Constructing, Repairing and Charging Lithium battery packs

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burger2227
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Constructing, Repairing and Charging Lithium battery packs

Postby burger2227 » Sun Mar 02, 2014 9:47 am

When I bought my Rockwell Oscillating Tool, I got another set of batteries with the replacement tool:
Image
Both of the batteries in the replacement tool were already bad enough that they only lasted 15 minutes, so I
decided to take one of them apart to see how it was constructed.

The 11 volt 3 battery packs also came with an extra charger that uses side tabs to monitor each battery:
Image
I mapped out which tabs were connected to each battery for reference later. I figure I can use the other charger
to charge batteries for something else. I have a 12 volt drill and hand vacuum that may need battery packs someday.

The tabs monitor the separate battery voltages during the charging process, yet allow the series battery
connection when the battery is actually in use. In this tool, the battery protection tool is also used to
determine when the battery needs charged and flashes the work light and shuts it off.

Here's the large Rockwell charger circuit. The raised board has the 4 colored wires that go to the battery
pack with2 larger wires going to plus and minus. Yellow is A and blue is B in my drawings:
Image
I can't imagine trying to add this big circuit to anything! The LED's on top tell the charging status of red
or green. It also includes a USB port for charging a cell phone on a work site. I'd need a 6 wire output
socket to use the unit to charge 3 battery packs as there are 2 main battery supply wires too.
A monitor circuit turns everything off. I'll have to investigate further to see if I need the main
battery cables with the unit

I was able to purchase a charging protection circuit that can also be used in the tool to protect the
batteries from excess discharge, shorts or overheating.
The triangular shape looks like it was made for Rockwell:
Image
The P+ and P- pins are wired to the load and a maximum charging input voltage of 12.6 volts.

The circuit board is made specifically for triangular 3 piece 18650 battery packs. When the batteries
are charged, the circuit limits current, voltage and heat and charges each battery separately as needed.

Here's a 4 battery charge and discharge Protection Circuit Module:
Image
Current prices are about $7 on Ebay.

Warning! Do not try to charge Lithium series battery packs without this protection!
Fire or injury could result!


P+ and P- connections are to the load and the charging input so existing DC charger connections
to tools should be OK. Charging protectors allow any DC charging voltages up to 20 volts. Naturally
larger pack protectors allow higher voltage.

My B&D drill uses a 12 volt detachable battery pack, but the charging input is in the drill handle.
Since the tool cannot hold the protector circuit, I will put it in the pack to receive charging
voltage from the tool or a separate pack charger.

If a tool charger is AC, make sure that the charging input is rectified to DC before it gets to the battery protector!
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Re: Charging Lithium battery packs

Postby burger2227 » Thu Mar 27, 2014 9:40 pm

The 555 Timer has many uses. Here is the internal schematic:
Image
The Trigger and Threshold levels can also be set using the Control Voltage pin 5 by using a Zener diode to set the
Threshold level while the Trigger voltage is half.

The 555 circuit below monitors the voltage supplied to both sides as a window comparator. Blue is the 555 output and
yellow is the battery voltage:
Image
The supply voltage to the 555 is 12 volts from V2, but the V1 voltage monitored ranges from 22 to 30 volts.
The 6.2 volt Zener diode holds the control voltage and threshold reference to 6.2 volts while the trigger is 3.1 volts.

The monitored voltage is put through a resistance voltage divider so that 22 volts sets the trigger voltage below 3.1.
The monitored voltage on the other side is also divided to return more than 6.2 volts when the V1 voltage is over 30.
The output goes high on Pin 3 when the voltage drops below 22 volts and goes low when the voltage exceeds 30.
This 555 comparator can be used to charge a battery without using two Op Amps! The 555 does it all.

The 555 output voltage(12V) could drive a transistor or relay to connect charging current to the battery or turn on a charging circuit.
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Re: Charging Lithium battery packs

Postby burger2227 » Tue Jul 01, 2014 3:07 pm

Bought another cell phone charger. This one is solar with the red LED light a battery charging indicator.
Image
I bought it from NewEgg, but it was full of scratches when it arrived and the package mailer was not damaged.
After I complained about the used condition, they refunded the $6. Glad I didn't have to ship it back...

Four blue LED's indicate charging status when plugged into a USB port. After the battery is full, the solar panel can keep it charged up hopefully:
Image
Pressing the button quickly will indicate the battery charge level.

