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

[tb <tbamc gbta net>]

In my experience, good batteries, fully charged, read closer to 6.4v than 
6.2v.  Big difference.  That said, when my voltages "a while" after 
charging, are around 6.24, I can mow for at least an hour, maybe 2.

You could also check your Landis by just charging one, or two, pack 
batteries with a car charger.  If they end up significantly above 6.24, 
there's your answer.

Thon


On May 17, 2017, at 5:24 AM, Briggs, Michael wrote:

> 
> Hm, ok, I'll first try to measure the voltage of the pack under load. I 
> measured each battery individually yesterday (with no load, and a few 
> days since any charging had been done) and they all measured 6.22 to 
> 6.24 volts, which is where they should be. Measuring under load is a 
> little more difficult.... I could bypass the seat switch temporarily I 
> suppose. That would make it easy to measure the pack while the blades 
> are going. 
>    I don't suppose there's a known scale for the "fuel gauge", to know 
> what the voltage is if for example the gauge is right between green and 
> yellow? 
> 
> 
> Thanks,
> Mike
> 
> ________________________________
> Michael S. Briggs, PhD
> UNH Physics Department
> (603) 862-2828
> ________________________________
> 
> ________________________________________
> From: David Roden <etpost drmm net>
> Sent: Wednesday, May 17, 2017 1:03 AM
> To: elec-trak cosmos phy tufts edu
> Subject: Re: (ET) E-15 not getting out of first speed
> 
> 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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