Balance charging - always essential?

[Ian Whittaker]

At the field we have a charger which works perfectly well but needs a special balance device which I don’t have. It will however charge lipos without, on a specific Lipo program. My batteries are 6s 5200 and 5000Mah packs. They are rated at up to 3C recommended, although 5C is permitted.
would occasional charging them at 7A unbalanced be an issue? They are pretty new and in decent condition. I’ve done it once and the largest difference between cells was only 0.05V after charging.
I obviously don’t intend this as a regular thing, and they will be balanced correctly and balance charged as the norm, but this is a handy way of getting more flying in (my own balance charges only will do 2.4 and 3.4A so the 7A plus is a big bonus).

thanks all!

Edited By Ian Whittaker on 09/10/2020 11:36:15

[Nigel R]

"would occasional charging them at 7A unbalanced be an issue?"

Can't imagine so.

They will drift out of balance a little after a few goes at charging without balancing, but if you get them balanced after each session they will be perfectly ok. It's how you leave them for the long term that dictates their health (any overcharge / discharge aside).

[Chris Walby]

IMHO, can't see an issue

I charge all of my lipos at the field on non balance mode for two reasons

1. We have charging points and it takes additional space for the duration of a balance charge (generally longer that a non balance charge)
2. I want to reuse that recently charged lipo for another flight that day

I do charge them at home on balance and record the capacity and charge to full values, then enter the info into a spread sheet. What is interesting is the capacity starts to drop off over use/abuse and age so you get an idea which ones are on the way out.

There seems to be no rhyme or reason with some lipos as to end of life as I have some bought at the same time with one pegging it years before their brother/sisters and used in the same model. One thing for sure the harder you work them the less time they last.

[Ian Whittaker]

I generally take them down to 35-50% over a 4 1/2minute flight (helicopter). Until I started using the field charger that gives 7.1A they’ve never been charged at above 3.3A (an 80W charger). They’re up to about 40 flights each at present. I haven’t noticed any drop in performance yet - although I haven’t logged any other figures other than number of flights.
I’ve just used the field charger twice on one pack - the largest voltage difference between cells was 0.01v. Im reasonably happy with that!

[Keith Miles 2]

The harder that you work a battery, whether discharging or charging, the shorter it’s life will be.

The same, I imagine, applies to regular unbalanced charging, especially at higher charge rates.

The manufacturers, of course, will be more than happy to supply you with early replacements!

Speed and convenience or value for money?

Yer’ pays yer’ money, yer’ makes yer’ choice, I suppose!

[Chris Walby]

Its good practice to balance charge and in preference I would (at home) although I know people that never balance charge and they don't seem to have issues. Having said that they are using the lipos in low load models. I would assume the helicopter is close to edf discharge demand so hard on batteries so worth looking after them.

I don't think you are doing anything wrong as you are not deep discharging them and not charging them at a very high C rating so should get the best out of the batteries you have.

[Martin Harris - Moderator]

Perceived wisdom is that a 1C maximum charge is better for any LiPo regardless of claimed permissable charge rates. I have very occasionally exceeded this with claimed high charge rate batteries but I would recommend trying to avoid it if possible.

Chris - I'm surprised that you've found a significant balance time if your batteries are kept balanced regularly. Perhaps your charger is more finicky than mine but I find that the normal balance time on my batteries is in the order of just a minute or two after the termination of the main charge - which does admittedly taper off during the last few minutes.

[Ian Whittaker]

Posted by Martin Harris on 09/10/2020 16:20:55:

Perhaps your charger is more finicky than mine......

mine can take an age to do the balancing - am I that bothered about 0.01v? It’s not an issue at home but at the field it seems to drag on!

[Trevor Crook]

Ian, my view is that what you are proposing will not greatly affect the useful life of your batteries. Sure, in an ideal world you would always balance charge them at 1C maximum, but as Chris points out above, you are giving them a fairly easy life in the way you use them, which works in your favour.