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Re: (ET) Fully charged pack voltage
Ah-hah! I had been trying to find something like that on Trojan's website. Hm, so they say that the open circuit cell voltage should be 2.122 V for 100% charge, which translates to 38.2 V for a 36 V battery pack. Ok, that is definitely useful information. So, the Landis should definitely then be set higher than 38V.... According to page 12 of that document, they are indicating that you should charge it at 2.45 to 2.70 V (per cell) to get it up to 100% SOC. That translates into 44.1-48.6 V for our packs. I think I will try setting the Landis at 39 V and see how it works. That wouldn't be a great setting if I intended to leave it continually plugged in (i.e. all week long), since the pack voltage should apparently eventually drop back down to around 38.2 V (according to the info on that Trojan page) - so the charger would keep kicking on even though the batteries are fully charged. But, if the Landis is set at 38.2V, since the decay from the charging voltage back down to the resting voltage of the pack seems to be very slow, it would take a lonnng time for the pack to charge if the charger only comes back on when the voltage has dropped back down below 38.2 V. So, I'll try 39 V as a "happy medium" and see how that works. 

Thanks,
Mike

--

--------------------------------------------------------------
Michael S. Briggs, PhD
UNH Physics Department
(603) 862-2828
---------------------------------------------------------------

On Thu, 23 Apr 2009, SteveS wrote:
It actually can take up to 24 hours to get to resting voltage. And I don't think you can 'hurry' it up by momentarily applying a load. 

Here's a good reference:

http://www.trojanbattery.com/productLiterature/documents/UsersGuide_0109_English_001.pdf

- SteveS

Michael S Briggs wrote:


 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
>        ---------------------------------------------------------------
> > > _______________________________________________ 
>        Elec-trak mailing list
>        Elec-trak cosmos phy tufts edu
>        https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
> > > > 
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