On Thu, 23 Apr 2009, John J Casey wrote:
> In my experience, the onboard ge charger takes my newish T-105's up to
> 44-45v over an 18 hour cycle, the last 3-5 hrs between 44.4 and 45v for
> cell
> equalization. End the charge cycle and in a short time the voltage
> settles
> back to 39v.Jack
So, the fully charged pack then has a voltage of 39 V (since that is what
it settles to after charging).
One thing that is troubling me - what does it take a while for the
battery's voltage to gradually drop from the elevated charging voltage
down to its resting voltage. I know that while charging the voltage
applied will be higher than the battery's voltage due to the voltage drop
across the internal resistance of the battery (batteries) - but once the
charger turns off, I would think that the battery pack voltage would drop
rather immediately down to its resting voltage (the potential difference
that the chemical reactions taking place at the electrodes produce).
BTW, this has some interesting information about how the internal
resistance of the electrolyte changes with state of charge, which gives
lead acid batteries their unique voltage vs. state of charge curves:
http://www.arttec.net/Solar_Mower/4_Electrical/Battery%20Charging.pdf
The main thing I'm trying to figure out right now is what to set my
Landis charge controller to to make sure that the pack gets fully charged
(and doesn't take 3 days to get there). It would seem that the default 38V
setting is too low, since the pack should be higher than that when fully
charged.
Thanks,
Mike
> On Apr 23, 2009, at 8:13 AM, Michael S Briggs wrote:
>
>
> I just got a nice new pack of Trojan T-605s (slightly lower
> capacity than T-105s, with a proportionately lower price). I'm
> trying to figure out what the voltage of a fully charged new
> pack *should* be, and I have seen very different things as
> skimming through the archives.
> My understanding is that the chemical reactions taking place in
> a lead-acid cell produce a potential difference of 2.13 Volts,
> so a fully charged lead-acid battery measured with a very high
> impedance voltmeter should measure that 2.13 Volts per cell, or
> 6.39V for a 6V battery, and 38.34 V for a 36V pack.
> But, I have seen statements in the archives saying that a fully
> charged pack should have a voltage of 42V or so (various posts
> saying anywhere from about 40V up to 44V).
>
> Thanks,
> Mike
>
> --
>
> --------------------------------------------------------------
> Michael S. Briggs, PhD
> UNH Physics Department
> (603) 862-2828
> ---------------------------------------------------------------
>
>
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>
>
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