything else,
and Charge on!

Chuck

Rob Trahms wrote:

> Hi All -
>
> 1989 VW Cabby
> 16 x 6v US125XC batteries (96V)
>
> I have read on this site and the US Battery FAQ that the resting open
> circuit voltage for these 6V batteries is 2.17Vpc / 6.51V per battery /
> ~104V for my pack.  Is this most people's experience?
>
> I charge to an acceptance charge of no more than 7.75V per battery / 124V,
> but have never seen resting voltages above 101.5V for the pack.  Am I
> missing something?  Perhaps I am not leaving the batts at the acceptance
> charge long enough (1-2 hours after reaching the acceptance voltage).  The
> FAQ recommends 2-4 hours, but I wanted to check with other folks on their
> experience with US125XCs as well.
>
> Thanks,
> Rob
>
> -----
> Rob Trahms
> [hidden email]
> Electro - the Cabby-EV
> http://chaosmgmt.blogspot.com chaosmgmt.blogspot.com
>


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Usage guidelines: http://evdl.org/help/index.html#conv
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Re: US125XC Battery Float Voltage Puzzler

Rob Trahms

Thanks for the response Chuck!

I am trying to understand the guidelines given in the following FAQ from US Battery:

http://www.usbattery.com/usb_faqs.html

In one case, they are saying to leave a level acceptance charge for 2-4 hours, and right below it they say to use charge for 10 hours.   I would like to compare notes - are you using ~2.583 Vpc (7.75V per battery) acceptance charge for 6 hours in normal charging?  Why do US Batteries require a long hold time at this voltage?

Rob


Chuck Hursch-2 wrote
Well, to answer your question, Rob, it seems that at the EAA meetings I
went to in the past (mostly back in the '90s), people indicated that
new-ish batteries should be standing at 6.4-6.5V after several hours off
the charger.  Middle-aged batteries would be in the 6.30s.  (That's why
I've been wondering why mine, and yours, fairly new batteries are in the
high 6.30s.  I've also seen 6.30V specified as 100% charged.)  Maybe
6.20s for older batteries, although my experience has been that by the
time the batteries are resting in the 6.20s, they are more or less toast
for purposes of EV'ing and getting the car up the hill.

This morning, walked out to the car to unplug it, and the CanPulse light
was on, so over 103V about three hours after the timer shut off the
Zivan charger.  I am nearing the end of two weeks vacation, so the car
has been used sporadically.  The last charge before this one last night
was last Fri.  Little piddly trips:  Safeway on Sat (~6.9 mi), run to
the bank Mon or Tue (~2.7 mi, seems like 9.9 miles was on the trip
odometer), then take Mom to the doctor for her flu shot yesterday (ended
up with 12.3 miles on the trip odo).  Each trip had a run up the steep
hill to this apt (try to keep battery amps at 250 or less).  Per what
I've read on the EVDL (and here I'm primarily thinking of what of read
of Roland's), I hold off charging till 10 miles or over.  That's well
above 50% SOC, of course, but I do have a steep hill to worry about
bottoming cells with.  So I held off charging till last night.  I
decided to let it charge the full 7 hrs of my PG&E off-peak period at
8.5-9A.  I also felt that there were about 5 days of self-discharge, so
according to Lee, that's about 1%/day.  I saw 6.51kwh on the KillaWatt
meter.  (6.51/7=0.93, so average AC wattage is 0.93kw). As I said,
CanPulse light was on.  But I'll bet the sg readings are down 10-20 pts
right now.  On the road my voltages under load and standing according to
the expanded-scale SOC meter will be somewhat higher than in the
paragraph below.

When I'm doing the daily work commute, 12.6 miles round-trip, charge
every night, with the timer shutting off after six hours (I do an
informal guestimate of mileage / 2.5 at this charge rate - seems about
right), so timer dump at 6AM.  Will register usually 4.9 - 5.1 kwh on
the KillaWatt.  (5kwh/6h = 0.83kw tells me the charger ramped down
earlier here.)  CanPulse light will be off.  Sg readings will almost
certainly be normal, 1260-1285 (after letting the batteries rest at
least several hours).

What can I say...  I'll believe the sg readings more than anything else,
and Charge on!

