Slowww LiPo Charging Problem

[Tosh McCaber]

Hi all ,

I have been using,  with excellent results, the very efficient and versatile SkyRC D100V2 Dual Charger for the past few years.  However, during my last few charging sessions, in a marked change, it's taken a great length of time to fully charge (quite a few) of my LiPo packs. 

Most of them have been 3S, mainly 2200mah, 40-60c-  some older packs, but also two brand new packs.  What used to take 1/2 hour- 1 hour to full charge, charging at 2200ma, is now taking up to three hours.

The otherwise very efficient charger also has a built in internal resistance checker.  Readings have been well within limits (I hope?)-7-8 ohms, and the voltages of the cells have been similar all the way through charging.

Not sure why it's taking so long to charge?  Any suggestions appreciated!

[Engine Doctor]

Have you somehow put them into  balance charge ? That takes ages.

[Tosh McCaber]

Aha!  You may have the missing clue there, ED!   I am using "balance charge" mode!   I can't remember, but, from what you're writing, since this has just come about, I must have been using  just the "charge" setting previously?  

So, presumably, it's OK to just charge the batteries on regular "charge" mode, as opposed to "balance charge"?  If that's the case, when would I use the "balance charge" setting opon the charger with my liPo batteries?

[Chris Walby]

IMO the recommendation is to balance charge for the majority of your charges as that prevents one/some cells being over charged and some under charged. 

 

So all my home charging under supervision is balance charging, but once at the flying field then I use standard charge setting as balance can take ages (sometimes) to complete the charge. The other thing with charging at home was that I used to record the pre and post charge levels and compare that with the mAh's put back in. Stick it all in the spreadsheet and you can see the capacity start to roll off at about the same time the battery C rating starts to fall., but before major problems.

 

Its worth logging all this on expensive packs or models where the consequence of the lipo failing is really unwanted (twins, expensive model etc).

 

Now I tend to fill it up, start it, tune it and just go fly...

[leccyflyer]

3 hours ago, Tosh McCaber said:

Aha!  You may have the missing clue there, ED!   I am using "balance charge" mode!   I can't remember, but, from what you're writing, since this has just come about, I must have been using  just the "charge" setting previously?  

So, presumably, it's OK to just charge the batteries on regular "charge" mode, as opposed to "balance charge"?  If that's the case, when would I use the "balance charge" setting opon the charger with my liPo batteries?

Tosh - I balance charge every time and it certainly doesn't take three hours. Balance charging is best practice. As I said the other day, it's the very last bit of the charge that does take a little longer, If your charger is capable you could try setting your maximum charge level to something less than 4.20v/cell - say 4.18v/cell and see if that makes a difference in charge time.

 

You could also try charging just one pack at a time and noting whether one charging port is different in timing. One thing does spring to mind and I'm not familiar with the balance port configuration of your charger - if you are using balance boards plugged into each port you could try taking the plug out and remaking that connection afresh. If you have a multimeter you might check that your charging leads are in good condition, with low resistance.

 

[Tosh McCaber]

Hi Leccy, I'm charging a new pack presently- I'll see how I get on!

[MaxG]

on Youtube "Painless 360" did a recent video where he was talking about when packs get to retirement age. He said there that packs that take an age on balance charging is often because one cell is in difficulties. Check your cell internal resistances to see if one cell is out of line. If it is it could be the start of the end for that pack.

[Tosh McCaber]

Hi Leccy, Got a lot of info, discharging and recharging a couple of packs.  Unfortunately, my studies were disturbed by visitors- several readings that I wanted are missing, so I'll finish it tomorrow, and pass the info on.  (other than the length of time to charge being long, I think the readings were OK.)

[Nigel Sharp]

Do you charge with Dc100 on mains ac or 12v Dc input?

 

Ac mode you only have 50 watt per channel in the default settings.

 

If you configure DC(out) you'll get proportionally less in one or both Channels.

 

Dc input mode you get 100 watt per channel.

 

Are you charging one pack per channel or using parallel charging?

 

 

 

 

 

 

[Engine Doctor]

On 09/09/2024 at 20:36, Tosh McCaber said:

Aha!  You may have the missing clue there, ED!   I am using "balance charge" mode!   I can't remember, but, from what you're writing, since this has just come about, I must have been using  just the "charge" setting previously?  

So, presumably, it's OK to just charge the batteries on regular "charge" mode, as opposed to "balance charge"?  If that's the case, when would I use the "balance charge" setting opon the charger with my liPo batteries?

I only ever use the bslance charge once in a while or if i notice cells out of balance. Individual cell voltages can be checked while charging . Normal charged used nearly all the time. If cells keep going out of balance then check IR  of the cells . My Imax charger also has a fast charge option but never used it .0

[Ron Gray]

Personally I always balance charge!

[leccyflyer]

So do I - really don't see any advantage whatsoever to not using the balance charge facility. I consider it best practice to balance charge and to monitor individual cell voltage in use every flight and every charge, to turn up any potential degradation. Have only started to more regularly monitor individual cell IR as well. 

[Cuban8]

I don't have a charging rule but tend to go for a half std charge and half balance charge. Don't really notice much difference.

[Dickw]

I am another one who always balance charges. It seems safer to have all the cells in balance - particularly if you are going to be pushing the battery hard in use, and I do like to monitor the condition of individual cells.

Balance charging certainly doesn't seem to take a long time as I frequently charge between rounds at a competition. I suppose if you let a battery get way out of balance by not balance charging it could take a while to get it balanced again.

 

Taking a long time to balance charge suggest one of three things to me all of which might need further investigation :-
I discharged too low last flight and got it way out of balance as a result;
The pack may be getting past its useable life;
There may be a problem with the balance lead connections.

 

Dick

[Tosh McCaber]

Sorry for the late response.  I finally found out the root of the problem.  Having checked out several batteries- all on Balance Charge all at 1C I found that they were all taking a long time to charge- up to three hours!  However, all of similar voltage/cell, and of similar, acceptable internal resistanceThen a fellow club member came up with the cause.  There's an initial setting on the Sky RC charger, where it gives the option of DC charge current, whilst operating off AC.  Mine was set as below in thee first image, giving only 5w total charge.  I adjusted the DC supply to 0, and that brought the supply of permissable charge to my battery of 50w. 

Just recharged a 2200mah 3S 60C battery this afternoon after flying which was discharged to 3.8v/ cell, up to full charge took 40 minutes!  Very acceptable.

 

Many thanks for all your replies.  Very much appreciated!  And, I have to say that I have always used the balance charge mode on the charger.  Boy- I've learned a lot about LiPos and charging in the last few days!  ps- the bottom photo is that of a club mate's Overlander charger, which is virtually a rebranded Sky RC.

 

 

Edited September 13 by Tosh McCaber