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

["David Roden" <etpost drmm net>]

The Landis algorithm is, in my view, kind of ... unorthodox.  It's like a 
reversed hacked cycle-dropping algorithm.  

The cycle dropping design is commonly used in low-end automatic car 
chargers 
and in some cell-leveling BMSes for lithium batteries.  

A cycle-dropping charger turns off at the battery's "full" voltage 
(typically 2.35 - 2.5 vpc), and turns back on when the battery has fallen 
some tens of mv per cell below that.  This is usually a matter of seconds. 
 
It results in a similar cycling on and off, gradually more off than on, as 
the battery charges.  You thus get a rather crude approximation of an IU 
charge algorithm with an extremely coarse PWM.

One good thing about a cycle dropping charger: the upper voltage limit 
ensures that it's hard to overcharge your battery, as long as you use it 
within reasonable temperature ranges, and disconnect it when the "done" 
light is on for long periods with just brief flashes.  

It isn't an optimum charging algorithm, you almost never find temperature 
compensation used in it, but it's cheap to implement and it's better than 
nothing.  I give it a C+.

Mr Landis's algorithm has a lower limit, but no upper limit, only a fixed 
length ON timer (5 minutes, IIRC).  The only real upper limit is the GE 
charger's output voltage.  I've never seen his algorithm used in any 
commercial charger.  

With no upper voltage limit and no current regulation, I'd expect it to 
overcharge rather than undercharge.  However, if the setpoint isn't 
configured correctly on each charger (or, just as likely, is unstable and 
drifts with time and/or temperature changes), the results are 
unpredictable.

I should add here that Mr Landis and I have something of a long running 
amiable feud on this list over the utility of his gadget.  I respect his 
ambition and the thought that went into its development, but obvously I'm 
a 
skeptic about the resulting product.  :-)

As I understand it, he designed it as a battery maintainer, not as a 
charge 
controller for cyclic use.  However, my experience with batteries has 
shown 
me that battery maintainers usually do more harm than good.  

(More batteires die from overcharging than from undercharging. Almost all 
battery maintainers overcharge.  When your ET is idle, wipe the tops of 
the 
batteries clean.  Turn your normal charger on for a few minutes once every 
month or two.  You'll be fine. No gadgets needed.)

If you want to take better care of your ET's batteries and get longer 
cycle 
life from them, chuck the whole 40+ year old business and replace it with 
a 
good quality modern lghtweight switchiing type 36v automatic golf car 
charger.  (Or with an old but very good boat-anchor Lester Lestronic or 
Lestronic II.)

PS - if you'd like to experiment with building your own cycle dropping ET  
charger, here's a schematic of a 48 volt version you can try to adapt 
(probably just change the transformer and tweak the value of R-4 and/or R-
6).  It was used by Sebring-Vanguard in the late Citicars.

http://www.evdl.org/docs/c_car_charger.jpg


David Roden - Akron, Ohio, USA

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