Chuck

Rob Trahms wrote:
> Hi All -
>
> 1989 VW Cabby
> 16 x 6v US125XC batteries (96V)
>
> I have read on this site and the US Battery FAQ that the resting open
> circuit voltage for these 6V batteries is 2.17Vpc / 6.51V per battery /
> ~104V for my pack.  Is this most people's experience?
>
> I charge to an acceptance charge of no more than 7.75V per battery / 124V,
> but have never seen resting voltages above 101.5V for the pack.  Am I
> missing something?  Perhaps I am not leaving the batts at the acceptance
> charge long enough (1-2 hours after reaching the acceptance voltage).  The
> FAQ recommends 2-4 hours, but I wanted to check with other folks on their
> experience with US125XCs as well.
>
> Thanks,
> Rob
>
> -----
> Rob Trahms
> rtrahms@comcast.net
> Electro - the Cabby-EV
> http://chaosmgmt.blogspot.com chaosmgmt.blogspot.com
>


_______________________________________________
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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
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Re: US125XC Battery Float Voltage Puzzler

Roland Wiench



----- Original Message -----
From: "Rob Trahms" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, September 24, 2009 9:53 PM
Subject: Re: [EVDL] US125XC Battery Float Voltage Puzzler

I am trying to understand the guidelines given in the following FAQ from US
Battery:

http://www.usbattery.com/usb_faqs.html

In one case, they are saying to leave a level acceptance charge for 2-4
hours, and right below it they say to use charge for 10 hours.   I would
like to compare notes - are you using ~2.583 Vpc (7.75V per battery)
acceptance charge for 6 hours in normal charging?  Why do US Batteries
require a long hold time at this voltage?

Rob

Hello Rob,

Before I purchase my U.S. batteries, I contacted them.  The length of
charging times are just guildlines which depends on the SOC and ampere-hour
rating when first charging and how long does it take to get to 100% SOC
and/or 1.277 SG from a depth of discharge.

The 10 hours is a estimated length of time that it may take to charge the
battery during the normal charge and acceptance charge depending how many
ampere-hour is removed. The first time I charge these new batteries which
were only 2 weeks old and never been discharge, the resting voltage average
6.42 volts a specific gravity average of 1.275 which is consider 99.84% SOC.
Charging at C/10 to 7.75 volts took from 1 to 3 minutes to reach 100% SOC.
Check the level of the electrolyte which was about 1/2 inch below that fill
neck, which is now my reference level, so I do not overfill and dilute the
electrolyte.

Drove the first 5 miles, check the specific gravity level which was about
1.262 sg at 6.30 volts and re-torque the battery connectors to check against
any shrink back. Charge the batteries at 25 amps to 7.75 volts which took 50
minutes to the acceptance voltage and another 10 minutes to reach 1.277 SG.

Drove for one mile at 75 battery amps, and the specific gravity read 1.275
SG in one test cell and it only took 12 minutes at 7.2 volts which is a
trickle charge to reach 100% SOC at 1.277 SG.

To find out how long you need to charge after you reach the acceptance
voltage, take a specific gravity reading in about 15 minutes after you reach
the acceptance voltage and adjust your charger for that amount of timeout.

Roland

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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
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Re: US125XC Battery Float Voltage Puzzler

Rob Trahms

Thanks Roland -
I understand the time to achieve the acceptance charge will vary.  The thing I am trying to reconcile is that the acceptance charge recommended by US Battery (7.75V per battery) is so much higher than the guideline I read in Lee Hart's charging howto document (7.2V per battery).  Am I doing damage to the batteries holding them at this higher acceptance charge for a period of time?  The last thing I want to do is equalize them to death...

Speaking of equalization, what voltage do you use for the voltage limit on these US125XCs, and for how long at the lower current?

Rob


Roland Wiench wrote


----- Original Message -----
From: "Rob Trahms" <rtrahms@comcast.net>
To: <ev@lists.sjsu.edu>
Sent: Thursday, September 24, 2009 9:53 PM
Subject: Re: [EVDL] US125XC Battery Float Voltage Puzzler

I am trying to understand the guidelines given in the following FAQ from US
Battery:

http://www.usbattery.com/usb_faqs.html

In one case, they are saying to leave a level acceptance charge for 2-4
hours, and right below it they say to use charge for 10 hours.   I would
like to compare notes - are you using ~2.583 Vpc (7.75V per battery)
acceptance charge for 6 hours in normal charging?  Why do US Batteries
require a long hold time at this voltage?

