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Re: (ET) charger voltage




Dave,
Thanks for the feedback, that's essentially what I wanted to know - what the voltage is these 6 volt batteries will hold. As far as I see it, if they'll typically hold 6.3 V each (so just under 38V combined), there's no reason the charger NEEDS to put out 42-45V. That high of a voltage will charge it quicker, but won't give a more complete charge, since the pack itself can't stay above 38-39V or so, depending on the batteries. My charger is putting out around 39.5V roughly, which to me means it should be able to fully charge the pack - it will just take longer than it would if the charger was putting out a higher voltage. Since the Landis controller stops charging once the pack reaches 38V, it wasn't making any sense to me why people were saying the charger needs to put out 42+ V to fully charge the pack, since presumably fully charged is only around 38V. 42V+ will charge quicker (greater potential difference between the charger and battery pack, so more current will flow into the pack), but quicker isn't necessarily better, especially when dealing with charging batteries. I'll measure the capacitance of the charger capacitor anyway (have a multimeter that can measure capacitance) to see if it's ok or not though.

Thanks,
Mike

--

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

On Thu, 27 Jul 2006, David C Robie wrote:

Depends on the age of your batteries.   New batts are about 6.5 ea.
Average batteries chg to about 6.25 6.3 (where do you think vacuum tube
heater voltage std 6.3 came from?  2.2V/cell).  Older ones (like some I
got) chg to maybe 6.15. No matter how long or what rate you charge a lead
acid battery like we use, it will not go over this 'age and abuse
related' voltage.
   If you find one in the string that's consistantly low, swap it outa
there.  Your tractor will thank you.

Occasionally. people 'equalize' batteries by intentionally overcharging.
This ain't good for them.  If I find a low one. I put it on a separate
6V charger to bring it up as far as, by experience, I know it will go.
My packs were not bought new, they are recycles and inherently some are
better than others.  I make sure each fall that the best ones go in the
tractor that has the snowblower.

Charge em to the point that every cell is gassing.  Then leave em
overnite to remove 'surface charge'.  Test em in the morning.   That will
tell you where your batts are at agewise.   Of course, to charge them the
voltage of the charger must be a little over this.
   So, depending on battery condition, anything from half a volt over
about 36.5 to 39
will trickle charge em, and a volt or two above will hi rate charge em.
(the charge voltage automatically tapers down because of the capacitor -
it and it's winding is called a ferro resonant circuit which is a form of
regulator) (therefore, open circuit voltage means little except too low =
bad capacitor.

Dave
Weymouth MA



On Wed, 26 Jul 2006 18:50:03 -0400 (EDT) Michael S Briggs
<msbriggs alberti unh edu> writes:

I've been scanning through the archives, and also the Service
Manual, and
am seeing some mixed messages on this - what voltage should the
charger be
putting out to the batteries? Mine's putting out a shade under 40 V
(39.5V or so), and they seem to not be holding as much energy as I'd
like
(T-105s that are a few years old, bought used). According to the
Service
manual, 40-45 V is ok (well, not on exactly the same wires as I'm
measuring the voltage, I'm measuring across the battery pack, rather
than
at S3 and S1 directly on the charger, so there's presumably a small
amount
of voltage lost between the points the manual says and the points
I'm
measuring at, especially if some weak connections, such as at the
Diode
heat sink). According to the archives online, I've seen people
saying that
if the voltage isn't 42-45V, the charger won't fully charge the
batteries
enough (some people who replaced the capacitor when the charger was
only
putting out 39V or so, for example).
        With mine charging, the charge meter goes slightly into the
white
section - whereas in the archives, I've seen statements that if the
meter
doesn't go all the way to the high end of the white section, the
batteries
won't get a full charge.
        On the other hand, the Landis controller only has the
charger on
when the pack voltage falls below 38V, by default, unless you adjust
it
up. So, if charging to 38V will give you a full pack, then there's
no need
to have the charger putting out more than 39V or so (other than that
the
higher the voltage it puts out, the quicker the pack will charge).
        So, which is it? Is 39-40V from the charger ok, or should
it be
42-45?
        Essentially it comes down to - what should be the voltage
of a
fully charged battery pack (I know it's higher than 36V, but how
much?)?

Thanks,
Mike

--

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

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