I use a two-stage charge process. After the ride, at some point I will take them up to storage charge- 3.90V-3.95V /cell. Then check 'em. As I start to think about out going out, I will start the top charge while I ck. the tires and air shock. After 10 or 15 minutes, I'm usually between 4.00V and 4.10V, which is enough w/ my 12S/20Ah, 2S/2P pack. I never leave any of the BM's on while charging, since I'm not going to sit there watch for a stay cell. And you can't leave them on all the time because they drain the brick.
I like to keep the cells within 3 hundredths, but at extreme top charges(4.10V and above)sometimes they will stray a bit and I'll go at 5 hundredths. They tend to come back together during the dis-charge cycle.
I thought it would probably be a good idea at the beginning of the battery life to balance charge each pack individually a couple times before going to bulk charging,...
I used to cycle them a couple of times on my little RC balance charger, but the Multistar's are so steady out of the box, I don't bother anymore.
but if the cells in all packs are maintaining the balance, how important is it to have several separate BM's?
There are times. Say I just top charged and for some reason, I didn't go. So now I need to bring all 4 bricks down the storage level and since the BM's have the discharge rate akin to a melting glacier, I'll clip a BM on each brick and let them come down overnite. Or when I do something stupid like I did the other nite. The exact same scenaro, top charged and didn't go out. So I thought I would connect my monster h.lite, leave it on for a couple of hr.s and see what that did. Bad idea! It took all the energy from the first brick in my 2S/2P config. and not only was one brick way below the others, but the cells in that brick were all over the place! In that case, I set the BM values to match the single lowest cell(like 3.75V in this case) and they were still working when I got up in the morning.
I am planing to use a 14s2p configuration (like a few others I have seen recently), and with the Multistars, this means ( 2*4s+1*6s ) * 2, which would require 6 separate BM's.
Well, I would say 6. but look at it this way, you are already saving BIG $$$ by using LiPoly and if you follow my link on which BM's to buy, you won't waste money on the black BM's like I did.
One other thing I thought about and was wondering if it would help keep cells balanced is to parallel individual cells together across the strings using the balance cables and just leave them that way all the time.
No, you don't want to do that for several reasons, but suffice to say, you want all the speed the BM's will muster when you want to pull the whole pack down and that means a BM on ea. brick. And you are right about a low cell pulling down it's mate. Don't do it.
I had seen some discussion on one or two threads in ES about doing parallel then series connections vs. series then parallel, but I didn't really see an argument that I found convincing either way. I did a little looking at lunch time today and came across the following from batteryuniversity.com:
I series two bricks first, then parallel the 2 pr.s, 2 less Y-adapters needed. It's not like you are going to melt wires w/ the Multistars. In the same vein, although I make my own, you can use the skinny 14 Ga. "off the shelf" Y-adapters w/these low-powered systems.
There is a lot of good info in the batteryuniversity articles. I have seen a couple links to them in posts but I didn't check to see if they appear in some of the stickies or other reference materials in ES. If not it would be good to include some links.
Battery University is universally scorned here by the "experts". Unless you want to be derided, I wouldn''t mention that name again