mixing series/paralleling safely?

[ejonesss]

i am not sure if this is in the right place so you mods can move to the right place

i was wondering if i can mix series and parallels

i have this charger

http://www.hobbyking.com/hobbyking/store/__18066__Turnigy_Accucel_6_50W_6A_Balancer_Charger_w_accessories_USA_Warehouse_.html

it is a good charger unfortunately it only goes up to 6 cells lithium based.

charging 2 6s rc packs is easy since there are charging paralleling boards

i have http://www.hobbyking.com/hobbyking/store/__41302__Hobbyking_Parallel_Charge_Board_For_6_Packs_2_6S_EC5_USA_warehouse_.html in the deans/t connector (does not matter since the main leads connect to the charger).

i know i cant be able to connect up all the main power leads because of the different voltages

but the 6s pack would have it's main leads connected to the charger and it's balance leads connected to the charger.

then the 2s packs will be connected by their balance leads only to the charging board so.

the first cell of the 6s pack would be 4p because it would be carrying the load of both 6s and both 2s

the second cell of the 6s pack would be 4p because it would be carrying the load of both 6s and both 2s

the rest of the 6s pack would be 2p

it is like charging a 2s4p in series with a 4s2p pack.


can i be able safely mix multiple parallels by the balance plugs?

you may wonder why i want to do this.

simple as i said above the charger only goes up to 6s and a 48 volt lifepo4 is 16 cells and a 48 volt lipo is 14 cells so i would have to series 2 6s and 1 2s for a 14s1p lipo.

with shipping lithium becoming more difficult due to shipping laws (thanks snowden) getting a 48v 20a worth of lifepo4 shipped is going to be very expensive.

my calculations i can get


8 http://www.hobbyking.com/hobbyking/store/__16207__Turnigy_5000mAh_6S_20C_Lipo_Pack_US_Warehouse_.html for $360 +

4 http://www.hobbyking.com/hobbyking/store/__16783__ZIPPY_Flightmax_5000mAh_2S1P_20C_USA_Warehouse_.html for $60 for a total of $720

or

6 http://www.hobbyking.com/hobbyking/store/__29838__ZIPPY_Compact_5000mAh_10S_25C_Lipo_Pack_US_Warehouse_.html at $600

and disassemble the 10s packs and re wire the cells to my needs

or

56 http://www.hobbyking.com/hobbyking/store/__33117__Turnigy_5000mAh_1S_20C_Lipoly_Single_Cell_USA_Warehouse_.html for $521

or 16 http://www.a123rc.com/goods-468-Excitingly+Powerful+A+123+20ah+PRISMATIC+CELLS.html at $800 and re set the charger to lifepo4



and the good thing is i think hobbyking seems to ship illegally since i bought a transmitter battery and it did not have any hazmat clas9 labels or shipping documents

they just used a priority mail box

 

[dogman dan]

I'm sure I don't follow all of that.

But what I think I did follow, was chaging a 6s pack and a 2s pack, in one go.

This would mean 2 cells of your 6s pack would be undercharged, sharing the current with the 2p pack. So you'd end up wacky out of balance on the 6s pack, then the charger would take days to balance it up.

Line up your packs, paralleling like packs. Paralell all your 6 s packs, then charge em. Paralell up all your 4s packs, then charge em. and so on.

You could wire up 4s and 2s into 6s packs, to charge both at the same time as 6s packs. But the capacity has to match, so 4s 5ah, matches with 2s 5 ah.

 

[Wishes]

You cannot safely, or smartly at least, charge that many cells with RC chargers in 1 go. People who want to charge 48v worth of cells in 1 go, use a BMS board and a charger with the specific total voltage needed. The BMS board handles the balancing so you do not need a smart charger. Which do not come in more than 12s version, maybe 14s now. But they cost a fortune.

If you are going to use RC batteries, charge them like RC batteries. Like Dogman suggested, charge your 6 cells together and your 2 cells together. It will take your charger days to top off those 2 cells they way you are suggesting, even if it works, most chargers have very low current rates on the balance leads.

And from experience of using the hobbyking batteries with dean connectors for my RC applications. When you are using them on ebikes, leave the 5mm bullet connectors they come with. You can connect them in series and disconnect them easily to charge them in parallel. So you don't even have to dissemble the packs. It is the easiest, cheapest, less work and not the mention safest way versus trying to charging 16s in one go with an RC charger. The hobbyking lipo packs are cheap, but you have to use them safely.

Wishes