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Charging Lithium Battery Pack without Charger

whiteoutage

Jul 20, 2017
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Wife ran over the battery charger for my 20V Weedeater. Can I charge the battery pack with my adjustable 12-24V Universal Laptop Charger? Charger only has voltage adjustments, no current limiting. Just for kicks I threw the charger on battery pack for about 15 minutes @ 20V. Multimeter showed the battery pack taking .7A at start and faded to about .2A after 15 minutes. After short charge the packs voltage climbed from 2 volt to 11 volts. Can I continue charging? Not too concerned about hosing the bats as I got two years use out of the Weedeater, and they have been on the shelve for another three years. Also, I don't use Weedeater anymore but if pack is still usable it would be cool to use them for another project. Advice on DIY charging would be very much appreciated.
 

Bluejets

Oct 5, 2014
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20v pack down to 2v is knackered anyhow...no, charger arrangement not suitable either
 

73's de Edd

Aug 21, 2015
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Sir whiteoutage . . . . . . . . . ( No power outages HERE . . . . . .at least . . . . . not yet! )


Are Your WEED EATER branded battery packs being the smaller Black and Green WE20VRB 20V Lithium-Ion or the heftier / larger Black and Gray B16-2025, 20V Battery ?

Can you check the battery case and see if its 2 clam shells typical 4 retaining screws are something that you can handle. OR is it using sets of . . . SPECIAL TORX screws with the ADDITIONAL small SECURITY hole in the center ?

I have a full set of same, although, years/decades back, on my day-one encounter . . . I defeated them by using a hacksaw blade ground down with a Dremel cut off wheel to a just snug fit between two cross splines to get them broke loose and started out, then there was one of a standard jewelry screwdriver set, that fit in the same manner and then let me get them fully out.
Then I . . . .Dremel cut . . . . a slot across their ends to then make them standard slotted screws.

BECAUSE . . . . . you will need access to the packs individual cells.

2.5 V per cell is dropout voltage threshold detection / acceptance for a charger designed for LI - ION type cells CC charging, but it appears that some of yours are partially trying to respond to your charging effort.

Parts wise, do you have either an LM317 I.C. . . . . ./ or discrete components . . . . ./ as a plastic TO-220 or TO-3 NPN power transistor . . . . or tell us what variants thereof, you might have .
Also a PNP small signal silicon transistor and a 1/2 w 1.5K resistor and another resistor in the 22-47 ohm range . . .tell those values available, also.
Can / Do you sort of sarter . . . . . (solder) . . . .and micro build / breadboard / lashup ? (4 components)

73's de Edd . . . . .

upload_2022-2-4_5-5-38.png


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whiteoutage

Jul 20, 2017
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A few years ago I took out the four torx screws. Just noticed today when I lifted out the batteries that at least two of the ten cells have corrosion/expansion.
Yes, I can solder, like to repair things, but am a little electronically challenged. I occasionally scrap stuff and do have a couple unused small breadboards. Will check my de-soldered stock/circuit boards later tonight for the four components required. In the mean time here are three pics of the battery. I no longer have the charger -so test charge yesterday simply connected laptop charger's pos/neg terminals to bats pos/neg.
You are an angel from above! :)
 

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73's de Edd

Aug 21, 2015
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Sir whiteoutage . . . . . . . . .

On the photo of the battery pack there are 3 silver phillips screws on either side of two power Mosfets, both mounted on a common heatsink.
If they happen to be IRF1404's or equivalent N type Mosfet family, look and see their #'ing , as we can use one of them for the power transistor needed.

If that battery charger is this one being shown, I can see how a car tire could smush it !
The old first generation charger was as bulked up in its size and complexity,much as your batterys internal electronics is.
Why . . . why . . . why . . . didn't you save the compact SM wall wart power supply ? . . . . if it wasn't also on the garage floor ? . . . and not plugged into a wall socket.
upload_2022-2-6_8-1-47.png



Here is ALL of the info on that units Li Ion cells . . . . discard any others that show any onset of corrosion even starting through the case.
upload_2022-2-6_8-2-14.png
Thaaaaaaaasssit . . . . .

