Universal LiON Charger

[andrewwynn]

I built a universal LiON Charger.. it will charge any LiON Battery that can take a charge rate between 75mA and 600mA.

The charger is based on the circuit and chip shown here by DJ Park.

I have a need to charge both AAAs and AAs and flat-pack LiON batteries... I bought enough chips i was going to make several chargers, but realized I could have a switch change the feedback resistance and have a two-in-one charger.

I was going to build it into a tiny project box (about 1/3 x 1.5 x 2.25 inch) I have, but when i went to buy the switches, I saw a 2pole 6 throw rotary switch, and said 'hey, how about having SIX charge levels'?

Here is the finished product:

I have set rates for 75, 100, 150, 300, 425, and 600mA. The charger is supposed to handle 600mA.. funny thing... the power brick has to be able to supply that much for it to do so.. i upgraded from a 500mA 5V brick to a 2A 5V brick.. so now i just need enough battery to demand that much to test it.

The other part of the 'universal' comes from the fact that the charger itself has no cords.. it has a jack for 'any' 5V power supply with a suitable plug.. and a jack that uses an 1/8th inch 'mono' headphone jack for output.

I make use of the jack by wiring up a common battery holder (re-wired in parallel vs. series) and put a phono jack on it.. voila..

here is a picture showing the AAA holster.. will charge between 1 and 4AAAs:

Here is the rotary switch.. all wired up:

You can check out the whole photo album here.

If somebody is interested in making a clone, I will make a schematic of the rotary switch... you can 'brute force' wire it with about double the resistors, but i solved the design with about 1/2 the resistors by a little clever wiring.

For the past month or so i'd been just using the charger off the breadboard.. now i have the best of both worlds.. i can charge any rate w/o having to manually swap a resistor, and i have a test harness i can use to measure the inside voltages just like i'm used to on the breadboard.

Oh.. originally.. i only really wanted.. 600, 450, 300, 150 charge rates.. but the switch had 6 spots.. so i added 100 and 75.. hoping to get some smaller LiON batteries in the future so i'm prepared.. and also i can do a 'trickle charge' on my AAAs to get a little more juice in them.. when i charge them at 1/2C, they don't end up with as high a voltage as the other LiON batts in the house.. i'm doing a test right now, charging 3 at once at 150mA total.. time will tell if it works.. it does seem to.. it just stops charging if i try to charge a faster rate sometimes.

Hope you enjoyed checking it out.

-awr

 

[MrAl]

Hi andrew,

Thanks for all the interesting pics. I like the switch
idea...i'll probably have to do that too at some point,
once i get into the Li-ion AA cells a bit more.
My current charger was made for 1 amp, so that's a bit
too high, but with the multiple settings like that it
could handle smaller cells with ease.
Actually, the LM317 based charger could work like that
too i guess. The input resistor would have to be swapped
for different cells so it would involve more current,
but it should still work.
I dont know if i'll be able to use a low current switch,
so i was thinking more like binary weighted slide switches,
where each one increases the current by the 'weight' of
that switch (1,2,4). Three switches and three R's would
give 100,200,300,400,500,600, and 700ma settings.


Take care,
Al

 

[2dim]

Andrew does it again!!! Hip Hip Hooray, eh?

 

[flashlight]

Firstly, great work again! /ubbthreads/images/graemlins/thumbsup.gif

Er, being electronically-challenged, how do you know when it's fully charged & how to tell the cut-off voltage? Manually with a meter? /ubbthreads/images/graemlins/thinking.gif TIA

Would you consider making one for sale (for me)? /ubbthreads/images/graemlins/grin.gif

 

[andrewwynn]

flashlight: there is a feedback LED.. it turns on when charging and off when charged. If power is applied but no battery.. it blinks.

MrAl.. I was originally going to a binary solution with 2 or 3 switches.. i like the one rotating dial nicer now that i made it (even though like 15yrs ago i taught myself to count in binary on my hand, so it's second nature to me).

here is the diagram for the switch:

 

[BobVA]

Oh, if anybody duplicates this, make sure you turn it off and take out the battery BEFORE you unplug the battery holder. Audio plugs short briefly when plugged/unplugged and that might make your battery unhappy.

Cheers,
Bob

 

[flashlight]

Thanks Andrew. I understand from the other thread (which I should have read thoroughly first /ubbthreads/images/graemlins/rolleyes.gif ) that the voltage will cut off at 4.2V too which is optimal for most of these li-on cells right?

Please let me know if you get around to making these for sale as I'd be keen on one. /ubbthreads/images/graemlins/smile.gif

 

[andrewwynn]

BobVA has a good point. I had thought i checked to make sure the plug was break before make, but in testing just now it does short while plugging it in. I would definitely recommend not having batteries in the module when plugging it in. I haven't bothered unplugging the power to the unit when i've swapped the battery module, and i'm sure there is a spike through the charger when it shorts but it's only 'blinked' the LED and no harm so far.

flashlight: yes it charges to 4.2.. i was only getting about 4.1 charge on my AAAs when i charged with 150mA... but whoo hooo.. with the new, improved charger where i did a 50mA charge.. even the AAAs came off the charger with like 4.18V... in addition.. i have a poor AAA that had a direct short that lasted about a second (i call that 'spanked'.. probably 10A or something).. anyhow.. following 'the incident' that battery is now labeled with an 'x' so i know which it is, and it used to only charge to 3.9 afterwards.. when i charged it in parallel with two other bats and at 50mA each... it charged to a full charge.