Rob

Hello Rob,

Before I purchase my U.S. batteries, I contacted them.  The length of
charging times are just guildlines which depends on the SOC and ampere-hour
rating when first charging and how long does it take to get to 100% SOC
and/or 1.277 SG from a depth of discharge.

The 10 hours is a estimated length of time that it may take to charge the
battery during the normal charge and acceptance charge depending how many
ampere-hour is removed. The first time I charge these new batteries which
were only 2 weeks old and never been discharge, the resting voltage average
6.42 volts a specific gravity average of 1.275 which is consider 99.84% SOC.
Charging at C/10 to 7.75 volts took from 1 to 3 minutes to reach 100% SOC.
Check the level of the electrolyte which was about 1/2 inch below that fill
neck, which is now my reference level, so I do not overfill and dilute the
electrolyte.

Drove the first 5 miles, check the specific gravity level which was about
1.262 sg at 6.30 volts and re-torque the battery connectors to check against
any shrink back. Charge the batteries at 25 amps to 7.75 volts which took 50
minutes to the acceptance voltage and another 10 minutes to reach 1.277 SG.

Drove for one mile at 75 battery amps, and the specific gravity read 1.275
SG in one test cell and it only took 12 minutes at 7.2 volts which is a
trickle charge to reach 100% SOC at 1.277 SG.

To find out how long you need to charge after you reach the acceptance
voltage, take a specific gravity reading in about 15 minutes after you reach
the acceptance voltage and adjust your charger for that amount of timeout.

Roland

_______________________________________________
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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
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Re: US125XC Battery Float Voltage Puzzler

Roland Wiench
Hello Rob,

Before I equalize, I first drive about one mile and then check the voltage
of each battery. This amount of load will show more difference in battery
voltage then if you check the voltage just after charging because some
batteries may be down in ampere capacity.

I then record each battery voltage on a battery log, which I normally do
weekly until the warranty period is up. Then after the warranty period, its
about once a month just before I may have to equalize.

I first charge the battery at the normal charge voltage that may be anywhere
from 7.2 to 7.75 volts.  Normally for my daily drive this only takes 3 to 15
minutes at 25 amps to 100% SOC.

I let the batteries rest for 6 to 12 hours which could be the next day.
Applied a very little load on them by backing out and driving forward into
the garage. Then let the batteries set for about a hour, so the batteries
will defuse which is letting the deep acid come out of the plates into the
electrolyte.

Just after you shut down the EV, you will note the battery voltage will be
at a lower point and then will raise which is call battery defusing.

If you took another volt reading of each battery after applying a load, you
will note there will be more of a voltage difference in some batteries than
if they were just charge.

I find, that if I do a equalization charge just after a normal charge gets
to the voltage of 7.75 and continue on to 7.8 volts, It will applied more
heat to the battery at this time charging at the C/10 rate.

I prefer to only take the batteries to the 7.75 acceptance voltage and than
shut the charger off at that time and let the batteries rest for 1 to 2
hours so as to reduce the heat.  If I start to charge these batteries at a
battery temperature of 70 F, the battery temperature may raise to 80 F at
the end of charge.

According to a U.S. Battery tech, leave the voltage set for 7.75 volts for a
normal charge and do not do a temperature compensating of 0.028 volts
decrease for every 10 degrees below 80 F., because if the charging time is
longer for charging a battery that is between 50 to 80% SOC, the battery
temperature may normally raise another 10 degrees at this time.

I will then turn on the charger after 1 to 2 hours and adjust ampere to
about 25 amps that which will quickly get to 7.75 volts, I will than
increase the voltage and until it reads 7.8 volts which only takes a short
period of time to reach 100% SOC or 1.277 specific gravity.

