Battery build LiPo 20s2p I need advice

[MixhaL]

HI
I have studed forum for a several days and have few question.
I want to build 74V LiPo battery 20s2p
Please advice about my shoping list.
I will use this LiPo 8 pieces but first I will buy only 4.
Are they good? Or better to go with turnigy?
http://www.hobbyking.com/hobbyking/store/__16227__ZIPPY_Flightmax_8000mAh_5S1P_30C.html

To protect before deep discharge I will buy 8 of this for each battery
http://dx.com/p/2-in-1-1-8s-lipo-battery-low-voltage-buzzer-alarm-for-rc-helicopter-white-black-180468
It should make noise when battery drop to critical level during ride, am I right?

I need charger, found two:
http://www.hobbyking.com/hobbyking/store/__6609__iCharger_1010Bplus_300W_10s_Balance_Charger.html
or
http://www.hobbyking.com/hobbyking/store/__9005__iCharger_208B_350W_8s_Balance_Charger.html

Which one will be better for parrel charging 8 bateries?

I need power supply for this charger, I do not know which to pick, please help me to choose.

I want parallel charging so I need parallel charging board, I do not found any board on HK for 8 packs 5s, maybe better do like on the picture?



So I will buy JST-XH Parallel Balance Lead 5S
http://www.hobbyking.com/hobbyking/store/__27074__JST_XH_Parallel_Balance_Lead_5S_250mm_6xJST_XH_.html

And make the same with power leads

I will buy HXT 4mm connectors and power wire 12 AWG to do power leads
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9283
http://www.hobbyking.com/hobbyking/store/__9673__Turnigy_Pure_Silicone_Wire_12AWG_1mtr_RED.html
http://www.hobbyking.com/hobbyking/store/__9674__Turnigy_Pure_Silicone_Wire_12AWG_1mtr_BLACK.html

Balance Plug Savers (JST-XH 5s) to better unplug
http://www.hobbyking.com/hobbyking/store/__19942__Balance_Plug_Savers_JST_XH_5s_5pc_Per_Bag_.html

Do I need something more to build a battery pack?
Thank You

 

[Drunkskunk]

Looks good so far. Forget parrallel boards. Instead, get your self some of these:http://www.hobbyking.com/hobbyking/...Parallel_Balance_Lead_5S_250mm_2xJST_XH_.html

You can leave them onn the packs and keep your 2P connecte at the cell level, which will be better for long term balancing, and also mean yo only need 4 of those alarms.... If you realy want to run them.

Get 4 chargers, and charge them 2 at a time. Its going to cost a bit upfront, but it will save a lot of hassel and time later.

I've got some of these for power supplys: http://www.hobbyking.com/hobbyking/store/__9205__25A_14v_DC_Power_Supply_for_Chargers_350W_.html They haven't let me down or had any issues in 5 years.

 

[wesnewell]

You've got the right idea. Lots of ways to charge. Personally, I'd get this charger and charge them as 4 10s packs rather than 8 5s individual packs. Quicker and easier imo.
http://www.hobbypartz.com/75p-1220-charger.html?gclid=CNa3z9_N57ICFayPPAod10MAPw
1 6x charger cable.
4 5s 2x balance leads to parallel the packs, and 2 5s 2x balance leads for charging.

 

[MixhaL]

Thank You guys for fast help.
I will do as Drunkskunk wrote. I leave them as 2P at cell level and will be charging as picture below but I gonna use only one charger. 4 chargers is too expensive for me.

Drunkskunk those PSU which you linked me is out of stock
Is this will be fine
http://www.hobbyking.com/hobbyking/store/__16534__Hobbyking_PS35_DC_Power_Supply_for_Chargers_35A_350W_.html
Has more amps but is chepper

Thank You

 

[izeman]

looking at your charging picture keep one thing in mind: you have 2 packs connected all the time. those will be balanced on a cell level. but for charging you want to connect 3x 2p packs. if your cells are WAY out of balance when you do this, there will be a quite high current through the balance wires which could put a lot of pressure on them.
it's fine to do this as you want - just take care when connecting the packs. if one pack is empty, and the others are charged, prepare for some nice smoke
another tip is to do COLOR CODING of all connections. so every single connector will always be connected to it's designated partner. as long a you do connecting wires being concentrated, you're fine. but do it once in a hurry, and you may fail!

