Re: (ET) E-15 not getting out of first speed

["David Roden" <etpost drmm net>]

On 17 May 2017 at 0:35, Briggs, Michael wrote:

>  I'm wondering if I'm just not charging long enough. I'm using a Landis
> charge controller. 

I would definitely try bypassing it.  That said, if it's been 
undercharging 
the battery for some months or years, the damage to the battery (hard or 
permanent sulfation) is probably long since done.  

A sulfated battery will have a lower on-charge maximum voltage, lower 
operating voltage, and reduced capacity.  These phenomena aren't 
reversible 
in any meaningful way; the damage is permanent.

I already suggested measuring your batteries' voltage under load (while 
driving the tractor and perhaps mowing).  I don't see any other way you 
can 
determine whether they can maintain enough voltage to run the tractor 
properly without connecting a voltmeter to them and reading it under load. 
 
Sorry, but "they can hold a charge well enough to mow for a while" doesn't 
really tell us anything of value here.

As for measuring their capacity, the easiest and cheapest (if approximate) 
way I've found requires a 12v inverter, preferably with a capacity of at 
least 1000 Watts; an AC powered analog clock with hands (check garage 
sales 
and thrift stores); and a 120v load of some kind. 

The ideal load will put a 75 amp load on the battery, because then you can 
compare the battery's actual measured capacity to its factory reserve 
capacity specification.  For a golf car battery, reserve capacity is 
normally stated in minutes of operation at a constant 75 amps until the 
battery falls to 5.25v under load.

Most cheap inverters are around 70-85% efficient when running at around 
2/3 
load.  Let's take 80% as a reasonable approximation.  If you have a really 
good inverter with higher efficiency, just plug that value into the math 
that follows.

This is not lab equipment and the actual current and voltage will vary 
over 
the test, but remember, I said this is an approximation!  At an average of 
12v, an average 75 amp avg load will be an average 900 watts from the 
battery.  Allow for 80% efficiency and you get 0.8 * 900 == 720 watts of 
AC 
load to put on the inverter output.  This can be approximated pretty well 
with three 250 Watt incandescent light bulbs.  

If all you have at hand is a small (< 1000W) inverter, you can still do 
this 
measurement, but then you have to convert to amp-hours and adjust for 
Peukert capacity.  It's just a little more time and a little more math.

Connect the inverter to a pair of charged 6v batteries in series.  Set the 
clock to 12:00:00 and plug it into the inverter, along with the lights. 
Let 
'er rip. 

When the batteries are effectively flat (around 10.5 volts under load), 
your 
inverter should automatically shut down.  You may have to keep an eye on 
it, 
though, because some inverters will start up again when the battery 
voltage 
rises after a rest, throwing off the test.

When the lights go off and the clock stops, read the hours and minutes of 
reserve capacity from the clock.  Assuming you used 750W of lights, 
convert 
to minutes and compare to the batteries' factory specification.  Typical 
golf car batteries' RCs are 105 to 125 minutes.  A battery is considered 
spent when its capacity is below 80% of specification.


David Roden - Akron, Ohio, USA

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