Re-celling of Porter Cable 18V Batteries

[titusmc]

A friend at work gave me two dead Porter Cable 18V lithium batteries to work on since he knows I have built battery packs for my bike. I had spare high discharge cells (Samsung 20Q, LG HG2), so I decided to try re-celling the packs for him.

Each pack is 5 cells in series with a BMS. For the first pack I replaced the dead cells with HG2's, and the second with 20Q's. All connections for balancing wires are correct, but the packs read about 13V across the main power terminals (instead of 20V). I suspected that the BMS was doing something either because the cells were above 4.1v (I had read that the original cells in these packs were 4.1v - not 4.2v) or because they were out of balance. I tried to connect one of my imax B6's up to the pack to do a balancing, but I made an unknown connection error and magic smoke came out of the B6. Much to my surprise, however, the battery pack started putting out 20v again across the terminals, so I gave it back to my friend and it works in his drill.

I still have the second battery, and it still outputs only 13v. I don't want to blow up my only remaining B6, so I'm not sure what I should do. I'm wondering if I can hookup my imax b6 main leads to the pins on the battery to emulate the stock charger and get the BMS to do whatever it needs to do.

Anyone have a similar experience with re-celling drill batteries? Or just useful advice?

 

[titusmc]

Hmm... I'm a bit surprised there were no replies.

Anyway, I got it working. Here's an image of the pack for reference:

The pack has four male pins (visible, lets say 1-2-3-4 left to right) and a female pin (5, not-visible). Working packs have full voltage (20v) from 1 to 5. 3 and 4 are both low normally.

The packs I "re-celled" had 13v between the 1 and 5, 2 and 3 were low, and the voltage between 1 and 4 was 20v. I thought this was interesting, so I hooked up my imax b6 on pins 1 and 4 and did a slow discharge (0.3A) on the 5S setting. After a few minutes, I tested the voltage across 1 and 5 with my Extech DMM and it was 20v! I disconnected the B6 and checked all the pins with my multimeter and they all matched expectations for a functional pack.

I'm not sure what actually happened, other than that the BMS seemed to be protecting the pack until it saw a load across pins 1 and 4. If anyone knows more or can guess what is going on, I'd love to hear it.

 

[sc0obydo0]

I know this is an old thread, but you're the only one I can find that's tried rebuilding the lithium ion 18V packs.

I have two spent packs, so I broke them down and replaced the bad cells. I had a similar problem: Voltage was about 12-13V from pins 1 to 5, but 19-20V from pins 1-4 AND 1-3. I think 1-2 is the thermistor.

I tried using wires to connect to my reciprocating saw, pins 1 and 4. For a while, I was able to get the saw to work, but then all the sudden the voltage from 1-4 dropped to 0. Pins 1-3 were still at 20V. Pins 1-5 were still 13V (dropped while using the saw, but recovered). I never could get the voltage to go up for pins 1-5. And it felt like something got really hot on the BMS board, near where the thermistor wires in.

If I tried wiring pins 1 and 5 to the saw, pulling the trigger would drop the voltage to 0. Same if I swapped to pins 1 and 3.

Turns out, I swapped the pack with the other battery's BMS and it works fine...odd...so maybe that first BMS board is bad?

Any thoughts on getting that other BMS to work?

Thanks!

 

[flippy]

After making the connections you need to put iton the charger, that resets the bms. Some are quite difficult to reset as they require communication with the charger before turning on again.

 

[sc0obydo0]

Thanks, but that didn't work either, same as OP: rapidly blinking red light (equally spaced). Same response whether I put the recelled battery on before or after trying to trick it.

The oddity is the heat. If I charge the individual cells, then one of them will die if I leave the whole 5-pack connected to the board (I'll try it again and let you know which one, but I think it's the 4th one counting from the negative terminal). It took me a few times before I realized that's what's happening, so something is shunting just ONE battery.

Any other ideas?

 

[flippy]

blown board or its a internal "protecttion" that basically nerfs the brain box on the bms after a serious battery fault has happend. you usually see this with laptop batteries and some brands of bike batteries, those instantly commit suicide when a cell drops below 2v or soemthing.