73's de Edd . . . . .

upload_2022-2-6_8-5-36.png

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whiteoutage

Jul 20, 2017
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Sorry, got sidetracked. Thank you for the update. I do have a box of wall warts with barrel plug adapters to fit most everything but yeah, she broke that adapter too. I also have several power transistors and mosfets, plus a good selection of resistors and caps, but when I went through my parts bin I could not locate an LM317 or equivalent with adjustable voltage regulation. The five VRs I found all appear to have fixed voltages (12, 10, 10, 5, -5). May be able to score an LM317 in town, if not, order one online. Attached is a picture of the voltage regulators and resistors.
UPDATE: according to their website, American Science & Surplus may carry the LM317. I will check in the morning, or if out of stock just order a couple of em.
 

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whiteoutage

Jul 20, 2017
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No luck on buying locally. Pretty soon we will only be able to pee online. Ordered 10 chips but won't be here for a couple weeks.
 

whiteoutage

Jul 20, 2017
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So I took all bats out. Used a hacksaw until I noticed the two screws that join two parts of battery holder together, so the correct way to remove the bats is just to remove all the tabs holding the them together. While pealing them off one of the bats let of some gas under pressure (assume that one is hosed as well).
Interestingly, the two outer pairs and the middle pair still look good, while pairs two and four are "gas bombs". Voltage is 1.15V on four of them and .75 on the other two - not sure if 15 minutes test charge last week affected these numbers.
Wondering if there is a quick and dirty way to test one of them to see if these may be salvageable?

Update: Lettering on components is BN0712 and BN0714.
 
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whiteoutage

Jul 20, 2017
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Took awhile but found a youtube quick/filthy method. USB phone charger and two signal diodes in series drops voltage to a conservatives 3.9V so my 2.2A, 5V charger now has a hacked usb cord that is charging one of the cells. Took an hour just to get to 3.5V but V is still climbing so thinking to let it go until the V stops rising or battery gets hot. Battery is not even warm but I still have a kill switch and bucket of sand on hand in case of fire. Tuber says this method is for emergency use only, do outdoors, etc. Consensus is to bin em all - just want to know long bat can hold a useable charge, if at all.
Update: Too late, I quit - after 2hrs only 3.6V. May find some less resistive diodes to increase input voltage to 4.1 tomorrow.
 
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whiteoutage

Jul 20, 2017
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Input adjusted to approx 4.1V using two normal diodes. After another six hours Bat charge is only 3.9V. Have not be monitoring amperage but did just take a measurement (.027amps) and battery was near room temp the entire charge. I may mod an led flashlight to use it, but thoughts of charging an old ni/cd trim saw with em seem to be derailed.
Can someone explain how to ballpark capacity using a power resistor vs. time scale (resistor ohm size and watt rating, etc)?
 
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whiteoutage

Jul 20, 2017
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NOTE: This method did not work using a phone charger directly. Not sure why, possibly most phone chargers have voltage regulation built in so the diode does not drop the voltage you'd think. For me, each diode would only dropped a couple of volts, rather than about 6V. Why my 4-Port USB only phone charger drops expected voltage I don't know reason for that either.

In Summary, I was able to charge one of these old Lithium batteries but don't know how useful it is. Can someone please explain how to ballpark a capacity, using a power resistor vs. time scale (resistor ohm size and watt rating, etc)?
 
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Martaine2005

May 12, 2015
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For me, each diode would only dropped a couple of volts, rather than about 6V.
Where did you get that information?
Each diode would only drop 0.6/0.7 volts. Schottky diodes would be around 0.2/0.3volts.
As already be told, bin them. sometimes, the old label “no user serviceable parts” is correct!.
Buy the batteries you want with a dedicated charger. Be safe and fire free!.

Martin
 

cjdelphi

Oct 26, 2011
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if she ran over the AC end, any DC power supply at 20v would do as you can determine the + and - cables via the PCB

connect up your lab supply and the weed eater pack will charge the batteries...

unless I am completely missing something?
 

whiteoutage

Jul 20, 2017
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Where did you get that information?
Each diode would only drop 0.6/0.7 volts. Schottky diodes would be around 0.2/0.3volts.
As already be told, bin them. sometimes, the old label “no user serviceable parts” is correct!.
Buy the batteries you want with a dedicated charger. Be safe and fire free! Martin

Sorry, forgot the decimal points, and thank you for Schottky fact. Yes, .6-.7 is normal voltage drop, and depending on charger used, for me , a normal diode dropped between .6 to .2V. My uneducated guess is that regulation is better with higher quality dedicated OEM phone chargers, therefore the drop discrepancies.


if she ran over the AC end, any DC power supply at 20v would do as you can determine the + and - cables via the PCB

connect up your lab supply and the weed eater pack will charge the batteries...

unless I am completely missing something?