 

[flashlight]

[ QUOTE ]
BobVA said:
Oh, if anybody duplicates this, make sure you turn it off and take out the battery BEFORE you unplug the battery holder. Audio plugs short briefly when plugged/unplugged and that might make your battery unhappy.

Cheers,
Bob

[/ QUOTE ]

Bob, do USB connectors do that too?

Andrew, now I really want one. /ubbthreads/images/graemlins/help.gif

 

[andrewwynn]

FYI: parallel charging: make sure the voltage is the same on any batteries you want to charge in parallel... if they are 'close but not quite'.. i'll put a resistor between them to get them equalized slowly before charging.

USB connectors are non shorting. I'll point out... that i am going to make a USB cord to power my charger, just need the power plug, already have the cable. It won't be able to charge 600mA, but it'll run the lower rates I use.

In a couple months, I'm expecting a mass-production of LT4052 chargers, for my big flashlight project. Depending on the method used, it may be a very easy thing to make a version for sale.. for now... making just one or two is too taxing on my resources, so i'm sharing the plans so people can make their own. Total cost.. about $12-15.

 

[Sprocketman]

Thanks for putting up the plans!

I charge my NiMH 1/5A cells with a solar charger. It gives them a trickle charge, producing just 140ma at 6v or 70ma at 12v in full sun, probably a fraction of that for most of the day. Fine for Nicads or NiMH, but can I do the same thing with Li-ion 123's? Most Li-on chargers seem to have much higher charge rates. Does anybody know if long-term charging at lower rates will kill my Li-ion's? I really like running my lights with sunlight.

Randy

 

[Doug S]

[ QUOTE ]
Sprocketman said:
Thanks for putting up the plans!

I charge my NiMH 1/5A cells with a solar charger. It gives them a trickle charge, producing just 140ma at 6v or 70ma at 12v in full sun, probably a fraction of that for most of the day. Fine for Nicads or NiMH, but can I do the same thing with Li-ion 123's? Most Li-on chargers seem to have much higher charge rates. Does anybody know if long-term charging at lower rates will kill my Li-ion's? I really like running my lights with sunlight.

Randy

[/ QUOTE ]
"Trickle" charging is generally defined as charging at a very low rate using a source with an open circuit voltage above the charging voltage of the cell. The solar charger you describe certainly fits this definition if used to charge a li-ion cell. Yes, trickle charging will kill a li-ion cell. You could modify a solar charger with a *shunt* voltage regulator to limit the voltage rise. I would recommend the shunt regulator be set at 4.15V max for good cell life.

 

[andrewwynn]

I saw a very good demonstration ckt at linear for just such a charger... my charger will handle any voltage from 4.5 to 6.5, so i would have a filter on my solar panel to hold back the voltage to 6V before going into the charger... ironically.. with a battery (like SLA maybe) to help hold back that energy (why waste it).. so.. the solar panel goes into this 'filter' that has an SLA battery of 6V.. that gets charged with any extra voltage, but there is a zener or op-amp ckt to keep the output 6V.

 

[andrewwynn]

I'm making a 'small' mod to this charger... i built it so i can charge my AAA batteries for my peak aaa mod.

The 'small' is because i'm going to build the charger into the head of an AAA light... I will be posting the circuit diagram and 3D model.. i'm planning to build it 'dead bug' style on a disc 10mm diameter.

-awr

 

[Sprocketman]

[ QUOTE ]
Doug S said:
Yes, trickle charging will kill a li-ion cell.

[/ QUOTE ]

Thanks. That clarified the question. I need a voltage limiter. Linear has three types of chips, so I ordered some of their 10-to-150 ma variety. Since they designed the chip this way they apparently think it's ok to charge Li-ion cells at low ma rates, so I'm going to build a charger and power it with a small solar panel.

I still like the idea of twisting my EDC on and having it pour out sunlight.

Randy

 

[andrewwynn]

[ QUOTE ]
still like the idea of twisting my EDC on and having it pour out sunlight.

Randy

[/ QUOTE ]

one of my micro lights is brighter than the sun from some distance.. i can put a spot on a sun-lit surface.. i'll have to check how far.. but it's pretty darn bright.. check out the beamshots on the link.

 

[andrewwynn]

OUCH.. found out the hard way tonight.. don't put your battery in backwards... smoked the LT4054 chip apparently.. fortunately the design i used I made a 'socket' for the chip... i had a spare socket and a few spare chips from my initial order.. 30 minutes of soldering and bingo back in operation... My dad once printed 'THINK' on his analog multimeter.. good advice.

-awr

 

[andrewwynn]

microsized:

shrunk the charger down to fit inside the head of an AAA light.

just realized.. i have a photo of this charger:

 

[rayearth]

I'm curious - what program are you using to that that cool drawing?

 

[andrewwynn]

sketchup.. get a free demo: here