determining flooded deep cycle SOC?

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rqlhgl@ieee.org - 21 Jun 2008 22:23 GMT

I recently replaced my two Interstate SRM27 (85ah) with SRM27X (105ah)
and would like a non-destructive test of their ah capacity. I propose
using and inverter to load each battery at 10A and measure the
terminal voltage with a usb data-logger. Interstate give a table of o/
c voltage vs SOC from -17.8C to 48.9C however I don't want to wait
for the terminal voltage to recover to these o/c values before taking
the next sample. I have been told that measuring SG is more reliable
but I can't do that with a simple data-logger and anyway I think some
wait for H2SO4 diffusion to subside would still be needed. Anyone have
a SOC vs on load table? Hans Kroeger where are you?
Dick

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Yevgen Barsukov - 26 Jun 2008 14:08 GMT

On Jun 21, 4:23 pm, "rql...@ieee.org" <rql...@ieee.org> wrote:

> I recently replaced my two Interstate SRM27 (85ah) with SRM27X (105ah)
> and would like a non-destructive test of their ah capacity. I propose
[quoted text clipped - 7 lines]
> a SOC vs on load table? Hans Kroeger where are you?
> Dick

SOC vs load (and temperature) are not going to be generic because
IR drop is highly dependent on particular battery design.

And even if you would measure profile for a particular design "new"
battery, impedance changes very fast with aging, so your IR drop
will quickly become different enough to throw off the calculation.
For that reason, accurate capacity gauges (such as impedance track
series)
are actually measuring IR drop and adjusting it for aging.

Regards,
Yevgen

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rqlhgl@ieee.org - 04 Jul 2008 00:12 GMT

> On Jun 21, 4:23 pm, "rql...@ieee.org" <rql...@ieee.org> wrote:
>
[quoted text clipped - 22 lines]
> Regards,
> Yevgen

Yevgen,
Do you then recommend that I assume full original capacity, measure
the SG, discharge at AH/10 rate for say 50% rated SOC, wait 1hr and
remeasure the SG?
Regards, Dick

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Yevgen Barsukov - 05 Jul 2008 15:42 GMT

On Jul 3, 4:12 pm, "rql...@ieee.org" <rql...@ieee.org> wrote:

> > On Jun 21, 4:23 pm, "rql...@ieee.org" <rql...@ieee.org> wrote:
>
[quoted text clipped - 28 lines]
> remeasure the SG?
> Regards, Dick

I think for lead acid battery you need to wait much longer, say 10
hrs.
And I would measure at more points, say every 20% discharge.

Regards,
Yevgen

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rqlhgl@ieee.org - 05 Jul 2008 17:52 GMT

> On Jul 3, 4:12 pm, "rql...@ieee.org" <rql...@ieee.org> wrote:
>
[quoted text clipped - 37 lines]
> Regards,
> Yevgen

Thanks Yevgen,
When my ordered hydrometer arrives I will conduct such a test and
report back.
Dick

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Natural Science Forum / Chemistry / Electrochemistry / July 2008

determining flooded deep cycle SOC?