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  #1  
Old 07-05-2012, 04:17 PM
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Default [EVDL] Am I overcharging by charging my lead-acids too slow?

My Bycan charger has a quite simple charger profile,
the ferro-resonant transformer supplies a moderately
constant current into the pack during bulk charge
then towards the end it will detect when the pack
goes above 147V (2.45V per cell) and starts a 2-hour
timeout for a moderate equalization or it can be
manually set to 6h for a full equalization, during which
the pack voltage usually hovers around 150V (2.5V per cell)
depending on temperature.

It occurred to me that by charging from 120V instead of 240V
as recommended by Bycan (charge at C/10) the pack will reach
the 147V at a higher SoC than when charging at 240V.
In other words, at 120V there will be greater risk of
over-charging the pack than when charging at 240V.

I notice that the inside of the white cell caps has a dark
grey covering. When I take caps off during the equalization
then I notice that droplets jump up from the cells as a
result of bubbles that reach the surface and burst, so I can
see how the electrolyte will cover the entire surface of the
inside of the cell, including the caps.
But I am surprised to find a dark grey color on the inside
of the cell caps. Is that normal?
Sorry for the rookie question - this is my first month of
charging Golfcart batteries and I am using the truck almost
every day (450 miles in a month).

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203

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  #2  
Old 07-05-2012, 04:45 PM
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Default Re: [EVDL] Am I overcharging by charging my lead-acids too slow?

Hello Cor,

Yes, the dark gray coating is normal. All my lead acid batteries have this
same result since 1976. I never had this analyzed, but I think it's the O2
that leaves the positive plate to combined with the electrolyte which is H2
S04 which releases one part of oxygen with the H2 making more H20 which
lowers the specific gravity of the electrolyte when discharge.

When the electrolyte gasses, it will carry some of the other part of 02 or
one part of Oxygen as vapors and maybe some part of sulfate or SO4.

The standard battery caps are vented, so this may mix with the compounds
that are in air. My first battery had a cap on it that is call a Hydro Cap
which seals the battery. It has a chemical compound in the cap which when
the battery vapors go into this cap, it returns it back into the battery as
water.

Roland


----- Original Message -----
From: "Cor van de Water" <xxx@xxx.xxx>
To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
Sent: Thursday, July 05, 2012 4:05 PM
Subject: [EVDL] Am I overcharging by charging my lead-acids too slow?


> My Bycan charger has a quite simple charger profile,
> the ferro-resonant transformer supplies a moderately
> constant current into the pack during bulk charge
> then towards the end it will detect when the pack
> goes above 147V (2.45V per cell) and starts a 2-hour
> timeout for a moderate equalization or it can be
> manually set to 6h for a full equalization, during which
> the pack voltage usually hovers around 150V (2.5V per cell)
> depending on temperature.
>
> It occurred to me that by charging from 120V instead of 240V
> as recommended by Bycan (charge at C/10) the pack will reach
> the 147V at a higher SoC than when charging at 240V.
> In other words, at 120V there will be greater risk of
> over-charging the pack than when charging at 240V.
>
> I notice that the inside of the white cell caps has a dark
> grey covering. When I take caps off during the equalization
> then I notice that droplets jump up from the cells as a
> result of bubbles that reach the surface and burst, so I can
> see how the electrolyte will cover the entire surface of the
> inside of the cell, including the caps.
> But I am surprised to find a dark grey color on the inside
> of the cell caps. Is that normal?
> Sorry for the rookie question - this is my first month of
> charging Golfcart batteries and I am using the truck almost
> every day (450 miles in a month).
>
> Cor van de Water
> Chief Scientist
> Proxim Wireless Corporation http://www.proxim.com
> Email: xxx@xxx.xxx Private: http://www.cvandewater.com
> Skype: cor_van_de_water XoIP: +31877841130
> Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to xxx@xxx.xxx.edu only.
> | Multiple-address or CCed messages may be rejected.
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> | OTHER HELP: http://evdl.org/help/
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>

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  #3  
Old 07-05-2012, 07:27 PM
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Default Re: [EVDL] Am I overcharging by charging my lead-acids too slow?