The end of the charging unit has a USB slot for a device on the left. It also came with several adapters for different phones
Image
The right outlet is for a mini USB connector to a computer or USB charging outlet.

The 3 round LED's will light if the button is held down 5 seconds.
Image

I plan to put it in my car near a window to keep it fully charged for charging my cell phone.
To charge the battery fully, the solar panel takes at least 13 hours in full sun. We shall see how it works!

After a year of sun on the car dashboard and some external covers came off it died:
Image
The solar charging never seemed to work real well and the battery probably gave out with heat.

Recommendation: Solar panel does little! DO NOT BUY!
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Re: Charging Lithium battery packs

Postby burger2227 » Sat Jul 19, 2014 8:45 pm

After testing the unit, it appears to charge slowly but well. It took one quarter charge to recharge my cell phone in half an hour. Leaving it on the dashboard recharged the unit's battery to full in a day or so, so it may work out.

After sitting on the dashboard it gets quite hot and the film on top came loose enough for me to remove it, like I was SUPPOSED TO DO when I got it and vwella the scratches were gone too... However part of the surface came with it too!
Don't know how long it may last in the hot sun.

I mounted it with Velcro, but even the tape glue seems to want to melt.
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Re: Charging Lithium battery packs

Postby burger2227 » Sat Jan 31, 2015 5:41 pm

Today I found that my spare lap top battery was not charging up so I tore it apart:
Image
I found 6 18650 batteries wired up as an 11.1 volt battery supply. There were also 3 dummy tubes where another parallel set could have been.
That third set would add longer current life to the battery which only cost $15 when I got it a couple of years ago! Watch out for cheapos!

I took all the batteries apart to check each one and found them all to be about 3.6 volts! Never did find out why it quit working!

I'll save them for a power pack later! Maybe they will hold up. They all read fully charged in my 18650 chargers.

There is an indicator button you have to push to tell the battery charge status:
Image
The bottom side of the battery is soft near the 5 indicator LED's to enable you to press the button in.
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Re: Charging Lithium battery packs

Postby iamdenteddisk » Tue Jun 09, 2015 7:40 pm

if 1.7v batteries are reading 3.6v the batteries are most likely bad.

nicads i know will do that if over charged,(left on charge to long), and have been known to explode when used because of this. the liquid boils as current passes. if overcharged to double capacity then you can expect double current to come out. if on a small device it will over current probably boil till battery shell it's self ruptures.. thats with some probability..

it is important to stop a charge cycle once full capacity is reached for that reason. remember how in general things are engineered to double stated limits. <thats why..
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Re: Charging Lithium battery packs

Postby burger2227 » Tue Jun 09, 2015 8:00 pm

The Lithium 18650 batteries are 3.7 volts when fully charged. 3 * 3.7 = 11.1 volts. Lithium series chargers use connections between each battery to monitor each cell individually to prevent overheating or overcharging.

They do not seem to drain out as fast as nicads do when not being used either. The charging circuits can also monitor the batteries to protect them from too much discharge too. That really kills lithium batteries too!
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Re: Charging Lithium battery packs

Postby iamdenteddisk » Sat Jul 04, 2015 12:50 pm

where nicads are like a cup o current being poured, lithium cells are more analogous to a high tension wire.

basically, when a nicad pours out current both voltage and current reduce, till the cup is "half full" and voltage is half the cups rating then it stops.

with lithium it maintains its tension "current ability", till the voltage reduces to nill. (meaning current capability stays the same till its voltage is drained).

the lithium cells drain much lower having a .7v "per cell layer", at depletion. versus the nicads single 1.5v chemical cell that only drains to .75

it is this "per layer and number of layers", that make a longer drain or load life.

in reality we don't see the number of internal cells, the nicad AA cell is a single cell....which IMO is really doing well to compete with lithium.
the nicad could be just as strong if not stronger "if we added the same number of cells as is inside the lithium pack" but the battery would be way to bulky and heavy to cary.
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Re: Charging Lithium battery packs

Postby burger2227 » Sat Jul 04, 2015 10:49 pm

NiCads wear out just sitting there. Lithium not so much! Both die quicker if you discharge them too much. Lithium should never be discharged below half voltage and NiCad should never go below .9 volts for a 1.25 volt unit.

