Battery balancing.....voltage variation between cells????

[v2kdj]

Here's one you may find interesting ........ or not as the case may be!!

Balanced 3 batteries last night, all Turnigy....new (ish) and when i later check them on a battery checker the cell vary from 4.2v to 4.18 or around those figures. It also took a while for each battery to finish the balancing cycle.

How important is it that the cells are the same (without being too picky)?? I know they won't be spot on the same voltage but what difference should i expect?

Do i need to balance them every time or will a standard charge be ok (and quicker) then balance them once a month for example?

Batteries......a science in themselves eh!

Thanks, Karl.

[st200ol]

What charger and what battery checker, one or the other may not be 100% accurate. I would say a .02V undercharge a one or more cells is OK.

Most of the chargers and checkers we use are uncalibrated, cheap, Chinese low cost hardware after all.

[stanley1]

i notice the same sometimes on my bc6. not the best charger in the world but ok i thought, is a good quality charger always gonna read 4.20 across all cells after balancing then?

[barney]

It all depends on how well matched the cells are and there individual condition. The fully charged V is not quite so important as the voltage remaing after a flight per cell. Just keep the lowest cell around 3.5v after flight so your not overdischarging the weakest cell.

Straight from the charger the cells v will be bang on but they do settle after a short time, As batteries age the imbalances increase and the time it takes the charger to balance off the cells becomes longer.

Brian

[v2kdj]

Charger is a 'Pro Peak - Sigma 2 EQ' so it's a pretty decent one and the checker is a 'Fusion - Smart Guard' again not a cheap one!!
Buy cheap pay twice.....lesson learnt that in the past

Well......hope they are good quality anyway....someone's gonna tell me they are sh*t now....lol !!

Again....is it better to just charge the batteries and balance them occasionally?

[BenjaminKenobi]

Those voltages look completely fine. 4.2v and 4.18v is not much of a difference at all. And lipo chargers/checkers can vary in their accuracy. I personally balance my packs everytime but once in a while would probably be okay.

[barney]

Personally I just leave my chargers in balance mode, but if your packs are in good shape every few cycles is fine. For my own packs I charge at 2C which is a 30min charge.

[v2kdj]

Personally I just leave my chargers in balance mode, but if your packs are in good shape every few cycles is fine. For my own packs I charge at 2C which is a 30min charge.

Thanks. Just to check, what would 2c be for a 3s 2200mah 11.1v 25-30 burst rate?

[400blade]

2c would 4.4 amps on a 2200mah pack

[tourerjim]

It all depends on how well matched the cells are and there individual condition. The fully charged V is not quite so important as the voltage remaing after a flight per cell. Just keep the lowest cell around 3.5v after flight so your not overdischarging the weakest cell.

Straight from the charger the cells v will be bang on but they do settle after a short time, As batteries age the imbalances increase and the time it takes the charger to balance off the cells becomes longer.

Brian

Seems a lot of confusion over how much discharge" i was reading on another forum debate about how much discharge & main suggestion was best to only discharge lipo to 3.7 as this will insure a good balance everytime & anything below the3.7 can start to weaken to balance & cycle of the battery, i dont want topinch this post but maybe Stuart can set up a link something like (Battery Safety Guidlines) this would then give a firmer guidance & for those that just come on board, to be honest with you i've been on the forum since 2008 & still unsure.

[v2kdj]

2c would 4.4 amps on a 2200mah pack

Ahhhhh...the penny drops so 1c for a 2200mah pack is 2.2 amps per hour so for a 25c pack divide 60 minutes by 25 = about 2 minutes an 24 seconds for a burst rate of 25c??? confused....you will be!!!!!!!!!!!

Or am i wrong?? LoL.............

[cjcj1949]

I discharge to 3.6V on load. Leaving 20% in the battery seems about right.

Balancing is really a safety feature to prevent overcharge on one or more cells by keeping them all the same. Balancing itself actually causes problems by taking current from the cells with higher internal resistance. As the current drops towards the end of charge these cells will drop in volts and the current will be taken from the other cells.

If your cells all have the same internal resistance and capacity you can charge unbalanced after balancing once. If there is much of a difference though one cell will go over 4.2V. The amount will depend on the charge current and the internal resistance difference to the other cells. As the current drops the volts will end up the same, but one or more will have gone over 4.20V.

[stanley1]

hmmmm, sometimes my charger doesent balance all cells to 4.2 and on completion one or two may read 4.19 or even 4.18, does this then mean my charger is a bit dodgy? or is it just compleating the charge as the total voltage is 25.2?
im only using a bantam bc6 at the moment but thought although quite slow wasnt too bad of a charger. i have however noticed that after discharge all cells read the same voltage

[cjcj1949]

There are only two things that really matter. On charge don't exceed 4.20. On discharge don't go below whatever voltage you choose. The less you discharge the cells the longer they'll last. This isn't always good, as it can stop you buying the latest cells that are much better than the ones you've got.

Knowing how much you are putting into each battery is useful, probably essential, to keep track of things going wrong before they cause a crash. I also find my discharge monitor very useful for when I put a flat battery on the heli instead of a charged one, and when I forget to set the timer.

[rockaroller]

Gents would like to ask another question as this is the same charger as what I have. I charged one pack yesterday and now today when I plug it in its telling me that two cells are 1.5 v compare to the other being 3.77. I am changing align 25c 22.2V 2600mAh batts. I have checked the balancing port and all the pins are fine. I have also checked the battery with a tester and all the cells checked out fine. I have also tried all 4 my batteries and they are all giving the same error. Is my charger busy die'ing?

Sigma 2 EQ.

RaR