[quote]On 5 Jul 2012 at 15:05, Cor van de Water wrote:

> It occurred to me that by charging from 120V instead of 240V
> as recommended by Bycan (charge at C/10) the pack will reach
> the 147V at a higher SoC than when charging at 240V.
> In other words, at 120V there will be greater risk of
> over-charging the pack than when charging at 240V.

I don't know what kind of charge controller the Bycan has. However, I'd
guess that if it's able to reach that threshold voltage, the transformer's
voltage output is about what it should be. If anything, I would think the
final charging current would be lower, which (given a fixed equalization
period) would be more apt to undercharge than to overcharge.

The nice thing about flooded batteries is that you don't have to guess or
rely on OC voltage to estimate (very roughly) the SOC. You can measure the
actual SOC with a hydrometer.


>
> I notice that the inside of the white cell caps has a dark grey
> covering.

I've noted that deposit on the inside of the caps of golf car batteries too.
I've always assumed it was lead sulfate that would otherwise precipitate.
I'm no electrochemist, so that's little more than a WAG. Maybe someone who
is (Nawaz?) will give us a more definitive answer as to what it is, and what
it means.

David Roden
EVDL Administrator
http://www.evdl.org/


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  #4  
Old 07-05-2012, 08:55 PM
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Default Re: [EVDL] Am I overcharging by charging my lead-acids too slow?

[quote]Cor van de Water wrote:

> My Bycan charger has a quite simple charger profile,
> the ferro-resonant transformer supplies a moderately
> constant current into the pack during bulk charge
> then towards the end it will detect when the pack
> goes above 147V (2.45V per cell) and starts a 2-hour
> timeout for a moderate equalization or it can be
> manually set to 6h for a full equalization, during which
> the pack voltage usually hovers around 150V (2.5V per cell)
> depending on temperature.

A "moderately constant current" during bulk charge would not be typical of most ferroresonant chargers. Typically these types of chargers exhibit a "taper" charge behaviour, which is that the initial charge current is briefly near to the charger nameplate rating and then tapers continuously down as the battery voltage rises. Somewhere about 2.4V/cell the current will typically have dropped to perhaps 1/2 of its initial value.

A typical ferro will be capable of at least 2.65-2.70V/cell at the end of charge, and healthy floodeds should easily exceed 2.6V/cell with the charger current at a few percent of the C/20 capacity. That yours appears to top out at about 2.5V/cell suggests that your batteries may be in poor condition, or (more likely, I suspect), the input voltage to your charger may be a bit low (while ferros usually have reasonable immunity from line variations, they are not immune if the line sags sufficiently).

Depending on what the charge current is doing when the voltage reaches 2.45V/cell and the "equalization" timer starts, it may not be providing as much of an equalise as you might expect. If the current is still significant at this point, then 2h is probably not sufficient to achieve the 110%+ overcharge that is almost universally accepted as required to keep flooded batteries happy. You may find that you need to set the charger to the 6hr finish at least once a week; keep an eye on the SGs - they'll let you know if the batteries are happy or not. ;^>

> It occurred to me that by charging from 120V instead of 240V
> as recommended by Bycan (charge at C/10) the pack will reach
> the 147V at a higher SoC than when charging at 240V.
> In other words, at 120V there will be greater risk of
> over-charging the pack than when charging at 240V.

Not necessarily, and probably not to a significant degree.

Yes, at 120VAC the charge current will be lower than at 240VAC input, and the lower current results in less IR drop in the wiring and internal resistance so the battery will be at a slightly higher voltage when the charger sees the 147V setpoint, however, the difference in SOC is likely to be modest.

> But I am surprised to find a dark grey color on the inside
> of the cell caps. Is that normal?

Yes. As you observed, if you gas the cells vigorously enough, and if the electrolyte level is high enough, then as the gas bubbles reach the surface and burst some electrolyte will splash up onto the bottoms of the cell caps. Suspended particles in the electrolyte (typically tiny bits of shed active material, etc.) will be deposited on the cell cap and eventually accumulate to leave the residue you observe.

Cheers,

Roger.


