DIY Charger - Possible Project

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Andrew_Debbie
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DIY Charger - Possible Project

I’m thinking about scratch building an instrumented battery charger. Why? Hobby. I can build exactly what I want.

Some of my projects never get past the back of an envelope. Most of the time, I complete the design but never order parts. Others have made it to working prototypes. I’ve never built more than two or three of anything.

We will see how far this gets.

Constructive comments very welcome!

Step 1 Requirements and design goals:

  • Must be something I can build at home.
  • Must be possible to model in Spice or LTSpice
  • Able to charge 1 to 4 cells.
  • Up to 4 independent charger circuits.
  • Multi Chemistry Li-Ion, LeFePo4, NiMH
  • Programmable or adjustable charge rate.
  • Maximum charge rate of at least 2 amps. 4A preferred.
  • Battery temperature monitoring. Charge termination on over / under temp.
  • V, Current, Ah logging
  • Internal resistance measurement
  • Computer interface. (Serial / BT / Ethernet to be determined later)
  • Modular design.
  • Will operate stand-alone without external computer or controller
  • DC power input
Edited by: Andrew_Debbie on 11/26/2017 - 03:20
Andrew_Debbie
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Battery Charger IC Selection

I’m going to use a commercial battery charger IC. No point in making this harder than I need to.

To make selection easier, I am limiting myself to parts from Linear Technology. This cuts down on the number of data sheets and application notes I need to read. More importantly, many of their parts have LTSpice models.

My Long list of candidate ICs:

Buck Switch Mode
LT 1511
LT 1505
LTC 4000
LTC 4008
LTC 4009
LTC 4012
LTC 4013
LTC 8490

Buck-Boost Switch Mode
LTC 4110
LTC 4020

LTC 4000 + Switcher

USB or Wall power
LTC4155
LTC4156

Linear
No LT parts meet design goals.

LT 1511 and LT 1505 do not support LiFePO4. I will probably eliminate them early on.
LTC 4000 reference designs have a high parts count. I will probably eliminated it.

That’s all for now. I’m off to read some data sheets.

Reference:
http://cds.linear.com/docs/en/solutions-manual/Linear-Battery-Charger-Br...

mrheosuper
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im Curious now

Forgot my pen

Andrew_Debbie
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Updated the candidate list:

LTC 4009
LTC 4012
LTC 4020
LTC 4110
LTC 4020
LTC 4155
LTC 4015

Andrew_Debbie
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I’ve updated the requirements to explicitly mention independent charger circuits. It isn’t safe to run all four slots in parallel from a single charger. While this is obvious, I thought it was worth a brief explanation.

We don’t know the chemistries or the state of charge(SOC) of the 4 cells in the slots. For example LiIon and LiFePo4 have different CV voltages. The charger would end up over or under charging some of the batteries.

Even if all 4 batteries are identical types, we don’t know the SOC.

Imagine what would happen if a fully charged INR18650-30Q was in one slot and a discharged INR18650-30Q was in the second.
The two batteries would be in parallel. The batteries would be connected together with only about 40m ohm load. I = 2V/0.04 ohm = 50A.

50 amps is a bit more than the recommended 4A rapid charge current. I’m not sure what would happen but it wont’t be good.

Of course we could put a protection fuse or resistor between the charger slots, but independent chargers is much better.

Andrew_Debbie
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LTC 4015 looks promising.

http://www.linear.com/product/LTC4015

Datasheet: http://cds.linear.com/docs/en/datasheet/4015fb.pdf

product video:

https://www.youtube.com/watch?v=ishYos8mXEo

I’m going to have a quick look at Maxim, TI and whatever else google finds.

Andrew_Debbie
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mrheosuper
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you look quite lonely, but dont be discouraged and stop posting, keep sharing, i bet there are many people still reading, at least i am

Forgot my pen

Andrew_Debbie
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Texas Instruments has too many choices. Lots of reading ahead.

bq24190 Lithium only.

bq25601
http://www.ti.com/product/bq25601/datasheet

http://www.ti.com/lit/ds/symlink/bq24190.pdf

bq25890 and bq25892 Lithium only.

http://www.ti.com/product/BQ25890

bq25898
http://www.ti.com/product/bq25898/description

The features look good but it comes in a microscopic DSBGA package. It has 42 pins in a 2.8 × 2.5 mm package. PCB layout and assembly will be challenging. I will probably skip this part because of the package.

bq24725a

http://www.ti.com/lit/ds/symlink/bq24725a.pdf

bq24735
http://www.ti.com/lit/ds/symlink/bq24735.pdf

For later — I2C keypad scan IC. May be handy if I put a keypad in the device.

http://www.ti.com/product/TCA8418

PCA9557 I2C and SMBUS I/O expander – 8 bit parallel port

http://www.ti.com/lit/ds/symlink/pca9557.pdf

Andrew_Debbie
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mrheosuper wrote:
you look quite lonely, but dont be discouraged and stop posting, keep sharing, i bet there are many people still reading, at least i am

Will do!