Chips I get from China stop the AA discharge at .9 by shutting down the jewel thief circuit. I've gone through a TON of NiCad battery tools because the batteries suck! I'm planning on replacing the ones I can with Lithium.
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Re: Charging Lithium battery packs

Postby iamdenteddisk » Sun Jul 05, 2015 11:57 pm

right i agree but now about the lithium dieing when you discharge it.

they do that because if drained to low, they will allow to much forward current when charging allowing current spike damage to the battery cell layers.

they want an aggressive constant current when charging say a 3.7v. that is usually charged @3amps for 2.5 hours <notice it's strictness, a requirement for the battery to (load each seat on the bus with electrons. but without burning the cell layers)..now it is done with a 4.7v charger to account for the resistance of the battery, that worked for all other batteries...not lithium, it does not present resistance of other battery types. that is what that little circuit board is for "a parallel load device" a kind of resistive fuse link (to protect you from pow or smoke or what ever they do) I haven't had the experience yet. my experience with charging them with solar panels though has been a great success. only because i discovered the need for the parallel load. it also current limits when charging also. I am sure the ones we see now are probably a load of ic's having a variable resistance regulator to bleed away any over voltage, causing, over current. blistering the cell membranes.

now the little solar charger i made from a led flashlight, the panel's produce 8.1-8.5v in full noon sun@ 1600ma, that is cut in half by rectifiers in the circuit to the 4.2 (minus the parallel load resistance) so 3.7 and I am also using much lower current. which is part of the test to find an optimum minimalist object, "ideal voltage". the 1600ma is a adequate charging(peek current) while 160ma enough for the actual load

or (an available and affordable solar array for the project). on the basis the lithium are happy between anywhere 3-7 volts till fully charged <there is the evidence of the theory there and is the reason your battery gets hot when it has reached the optimal output point signaling its used it's electrons up. now let it cool before charging (to cycle the battery before recharging) so, again promoting internal resistance <this promotes potency and extends life.
my batteries never get hot, yet my project fully charges in two days and last for about 19 hours really bright yet a viable flashlight still after 40 hours use. that solar charges daily on the fence,window sill. with certain color leds, I can point it at the mailbox about 120 feet away in the day light and still see the circle silhouette on the bank behind the boxes. i get that 19hrs. action reliably...<maybe not worth patenting as a product IDK?
it's great for camping, on the farm, reliable.
on a day charge you get 8hr so its a perfect for every day light use. hope this helps understand the lithium battery, was my intention.

now your addition of the Joule thief there that is a radical and unique endeavor of interest.

I say bravo on the lithium tool upgrades. definitely be more reliable but I would stick to tools that don't "bind much" to (keep current spike down)..when they bind they over amp the motor and thus current spike the battery. unless you add also a resettable breaker (electronic fuse) to go in also to protect the battery MAX current on both charge and discharge.<that be ideal..
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Re: Charging Lithium battery packs

Postby burger2227 » Thu Aug 13, 2015 10:32 am

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Re: Charging Lithium battery packs

Postby burger2227 » Sun Mar 13, 2016 4:29 pm

Decided to tear apart one of my NiMH battery packs for my drill. Each pack gets charged through the drill.
Image
The pack voltage was less than 6 volts so I want to see if three 18650 lithium's will work instead.

Four torx screws hold the lid down, the spring loaded release pops it off. Contact piece slides down:
Image
The entire battery pack comes out easily with the contact assembly on top. 10 batteries make 12 volts.

A three cell 18650 lithium cell holder cannot fit inside without major alterations :
Image
Three cells can fit if they are solder tabbed, but I wanted to make it simple to replace cells.

So since I had only one one cell holder, I decided to cut one cell holder off and see how it worked:
Image
I found that a third cell on top of two was too high, so I cut each cell holder apart. It will fit if
two cells are set apart in the bottom with a third cell on top, partly between them facing down.
Note that there appears to also be plenty of room for a protection circuit board on the sides.

So after doing all that I may as well test it out so I wired each holder in series with the top one first.
The batteries were already charged up so I tried the pack out and it worked great in my drill!

Now for the hard part! I need a charging protection circuit and found one with a heat sensor for $9:
Image
Current is rated at 8 A charging and discharging. The Triangular one I have is not for power tools
according to one seller who had one rated at 2 amps. Gotta wait for shipment from China...

The board measures 30mm by 70mm long and it can fit on the side of the 18650 batteries:
Image
The board has a heat probe I can place below the top battery for safety. Also has 4 status LED's
with a button to check status. I may be able to mount the board so that it can be pressed from
the side of the case or through a finger hole with an LED viewing window slot.

