<VV> Electric Corvairs

Thu Dec 1 19:56:35 EST 2011

 It's not so much the same voltage among the cells, it's the issue of overcharging/undercharging any given cell, which is utterly fatal to Li-ion cells. As such, each cell needs to be monitored and charged individually. Look at a laptop battery connector. The number of terminals is the number of cells +1 for that reason. 

Fortunately, thanks to cheap integrated circuits, there's lots of chips out there that do exactly that function, and lots of times, they're built right into the battery. 

That way, the battery, at the end of charge, has all the cells fully charged and none overcharged. Also, when the battery is discharged, the battery shuts down when any one cell hits the low voltage threshold. 

John Roberts

-----Original Message-----
From: Ulli Dittmar <info at california-camping.de>
To: Joel McGregor <joelsplace at earthling.net>
Cc: virtualvairs <virtualvairs at corvair.org>
Sent: Thu, Dec 1, 2011 5:47 pm
Subject: Re: <VV> Electric Corvairs

The major thing on charging lithium -Ion batteries is that any cell has to have 
almost the same voltage - there is a min/max difference between the single cells 
of 0,01 Volt.
This is the challenge to any charging unit- the charging is the key to have a 
reliable system and enduring batteries. You have to monitor any single cell and 
have to have a monitoring and a charging curve for any cell in the system.

Ulli

* This E-Mail was made with 100% recycled electrons!

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California-Camping.de by blendend

Ulli Dittmar
Ahornweg 4a
D.85354 Freising

Tel.: +49 - (0)81 61 - 533 84 78
Mobil +49 - (0)172 - 850 53 74
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www.california-camping.de

Am 01.12.2011 um 22:41 schrieb Joel McGregor:

> The car batteries are treated much better.  I think the computer in the car 
keeps the charge level between 10 and 90% or something like that.  They all have 
cooling systems for the batteries too.  Heat and over/under charging are the 
quickest way to kill Lithium-ion batteries.  Most laptops will completely charge 
and discharge the battery which supposedly shortens the life significantly.  My 
experience with laptops is that newer batteries are much worse than older ones.  
I have a Compaq R3000 that is about 8 years old and the battery is still fine.  
A lot of other laptops I've had the battery starts degrading quickly after about 
a year.  My Fujitsu charges the battery to 100% but won't start charging again 
until it drops below 92-94%.  The Fujitsu will completely self discharge in a 
couple of weeks where the Compaq only loses around 2%.  I've had much better 
luck with cell phone batteries but my phones all quit charging when the battery 
gets hot.
> Corvair content:  The laptop I use to monitor/tune the Megasquirt in my '65 
has about a 10 year old battery in it and only lasts about 2-3 minutes which is 
good enough for when the inverter drops out when I'm starting the car.
> Joel McGregor
> ________________________________________
> 
> If lithium-ion batteries are so long lived, then why do the ones we use in
> our laptops die out after 4 or 5 years?  The first one I got with my Dell
> lasted a little over 4 years and the second one is already down almost 40%
> in  capacity after about 3 years of use.  My usage is primarily plugged into
> 120 volts AC with only very occasional use on only the Li-ion battery.
> What aging experience do the rest of you get with the Li-ion batteries in
> your laptops??????????
> 
> Frank Burkhard
> Boonton, NJ
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