I’m surprised no one has jumped in to tell me this It has already been done.

I’ll work on this when I have time.

Andrew_Debbie
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Analog Devices:

ADP5350
http://www.analog.com/en/products/power-management/battery-management/ba...

http://www.analog.com/media/en/technical-documentation/data-sheets/ADP53...

I like the 1.5MHz switching frequency.

5 Channel LED driver. The charger could double as a dim flashlight Smile It is suppose to be a backlight driver.

Full I2C programmability. I2C fuel gauge and temperature sensor.

AD5062 Linear
http://www.analog.com/media/en/technical-documentation/data-sheets/ADP50...
Fully programmable I2C.
AC or USB power. USB 3.0 with external USB controller chip.
Limited to 1.5A though.

Of interest for later:
AD7824 Battery monitoring system. Primary use is monitoring series cells in automotive applications. Could be useful.

Andrew_Debbie
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So far, I like LTC 4015, ADP5350 and AD5062.

The TI parts look like they will be too hard for a one-person DIY.

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I never saw this until today. Now I’m watching to see what happens. Glasses

Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone.
-Ayn Rand

Silent_Star
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Cool project, Andrew.
Thank you!

 Genesis 1:3 "And God said, "Let there be light,"  and there was light."

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Wish I could help in some way but this is beyond me.
Good luck with it, I will be watching and learning.

Andrew_Debbie
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ADP5350 maxium fast charge current is only 650ma. Otherwise it was looking good. It has a lot of extra functionality that could have been usefull. I’m going to keep that one in mind for future projects.

I will probably go with the LT4015 but am going to look at the AD5062 first.

Andrew_Debbie
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ADP5062 has great features:

  • Standalone or I2C control. In standalone, basic settings by jumpers
  • Thermal limiting and battery temperature limits.
  • Very low external part count.
  • Battery Isolation FET. Useful
  • USB or external adapter power.
  • Battery short detection.
  • Dead and weak battery trickle charge rates.
  • Optional JEITA battery temperature charging rates —> reduce rate if battery is too cold or too warm. Adjusts CV voltage too.
  • Programmable Charging termination voltage between 3.6V and 4.5V in 0.02V steps. Smile
  • Programmable fast charge current between 50mA and 1300mA in 50mA steps
  • dead battery, trickle, watchdog and safety timers Smile
  • programmable LDO for system power – I can use the 5062 to provide power the rest of the device.
  • Good application support including PCB layout guidelines.

Layout guidelines are sooo helpful.

The part is missing a few features. 1.3A charge current is below my design spec of at least 2A. 1300mA just barely covers the standard charge rate for some 18650 cells. I’d like to be able to test and use rapid charge rates too. An INR8650-30Q or 25R can rapid charge at 4A.

Panasonic NCR18650B standard charge rate is 1.625A

1.3A is not enough. *I like the ADP5062 but it won’t work. *

http://dalincom.ru/datasheet/SAMSUNG%20INR18650-25R.pdf
http://www.batteryonestop.com/baotongusa/products/datasheets/li-ion/SANY...

Andrew_Debbie
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The MAX1645 and 1647 are primarily meant for use with smart batteries. Not what I’m looking for.

I’m going to give the LTC4015 a closer look.

For those reading along, here is the product page and datasheet again.

http://www.linear.com/product/LTC4015

Datasheet: http://cds.linear.com/docs/en/datasheet/4015fb.pdf

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I would approach this from a different direction, battery charger ICs are designed for minimum cost low parts count commercial projects and can be fussy to operate outside designed goals. Starting with the goal of flexibility and maximum control I would use something like an arduino with software to control and measure current and voltage with basic power chips instead of battery specific.

Still a bit dim

Andrew_Debbie
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I’ve thought about that. I agree that most of the battery charger ICs are designed to be part of a device like a tablet or laptop.

In the end, I may end up going with the flexible option.

Before I do that, I want to explore the more integrated parts to see if there is one I can make work.

I’ve already eliminated quite a few of the low part count ICs so because they don’t meet requirements.

Going the Arduino + power supply route puts the parts count up a lot and possibly the load on the Arduino. It means my code and external hardware is responsible for safety checks.

