CloudSkipper

Hi,
From reading I've determined so far that discharging is not an important function for LiPo's. So I'm ignoring that feature.

But balancing is important... I'm looking at what charger and balancer to buy and some questions come to mind...

Do LiPo's go out-of-balance by themselves over a short period of time (like say in a few days only)? Say for instance you don't end up using a lipo pack one day, so it's left charged... when you use it the next day, will it be still be balanced?

Do LiPo's always necessarily need to be charged with balancing? Or do you really only need to balance them every several charges or so?

See, I could get a charger/balancer or a separate charger and separate balancer. With either option there are different pros and cons with what's available. That's why I'm wondering about the above questions.

Thanks

Swift427

1. Just the opposite! - LiPo's having unequally matched cells will get out-of-balance during use/discharge even though when balance charged to 12.45v they may be within 0.05v of each other. The longer they rest after flying the more the cells will equalize as the greater voltage & capacity of one cell will be siphoned over to the other cell(s) with lower voltage & capacity.

2. If you pay top dollar for a LiPo with equally matched cells and don't abuse it during discharge and charge you may only need to balance charge it every 5-10 flights depending on their 'equal' A+ quality. However, to be on the safe side it is best to always balance charge a LiPo because the chances are 50/50 as to the cells being 'equal'. They may only be of C+ quality. When charging a 9.0v LVC LiPo to 12.45 volts the cells will tend to equalize themselves during the charge more than unequalize themselves. Any out-of-balance inequality is most noticeable if you were to check individual cell bounce back voltages 30-60 minutes after LVC before recharging. For example a 3S A+ Lipo's cell bounce back voltage readouts might look like this after one hour (depending on the discharge rate) 3.54v / 3.56v / 3.55v. A C+ LiPo's cell readouts would look more like this 3.48v / 3.23v / 3.38v or the 3.21v / 3.40v / 3.23v you get the gist?

Balance charging a LiPo can't turn a C+ LiPo into an A+ LiPo, but it can insure that you get the best performance possible from your C+ LiPo as well as prolonging its life so it doesn't go from C+ to F(overheating, puffing, danger).

CloudSkipper

Thanks for the detailed reply. It explains a lot that I wasn't sure of.

That makes sense that the lipo cells would naturally balance when left alone. I guess if someone were using a charger without an in-line balancer, and charging the packs right after flying them (no rest period) then his packs would become quickly and badly unbalanced, correct?

The more I've read about this, the more I realize that I need to get a quality charger/balancer and quality lipos.

Thanks for your help

Swift427

It depends on the quality and similarity of the individual cells in any LiPo. For example the bounce back cell voltages in an A+ LiPo would be almost identical 10 minutes after LVC 3.45v / 3.46v / 3.44v so it wouldn't even be necessary to use a balancer. But the LEDs of a Blinky also serve as a monitor. In other words if the LEDs are alternating equally you know the cells are equally balanced, but if one or two of the LEDs are doing most of the blinking that means they are depleting voltage from that cell to balance it with the lower voltage of the cell whose LED isn't blinking. This prevents an unbalanced charging from overcharging one or two of the cells.

The greater difference in the bounce back cell voltages in a pack 10minutes, 30 minutes or 1 hour after the 9v cutoff the more important it is to use a balancer. So, when someone says you don't need to balance charge every time they are really saying you don't need to balance every charge cycle IF each cell in your LiPo is equally matched to one another. However, logic would say that may be true with a new A+ LiPo, but with usage over time it will degrade to a B+ LiPo, then a B LiPo, and a C+ LiPo and eventually a D LiPo.

Leo L

I'm not sure what is meant by A+ Lipo vs. B vs. C etc. I've been using LiPo's for about 16 months and have only bought the "no-name" brand from e-bay. I've never used a balancing charger and have yet to have a battery go bad. My understanding is that the larger the cells, and the more cells per battery, the more you need to balance the battery. All of my LiPo's are 3-cell, with the largest being 2200mah, but most are 1800, 1200, and 800.

CloudSkipper

And I guess if you're using a 6S that costs hundreds, it's a small thing to get a balancer or balancing charger to keep the investment healthy.

I'll still balance charge mine even if they are 3S. A balancer is not a big expense anyway.

Swift427

I trust Leo's advice and his view is valid to a certain point; especially if you know how to treat your LiPos and not abuse them. Also, if you do get a dud with mismatched cells a balancer isn't going to make it better.

The following article is from a vendor whose top quality LiPos have cells so well matched that they apparently never need balance charging when treated right. This article was on their website a month ago, but they have since removed it. It expresses their view of balancing; which goes against the common grain of thinking, but is valid assuming your packs have equally matched cells and you treat your LiPos right.

NO GIMMICKS

For years we have sat quietly aside watching the proponents of "pack balancing" spew forth misinformation. The truth is that a properly matched pack will not require balancing. Yes, we're sure this is a shock to many of you who have fallen for the balancing gimmick. Yes, Apogee was the first to put commercial grade plugs on all packs due to customer demand. We've had and seen enough.

Pack balancing is a gimmick perpetuated by companies who make balancers, and by other companies who do not match battery cells within the pack. A properly matched pack will not require balancing, and in fact will mask a failing cell. Balancing is a band aid for companies who lack the proper equipment to do cell matching. All Apogee packs have been cell matched since the day we started.

Due to misinformation, more packs have been damaged during balancing than have been helped. If you insist on balancing a pack (If it makes you feel warm and fuzzy inside, and you sleep better at night, have at it), please, please, only balance fully charged packs.

Why only balance fully charged packs? All properly matched cells are mated together so that the high and low voltages will coincide. There may be mid-point voltage variances. Balancing a partially charged pack can cause the high and low voltages to become unbalanced. Again, please, if you insist on the balancing gimmick, please only balance fully charged packs.

Swift427

The following examples using a battery monitor give an idea of what I meant. In other words as LiPos age they gradually deteriorate and any differences between individual cells become more apparent. The Electrifly's performance is now what I would call a C Lipo. The CommonSenseRCs performance is B+, and the ParkZone's performance is AOK.

In the following test the throttle was advanced to an initial motor load of only 75w and left there. The following bounce back voltages were taken 1 hour after LVC.

10.30v = 3.42v / 3.49v / 3.39v = Electrifly 910mAh 15C
10.62v = 3.53v / 3.57v / 3.52v = CommonSense 2000mAh 8C
11.44v = 3.81v / 3.82v / 3.81v = ParkZone 2200mAh 12C
( the only one to get warm enough to notice by touch (felt as warm as my hand) at its LVC of 9.6v was the 910 15C )

Conclusion: The PZ LiPo has the best matched cells of my 3 tested LiPos, and the aging Electrifly's performance is what I'd call C-