I will also need to reduce the charging input voltage to 12.6 Volts DC and add a capacitor to smooth
the rough rectified DC voltage out better. I have some 12 volt 3 pin voltage regulators to try.
Image
If not, they also sell 12.6 volt, 1.5 amp power supplies. The P+ and P- connectors go to the drill.

I may decide to add a DC input plug to the battery case itself so it can charge separately.
Now All I can do is WAIT and see how the lithium cells keep their charge while not in use...
The drill is already noticeably lighter.
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Re: Charging Lithium battery packs

Postby burger2227 » Tue Mar 15, 2016 12:01 pm

While waiting for parts, I decided to try the Dust Buster 18 volt AC charging adapter with this charging circuit.
Since it is AC, I added a 1N4007 diode and a 10 uF electrolytic capacitor after it by polarity + to cathode of
the diode. This reads over 30 DC volts unloaded, but only 24 volts connected to the regulator cut off circuit
board. The green ground wire goes to - of capacitor and to common black wire of regulator cut off circuit.
Image
Cathode of diode and + of capacitor are jumpered to the yellow input wire of the circuit. Connecting a
variable power supply to the circuit's green jumper I set it to trip at 12.6 volts, dropping LM338 regulator
output voltage to 1 volt on red wire. Turning the voltage down to 11.7 volts turns off LED and charges again.
Image
The 100 uF capacitor on op amp pin 2 keeps it low on power up to briefly light the LED indicating power.
If another LED indicates power, the 100 uf capacitor need not be added. I added it because otherwise a
user may have no other indication that the charger is powered up. A larger value will keep it lit longer
if you have the space for it. A cheaper BC547 transistor can be substituted for the 2N2222

Testing a 12 volt DC, 1 Amp wall supply, it output 15 volts DC. The cutoff voltage set worked at 12.6 V,
but the restart voltage went down to 11 volts. I will probably need this supply as the original supply is
only 100 ma and would take 40 hours to charge 4,000 ma lithium batteries. This would only take 4 hours!

Here is the final hard wired circuit with the 100 uf startup capacitor added to indicate power on.
Image
Used a pre-drilled and IC formatted board from Radio Shack with some lead to lead soldering.
Image
Note that the LM338 regulator is on the side of the board in case it needs a heat sink bolted on...
Image
Yellow goes to charging input AFTER the diode in the tool if the charger is AC. Add diode when necessary.
Black goes to common which should also be black in most tools. Only one common connection should be required.
Blue goes to the indicator LED anode(long leg). A current resistor should also be in series to common.
Red is connected to the + battery. The regulator voltage output can also be read before connecting to battery
Green wire is normally connected to the battery with the red wire. It can also be wired to a variable power
supply or know fully charged battery to check shutoff and restart voltages.

To set the LM338 Output voltage: With volt meter on red and black and input to yellow, adjust the
P1 trimmer to 1 + 1/6 battery voltage. Once set, the output voltage on the red wire should not vary.
The rectified charging voltage coming in to the regulator will normally be much higher than battery
voltage. The charger current should remain the same as the current the charger delivered previously.
Highest DC output battery charging voltage range is 1.2 volts less than the DC input voltage

................To set the cutoff voltage........................
Turn on board with yellow wire to charging input and black to common. Blue to LED to 1K ohm to black.
Then...
With a variable power supply + to the green and - to black wires, set the cutoff voltage desired.
OR
With the battery fully charged and red and green wires to the positive, common to negative battery.
Then...
If LED is on already adjust trimmer down to turn it off. Then turn opposite way until LED turns on again.
Turn trimmer one quarter turn in opposite direction. This may take several adjustments to work properly!
Cutoff voltage will turn on LED and cut voltage to the battery down to 1.25 volts on red W/O battery.
Image
The voltmeter on right shows the actual charge output voltage(red wire) set previously above and cutoff below.
Image
Charge voltage will return when battery voltage is about one volt less than cutoff with 1M ohm hysteresis .
A 2 mega ohm resistor from op amp pin 6 to 3 will cut voltage difference between shutoff and restart in half.

Note: LED may stay on after starting a new charge cycle. If so just stop and start it again quickly.

The LM338 can deliver 1.2 volts to 32 volts at 5 amps with the device reducing input 1.2 volts itself.
The CA3140 op amp can operate at supply voltages from 4V to 36V (either single or dual supply).

Thermal Design with Linear Voltage Regulators (heat sinks)
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