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| Please take those discussions elsewhere. Thanks.
|
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  #5  
Old 07-05-2012, 11:07 PM
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Default Re: [EVDL] Am I overcharging by charging my lead-acids too slow?

Hi Roger,
Thanks for the numbers!
Indeed the ferro-resonant charger tapers from and initial
12 Amps or so to around 9-10A at 130V for most the bulk charge.
Since my typical commute is 10 miles, I only need to put back
about 40Ah or approx 4.5h charging before the voltage rises
quite rapidly from 130V to 150V and the charger enters into the
equalization timeout, delivering about 3-4A into the pack.
So, for my typical driving I will charge almost 120% (40Ah +7Ah)
and only when I make a long trip (longest until now were some trips
in the 25 mile range where I have to put back at least 100Ah,
then the equalization may come up a little short.
But that will certainly be compensated the next commute
(charging at each end).

I forgot that I now need to check SG (I did remember that I need
to water the batteries - I already checked them before starting
my regular commute for enough electrolyte level to avoid damaging
the tops of the plates. OK, so I need to get a meter.
Is the best still a glass instrument from a forklift place?

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
Behalf Of Roger Stockton
Sent: Thursday, July 05, 2012 7:43 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Am I overcharging by charging my lead-acids too
slow?

[quote]Cor van de Water wrote:

> My Bycan charger has a quite simple charger profile, the
> ferro-resonant transformer supplies a moderately constant current into

> the pack during bulk charge then towards the end it will detect when
> the pack goes above 147V (2.45V per cell) and starts a 2-hour timeout
> for a moderate equalization or it can be manually set to 6h for a full

> equalization, during which the pack voltage usually hovers around 150V

> (2.5V per cell) depending on temperature.

A "moderately constant current" during bulk charge would not be typical
of most ferroresonant chargers. Typically these types of chargers
exhibit a "taper" charge behaviour, which is that the initial charge
current is briefly near to the charger nameplate rating and then tapers
continuously down as the battery voltage rises. Somewhere about
2.4V/cell the current will typically have dropped to perhaps 1/2 of its
initial value.

A typical ferro will be capable of at least 2.65-2.70V/cell at the end
of charge, and healthy floodeds should easily exceed 2.6V/cell with the
charger current at a few percent of the C/20 capacity. That yours
appears to top out at about 2.5V/cell suggests that your batteries may
be in poor condition, or (more likely, I suspect), the input voltage to
your charger may be a bit low (while ferros usually have reasonable
immunity from line variations, they are not immune if the line sags
sufficiently).

Depending on what the charge current is doing when the voltage reaches
2.45V/cell and the "equalization" timer starts, it may not be providing
as much of an equalise as you might expect. If the current is still
significant at this point, then 2h is probably not sufficient to achieve
the 110%+ overcharge that is almost universally accepted as required to
keep flooded batteries happy. You may find that you need to set the
charger to the 6hr finish at least once a week; keep an eye on the SGs -
they'll let you know if the batteries are happy or not. ;^>

> It occurred to me that by charging from 120V instead of 240V as
> recommended by Bycan (charge at C/10) the pack will reach the 147V at
> a higher SoC than when charging at 240V.
> In other words, at 120V there will be greater risk of over-charging
> the pack than when charging at 240V.

Not necessarily, and probably not to a significant degree.

Yes, at 120VAC the charge current will be lower than at 240VAC input,
and the lower current results in less IR drop in the wiring and internal
resistance so the battery will be at a slightly higher voltage when the
charger sees the 147V setpoint, however, the difference in SOC is likely
to be modest.

> But I am surprised to find a dark grey color on the inside of the cell

> caps. Is that normal?

Yes. As you observed, if you gas the cells vigorously enough, and if
the electrolyte level is high enough, then as the gas bubbles reach the
surface and burst some electrolyte will splash up onto the bottoms of
the cell caps. Suspended particles in the electrolyte (typically tiny
bits of shed active material, etc.) will be deposited on the cell cap
and eventually accumulate to leave the residue you observe.

Cheers,

Roger.


