Re: [EVDL] New gel battery breakin. Still low.

Re: [EVDL] New gel battery breakin. Still low.

Voltage in rest is a *unreliable* indicator of
the quality of a battery, unless it is way out of
line, like 11V instead of 13V.
The *only* way to test a battery reliably is to
test it under load, at minimum to take a voltage
reading under a serious load (like 50A or so)
and preferably to check capacity (run a known load
until the battery reaches its LVD (Low Voltage
Disconnect) threshold, typically 10.5V for a 12V
lead-acid. Measure the time and calculate the Ah
capacity, compare with the spec and you know how
good or bad the battery still is.
I used to have several batteries that charged
normally, showed more than 11V on a heavy load but
had almost no capacity, they fell from 11 to 9V
after a few minutes load, so one cell was severely
out of balance and reversed too often to allow a
decent amount of Ahs.
Note that I tested if the cell was just out of balance
or had reduced capacity by drilling a small hole =

through the top of the case into the cell interconnect
and slowly charge the one cell until it received a full
capacity worth of charge. It still behaved the same,
so the 110Ah battery was toast (5 cells with good capacity
and 1 cell with about 5Ah)
On the other hand I have a few Hawker SBS30 batteries
from 1994 (17 years old!) that still are close to their
spec, when loaded with 30A (1C load) they give about 15Ah.

Success testing,

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 Behal=
f Of Lawrence Rhodes
Sent: Thursday, January 20, 2011 3:10 AM
To: [email protected]
Subject: Re: [EVDL] New gel battery breakin. Still low.

I just checked again. I have three stinkers. 12.9, 12.94 & 12.95. =
The rest after four days sitting were 13.1 to 13.2vdc. The lowest at 12.=
9 was the new battery. Lawrence Rhodes...

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Re: [EVDL] New gel battery breakin. Still low.

When my AGMs were new, they would sit at 13.25V several hours after
charge end.
They were certainly not over-charged as I had trouble to get the voltage
high enough,
typically they were sitting at 13.8 - 14V for a few hours and I just
hoped they would charge enough during the (fixed) charging period. (ToU
low period midnight - 7AM)


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 Lee Hart
Sent: Friday, January 21, 2011 12:46 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] New gel battery breakin. Still low.

Lawrence Rhodes wrote:
> I have three stinkers. 12.9, 12.94& 12.95. The rest after four >
days sitting were 13.1 to 13.2vdc.

Cor van de Water wrote:
> Voltage in rest is a *unreliable* indicator of the quality of a
> battery, unless it is way out of line, like 11V instead of 13V.

Open circuit voltage is a good way to estimate the state of charge of a
lead-acid battery. However, it must be left sitting 24 hours or more
with no load and no charging, or you'll get a false reading.

Open circuit voltage also tends to fall as the battery ages. Some of the
acid is lost in forming lead sulfate that has detached itself from the
plates. If the plates use lead alloys instead of pure lead, the antimony
or calcium used also migrates to the surface of the plates over time,
lowering the voltage.

The exact numbers vary depending on the type of battery (flooded, AGM,
or gel). The battery's manufacturer can provide more exact data.

The more pure the lead in the plates, the higher the voltage. Also, the
higher the acid concentration, the higher the voltage.

Gels tend to use pure lead plates; this raises their fully charged
voltage to around 13.0-13.1v. I'd worry a bit about one at 13.2v; it may
have been overcharged and vented off some water, leaving the acid too
strong. Acid concentrations above about 1.300 specific gravity begins to
attack the plates, causing grid corrosion and shortening life.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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