# [EVDL] Am I overcharging by charging my lead-acids too slow?



## EVDL List (Jul 27, 2007)

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" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
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: [email protected] 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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## EVDL List (Jul 27, 2007)

> 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
> ...


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## EVDL List (Jul 27, 2007)

> Cor van de Water wrote:
> 
> > My Bycan charger has a quite simple charger profile,
> > the ferro-resonant transformer supplies a moderately
> ...


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## EVDL List (Jul 27, 2007)

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: [email protected] 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: [email protected] [mailto:[email protected]] 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?



> Cor van de Water wrote:
> 
> > My Bycan charger has a quite simple charger profile, the
> > ferro-resonant transformer supplies a moderately constant current into
> ...


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## EVDL List (Jul 27, 2007)

> 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
> ...


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## EVDL List (Jul 27, 2007)

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" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, July 06, 2012 9:56 AM
Subject: Re: [EVDL] Am I overcharging by charging my lead-acids too slow?




> > 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
> ...


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