_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to xxx@xxx.xxx.edu only.
| Multiple-address or CCed messages may be rejected.
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| Please take those discussions elsewhere. Thanks.
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  #6  
Old 07-06-2012, 10:05 AM
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Default Re: [EVDL] Am I overcharging by charging my lead-acids too slow?

[quote]On 6 Jul 2012 at 6:29, Jay Summet wrote:

> Also, unless you need to find out if a specific cell in a 3 or 4 or 6
> cell battery is different from all the other cells, it's a lot easier
> to measure the resting voltage and use that the approximate the SOC
> and SG (they are relatively well related.)

Maybe I'm misunderstanding what you're saying, but if I'm getting you, that
hasn't been my experience. I find that voltage is a very poor indicator of
lead batteries' SOC.

The beauty of flooded batteries is that you can use a hydrometer and get an
exact SOC measurement, something that's not possible with AGM and gel
batteries.

David Roden - Akron, Ohio, USA
EVDL Administrator

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  #7  
Old 07-06-2012, 11:25 AM
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Default Re: [EVDL] Am I overcharging by charging my lead-acids too slow?

When I first pick up my first EV back in 76, Bob Aronson of the Electric
Fuel Propulsion Co. in Troy, Michigan, said the on board charger rate is set
for 10 percent of the ampere hour rate of the battery. I had 300 ah
batteries, so the maximum charge rate was set at 30 amps.

The maximum voltage was set at 2.6 volts per cell. These batteries lasted
about 10 years driving about 5 miles a day.

Also, I was warn that do not add any distill water when the batteries are
discharge below 80 percent SOC, because when batteries are discharge, the
electrolyte level will drop when discharge and rise when charge.

At 50 percent SOC, the electrolyte should be above the plates, if not, than
add just enough distill water to get the electrolyte level above the plates.
Charge the battery to about 95 SOC and than check the electrolyte level
again. If it below the recommended fill level which in my case, is just
above the bottom of the fill neck.

Than continue to charge to 100 SOC. Right after the full charge cycle,
check the specified gravity of the electrolyte. Even though a full charge
battery battery is said to be 100 SOC at about 2.123 volts per cell after it
rest for at least 24 hours, It may read 2.6 volts just after charging.

If the voltage per cell reads 2.123 volts hot just after charging, the SOC
may still be in the 80% range cold.

Another thing to watch out for, is if take a specific gravity reading of a
battery that been setting about 24 hours cold, is that the heavier acid
(H2SO4) settles to the bottom of the cell making the top layer of the
electrolyte weaker. If you test the sg at this time, you would think that
the battery is discharge.

First charge the battery after you add water or if the battery been setting
for awhile, so as to better mix the electrolyte from the bottom to the top
of the cell to give you a good SG reading.

HOT may mean that the SG reading may read as high as 1.300 sg with the
electrolyte temperature over 80 F. At 80 F. the normal reading may be at
1.275 sg at 2.123 volts per cell which is consider 100% SOC.

Roland




----- Original Message -----
From: "EVDL Administrator" <xxx@xxx.xxx>
To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
Sent: Friday, July 06, 2012 9:56 AM
Subject: Re: [EVDL] Am I overcharging by charging my lead-acids too slow?


[quote]> On 6 Jul 2012 at 6:29, Jay Summet wrote:
>
> > Also, unless you need to find out if a specific cell in a 3 or 4 or 6
> > cell battery is different from all the other cells, it's a lot easier
> > to measure the resting voltage and use that the approximate the SOC
> > and SG (they are relatively well related.)
>
> Maybe I'm misunderstanding what you're saying, but if I'm getting you,
> that
> hasn't been my experience. I find that voltage is a very poor indicator
> of
> lead batteries' SOC.
>
> The beauty of flooded batteries is that you can use a hydrometer and get
> an
> exact SOC measurement, something that's not possible with AGM and gel
> batteries.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> EVDL Information: http://www.evdl.org/help/
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> Note: mail sent to "evpost" and "etpost" addresses will not
> reach me. To send a private message, please obtain my
> email address from the webpage http://www.evdl.org/help/ .
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to xxx@xxx.xxx.edu only.
> | Multiple-address or CCed messages may be rejected.
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>

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