I find it is better to reduce the ampere as the voltage rises from 7.75 to
7.8 volts while the ampere is reduce from C/10 or 25 amps to 5 amps.  If I
time it just right, the battery will be right at 100 % SOC when the battery
ampere reaches about 2% of the ampere hour rating of the battery.  For a 242
AH battery this would be about 4.8 amps.

Roland

Roland




----- Original Message -----
From: "Rob Trahms" <[hidden email]>
To: <[hidden email]>
Sent: Friday, September 25, 2009 10:32 PM
Subject: Re: [EVDL] US125XC Battery Float Voltage Puzzler


>
>
> Thanks Roland -
> I understand the time to achieve the acceptance charge will vary.  The
> thing
> I am trying to reconcile is that the acceptance charge recommended by US
> Battery (7.75V per battery) is so much higher than the guideline I read in
> Lee Hart's charging howto document (7.2V per battery).  Am I doing damage
> to
> the batteries holding them at this higher acceptance charge for a period
> of
> time?  The last thing I want to do is equalize them to death...
>
> Speaking of equalization, what voltage do you use for the voltage limit on
> these US125XCs, and for how long at the lower current?
>
> Rob
>
>
>
> Roland Wiench wrote:
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Rob Trahms" <[hidden email]>
> > To: <[hidden email]>
> > Sent: Thursday, September 24, 2009 9:53 PM
> > Subject: Re: [EVDL] US125XC Battery Float Voltage Puzzler
> >
> > I am trying to understand the guidelines given in the following FAQ from
> > US
> > Battery:
> >
> > http://www.usbattery.com/usb_faqs.html
> >
> > In one case, they are saying to leave a level acceptance charge for 2-4
> > hours, and right below it they say to use charge for 10 hours.   I would
> > like to compare notes - are you using ~2.583 Vpc (7.75V per battery)
> > acceptance charge for 6 hours in normal charging?  Why do US Batteries
> > require a long hold time at this voltage?
> >
> > Rob
> >
> > Hello Rob,
> >
> > Before I purchase my U.S. batteries, I contacted them.  The length of
> > charging times are just guildlines which depends on the SOC and
> > ampere-hour
> > rating when first charging and how long does it take to get to 100% SOC
> > and/or 1.277 SG from a depth of discharge.
> >
> > The 10 hours is a estimated length of time that it may take to charge
> > the
> > battery during the normal charge and acceptance charge depending how
> > many
> > ampere-hour is removed. The first time I charge these new batteries
> > which
> > were only 2 weeks old and never been discharge, the resting voltage
> > average
> > 6.42 volts a specific gravity average of 1.275 which is consider 99.84%
> > SOC.
> > Charging at C/10 to 7.75 volts took from 1 to 3 minutes to reach 100%
> > SOC.
> > Check the level of the electrolyte which was about 1/2 inch below that
> > fill
> > neck, which is now my reference level, so I do not overfill and dilute
> > the
> > electrolyte.
> >
> > Drove the first 5 miles, check the specific gravity level which was
> > about
> > 1.262 sg at 6.30 volts and re-torque the battery connectors to check
> > against
> > any shrink back. Charge the batteries at 25 amps to 7.75 volts which
> > took
> > 50
> > minutes to the acceptance voltage and another 10 minutes to reach 1.277
> > SG.
> >
> > Drove for one mile at 75 battery amps, and the specific gravity read
> > 1.275
> > SG in one test cell and it only took 12 minutes at 7.2 volts which is a
> > trickle charge to reach 100% SOC at 1.277 SG.
> >
> > To find out how long you need to charge after you reach the acceptance
> > voltage, take a specific gravity reading in about 15 minutes after you
> > reach
> > the acceptance voltage and adjust your charger for that amount of
> > timeout.
> >
> > Roland
> >
> > _______________________________________________
> > General EVDL support: http://evdl.org/help/
> > Usage guidelines: http://evdl.org/help/index.html#conv
> > Archives: http://evdl.org/archive/
> > Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
> >
> >
> >
>
>
> -----
> Rob Trahms
> [hidden email]
> Electro - the Cabby-EV
> http://chaosmgmt.blogspot.com chaosmgmt.blogspot.com
>
> --
> View this message in context:
> http://www.nabble.com/US125XC-Battery-Float-Voltage-Puzzler-tp25565551p25622487.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>

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