Charging Li Ion batteries.

[Jim-The-Dinosaur]

Ask me about lead acid and I'll write you a book.

But I have a Chinese 36V 5AH (on the label) Li Ion battery pack. I want to charge it and not die or burn my shop down.

Eyeballing what's at hand: a variac, bridge rectifier, capacitors, multimeter, resistors, battery pack.

So can I just fly variac, rectify, filter, current limit, and drive the pixies home at 36VDC?

(for this particular problem, I'm not designing and building a regulated 36V power supply)

I did Ohm's meth, and 48 - so call it 51 Ohms in series will be about 750mA to the battery pack

I don't care if it takes all night .. I just don't want to blow shite up on a Friday night.

This janky setup going to be okay enough?

 

[danadak]

LiOn batteries have significant SAFETY ISSUES.

I place packs outside, rain protected, to charge using battery recommended
charger. Trust from all the LiOn fires I see on news make me very cautious.

A properly design charger detects pack T and manages based on that,
current and V.

So janky approaches make sure your building insurance up to date
and policy covers LiOn battery presence.

USE A PROPERLY DESIGNED CHARGER

Get datasheet for the pack you are using to see what protection circuits
they may/may not have.

Or use your variac, a rectifier, connect up and run away !

 

[Jim-The-Dinosaur]

Well yes, if I had the proper charger I would be using it.

If the pack isn't buggered, I'll look into building a proper charger.

If it is buggered, I'll tear it down and do have a charger for individual 18650 cells.

I'm just wondering if pounding 3/4 of an amp up the butt of a 5AH pack at loosely regulated sticker voltage is going to be kosher.

 

[bertus]

Hello,

Read the following pages from the battery university about li-ion batteries and safety:

BU-205: Types of Lithium-ion

Become familiar with the many different types of lithium-ion batteries: Lithium Cobalt Oxide, Lithium Manganese Oxide, Lithium Iron Phosphate and more.

batteryuniversity.com

BU-304a: Safety Concerns with Li-ion

Learn what causes Li-ion to fail and what to do in case of fire. Battery makers are obligated to meet safety requirements, but less reputable firms may cheat.

batteryuniversity.com

BU-304b: Making Lithium-ion Safe

techniques for making lithium-ion batteries safe including the role of protection circuits

batteryuniversity.com

BU-304c: Battery Safety in Public

BU meta description needed...

batteryuniversity.com

BU-409: Charging Lithium-ion

Figure 1 shows the voltage and current signature as lithium-ion passes through the stages for constant current and topping charge. Figure 1: Charge stages…

batteryuniversity.com

Bertus

 

[Martaine2005]

Have a watch of EEVblog from many years ago.
Lithium ion/polymer charging tutorial

 

[Jim-The-Dinosaur]

Have a watch of EEVblog from many years ago.
Lithium ion/polymer charging tutorial

Ah, good ol' Dave. Yeah, I think that gave me my answer. Unfortunately to questions I didn't know I had to ask.

Which now leaves me with a pickle as to whether build proper kit which may come to naught if the pack that someone else tossed, and I don't actually need, is junk- or put it in the get around to it bin