Charging

[Adrian Harrison]

Opinions please (exc Wiz Woz!)...charging 10s packs - is this best as a 10s unit or 2x5s and why.
Thanks
Adrian

[chris bond]

Not sure what is best but I  charge 2 x 5s simply because it is easier and there are now quite a few dual output chargers that will provide good power for each output and hence you can charge quicker. I use the hyperion Duo 11 which gives two outputs of 180w so two  5s packs can be charged  in about an hour. I have never felt the need to charge above 1c however. If you charge a 10s then you will need at least a 250w charger

I do not believe that there are any problems with the two packs not being identical voltage as we will connect them in series. Perhaps it would be different if they were to be connected as 5s2p

[Richard Christopher]

Hi Adrian,

Charging 5s x 2 as two separate packs
The 5s x 2 packs that I have used have been charged as "two 5's" and as "10's". I initially charged as two separate 5's as the charger I had was equipped with two outputs with their own individual balance ports (i.e. effectively two chargers in one case). Initially each half would always match, but after 15 or so cycles it was common to find a SMALL variation in voltage (21.00V 'v' 20.94V is the worst I have seen). This seemed to have no noticeable effect on performance and may be down to inaccuracies/tolerances between my chargers two ports (I never verified this by measuring with a common voltmeter!)

I charged like this until I started using some 10s packs - this forced me down the route of a charger that could charge a 10s.

Charging 10s as a ten
For charging 10s I opted for the ThunderPower TP-1010C in conjunction with a TP-210V balancer as this ensures all 10 cells are balanced to each other (i.e. not two groups of 5). Since I have had this charger I have always charged my 5s x 2 packs as a ten. The charger/balancer instruction booklet show a diagram of how the cells in a 10s should be configured. I found that FlightPower and ThunderPower are the same but you should identify which half of your two 5's is "group A" and which is "group B". With a voltmeter and the ThunderPower diagrams this is relatively easy to work out and the balance leads can then be labelled. Obviously other manufacturers batt's and chargers would need to be checked for wiring configuration before being sure that everything is ok.

I guess another option is charging as a 10 but with two 5 cell balancers? - I have no experience of this arrangement and so can offer no advice.

I have noticed no difference in performance whichever of the two methods I employed although when charged as a 10s the packs seem to take less time to balance - this could just be that the balancer I use now is better (i.e. discharges high voltage cells more quickly).

Something tells me that balancing a group of ten is better practice than 2 groups of five, but in reality it doesn't seem to matter (in my experience anyway).

My charge history for my 5s packs...

Pack 1 = 48 charges as 2x5s, 9 charges as 10s
Pack 2 = 49 as 2x5s, 8 as 10s
Pack 3 = 60 as 2x5s, 10 as 10s
Pack 4 = 67 as 2x5s, 12 as 10s
Pack 5 = 37 as 2x5s, 5 as 10s
All packs still in use.

PS All my charging is at 1C or less.

Regards,
Richard.

[Adrian Harrison]

Thanks Chris/Richard excellent info.
I have an iC1010B+ charger which will do 10cells and balance all 10 cells as a unit so this how I will proceed. Done the initial charges at 0.5C on 5000mah Zippies
As a sup. question how have you 'run in' the packs.
Thanks in advance
Adrian
ps Bobby Woz take note you may need to know all this one day.

[Richard Christopher]

Hi Adrian,

Unfortunately, I was a bit rushed due to getting the Integrals airbone quite late at the start of the season so didn't break them in perhaps as gently as would make sense. I just tried not to do too many long vertical uplines initially and perhaps more importantly, landed straight after a schedule to prevent running near the packs rated capacity. After 5 or 6 flights like this, I wouldn't have any worries about operating as you would wish, i.e fly a schedule as normal, perhaps 1 or 2 more repeats of "problem" manouevres. I find 8-8.5 minutes is a good time limit to keep to.

When I started with electric in March last year I was told that it was good practice to work at 80% of the rated capacity to maintain a good number of cycles (I think this is less critical now on later generation packs). Easier said than done when you just want to do "one more" practice manouevre before landing! Using a timer is a must - it's so easy to forget how long you've been airborne. I have used 100% capacity on the odd occassion and whilst not recommended it hasn't damaged my packs. Most of my packs are currently at 60 to 80 cycles.

Others may have more experience on "breaking-in" packs......

[Alan Simmonds]

I have no experience of breaking-in new packs and didn't know it was a recommended procedure until I read this article on the Flightpower website at the end of last year: http://www.flightpower.co.uk/newsOpenArticle.asp?articleID=97 

Luckily(?), my 2 best packs are still working well. The other 2 are working, just not so well but whether that's a result of me not knowing any better and thrashing them  or they were never that good anyway, I can't tell.

I will be taking more care in future!!!

I've bought an FMA Cellpro 10 charger and a good 25A power supply for charging 10S packs. I chose this charger because the balancer is built-in and can display a reading of each cell's internal resistance which I believe may be helpful in monitoring the quality of the pack and it's degradation over time.

Regards
Alan

[Adrian Harrison]

Good stuff Alan thanks.
A

[David Kirk]

I do not believe that there are any problems with the two packs not being identical voltage as we will connect them in series. Perhaps it would be different if they were to be connected as 5s2p

Worth noting that this is the exact opposite of what is true. Cells of different voltages are what causes the problems and is the reason we go to great lengths to balance them. Packs in parallel will self balance. In fact quite a few packs on the market are made up of parallel cells to accomodate different capacities and/or form factors.

Dave

[chris bond]

Hi David
Noted and agreed
 Is the self balancing of parallel cells instant?
So is there any merit in touching the two packs together red to red and black to black momentarily ?


Chris

 

[Ashley Hoyland]

Chris

I believe short circuiting any battery is detrimental and should be avoided at all cost, with Li Pos of the power F3A models use I believe it is dangerous.

The way I understand it is: cells in a pack which is not being balanced may overcharge during the charge cycle and this can be dangerous.  The balancer is there to avoid any cell being over charged and reaching above 4.21 volts. (slightly different parameters apply if you are charging in low temperatures).  Providing the cells do not over charge, 'in-balanced packs' are not really a problem until you get towards the end of your flight when the low cell may go beyond the critical 80% percent discharge level.  This may not be detected until it is too late and the pack (or that cell to be more accurate) is destroyed.  Again the advantages of a system which balances all 10 cells in a F3A pack rather than treating them as 2 separate 5 cell packs are clear.  This was the source of the models being destroyed by fire in the early days of electric flying.

With some balancers I have known it take up to 70 minutes (off charge) to completely balance a pack.  As Richard says in his post above, the time taken of course depends on the load the balancer applies to the 'high cells'.

Ashley