Four of the batteries were discarded (3 swelled up and 1 hissed at me while removing. Would like to reuse the charger, but not sure if circuit board can smoothly charger all six equally, now that four are gone. Don't have a lab supply.
 

Harald Kapp

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Nov 17, 2011
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not sure if circuit board can smoothly charger all six equally
Only 5 batteries visible in post #5. 5 Batteries @ 3.7 V each makes 18.5 V, a likely configuration with an "optimistic" sales announcement of "20 V" technology ;).
The batteries are in series and you need a full assembly for the charger and the weedeater to work. Best idea is to replace all 5 batteries (or 6?) by a full set of new ones. Provided this isn't more expensive than a new weedeater, as is unfortunately often the case nowadays.
If the charger carries deserves to be called "charger", it should provide charge balancing between the cells to accomodate differences in capacity (unavoidable, even with high quality brand cells). You can recognize this feature if the charger has additional wires going to the connections between cells within the cell stack. These wires are used to sense individual cell voltages and to bypass charge current around fully charged cells. If these wires are present, make sure you connect them to the same positions in the new cell stack.
 

whiteoutage

Jul 20, 2017
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Thank you for reply. Yes, was a double stack of 5, or 10 Bats total. Will reassemble this weekend (took pictures to avoid problems), and see if it likes charging top row or half of them in series @ 20V. Of course, charging will be done outside in driveway with garage fire extinguisher, safety glasses, suit, etc. Yea, I understand this is probably all for not, and is only being done in the name of science.
 
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whiteoutage

Jul 20, 2017
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Thank you for reply. Yes, was a double stack of 5, or 10 Bats total. Will reassemble this weekend (took pictures to avoid problems), and see if it likes charging top row or half of them in series @ 20V.

With only half of the Bat pack the charger wants to give Bats twice the current (about 3.25A) so put a 12V, 1.5A car lamp in series and circuit is drawing a little less than an amp now. After 15 minutes amperage dropped to .67 and pack voltage is already 19. Have not burned down the house, yet - not sure why but bulb is barely glowing? When charger voltage hit 19V x .67A, the volts jumped to 19.45 and amps fell to .35. Otherwise has been steady voltage climb, amperage fall. Back now to steady volt rise/amp fall - approx. 1 hour in and volts is 19.55 and .27A. Stopped after 1 hour 45 minutes (19.95V only drawing 7mA) - quit for today. Load test still to come, if Bats don't die tonight. BATs never even got warn.
The single Bat charged earlier in this thread is still holding 3.9V but was not sure how to load test it.
 
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whiteoutage

Jul 20, 2017
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1st pic is of reconstructed Bat pack in its partially assembled case along with my DIY charging setup. 2nd picture has a black component encased in white opaque hot-snot that was originally snotted to first Bat. It measured open but I patched it back in circuit anyhow - not sure what it is or what could be used as a replacement, suggestions? Circuit is still functioning even though I think maybe it possibly blew?
While taking a final pack voltage measurement last night, like the greenhorn I am, I left the meter on amp setting. The meter took a nasty shock and discharged about half a volt from the pack? Meter seams OK, but a recharge this mourning for 45 minutes until amperage was 5mA was necessary.
CORRECTION: all the pack voltage readings I gave above were the voltages being feed from my laptop charger, not the pack voltage. Laptop charger was set to 20V while final pack voltage was approx. 19V, not 19.95V. I don't have a 21Volt charger so will settle for a 19V pack. The pack has a button to test voltage state. Indicator says pack is charged between 80-100%, but am not relying on this since pack has been modified.
 

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whiteoutage

Jul 20, 2017
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Opps, the 10A fuse did actually blow, fortunately a 5A fuse got her going.
Laptop charger's 20V setting actually outputs 21 volts so another hour charge will charge pack to max capacity.
Will attempt cutting up some plywood with this 14.4V panel saw. https://www.electronicspoint.com/fo...rcular-saw-with-dc-motor-problem-help.296577/

Staying after school to write 100 times: :-(
I will not use meter unless I confirm what position the leads are in
I will not use meter unless I confirm what position the leads are in
I will not use meter unless I confirm what position the leads are in

...

Update - cut a foot of 1/4" plywood. Fully charged pack of 20V dropped .5V. Not a real load test but good enough for now. Perfect cut and not as noisy as I thought it would be - will be good for small projects for sure.
 
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