Hi All, hope I have posted in the correct place.
I need your expert help please, I have an old bright worklamp, the USB C charging port fell off so I opened the lamp to attach it back on to the PCB, the lamp has only 1 x 18650 rechargeable in but there is room for 2 more, what I would like to do is add 2 more so the lamp I can use for longer, heres a few pics of the lamp


as you can see I can squeeze 2 more in there



red / green to battery

here's the other end, the little control / charging board



on the other side of that board it has the on, bright, on not so bright, off switch (3 clicks) usb C for charging the internal battery and also a usb out for charging other things, the USB out Im not worried about, dont need it, I also have these:




old laptop betterys, The 4 cell one is good, so the question is can I just add these, will the little charging unit that in there charge these or is it best to get something else?

Thanks

 

Have you been able to determine the charger function? The new batteries need to match the existing batteries in voltage and charge rate. I suspect the charge rate will be different. Are the batteries the same chemistry? Is the PCB a battery charger that is compatible with the laptop batteries?

How are you going to wire in the new batteries? Are they going to be serial or parallel? Important difference. If you wire them serially, the total voltage will likely be too much for the light. If you wire them in parallel, then the additional running time may disappoint you.

 

Thanks for the quick reply, yes I was going to wire them in parallel, as you say the voltage will be tripled and the LED strip might not like that.
sorry Ive not looked at anything as yet regarding charge rate, the voltage of the batteries are all the same, so Im wrong in thinking adding 2 extra batteries will add to running time ?

 

Battery voltages may be printed as being the same but there's ALWAYS a slight difference. What can happen is one battery can take more charge than the rest. Heat up and draw even more current. Then things can get ugly. The right solution would be a battery charge monitor board for each battery. That way no matter what one battery does or another does, each battery will be properly charged. Then when you use them as a light you'll have the longer run time.

 

Thanks for the input, could someone post a link to the battery charge monitor boards that I would need, also if Ive 3 boards can have 1 charge input for all 3 ?

 

If you charge (or discharge) each 18650 separately to the same final voltage, it'll be fine to wire them in parallel. Charging a higher capacity pack with the original board will just take longer to get a full charge. If the old battery had a protection board, wire that to the new cells the same way; it may be hidden under the insulator cardboard at the end, or under the heatshrink down the side. I've seen gadgets that put the battery protection on the main board, usually a 6-legged DW01 chip. If there's no evidence of such an animal, and you want protection from over-charge and over-discharge, search ebay for 1S PCM BMS. Or salvage the PCM from some e-waste that has a 4.2V lithium pack and looks like it might have run at a comparable discharge current.

 

If you charge (or discharge) each 18650 separately to the same final voltage, it'll be fine to wire them in parallel. Charging a higher capacity pack with the original board will just take longer to get a full charge. If the old battery had a protection board, wire that to the new cells the same way; it may be hidden under the insulator cardboard at the end, or under the heatshrink down the side.

I'm not sure I'd agree with this approach.

 

Here's the charger/controller that the lamp is fitted with, the battery has a resting voltage of 3.05 volts,
the output to the led strip is on bright 2.81 volts, switch again lower setting 2.48 volts but the battery is flat as the unit switches itself off, I was going to charge it when the USB C connector fell off the board

 

I don’t see an issue with this. If in doubt change all the batteries to the ”new” used batteries so they’re the same. Just remember the batteries in parallel and will balance each other. Can’t tell much from looking at that board, it’s a buck with some sort of charge controller. I wouldn’t change it just live with a 3x longer charge time for 3x longer run time.

 

Ive split the laptop batteries and going to charge one at a time until the LED on the charger stops flashing, indicating full charge, Ive been checking the voltage on the 1st battery and its staying around aprox 3.80 volts, nothing getting hot and no smoke,, once they're all charged, I'll check the voltage again, if all good, I'll wire them up and see how long the lamp runs for on 3 full charged batteries

 

They should get to about 4.2v fully charged

 

Yep that led stopped flashing at 4.17v, took a little time to squeeze the last .17 volts in, charging bat 2 now Ill now leave 1st one for a couple of hours to see what the resting voltage drops to

 

After an 8 hour rest the voltage on these new to lamp used batteries is 4.05(ish) volts, none below 4.00v,
current draw on high bright is 1.57 amps, on the lower setting only 0.40 amps

run times so far, low brightness:

1 hour......3.94v,
2 hours.....3.70v
4 hours.....3.64v
6 hours.....3.54v
9 hours......3.51v

Ive no idea what the low voltage cutout is on these batteries

 

Yes you can use the same charger ... Just wire the additional cells in parallel with the original one ... the charger will just take longer to charge ...you can put 100cells in paralel if you like , the charger will just deliver the same current , so take 100 times longer to charge ... before you connect additional cells they should be at the same voltage (within about 0.1V of each other) .. cells are nearly empty at 3.5 ..... the device should prevent too low discharge , not good for cells to go below 2.5V

 

This charging board, its a 5 volt in (usb c) anyone know if it can have a little more pumped in, like 12 volts, dont want to smoke it now Im this far

 

Don’t do that... it doesn’t work like that. The low voltage cutout is about 2.9-3 volts. While it’s possible to charge faster, it’s also more dangerous which means more complicated circuits and thermal sensing.

 

Another option not mentioned yet is to have a switch so that you can switch between batteries, and as one runs low switch to the next one. No redesign, No needing to balance the voltage, and no need to change hardly anything. But you will need to charge each battery, either one at a time or possibly all at once for three times as long. OR use 3 chargers.

 

I did think that but the way my life works is it would switch off and need a switch over just at the wrong time when I needed most just like the other lamps do, thats why I wanted something that was going to last a bit longer

 

I added a L7805cv3. problem is its getting very very hot, any idea why the 12v in is a regulated PS and surly the little charging unit wouldnt be drawing that much current, Ive clipped some makeshift heatsinks to it just to keep it cool, any ideas as to why its getting so hot

 

If you're feeding it with 12 VDC and it's regulating at 5 VDC then it has to drop 7 V. That's a big drop; and it's going to have to dissipate that extra voltage as heat. Even if your tiny little board draws just a few milliamps, there's still all that excess voltage that has to go somewhere.

If you want (need) 5 V at low amperages just get an old cell phone charger, they're usually capable of 500 to 700 mA. They're already built to handle the job nicely.