Li-Ion Battery Charger

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Datasheet says 400mA charge current.

A couple of questions to potentially save time...

Do you mind working with inductors?
Do you mind working with surface mount components?
I don't mind working with Inductors or surface mount components.
 

GopherT

Joined Nov 23, 2012
8,012
Hi Bertus

I have it, Thank you for your help
@RodneyB
Good luck with your lithium battery charger. All advice on the electronics is good and your concern for safety is good as well so I assume you are fully aware if the fire hazard. Just one practical suggestion while you experiment, is to put the battery in a ceramic flower pot, or on some bricks or other non-combustible surface. Lithium batteries burn very hot and water will not put out the fire. Either let it burn (if you can deal with the smoke) or, better, get a pile of sand or sodium carbonate ready to dump into the flower pot to put out a lithium fire. Make sure the sand is dry.

Good luck.
 

MrAl

Joined Jun 17, 2014
7,882
They don't it's their protection circuit - please don't give advice on semi-dangerous stuff if you don't really understand it yourself.
Hi,

I never do.

Gee, i wonder how a protection circuit compares to a circuit that monitors battery condition in case anything goes wrong :) :) :) :)
 

Søren

Joined Sep 2, 2006
472
Gee, i wonder how a protection circuit compares to a circuit that monitors battery condition in case anything goes wrong :) :) :) :)
The protection circuit should never be used as a charge limiter.
A charger should be build safe and as if there wasn't any protection - then it's got a greater chance of being... safe
Relying on a protection circuit was never intended, it's the last resort - keep charging within limits that doesn't trigger the protection (some protection circuits are one-time protection, with an unuseable battery when the circuit opens).
 

Søren

Joined Sep 2, 2006
472
I don't mind working with Inductors or surface mount components.
Great, that really widens the range.
The MAX1758 would work. It's got internal switching (i.e. no external MOSFETs needed), it comes in a 28 pin SSOP and only needs a single inductor to work.
http://www.maximintegrated.com/en/products/power/battery-management/MAX1758.html

Fetch the datasheet (from that page) and have a look at it.

I have no idea what it would cost you, but you might be able to get it as a free sample from Maxim :)
 

MrAl

Joined Jun 17, 2014
7,882
The protection circuit should never be used as a charge limiter.
A charger should be build safe and as if there wasn't any protection - then it's got a greater chance of being... safe
Relying on a protection circuit was never intended, it's the last resort - keep charging within limits that doesn't trigger the protection (some protection circuits are one-time protection, with an unuseable battery when the circuit opens).
Hi,

Oh i agree fully, but we have a slight conflict here. The pack is made of four 4.2v cells in series, and there are only two leads. That means we dont really have the option of monitoring each cell individually, a method i would prefer myself. But we still have to be able to charge the pack, so we have few options.
If there was a way to add wires to the pack that would be great.
For my own purposes i ALWAYS monitor each individual cell, and never charge in series. I dont even like to charge in parallel, but once in a while i MUST because some devices take two cells and the are in parallel in the device, so the charge voltage should be very close for both cells so after checking them both i top them off in parallel.

I'd very much like to hear your knowledgeable ideas about this too (series and/or parallel charging).
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Great, that really widens the range.
The MAX1758 would work. It's got internal switching (i.e. no external MOSFETs needed), it comes in a 28 pin SSOP and only needs a single inductor to work.
http://www.maximintegrated.com/en/products/power/battery-management/MAX1758.html

Fetch the datasheet (from that page) and have a look at it.

I have no idea what it would cost you, but you might be able to get it as a free sample from Maxim :)
The only supply in Africa that has they are US$20.00 each before freight and duty. Let me do some more research
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Great, that really widens the range.
The MAX1758 would work. It's got internal switching (i.e. no external MOSFETs needed), it comes in a 28 pin SSOP and only needs a single inductor to work.
http://www.maximintegrated.com/en/products/power/battery-management/MAX1758.html

Fetch the datasheet (from that page) and have a look at it.

I have no idea what it would cost you, but you might be able to get it as a free sample from Maxim :)

I have managed to be given a few of the LT1512 IC's in the 8 Pin PDIP package. So thought if you agreed would build the Circuit shown as the "Typical Application" Shown on the Datasheet attached. I cant see to see the current rating of L1 and L2 and not sure how to Limit the current to 400mA
 

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