Lithium care?

[BrianG]

OK, I read the FAQ about Lipos, but didn't find the answer to my question. In the near future, I plan on getting some Lithium-based batteries (probably Li-Ion or Li-Mn) and want to make sure I understand a couple of things.

1: I understand a balancer keeps each cell in a multi-cell pack at the proper voltage, but when do you use it? While charging, after charging, during use? Why aren't there chargers that simply charge each cell individually (like having several seperate chargers in one box)? Would that eliminate the needs for a balancer?

2: What is a reliable charger that will do 5s or 6s at ~5A (for future battery purchases)? Most I've seen either only go up to 3s or 4s, or they do only ~2-3A. I was at my LHS today and saw this really small charger that looks just like this (Pro-Peak Prodigy II), but red, that will do NiMH/NiCd, and Li-XX cells 1s-5s @ up to 5A for $130. It was a brand that I haven't seen though, and I don't want to trust multi-hundred dollar batteries to just anything. I want to make sure that whatever I get will be solid and is not susceptible to overcharging through electronic errors. Ideally, it should be able to be run from household AC as well as 12vDC.

I'm willing to spend the bucks for good quality stuff, but don't want to spend money needlessly for overpriced stuff. I don't want to learn my mistakes the hard way! :)

[squeeforever]

Well you can balance the pack as it charges or after. If after, it will reduce the voltage slightly and thats why most would do it during. The Multiplex charger Mike carrys is a very nice charger. Actually, the Pro-Peak Prodigy II is the same thing as the Multiplex. So buy from Mike ;). I don't however think that its a AC/DC.

[BrianG]

Doh! Of course I'd buy from Mike if I was not blind! I just went through there and didn't see it. :007: Plus, it's way cheaper than my LHS. It must contain a DC-DC converter since 5s is over the supply voltage. It's just so small though! Does it heat up? My MRC Superbrain 959 heats up a bit when charging at ~3A or higher.

As far as AC/DC operation, I can use the 12v line from an old ATX computer power supply, or even build a linear supply easily enough - I was just hoping for a one-piece design.

It doesn't look like that particular model has a balancer, and Mike doesn't have a 5s capable balancer. Is there one you recommend? I'll see if Mike can get it instead of ordering it somewhere else.

So, how does a balancer actually work? If one cell is too high, does it simply shut off the charge voltage to the whole pack, or does it stop charging just the one cell?

Thanks Squee!

[squeeforever]

From what I understand, the balancer is completely independant of the charger. It balances the cells by taking the higher voltage from one cell and balances it by giving it to the lower voltage cells. If that makes any sense. I think a TP balancer would be good although the blinky balancer type thing that Mike sells is a good way to go. Most people just check the cells with a voltmeter and charger them individually if there out of balance. Balancing isn't something that needs to be done all the time though. They shouldn't get out of balance often if ever to be honest. I have heard of some where there packs stayed in balance for going on 3 years and have yet to be balanced once. I think the item Mike cells would suffice and if they got far enough out of balance, you can charger them individually.

[BrianG]

OK, that makes sense I suppose. I will probably pick one up just to be sure. However, Mike's balancer is only good for up to 4 cells. I plan to use 5s.

That aside, you mention an alternative method of measuring the voltage on each cell and only charge/discharge the cells that need it. Do you use the balancer leads to do this? If so, then the balancer must be doing this when it is hooked up during charging right?

[squeeforever]

Yes, thats exactly right. You just use the balancing taps to do so. That is how they remain separate from each other.

[BrianG]

Sounds like they should make a charger than actually is several seperate 1s chargers. That would work better than a charger with a seperate balancer, but I guess would be more expensive due to the duplication of parts...

Thanks for clearing this stuff up for me Squee!

[squeeforever]

No problem. What I dont understand is why there isn't more chargers with balancers built in. The FMA chargers are the ONLY ones that I am aware of that do this. I however don't really like them because they only have lights on them, and no lcd screen.

[JOHNNYMAXXIMA]

Brian,
I just bought a couple of those Multiplex chargers from Mike. They are good little charger as far as I can tell so far. I've charged some 7cell NiMh's @ 4A and also my 5s LiPo's and didn't see any signs of heating up like my 959's do.
I also bought a balancer for my LiPo packs as well. I got the Maxxamps packs and they install the balancer plug (taps) on there for you, that is an optional feature I guess? Their balancer will balance up to a 5s pack. They also include with their balancers, adapters for a 2,3, or 4s packs as well. I havn't used my packs yet but the instructions for the balancer looks pretty straight forward.

[MetalMan]

http://www.commonsenserc.com/product...products_id=40
Another balancing charger. There is another based off the design that the Multiplex LN5014 uses (5s Lipo/14 NiMh, 5amps), but I can't find the link right now.

The Hyperion LBA6 balancer (I'm pretty sure that's what Johnny is talking about) is a good balancer. There is a modification that can be done for charging at rates higher than 3amps that is a very good idea to do. http://www.rcgroups.com/forums/showp...&postcount=189

Balancing is best to be done during a charge. If you do it after, one of the cells in the pack could have gone above 4.20v, which isn't a good thing. Balancers shouldn't be used on discharge because under about 3.8v/cell the voltages of the cells won't be similar to each other as much as they are at 3.8v and higher (I know it doesn't make much sense, it's hard to explain).
Balancing isn't about taking from one cell and giving to another, it involves a processor watching the voltages of each cell and applying a load to the ones with higher voltage to reduce them down to the level of the lowest voltage cell.

Probably the best balancer out there would be the TP-205V (for 5s Lipo). It has a higher drain rate than the Hyperion LBA6, which means that it can balance packs faster, keeping them further out of harms way. It also has a more intuitive design, with multiple LEDs that can flash error codes, balance status, etc.

[JOHNNYMAXXIMA]

How long does it take to balance a 5s pack? Do they balance faster if you balance them during charging or after or is it the same?

[MetalMan]

You can't know how long it will take to balance a pack because it is very difficult to find out how much capacity the balancer has to drain in order to get a cell/cells to the same voltage as the lowest one.
It would be faster (and safer) if you balance during charging because the balancer can operate the whole time. Whereas if you plug it in after the charge, it starts the balancing right then and will add extra time.

[coolhandcountry]

How important is it to balance a pack? I haven't got a balancer yet. I need to check the voltage in the packs and see.

[MetalMan]

If the cells are out of balance, then it's important. If they aren't out of balance, then it isn't as important. IMO, it's best to be safe and use it all the time. It will allow you to get maximum life out of your batteries.

[squeeforever]

Metalman, is the Hyperion EOS7I charger and Hyperion LBA6 balancer a good combo to charger some 8000mah packs? I had planned on running 5S (one 2S and one 3S).