Re: FW: (ET) batt's, new gauge points, and a faq draft for discussion

[<daveb seanet com>]

For me this is a great and timely write-up.  Thanks Larry!

I just bought 6 brand new US2300 deep cycle batteries. BTW the caps on 
these 
are really slick being tied together with an easy thumb fore-finger grip 
to 
loosen and remove all 3 caps at once.  very nice.  And they're less likely 
to 
get lost or knocked about.

Anyway I've had these questions about the timer of my E15S's charger:

1.  It doesn't appear to matter if I turn the knob clockwise or 
counter-clockwise.  True?  Or am I damaging (have damaged) something doing 
this?  Usually I turn it counter-clockwise to the desired (guessed at) 
setting.

2.  From memory I think the knob has these 3 markings  1-2yrs,  3-5yrs, 
5-6yrs
with 1-2yr giving the longest charge (about 18hrs?).  For me, Larry's 
write up 
begs the question of what setting is best for my virgin batteries?  Or 
should I 
baby sit them the first coupla times taking voltage readings every 3 or 4 
hours 
(difficult for me to do because the e-trac is not at home being at best an 
hour 
away)?  I realize new batteries will have larger capacity than old 
probably 
sulfated batteries hence the longer charge times for new batteries. 
Correct?  
but is it advisable to "bulk" charge brand new batteries for a full 18 
hours?