Some of the charger ICs have programmable temperature, voltage and time checks. They go into a fault mode if when any of the limits are exceeded.

Since I plan to have 4 independent chargers, part count is important.

======================

I’m impressed by just how few external parts the new charger ICs need.

This is an SLA charger I built in 2012. It charges a single 6V battery. Look at the parts count!!

Andrew_Debbie
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OnSemi have a couple of parts that might have worked. They are in microscopic packages.

OnSemi also have a controler for next-generation power packs. Along with supporting the latest high speed charging protocols, the IC can communicate with the device it is charging.

It was interesting to look over but not useful for this project.

I’m sure we will see much smarter power packs in the near future.

Danglerb
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I bought a Litokala 500 engineer from Alibaba for $14 shipped, taking one of them apart might be instructive. The insides of one of the USB doctor measurement devices might be useful too.

Still a bit dim

tempo
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i ll check back in 3 months if the project is still going strong.
i will be off on Xmas season vacation until mid January, enjoying ski trip with family and friends.

have phun Facepalm

bye.

Andrew_Debbie
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I ordered two LTC4015E samples. (commercial temp range)

Time to get on with block diagrams and Rev. 0 schematic.

I may need to update Eagle on my machine. I own a paid license.

Andrew_Debbie
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Danglerb wrote:
I bought a Litokala 500 engineer from Alibaba for $14 shipped, taking one of them apart might be instructive. The insides of one of the USB doctor measurement devices might be useful too.

Good idea. I’ve got an Lii-500 on the way Smile

I’ll open it up and post in this thread. That may not happen until after Christmas or it could be next week. Shipping from China is unpredictable.

Andrew_Debbie
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Any suggestions on form factor?

My initial thoughts are 100mm x 100mm 2 layer to hit the $5.00 for 10 deal at PCBWay. 4 layers takes the price to $49.00 Still a bargain.

OR

Arduino shield.

OR

???? suggestions?

They are also running an $88 for 10 PCBA deal. That puts the impossible to DIY TI and On Semi parts back into the running.

Andrew_Debbie
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I generally use Eagle early in the design process to get a rough schematic and block diagram. Eagle is a bit quirky but works better than any freeware I’ve tried. I also use LTSpice to simulate parts or all of a project. I don’t much care for the schematic capture in LTSpice. I often use Eagle to get my ideas down and then go on to simulations.

Cadsoft GMBH sold out to Autodesk last year. Crying My Cadsoft EAGLE 7.4.0 doesn’t play nice with MacOS 10.12. Ughh I’ve installed Autodesk Eagle 8.4.3. I’ll need read up on what’s new and then merge my device library.

EAGLE 8.4 includes spice. I may stop using LTSpice and do capture and simulation in Eagle.

For those following along, here is the product page:

https://www.autodesk.com/products/eagle/overview

There are plenty of tutorials on YouTube and now support from Autodesk.

Eagle runs on Windows, MacOS and Linux.

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Subbed and following this thread.

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Andrew_Debbie wrote:
Any suggestions on form factor?

My initial thoughts are 100mm x 100mm 2 layer to hit the $5.00 for 10 deal at PCBWay. 4 layers takes the price to $49.00 Still a bargain.

OR

Arduino shield.

OR

???? suggestions?

They are also running an $88 for 10 PCBA deal. That puts the impossible to DIY TI and On Semi parts back into the running.


Are you making these to sell? Will you be sharing your Eagle files here? If you’re not doing this as a community shared project, then do whatever works best for you. If you ARE going to share the files, then it might be nice to keep in mind OSH Park pricing as well, which is $5 per square inch with free shipping for three copies on all 2-layer boards. A lot of members here use Eagle, and also OSH Park. With that fixed pricing, the smaller the design is, the better.

Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone.
-Ayn Rand

Andrew_Debbie
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Quote:
Are you making these to sell?

Probably not. I don’t want to string anyone along. I’m doing this in my spare time.

If I get as far as having boards made, I’m open to selling extras at cost. I live in Wales. Postage to the US is going to be a few £‘s.

I’ve been satisfied with PCBWay and haven’t looked elsewhere.

I’ll keep OSH park in mind. I’ve never used them. At a minimum I’ll check against their design rules.

Quote:

Will you be sharing your Eagle files here?

Absolutely YES. I’ll also share my bill of materials.

Thinking about including this optional module in the project. Stay tuned.

Andrew_Debbie
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DavidEF wrote:
Are you making these to sell?

I would consider a PCBA (assembly) group buy for a bare board with sub-mm pitch parts installed. The LTC4015 is QFN38.

I need to get a rough schematic / block diagram up.

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