crud on battery caps

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crud on battery caps

Al-57
I have a pack of Trojan T-125 floodies. I noticed when watering that the
bottom of the cell caps have a thin coating of gray material on them (lead?)
Is this normal or are my batteries being fried by the charger? Once, when
the Zivan was on yellow topping up mode I read 157V across a 120V pack.
Thats 2.6 VPC !! Is that too high?

Thanks, Al

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Re: crud on battery caps

Roland Wiench
Hello Al,

That gray or dark gray on the bottom of the caps is normal.  As batteries
are charge, the sulfate SO4 is being remove from the negative plates and is
going into solution.  If you charge at a very high current, this sulfate
particles will exploded off the negative plates more rapid which does not
allow time to be exchange with the H2O of the water to make more H2SO4 which
is the battery acid.

Over time, even over a slow charging, you will get this build up on the
bottom of the caps, because the batteries are still at a low simmer
bubbling, the hydrogen vents H leaving SO4 sulfate which does not vent on
the caps.

My bottom of my caps are almost black now which may even contain some oxide
from the positive plates.  I was told long time ago, not to clean them,
because when they are in this condition, they may act like Hydrocells which
I had at one time.  The excess gassing which releases the hydrogen may react
with this compound on the caps and it returns some of it to the cell, thus
less loss of the hydrogen and electrolyte.

About every three months after I do a equalizing charge to about 90 to 95%,
I than water the batteries and than do a finish charging for the last 10%,
so the water will better mix with the electrolyte.

My batteries which are Trogen T-145's are still perfect after six years of
running every day at a average of 5 miles a day.

The 2.6 per cell is a equalization or balance charge voltage which I do only
every 3 months or about every 500 miles.  This is 7.8 volts per battery or
156 volts for a 120 volt pack.

My normal charge is at 7.5 volt per battery or 2.5 per cell at a
temperatures of 60F to 80F.  Over 80F battery temperature, I drop it to
about 7.4 volts per battery.

Look at the Trojan Company Maintenance Web Site, there are charging data
tables there that will tell you the exact charging methods for these types
of batteries.

Roland




----- Original Message -----
From: "Al" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Sunday, August 12, 2007 9:39 PM
Subject: [EVDL] crud on battery caps


> I have a pack of Trojan T-125 floodies. I noticed when watering that the
> bottom of the cell caps have a thin coating of gray material on them
> (lead?)
> Is this normal or are my batteries being fried by the charger? Once, when
> the Zivan was on yellow topping up mode I read 157V across a 120V pack.
> Thats 2.6 VPC !! Is that too high?
>
> Thanks, Al
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Re: crud on battery caps

Lee Hart
In reply to this post by Al-57
Al wrote:
> I have a pack of Trojan T-125 floodies. I noticed when watering that
> the bottom of the cell caps have a thin coating of gray material on
> them (lead?) Is this normal or are my batteries being fried by the
> charger?

A small amount of this is normal for flooded batteries. These are
microscopic bits of active material that were shed by the plates, and
thrown up there by the gassing and bubbling at the end of a charge cycle.

It could be a problem if your end-of-charge current is too high; like
more than 2% of the battery's amphour capacity. This makes the gassing
pretty vigorous, increasing this shedding and deposition.

> Once, when the Zivan was on yellow topping up mode I read
> 157V across a 120V pack. Thats 2.6 VPC !! Is that too high?

Yes, that's a bit high. New batteries might tolerate it (US Battery
recommends 2.58v/cell), but doing this with older ones will certainly
lead to excessive gassing and water usage.

--
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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Re: crud on battery caps

Joseph T.
"US Battery recommends 2.58v/cell"

The lowest the cell voltage of a lead acid battery can go under load
(pulling lots of amps) is 1.5 volts, right? And the lowest the
cell-voltage can go under no load is 1.5 volts also, when it is
considered 100% discharged, right?

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Re: crud on battery caps

Lee Hart
In reply to this post by Al-57
From: "Joseph T.
> The lowest the cell voltage of a lead acid battery can go under
> load (pulling lots of amps) is 1.5 volts, right? And the lowest
> the cell-voltage can go under no load is 1.5 volts also, when
> it is considered 100% discharged, right?

Well... the voltage can go to ZERO volts under load, or even negative if you have many cells in series. However, if this happens you are ruining your batteries.

I think what you meant to ask is how low the cell voltage should be allowed to go without damage. The usual rule of thumb is 1.75v/cell minimum under load. Manufacturers sometimes specify a lower voltage anyway, just to increase the battery's apparent current rating. But the lower you go, the greater the risk of damaging the battery.

--
"Excellence does not require perfection." -- Henry James
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net

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