Gotta do the quasi-necro on this thread.
Ontheroadagain (great track btw) is correct in that "it would be nice" if there were a simple, cheap, recommended bms or voltage limiting device that made the top balancing process fool proof. As a beginner to lifepo4 diy, I will say that if that product existed, it would be on the cells I'm balancing. Also, Will in his video gives the impression that top balancing is safer, more straight forward, more "idiot-proof" than it is. This of course is no fault of his own, and if memory serves, he does in fact say all the correct words when outlining the process. His attitude toward top balancing is somewhat cavalier, because it is quite simple for him, and surely for many reading this thread or this site for that matter. Keeping in mind that Wills audience, and this forums audience does include junior members such as myself, I think it prudent to point out that vigilance in teaching the instructions and caution associated with some of these diy procedures will only help less experienced members. A cavalier attitude, while accurate and true, will surely encourage a similar attitude in those of less experience, and potentially cost them big time.
All the rest of you folks are of course 100% correct in your assessments. Don't eff with the knob, listen carefully, don't make mistakes, and win.
Speaking of mistakes, I made one earlier this evening.
Top balancing 16 REPT cells for my maiden voyage (I like living on the edge), simple longwei PSU. Had to take down and reconstruct the ?array?(1S16P). Reconstructed. I got a dang phone call during which time I connected the positive lead of my PSU to the negative post, went to connect the negative lead to the positive post, got a spark (mild), tapped again another spark. The PSU was turned off but plugged in.
Disconnected my leads, examined the unit, attempted to turn it on, no voltage reading possible, then .6 volts. Confirmed accurate with multimeter, unit was capping out at .6 volts. I adjusted the amperage dial up and down. I heard a pop inside the unit, smelled a little burn, and immediately the voltage came back! Voltage dial appeared fully functional.
Opened up the unit (rattling sound inside). Located what I believe is a "protection diode"? on the floor of the PSU case, barrel/tube style plastic, cracked clean in half, and a curved wire with a small disc on the end of it.
I think I may have located where it desoldered from, but I can't be sure. I am inclined to swap the unit through cramazon tomorrow.
My question is this, and thank you for hanging in there:
The PSU is CV at 3.63V as measured with a multimeter. It is connected to my array giving 10.1A, and oh so slowly charging them up (3.31X and counting). This is exactly the same display and function as the unit was producing before my mistake.
1. Is it necessary to address the protection diode "issue" immediately? What the heck is a protection diode anyway? It sounds important at least.
2. Did I damage my cells at all by putting positive PSU to negative terminal and vise versa? I'm guessing no, but that spark, its got me a little shook on $1600. (Reassurances welcomed)
My thinking is that with such massive cells at a clearly middling SOC, and a PSU at 10A max, even if the voltage on the PSU went wild overnight, there is no way the batteries can actually rise to that voltage. Keep in mind I am generally watching the process like a hawk.
Anyway, appreciate all the time you knowledgeable folks put in here. I am putting together some pictures of my unboxing my REPT cell order from Shenzen Starmax. So far looking really good. Will make a thread when I get a little further along.
