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Author Topic: 18650 Battery Charger Circuit  (Read 1619 times)
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metal
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« on: June 27, 2018, 09:29:36 09:29 »

I need to make my own 18650 3.7V 3500mA battery charger that supports 2 cells, what is the best schematic for this project?
« Last Edit: June 27, 2018, 09:35:05 09:35 by metal » Logged
bigtoy
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« Reply #1 on: June 27, 2018, 03:10:24 15:10 »

2 cells in series or parallel?

If in series, need balancing?

For a start, here's a cheap Microchip part that can do 2 cells in series, no balancing. I've used a similar Microchip part for doing LiFePO4 charging and it worked well.
http://ww1.microchip.com/downloads/en/DeviceDoc/21823D.pdf
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Parmin
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« Reply #2 on: June 27, 2018, 05:44:45 17:44 »

+1 I use Microchip's circuit, works well.
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Gallymimu
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« Reply #3 on: June 27, 2018, 11:30:31 23:30 »

I'd definitely get a COTS charging IC like the ones above.  You don't need balancing with 2 cells, especially if they come reasonably matched (same brand, batch etc).

if you happen to be hung up on doing your own charger from scratch it can be done but ya gotta be careful.
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Old_but_Alive
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« Reply #4 on: June 28, 2018, 01:08:40 01:08 »

anyone know of 4/5/6 series cell controllers ?
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« Reply #5 on: June 28, 2018, 01:20:45 01:20 »

anyone know of 4/5/6 series cell controllers ?

Lots of 4-6 cell charger modules on Ebay for a few bucks, they are designated 4S, 5S or 6S...
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« Reply #6 on: June 28, 2018, 03:46:42 03:46 »

I know that, and I have loads of them.

I was interested in designing my own
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metal
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« Reply #7 on: June 28, 2018, 04:05:20 04:05 »

me too, look at this one: http://www.shapely.asia/charge1.html
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« Reply #8 on: June 28, 2018, 07:30:23 07:30 »

after 1 or 2 li-Ion cells, it seems to get very complicated.

Linear Tech and TI seem to be the main chip manufacturers, but charge balancing seems to be a major complicator.

I have many china modules, but of course, theres no schematic or info.

I was given nearly 100 18650 2.2AH Sony cells, so  want to try to use them in my drills etc
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« Reply #9 on: June 28, 2018, 08:53:59 08:53 »

anyone know of 4/5/6 series cell controllers ?

We were doing some 4-5 cell charger designs.  I can't remember exact parts but I am nearly certain TI had 4-6 cell options with separate chips required for balancing.
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« Reply #10 on: June 28, 2018, 04:12:43 16:12 »

I have many china modules, but of course, theres no schematic or info.

Have you looked at the datasheets for the chips they use on the modules?  Generally, the Asian modules are textbook datasheet examples for the chips...
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« Reply #11 on: July 18, 2018, 07:16:10 07:16 »

here there is a good project that use 18650, based on LT3650-4.2 and AP9101C to protect battery

http://kitsune-denshi.net/projects:tek222bat

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« Reply #12 on: August 29, 2018, 08:47:55 20:47 »

The effective option is to go for a P-channel based mosfet circuit using attiny85 microcontroller. The charging topologies are given in numerous datasheets. You can convert it to simple C code and get your job don.




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« Reply #13 on: August 30, 2018, 01:16:01 01:16 »

I bought lots of Li_ion charger/protection cheap boards from China.

Some use an excellent IC, the BM3451, which does 3,4,5 cell charging/discharging and balance protection.

here is a link to the modules

https://www.amazon.co.uk/gp/product/B075TBKV7P/ref=s9_dcacsd_dcoop_bw_c_x_2_w

Aliexpress sell them for $4

BM3451 datasheet attached
« Last Edit: August 30, 2018, 01:34:05 13:34 by Old_but_Alive » Logged

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