iPhone 1G, 3.7V 1400mAh battery PCB circuit diagram anyone?
I ordered a replacement battery for my 1G from iFixit (solderable). When it arrived I tested it and it showed no voltage. I thought perhaps it was shipped in a discharged state, so I continued installing. To make a long story short, iFixit sent me another, they are great! I tested the replacement when it arrived and it showed about 4V, seemed good.
-BUT- I installed it and the smoke got out within a few seconds of soldering the final (black) lead. bummer. and yes, I followed the directions from several different sources, wiring left to right 'red', 'white', 'black'.
1) read about the Protection Circuit Module ( PCB ) installed on li-ion polymer batteries.
2) carefully tore down both batteries, removing the tape etc. until I could see the layout and what remained of the wires from the battery to the PCB.
3) began carefully rebuilding the wiring to the PCB on one of the batteries. These things are pretty small, I'm having to squint through my magnifier. But I wouldn't have attempted this if I didn't think I could pull it off.
Both batteries are good (4V @ their terminals).
Both PCBs seem identical and showed similar resistance readings 18.5MΩ across their fuses <- maybe that is the problem?
But why are the readings so similar?
My questions are these:
1) I don't know what I did ( if anything ) to smoke the thing, I don't think I was being too hamfisted... all I can think is maybe I touched the case by the solder points with some extra solder? What else might cause the wires to melt? I'm talking about both leads from the battery terminals to the PCB.
2) I can't see how the negative(blk) wire is supposed to be routed from the battery terminal to the PCB - the red and black got fairly charred. But, after close inspection, the PCB's seem to differ as to where they were originally soldered. Perhaps this is the problem with the one that was DOA, the solder looks undisturbed on the 'B-' solder point whereas the battery which arrived in good working order appears to have some jagged leftover solder on the 'B-', as if that point was used.
I have rebuilt one of them now, attached the black lead from the battery to the 'B-' solder point on the PCB. But I get only about 40mV across the red and black PCB outputs. The fuse does not 'seem' blown. maybe it is... anyone know anything about these boards? The DOA battery seems to have routed the black wire directly to the output. I'm sure that will 'work', but is it proper?
Yeah, I'm being quite careful with these, I want no fires.
3) is it normal for the solder point on the phone for the neg(black) wire to show continuity with the silver case which surrounds those solder points? The white and red do not show continuity.
4) I could see that the windings of the leads from the battery to the PCB on the one which smoked as I installed it were wrapped around each other, VERY close proximity. Any breakdown of the insulation at all == a short. Could I have gotten lucky and received more than one defective battery?
thanks if anyone has any answers!
Final note - I ordered another battery and disassembled it to see how it was wired. As suspected the negative (black) lead from the battery goes to the 'B-' solder point, the positive ( red ) to the 'B+'.
Since I rewired the PCB I smoked in the correct fashion, I must have blown the fuse or a chip when I did whatever I did to smoke it, it only puts out 40mV on the leads now.
I tested this final battery via some leads I had soldered into the phone, just
to make certain it wasn't going to blow after the real job. Worked fine, back in business.
The PCB within these batteries hides an interesting winding of the positive wire around the negative right at the negative solder joint. Strain relief maybe. But excess heat or rubbing might easily short the thing.
Is this a good question?