thanks again,
dave
E12S
Seattle


> 
> I feel a bit humbled.  Over a week ago, after posting a quick suggestion 
> on 
charge
voltage, I was corrected by Harry Landis and Marty Canada.  Although I 
have 
worked with
automotive charging systems for years, and have 4 ET's at the moment, I 
began 
to doubt
some voltages I had read.  In private E-mail, Harry was quite persuasive 
on the 
levels I
was claiming AFTER charging.  I have been working with ET's for years, and 
they 
have not
all been in the same condition.  That troubled me.  So, last weekend, I 
decided 
to check
the gauge on some tractors.  I had before, but, hey, let's be sure.  I 
used a 
good HP
power supply, and a DVM that does true RMS, although the AC ripple from 
this 
supply is
tiny, to make sure that I read what the gauge read.  Turns out my 'best' 
gauge 
did NOT
agree with my old numbers.  These are quite different.  The error 
increased 
with voltage,
at least until in the 'charge' range.  In the past, I usually only got out 
the 
DVM at the
end of charge to make su!
> re the batteries were all the same.  I have indeed charged to VERY high 
voltages but in
most cases, at the time when I started mowing day-to-day, I just read the 
gauge 
with my
marker notes on the face.  Those face notes were based on bad data.  I'm 
sorry.  
I still
stand by all the numbers on charging for cars (something I do know about) 
and 
the point at
which I stopped charging, because I often measure it.  But all my ET 
OPERATION 
numbers
were just TOO HIGH.  That said, going back over my typical charge numbers; 
I 
end my charge
at 42V to 43.5V, (in the white region) as measured by a good DVM, on all 
tractors, and may
have never exceeded 45V.  I have measured over 40V one hour after charge, 
but 
probably
never significantly more.  Probably never that high on the next day.  I 
normally am seeing
about 39V a day or more after charge, as measured by a good DVM; these 
last 3 
represent
different values than I have given in the past.  These more reliable 
values 
should be
represented !
> on any FAQ.  That said, 38 or 39V at the end of the charge cy!
> cle (with the charger still on) is too low to get to the right cell 
> voltages 
except
possibly with a perfectly balanced set of new batteries.  That was and 
still is 
my main
point.  For more on that, see below.  Based on other e-mail, I think most 
of 
this is
agreeable to Harry by now.  Are other gauges different?  Perhaps.  4 
Tractors 
(and one was
bad) does not make for good statistical data.  Thank you to those who 
corrected 
me. 
Comments are welcome.  More data is welcome as well.  I hope any faq is 
based 
on data and
not opinion, or at least, not on just one opinion.
> 
> I'm going to find a 2" round Digital/Analog so I can really keep track.
> 
> Open for discussion.
> 
> Comments, suggestions?
> 
> Preliminary FAQS on Meter Voltage (Fuel Meter)
> Standard Charger, charging voltage and battery voltage
> Meter Current (Load Meter)
> 
> The Fuel Meter on the GE, WheelHorse and New Ideal electric tractors are 
similar.
> 
> As far as we know, of the units based on a '36V' battery system use the 
> same 
2" gauge. 
The gauge is a Volt-Meter.  It's purpose was to tell the user roughly how 
much 
charge was
still in the battery pack in operation, and to give some indication of how 
if 
the
batteries were taking a charge.  Unfortunately, after 30 years, many of 
these 
gauges have
gotten moist on the inside and either failed or have had the needles the 
workings run on
go bad.  Often they are not operable.  Even worse; some gauges require 
voltages 
higher
than intended to show a given level of charge.  New gauges are available 
from 
Bill Gunn. 
Some people have replaced them with standard 2" gauges, but to do so one 
must 
understand
something of the scale of the gauge.  It does NOT start at 0V.  The 
following 
is a table
of needle reading and measured voltage for a gauge in correct working 
condition.  'E'
stands for empty, green is normal operating condition, with 'F' standing 
for 
full and
white is charge only ra!
> nge.  The numbers are when the needle splits the line between colors.
> 
>                                                               
> Needle just moves                                     19.8V           
> Bottom of red                                         26.7V
> Top of red, bottom of green, "E"              33.1V
> Top of green, bottom of white, "F"            39.0V   
> Top of white, bottom of upper red,            45.5V
> Top or upper red                                      47.3V
> 
> An earlier table has been posted (by me) with numbers on an old gauge.  
> At 
the bottom of
the gauge, the needle required an extra volt to register.  In the 
operation 
mode, it
required an extra 2 volts for the same position.  At the bottom of the 
charge 
region, the
error was 6 volts!  If your gauge reads far off the above values, you 
probably 
should
replace it.
> 
> It becomes clear from this table that the term '36V' tractor is a bit 
misleading.  By this
chart, 36V is almost 'empty'.  That is not really fair, as there is a lot 
going 
on in the
tractor.  The gauge is was a compromise, and one must understand a bit 
about 
both the
charger, the batteries and loads to understand how to interpret it.
> 
> First, the battery pack consists of (6) deep discharge wet cells, each 
containing 3
individual cells, all wired in series.  '36V' is a term used to describe 
what 
it is, but
is not a very complete description.  The following table gives normal 
voltages 
for each
cell, battery and for the complete pack by capacity or charge level (this 
is 
typical for
these tables, the values below 40% may change depending on manufacturer, 
at 
room
temperature with good batteries)***
> 
> Cell  Battery Pack    Charge Level
> 2.12  6.35            38.1            100%    *
> 2.08  6.25            37.5            90%
> 2.07  6.21            37.3            80%
> 2.05  6.16            37.0            70%
> 2.03  6.10            36.6            60%
> 2.01  6.03            36.2            50%
> 1.98  5.95            35.7    40%
> 1.96  5.88            35.3            30%
> 1.93  5.79            34.7            20%
> 1.89  5.66            33.9            10%
> 1.75  5.25            31.5            0%      **
> 
> *This battery has been fully charged to the design limits at a HIGHER 
> voltage 
and has
settled to this point in time.  See below.
> 
> **Essentially, although a single battery has some charge in it, it can 
> no 
longer do
effective work.  You may get the ET to work below 31.5V total with 5 
batteries 
well
positive and one battery 'reversed'.  The sum is less than 31.5V.  I have 
indeed seen
this.  See below.
> 
> The first question people may ask is:  Why the '36V' battery pack is not 
'full' until one
reaches more than 38V?  The answer is that each cell has been given a 
nominal 
value of 2V.
 When batteries in cars were 6V, the error in that statement was minor.  
With 6 
batteries,
the error is more obvious.
> 
> The second and more important question is: Why did GE mark the gauge so 
> badly 
to this
table?  Well, they weren't really marking to fit the table.  Nor did they 
do 
too badly. 
Several things come into play.  The state of charge table is talking about 
room
temperature voltage before use, not during load or charge.
> 
> First, let's talk about the bottom of the gauge.  The fuel gauge would 
> be 
used part of the
time under load.  Since a normal ET load is 50 to 100 Amps (see the load 
faq) 
this is
enough to lower the apparent voltage at the meter under operation.  This 
is why 
one can
mow until the gauge drops to the bottom of the red or even lower, which 
from 
the 'charge
table' above is BELOW 0% of capacity.  It isn't really less than 0%; if 
the 
load were
turned off under these conditions and one were to wait, the voltage would 
return into the
lower part of the red range in a few minutes, and in a half-hour may even 
return into the
green.  The battery has not 'recharged' but has indeed recovered a bit.  
If at 
that point
it is indeed at the bottom of the green, that is only 20% of capacity from 
the 
chart
above, much to low to do much except perhaps drive itself back to a wall 
plug. 
Regardless, the meter reading under load is always LOWER than it was 
sitting.
> 
> Second, let's talk about the high-end, the charge end of the gauge.  Why 
> did 
GE need a
gauge that displayed anything above 38 or 39V?  A typical assumption is 
that if 
2.12V per
cell is charged, than all one needs to provide is 2.12V per cell.  
Unfortunately, it isn't
that simple.  If you apply 2.12V per cell average, and then turn off the 
charger, you
would find that the batteries dropped to less than 2V per cell in an hour. 
 
