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

[john j casey <jjcrmc verizon net>]

Would a specific gravity test be in order?
Cheers, jack

On May 17, 2017, at 1:03 AM, David Roden wrote:

> 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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