Luke, the Battery Medics have two modes, balance and discharge. In the balance mode, the high cells are brought down to level of the low one, just like every other RC balancer we've used for years. The discharge mode works like our BMS shunt circuits, where each cell is brought down to programmable set point, like 4.10V. For the BMS testing, I've been using 4.00V. Anyway, when all the cells are discharged to that point, the unit stops. In the balance mode, it gets all the cells down to the level of the lowest, but I think sometimes it can overshoot a bit, and this cell now becomes the lowest, so all the rest are brought to this level. The cells all seem to stay within 4-5mV, but I have seen them "keep going" like this. I guess I'll really have to watch this, with the booster connected, because it certainly will take a lot less time.
What I will do is only use the balance mode if I happen to be using these while charging the pack. Otherwise, I'll use the discharge mode, set to something like 4.10V.
Mike, are you talking about the ATA6870 chip? This looks similar to the LT chip that Patrick (methods...) has been using in his 36-channel monitoring system he's working on. I went through the 6870 datasheet, and I see how it can be used to drive a standard shunt circuit, but I didn't see any reference to a charge pump-type setup.
As for top vs. bottom balancing, all I can say is bottom balancing is not something I would ever consider. Even with cells that are closely matched in capacity, etc., there will always be one that will "jump off the cliff" first, so trying to catch them right at that point is risky, at best. This whole top vs bottom balancing is really more applicable to larger capacity cells like the ThunderSkys, which seem to have quite different capacities, RIs and temp coefficients. This causse them to get out-of-balance, in relation to each other, quite fast, sometimes with every cycle if they are discharged far enough. For these types of cells, doing "top balancing" doesn't really make a lot of sense, because what happens is that the lowest capacity cells have to wait around, shunting current, while the high cells get fully charged. As long as you do cell-level low voltage protection, to keep the "cliff jumpers" at bay, you don't really need to do top balancing. What many BMSs used with these cells seem to do, though, is simply stop the charge when the first cell hits the HVC point. The problem with that is that the cell really isn't getting full charge. In order to get full, the voltage needs to be held at the HVC point, and the current allowed to taper off. This is exactly what our charge controller does. It uses the HVC signal to keep the cell right at that HVC point. Without any shunt circuits, the low capacity cell will control the current tapering down, so this way at least it is getting full. There is one problem with this "no balance" approach, however, and that is the case where you may have cells with similar capacities, but different states of charge. What happens is the "usable" capacity is reduced, so you end up with less range. To fix this, you still need to do periodic balancing, of some sort, but it doesn't have to be top balancing. You could use something like this boosted Battery Medic to balance the cells, after a charge, either to a fixed point, or to the low cell, so that they are all at the same point, and then charge them to where the low capacity cell is fuil.
The LiPo packs we've all been using are a different animal. For the most part, the differences we see in voltages between cells are due to differences in state of charge. Eventually, the cells will drift apart more, but even then most of the deltas are going to be because the cells are unbalanced, not because one cell has a significant difference in capacity and/or internal resistance. For these, balancing is a good thing, but it doesn't need to be done with every charge, because the cells just don't get that far apart, under normal use. What will get them a bit unbalanced, is discharging them down to the LVC point. While the LVC circuits will stop the cliff jumping, the first one to get close to the ledge, so to speak, will not be allowed to commit suicide, but this cell will end up farther out-of-balance with the rest of the pack.
Here's what the new combo LVC/HVC-6s4p Parallel Adapter boards look like:
There are several "external" connection options, a standard 7-pin JST-XH pigtail, a Molex MicroFit 3.0 connector, or a 3.5mm mini-terminal block. I mostly use the Microfit 3.0 plugs and connectors, which are a lot more robust than the JST-XH connectors, and can take 18-gauge wires. I'm also able to use the same ridiculously expensive crimping tool, with these, that I bought for use with the larger Tyco/AMP VAL-U-LOK 4.2mm PE Series connectors. I'm also in the process of having some "pre-crimped" wires made made up, so I can offer cables with matching MicroFit plugs on each end. Finally, because my next LiPo pack is probably going to based on the new Turnigy 8s-5800 packs that HC is now selling, I'm going to do an 8s version of the LVC-HVC board. I just got a bunch of 9-pin JST-XH, 9-pin MicroFit connectors and 9-pin 3.5mm terminal blocks in this morning.