Hi y’all, I’ve got a problem with a Black & Decker VPX 7V Li-ion battery pack for a cordless drill. When I bought the drill a while back the VPX system was brand new and they gave away a mail-in bonus free battery pack. I got that pack in and wrote the date on it, put it away for a while to see how the original cell held up.
Well, the original cell is still going strong, lasts a long long time between charges. So long, in fact, that me and my horrible time sense failed to pull the new cell out of the package and keep it charged. It’s supposed to be a 7V pack, the original one just came off the charger at 7.15V but the freshly opened one is at 3V. The charger won’t do anything with it.
By the sounds of it the internal circuitry in the battery tripped. Hypothetically you could take it apart and try to fix it that way, but I don't think there really is much you can do. You could try just charging it with a hobby charger though, I'm guessing it is a Nicad?
Lol, just bustin your chops a little, it’s a Li-ion 7V battery pack. My original pack that came with the screwdriver is still charging up to 7.15V and it’s 5 years old. I got this spare pack as a bonus and put it away, forgot to get it out and charge it. This all started several years before I got into lights.
I was using the screwdriver yesterday and today and charged it up afterwards and remembered the “brand new still in the package” pack in the drawer. Got it out and stuck it on the DMM and it’s low, real low. Like more than 50% low. There’s a proprietary charger that goes with the screwdriver but it won’t recognize the low pack.
If it's a li-ion pack, then I would personally recommend against using it. Once they get discharged past 2 volts or so crystals can form which means the cell could vent at most any time if you were to recharge it. :(
Ok, so here’s what it looks like on the inside. 2 18650 cells with very little by way of electronics. It appears there’s only the one little diode. So how do they get 7V on the label from 8.4V of battery? Hmmmmm.
So, if I separate these 2 electronically would I then be able to hook up my cottonpickers charger to one cell at a time and maybe revive them? Would that be safe? They’re spot welded tabs though so I don’t know if I can do much with em. I don’t have a hobby charger.
Anyone got any ideas? I mean, any that would be helpful here?
My DMM says one cell has 3.31V, the other cell has no reading. Can I get individual readings when they’re attached? Or would this reading indicate both cells total value? But if that’s the case, it would seem like I’d get the same 3.31V regardless of which cell I touched the probes to. Hmmmmm….
I cut the welded tab at the backside of the pack and sure enough one cell has 3.31V and the other reads 0.0V. I’m charging the one with a reading and it’s coming up just fine with the cottonpicers 480/700 with Voltage readout.
Attached a second cottonpickers charger at 90mA to the zeroed cell, the charger is lit but there’s no readout on the voltage meter. I’m giving it 10 minutes and we’ll see what happens.
Edit: Cottonpickers chargers with digital readout have a bottom end readout of 2.5V
The metal clips that look similar to fuseholders are the connectors for the screwdriver. It has blades down in the chamber that slip into these for the power connection. And yep, that’s all there is.
I pulled the zeroed cell after 10 minutes at 90mA and it’s now reading .33V on my DMM, so juice is going in! The cells are the type that have a vented looking top cap on the positive side, with a slightly raised pedestal on the bottom negative side. They are wrapped in a yellow wrapper but the whole cell is inside a cardboard sleeve so I can’t tell if there’s a brand name or capacity written on the yellow wrapper.
At this point, knowing there’s a critical imbalance between the 2 cells even if the one does charge up it’d be pretty foolish to try to charge them as a pack. So I think I’ll tear it down and see what kind of cells these are and maybe use the good one in a light.
From what you said (“slightly raised pedestal”), it almost sounds like they have protection PCBs on the individual batteries, rather than on the overall pack itself. Maybe that’s why there’s only a resistor in the pack.
These cells are A123 APR18650M1A cells. No indication of capacity.
These are LiFePo4 cells at 3.3V, no wonder. Glad I didn’t keep the one on the charger(my Li-ion charger got it up to 3.35V oops!), I’ll put it in the charger I have that has adjustable Voltage rate and see where it goes. The dead one won’t register on the other charger, so it’s going in the recycle bin.
I got the zeroed one up to 2.8V with my Cottonpickers charger, first at 90mA, then 200mA once it started showing some voltage then switched chargers and used 480mA then 700mA to get to the 2.8V. Now the Ultrafire WF188 set at 3.2V and 650mA is charging them both. We’ll see what it stops at.
Would you believe these 18650’s are capable of –60A-30A? For about 2 minutes. This according to our resident battery and charger tester, HKJ. He also says the WF188 will charge these cells just fine.
I can’t figure out why one cell was sitting at 3.31V (nearly perfect considering it’s been in the package 4 1/2 years!) and the other was dead. They were, after all, joined in a pack.
They are both holding a fairly steady charge with some leveling off but not too bad. I have an Nichia 219 on a copper star and an XP-G2 on same, wired them in parallel and powered them up with this cell and got a 1.87A draw. This is with the DMM inline between the battery positive and led’s positive. The 2 copper stars are Arctic Silver 5’d to a copper bar, no host. Very very bright! Room brightening bright. No reflector or optics, just the bare leds sitting on stars sitting on copper for heat sinking. Hooked up to this cell at 3.64V and pulling almost 2A between them.
