L-16 charging voltages [RE-wrenches]

Sat May 21 09:19:00 PDT 2005

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David wrote:
all the cells are equally charged. This can happen at voltages lower
than 15.5v

Hey David - here's my .02$US,

It really depends upon the charge controller in use.  If single stage,
you're gonna need EQ's, at least if you have paralleled batteries or
series strings.  In small cabin systems with a single stage Sun Saver, I
usually install an EQ switch that both bypasses the CC and turns on a
little red LED.  But if you have more than a cabin system, and a bigger
battery, you'd want a three stage CC. 

Some three stage CCs use a timed absorption period some of which are
programmable.  I feel the larger the battery, or at least the more
paralleled strings, the more time it should spend in absorption.  

Blue Sky uses a really cool method of determining the float transition.
When the amount of current it takes to hold battery voltage at the
absorption voltage set point falls below a programmable setting (float
transition current, based on battery size), the CC drops into float.
Theoretically, if some of the cells are still absorbing current, the
current will be above the float transition set point.  But, if the
battery had seen very slight discharge the night before, the CC will
spend very little time in absorption rather than the default 2 hours of
timed CCs.

Kurt Nelson

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Kurt Nelson
PO Box 309
Cornucopia, WI 54827
715-742-3406
sunwise at cheqnet.net

-----Original Message-----
From: David Palumbo, Independent Power & Light [mailto:ipl at sover.net] 
Sent: Thursday, May 19, 2005 3:51 PM
To: RE-wrenches at topica.com
Subject: RE: L-16 charging voltages [RE-wrenches]

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Wrenches,

Allan's charge voltages listed below look good. Of course the
temperature of
the batteries needs to be considered.

I do take issue with the statement on equalization though. The
definition of
an equalized battery is, all the cells are equally charged. This can
happen
at voltages lower than 15.5v (nominal 12v bat) although that works too.
I've
been working with deep cycle bats for 20 years and have seen plenty of
sets
have long service lives without ever going over 15v. It depends on many
factors. I have found that if the battery bank receives a full charge at
least once every seven to ten days then the need for an "equalization
charge" with an elevated voltage is typically not needed.

Living and working on off grid systems in the North East, where we
usually
have many cloudy days in Nov. and Dec., I saw many people running their
generators too many extra hours every month performing EQ charges. I did
some testing and experimenting with various battery banks and found that
much of the extra gen run hours was not necessary and wasted allot of
fuel
and gave off grid pv systems some bad publicity (too much running of
noisy,
polluting generators). The caveat is that you must have a well designed
system and pay attention to an accurate (and well programmed) amp hour
meter
to insure that the systems batteries are getting a full charge every
week to
ten days. Mr. Surrette told me years ago that in his view a fully
charged
battery was in fact an equalized battery. He recommended charging
voltages
of 14.6 to 14.8v, temp compensated.
When in doubt test each cell with a hydrometer, or refractometer.

Of course if you have a situation where the system is poorly designed,
or
people are abusing it etc. then the elevated EQ voltage may be
necessary.

Dave

<<From: Allan Sindelar [mailto:allan at positiveenergysolar.com]
Geoff,
30 volts isn't an equalizing charge. I generally shoot for 31-31.5,
which is
easily achievable with C/10 if the batteries are in good condition.

Here's Trojan's spec for their L16s: See
http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/Charging.as
px
Table 2. Charger Voltage Settings for Flooded Batteries
        System Voltage
      Charger Voltage Setting 6V 12V 24V 36V 48V
      Daily Charge 7.4 14.8 29.6 44.4 59.2
      Float 6.6 13.2 26.4 39.6 52.8
      Equalize 7.8 15.5 31.0 46.5 62.0

----- Original Message -----
From: "Geoff Greenfield" <Geoff at Third-Sun.Com>

finally - and this could be a separate thread - the US batt
website/instructions call for charge current at c/10 and charge voltage
at
2.583 per cell!  That is 30.966!!!! and then hold for 2-4 hours!!!!
What????
Their float spec was 26.04 Volts (2.17/cell).  I know that "cycled"
batts in
scrubbers in the different universe of grid fed chargers are different,
and
we often "modify" these parameters to find a balance between health of
the
batt, what the RE system can provide, and watering chore frequency...
but
these numbers seem off the charts.  I would equalize at 30!

WRENCH SURVEY:
Please share your set points for L-16s (T-105s?) KS-17s (Surette/IBE)
and
gells/AGMs - this I think would be very useful info.>>

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