Okay, more tests...
I hooked my new board into a 16s6p 48V/13.8Ah a123 setup that I have in a rack bag. Here's what it looks like:
It looks a bit busy in there, but it is actually quite roomy. This bag originally had two 12s3p packs that I used with my Townie. I rewired them so that all the cell junctions are paralleled, into a 12s6p configuration. Then, I added a 4s4p pack and a 4s2p pack, also paralleled at the cell junction points, yielding the final 16s6p configuration, all wired to a Molex-type connector that plugs into the BMS board. The bag fits on a rack, on the back of my 20" folding bike. Here's what it looks like on the bike:
My intent was to try and drain the pack down to cutoff, but I didn't have time. I did try shorting the LVC test pads, to make sure it would cut the throttle on the Cyclone 1000W controller, which it did. I then did a short 5 mile ride, which used up 3.117Ah. When I got back, I hooked up the NG1 which started charging at about 6A. The max rate for this charger is about 18A, but it only does this high a rate when the pack is pretty empty. I had only used about 22% of the capacity. Anyway, It took about 40 minutes to point when the first orange LED came on. Within about 5-6 minutes more, about half were lit. At the 55 minute mark, or 15 minues since the first one came on, all were on but three. At the 65 minute mark, all but one were fully lit, and the last one finally came on five minutes later.
Since having all the LEDs going is the worst case, for heat, I left the charger running for another 20 minutes, or so. The WattsUp showed the pack voltage was steady at 59.08V, and the current was bouncing around .40-.49A. I didn't have my temp gun, but I used my "calibrated" thumb, and touched all the shunt resistors. I could leave it on each one for about a second, or so, which tells me the temps were under 200F. Definitely no fan required.
All-in-all, I'm very happy with how this is working. Richard still is playing with the values of one cap and one resistor, but even they way it is, I'm a pretty happy camper.
I'm going to look at "pre-tweaking" the leads on the KSA931 parts, for the kits, so that we can use these with the existing boards. Eventually, once Richard gets done futzing around with the "final" design, I'll do a new layout with the right pinout for this part.
So, the kits will come with the big 6.8 ohm/5W resistors, like those shown above, and with 15 ohm/2W versions as well. If your application is something like a Ping 15-20Ah pack, where it is desired to seal up the BMS with the cells, you would use the 15 ohm shunt resistors. These setups usually have charge currents in the 2-4A range, which is a godd match for the 15 ohm shunt resistors, which will allow a bypass current in the 250-300mA range, which is 5-6 times higher than what most of the typical Chinese BMS boards will manage. For configurations which have higher capacities, and/or higher charge currents, the 6.8 ohm "fatboys" can be used, so long as there is some room around the board.
More tomorrow...
-- Gary