Why?  2.12V is
the room temperature voltage one can measure some time after charging that 
represents a
full charge.  Charging warms up the batteries.  Additional voltage must be 
provided to do
that.  In addition, each battery consists of 3 series connected cells.  
There 
are 6 of
these batteries in series.  The cells are not identical.  One cell may see 
or 
'take' more
voltage than another.  The charger must make sure the lowest voltage cell 
ends 
up with
enough voltage to make sure that 2.12V is in that cell some time after the 
charger is
turned off.  Wit!
> h 36 cells, and with owners who may have used different ages and brands 
> or 
sizes of
batteries, and different internal impedances, GE decided to go with a 
bulk-charger capable
of bringing voltages significantly above what might be needed for perfect 
batteries.  This
is not unusual; most if not all bulk chargers at auto parts stores provide 
2.5 
to well
over 2.6 V per cell, and these are only concerned with 6 cells, not 18.  
Many 
tables
suggest 2.58V per cell at room temperature may be required.  Many of these 
chargers go
into a low current or 'trickle' mode at the higher voltages.  Even then, 
at the 
beginning
of the 'charge' section of the GE fuel gauge, the batteries are receiving 
an 
average of
some 2.2V per cell; at the top of the white range we have 2.53V per cell, 
more 
than enough
to warm them and cause them to begin to gas (release water vapor and 
perhaps 
even a little
hydrogen gas) at these levels.  Actually, some bubbling may be good in 
that it 
mixes the
electrolyte, th!
> ough one could just bounce the ET around a bit to do this.  T!
> oo much gassing is bad.  So is too much heat.  That is why GE included a 
timer to limit
the damage one is capable of doing.  There are better solutions, today, 
but 
this one was
inexpensive and does charge the pack very quickly.  Speed of charge 
appears to 
be GE's
main intent.  The GE charger's rating is about 20 amps, and since the 
recommend 
charge
rate for flooded batteries is capacity (in amp hours)/10, for 180 to 230 
amp 
hour
batteries, the GE is just about as fast as you would want to use without 
shortening
battery life.  It can draw up to 14A off your house line.  With most 
fuses/breakers set to
15A, it really isn't too bad of a design for charging fast.
> 
>   Proper questions about charge would be:  "What was the charged 
> voltage?" 
meaning what
was the room temperature voltage of the battery pack hours after charging 
but 
before use,
or:  "What was the voltage when you stopped charging?"  meaning what was 
the 
ending
voltage when the ET charger was turned off.  These numbers may indeed be 
about 
several
volts apart.  Another helpful question might be:  "How long were you 
charging?" 
but this
one implies that the charger was working correctly; most of the ones I 
have 
used were not
until they were repaired; a leaky cap will not allow a full charge in any 
length of time. 
Numbers that would not help tell us about the level of charge would be:  
"What 
was the
voltage when you began charging?"
> 
> 
> So, where do I stop charging?
> 
> Good question.  GE recommended a time system based on the age of the 
batteries.  Some of
us wait until the charger produces a voltage at roughly the start of the 
'charge' section
of the gauge.  Other find this voltage (39 to over 45V!) to be unsettling. 
 If 
one has a
leaky capacitor on the old GE charger, you will probably be unable to get 
beyond 38V,
which at the end of a charge cycle will probably only yield 36V or so (30% 
or 
less)
charge.  That isn't really enough.  A typical charge on a set of more than 
1 
year old
batteries will require something of the order of 42+V at the END of the 
charge 
cycle (with
the charger still on) to fully balance the cells.  New batteries will be 
better 
balanced
and require less.  Several year old batteries will require more yet.  
Don't let 
the
voltage go above the charge limit into the red; you will boil the 
batteries dry 
and damage
them.
> 
> Balancing cells.
> 
> Often when the fuel meter shows 'low', only one or two batteries are 
> really 
low.  Why? 
The lift is wired to 18V (3 batteries) and the lights to 12V (2 batteries) 
 
