Re: (ET) Found the problem with the charger

["David Roden" <etpost drmm net>]

Yep, NiCd chemistry is touchier than lead, and lithium is an order of 
magnitude more challenging than NiCd.  

Flooded lead: a little overcharging is fine.  Gross overcharging shortens 
its life.  REALLY gross overcharging might be hazardous.

Valve regulated lead: overcharging shortens life significantly.  Gross 
overcharging might be hazardous.

Flooded NiCd: overcharging is part of its life.  Gross overcharging might 
be 
hazardous.  I know of a person who caught his expensive, irreplaceable 
NiCd 
EV battery on fire when he forgot and went to sleep while trying to charge 
the battery with a boat-anchor lead battery charger.

Lithium: I am far from an expert here, but from what I hear, overcharging 
can set the battery on fire!  Some species of lithium batteries have 
flammable electrolyte, which makes things worse.  A lithium fire burns hot 
and is hard to put out.  

http://www.gazettetimes.com/news/local/article_803a17e6-afd8-11e0-bedd-
001cc4c03286.html

http://tinyurl.com/czphnfj

Lithium batteries have a heaping helping of energy in a small, somewhat 
unstable package.  They deserve and require serious respect.  

You do not want to overcharge a lithium battery.  You need a BMS that can 
shut off your charger when it's full, AND a safety backup that can shut 
off 
the charger if the BMS fails or gets confused and doesn't do it.

There are applications where lithum makes sense - where you need maximum 
capacity and minimum weight.  It's hard for me to see how that applies to 
an 
ET in normal service, but maybe I'm missing something. 

Lithium makes sense for a push mower and I will probably head down that 
road 
sometime this summer or next.  However, I have no interest whatsoever in 
converting either of my ETs to lithium batteries.


David Roden - Akron, Ohio, USA

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