 Charging "nonrechargable" batteries
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Conundrum
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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
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Hi.
The recommended method that EPE published is a "burp" or "reflex" charger.
Principle is to deliver short, high current (500mA) pulses at around 2V/cell max at a duty cycle of 10% (100ms/1 sec) with a temperature feedback that lengthens the pulses (more off time) as the cell temperature rises and then shuts off if the cell exceeds 40C. Also its worth adding a failsafe that monitors the internal resistance by applying a load, if the load voltage collapses during charging then the cell is too far gone.
The idea is to allow time for the cell to absorb the charge and therefore not generate gas, but also to charge it in less than a couple of days.
*Never ever* trickle charge them as this will result in hydrogen buildup (electrolysis) and possible explosions!!!!!!! even after leaving the cell for days.
No known method I have run into can safely charge:- PP3's of any type, Li+ primary cells.
That said, I discovered that Li-Ion phone prismatic cells with the lost capacity syndrome *can* be safely recharged back to 75/80% capacity if they drop below 3V/cell by using a surplus 12V PSU fan. When fan stops, reconnect to phone.
I've also found that no-voltage Nokia packs are recoverable by peeling off the little telltale sticker near the contacts. under here is a bypass that connects to the cell and applying a very well regulated 4V via 100 ohm resistor here can get these going again enough to resume normal charging. I've used a 7805 with a Si diode in the gnd lead for this.
Measure first, if 0V on all pin/bypass combinations the cell is deceased.
#include "disclaimer.h"
#include "legal legal lawyers blahdeblah sue blah no chance.h"
Just my $0.02 worth.
-A
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