Especially if
the lift is used a lot (the rear-tiller for example) 3 batteries will be 
lower 
than the
others.  It takes extra time to get the voltage high enough to get the 
charge 
up in all
the cells.  Another way of handling this problem is to use a well isolated 
trickle charger
on the 'lower' batteries one or 2 at a time.  Either way, the ET begins to 
act 
very badly
with a low battery.  Under very bad conditions, one can even 
reverse-charge a 
battery. 
Reverse charge describes a condition where the + end of the battery 
becomes - 
and
vise-versa.  Leaving the battery in this state will permanently damage it. 
 The 
ET charger
probably may not bring a reverse charged battery back; a good 6V charger 
may be 
required.
> 
> What about when the ET is not used for long periods?
> 
> The ET charger is mostly a Bulk charger.  It dumps in voltage as fast as 
> it 
can. 
Absorption (or taper) chargers are a bit smarter; the voltage remains 
fairly 
constant but
the current tapers to a lower lever to prevent heat damage.  Most better 
auto 
chargers are
absorption chargers.  Float (often called maintenance or even trickle) 
chargers 
bring to
voltage to a set 'charged' level and then taper back to hold at roughly 
100% of 
the charge
level above.  Be careful; many so called 'trickle' chargers are really 
absorption
chargers.  If you want float, look for float or maintenance.  For long 
term 
use, a float
or maintenance charger is best.  There are controllers, like that by Harry 
Landis, which
operate by turning on the standard ET charger for a fixed time, based on 
the 
resting
voltage. This will dump in a slug of current whenever necessary to keep 
the 
pack topped
up.  This can indeed recover whenever the battery is sensed to be low.  
You 
don't want the
batteries to freeze, s!
> well and crack.  Leaky batteries damage the tractor.
> 
> Freeze?
> Yep, batteries can freeze.  The following is the GE table:
> 100% charge   -86F
> 75%                   -42F
> 50%                   -16F
> 25%                   -2F
> 10%                   +7F
> 
> In the north, if you park it for the winter with a full charge, it is 
> fairly 
unlikely you
will freeze a battery.  That said, a good charger can add years of life to 
the 
batteries.
> 
> Water level
> Check water level in the batteries periodically.  Check each cell.  
Especially if you have
been charging to a high voltage to equalize cells.  Cells lose water, even 
in 
normal
usage.  The batteries here carry extra water over the plates compared to a 
car 
battery. 
Water must NOT be below the plates, ever, if the battery is to be used.  
Distilled water
is best, but de-ionized will work in a pinch.  If the water is low, you 
will 
probably
overheat, warp and short out the plates.  Mixed and charged, the 
electrolyte is 
acid so be
careful.
> 
> 
> 
> Tractor Loads
> 
> There is no load gauge on an E8M or E10M.  The load gauge is a linear 
> current 
(amp) meter.
 An amp meter measures the voltage drop across a piece of wire of known 
resistance
(shunt).  The GE is marked by color, not current.  The shunt is a 20" 
piece of 
#6 gauge
copper wire.  The resistance of the shunt should be .000658 ohms.  A table 
of 
load
according to the gauge follows.
> 
> Bottom of green/0% = 0 mV.                            (Still 0)
> Top of green/bottom of yellow = 36 mV         (55 amps)
> Top of yellow/bottom of red = 64 mV           (97 amps)
> Top of red/100% = 90 mV                               (137 amps)
> 
> The table values courtesy Steve Naugler.  I don't guarantee the 
> condition of 
the gauge,
but I suspect they are about right.  Since a change of only 1/5" on the 
shunt 
length would
show up as up to an amp change, these values are probably no better than 
an amp 
or so. 
They compare well to a clip-on hall-effect probe, but it is pretty hard to 
change load
slowly enough to put the gauge needle right on a line and keep it there 
long 
enough to be
sure.  They are realistic based on how long 220 amp-hour batteries last in 
the
application.  It's also a bit humbling as 760 mechanical watts (and for a 
decent motor,
1000 electric watts) only puts out a single horse-power.  At 100 amps and 
36V 
we are only
doing around 3600 watts; ~<4 hp of work!  I think that's about right.  
Also 
note, normal
loads are less than 50 amps, and large loads (snowplow in heavy snow) are 
less 
than 100
amps.
> 
> Larry Elie
>