# A 500v 16A switch transformed to Li-on battery charger!!!



## petcnc (Dec 16, 2014)

From that:




To that:




*HERE IS HOW*

Dealing with portable computers I found myself possesing alot of LI-ON batteries.



I like them batteries as they have high capacity (they store alot of energy), they have a nominal voltage of 3.7 volts per cell and they have a very slow rate of self-discharge, so they can be used in numerous applications in the shop.
They have 2 major drawbacks though: They are tricky to charge:

_The Li‑ion charger is a voltage-limiting device that is similar to the lead acid system. The difference lies in a higher voltage per cell, tighter voltage tolerance and the absence of trickle or float charge at full charge.
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries_

They also need trickle charge (i.e very low amperage about 1/10 C) if the cell voltage drops below 3.0 volts.
To charge them properly you cannot use any DC power supply plug it in the mains and forget about it.
I was in search of a charger to be a) cheap, b) DIY and c) easy to make.

Mr Google drove me to the following webpage:

http://www.shdesigns.org/lionchg.html 

The circuit presented there, although old, is very well documented and can be build from parts I already have in shop.

After some modifications to the PCB board (we always do! Don't we?) I printed the copper side of the circuit on paper.




As you can see I have cut a piece of copper board, I secured the paper on the copper side using masking tape, drilled all holes and using nail varnish I paint all parts needed to be copper.

Some 10 minutes in a Ferric Chloride bath revealed the copper side of the PCB




I know it is not pretty but it does the job!

After soldering the components I made some charging tests and it worked like a charm!




Now I needed a box to put it in.
An old 500V 16A switch inspired me




After removing all the guts I ended up with a very nice aluminium box.




A cleaning process using the fly-cutter revealed its beauty.




It only needed a lid.
A scrap aluminium offered it.




The lid needed some ventilation grilles that my mill managed to make using a small circular saw.

Some polishing and the necessary labeling and job done! The box is ready to accept the electronics.




Started by making a cut for the voltage meter and a hole for the charging LED




Then the PCB secured in place, the connectors drilled and placed and the wiring between all them parts finished.




Final test! It works as designed! I secured the Lid and I stood proud of my new tool.




I know... I have to replace those ugly bolts on the lid. But on the other hand it shows primitive and "hand made"

I cannot decide on that... its a hard issue..

Thanks for reading this.

Petros


----------



## 12bolts (Dec 16, 2014)

Nice job.
But it would be more impressive if you left the 660 V switch mounted on the wall and made a socket to just plug the battery in to. Can you imagine the look on your friends face when you took his flat battery and plugged it in to that! :rubbinghands:

Cheers Phil


----------



## petcnc (Dec 16, 2014)

12bolts said:


> Nice job.
> But it would be more impressive if you left the 660 V switch mounted on the wall and made a socket to just plug the battery in to. Can you imagine the look on your friends face when you took his flat battery and plugged it in to that! :rubbinghands:
> 
> Cheers Phil



Phil it can be done in no time! 

I just have to replace the lid with the original one and support the switch underneath it!!!

Nice suggestion!

Thanks

Petros


----------



## petcnc (Dec 16, 2014)

*Li-on battery charger Final touches*

After my initial rush to complete the project, I left some basic functions and some details for later.

Later came!!! and I had to fix all the details!




In the design there was provision for two charging stages:

Trickle charge at 50 mA and
Normal charge at 500 mA

There was a jumper on the PCb for that but to change its position you had to remone the lid! Not very practical.
A switch on the front solved the problem

On the other hand the volt meter needed a cover to ease readings.


After that I think the charger is complete!

Not the prettiest you have seen but functional and safe to use.

Thanks for reading 

Petros


----------

