On Monday, October 23, 2017 at 11:01:42 AM UTC-7, sms wrote:
On 10/23/2017 10:53 AM, Ian Field wrote:

snip

I don't get it! - I use a simple DIY charger and never had an accident.
Commercial manufacturers seem intent on comic people cartwheeling
through the air.

If you're using protected cells you won't have any problem.

It's also very different when you're charging two cells in series at
8.4V or one cell at 4.2V. You already have two levels of protection, the
voltage is correct and the PCB in the battery doesn't let the voltage
exceed 4.2V.

At work, we had been charging unprotected cells with a variable power
supply at 8.4V. This worked just fine. Except when we had a product that
used a single cell and the tech hooked it up to the 8.4V--quite a mess
when it exploded and caught fire on the bench.

Commercial manufacturers are doing high-rate charging while monitoring
temperature. They are also often charging in parallel but discharging in
series, or a in series-parallel combination.

All of my speedos use 2032 cells. I used to just buy a card of them and insert new ones. Then I realized that they are Li-ion. Do these things charge up again?