 

[izeman]

one more thing: you MUST NOT leave the lipo buzzers connected when not riding the bike. those will drain your battery within a day or two. no problem when riding of course.
btw: i never hear them beeping/buzzing so i got rid of them and watch the cell level with a cellog8 (or equ) on a regular base until i know what the battery can deliver. after some rides you will know how deep you can discharge until your battery becomes unbalanced anyway.

 

[izeman]

Drunkskunk those PSU which you linked me is out of stock
Is this will be fine
http://www.hobbyking.com/hobbyking/store/__16534__Hobbyking_PS35_DC_Power_Supply_for_Chargers_35A_350W_.html
Has more amps but is chepper

i would recommend a server spare power supply. there are several which voltage can be raised for below 20$/€ and which will deliver very reliable power. 12v though is NOT enough to unleash the full power of the ichargers. they need 15v+ to deliver full amps. if you want to charge with max amps (of course you want - still takes ages with 6 packs paralleled)
if you want to charge 5s only i would go for the 208b which can do 20a. 1010b only if you want to do 10s charging. for both of them a 350w power supply (chinese unreal ratings) is NOT enough. i tested them, and they will just shut down when you go near ~250w.

 

[dogman dan]

Yeah, plug in the buzzers only when you ride. If you are paralleling packs later, you only need 4 of them. One for each pack, or each set of packs.

Get a wattmeter or Cycleanalyst. This will help you know where you are, and enable stopping long before the buzzers go off. At some point, you will know the pack well enough to not need the buzzers anymore, till later when the packs are dying and behave more erratic.

Any good 350w power supply will work. Meanwells are one popular choice. Either charger will work, but the 10s one makes sense for sets of 5s packs. Paralell in 10s rather than 5s.

You won't need to balance every charge.

 

[Drunkskunk]

What Izeman says is good advice on the charging. When you discharge in series, you can't charge in parallel. Cells don't always discharge at the same rate.

Lets say that the top 2 bricks in your picture are parralleled during a ride. The cells stay even when parralleled, but the 2nd cell down on one pack drops lower than the rest. the parralleled cell in the second pack feeds it power continously through the balance lead and they stay even, but together they drop .3 volts lower than the rest of the pack.

If you charge just those two packs, then the balance charger does it's thing, and there's no problem. But if you then try to connect the second set of bricks, and there cells are all at the same voltage, the second you connect the parrelleel cables, the 2nd pair of cells in the 2nd pair of packs will try to dump the total diffrence in current between the cells through those tiny little parralell wires. that could be several amphours worth of diffrence dumped in miliseconds. End result: a briliant light show. If you're lucky, it will vaporize the balance wire and plug, and maybe cause you a case of KFF.

So you'll have to charge them the way you discharge them. The bad news is it's more work. The good news is it will take about the same amount of time.

 

[wesnewell]

What Izeman says is good advice on the charging. When you discharge in series, you can't charge in parallel.

I do this all the time. Never had a problem in over 2 years. Did it with 6 6s packs, and 12 4s packs. If you get a cell group out by .3V you've got bigger problems.

 

[Tommy L]

. End result: a brilliant light show. If you're lucky, it will vaporize the balance wire and plug, and maybe cause you a case of KFF.

So you'll have to charge them the way you discharge them. The bad news is it's more work. The good news is it will take about the same amount of time.

These are awesome words of wisdom!

Also, you should know where your discharge cables are attached to each battery and where your balance leads attach to each cell. Learning and knowing the internal wiring diagram is priceless. What at times might make sense is also a brilliant light show in the end.

Tommy L sends.... \\m//