Advice/Insight please. Battery pack build and charger setup.

[RageNR]

Ok, I am gearing up to do this. Currently have my hands on 170+ 18650 cells pulled from a Tesla 90kWh pack.

My pack configuration will be a 24s7p overall, but I will be splitting it up into 4 smaller packs of 6s7p each. This is for several reasons:
#1 Flexibility (can run 2, or 3 or all 4 packs. Range limited, of course)
#2 Each pack will be 24v (easier to manage. Can be used in multiple applications)
#3 Separate packs offer flexible size config and placement
#4 Redundancy (in case one of the packs suddenly goes bad. Can still run 18s @ 65v or even 12s @ 43v)

Each cell is 3.6v nominal and ~3200mAh. So about 11.52Wh per cell. With 168 cells, that is around 1,935Wh for all the packs combined.

What I need to figure out is how to setup the charging. These are Tesla cells, and are safe to fast charge. I want to take advantage of that when I am OUT on the bike and may need a quick top up.

Mobile charging equipment will need to be as fast and small as possible. Here are my considerations...
- On-the-go charging units: Turnigy Reaktor 1000W 30A, iCharger 3010B, or iCharger 308 Duo
- Home chargers: Multiple smaller capacity Turnigy/iMax/iCharger chargers, Turnigy Reaktor QuadKore, or Turnigy MEGA 1344W 40A
- Charging power supply units: Server power supply units from either HP or Delta. 1000W-1400W range
I am really considering the Turnigy Reaktor 1000W. That would give me a 2hr recharge time for the 1,935Wh capacity, or ~1hr for a 50% charge.

What I am wondering though is, could I forgo the Turnigy while I am out and trust only the Server Supply to give me a quick charge? Mind you, I am talking a partial recharge, NOT to full capacity. If I could adjust the server supply to top out at 24.6V, that would give me a 4.1V charge per cell in 6s config.
edit: (this would require 2x server supplies cause they're 12V each. Prefer to only have to carry 1, so that's the reason for 24V packs and 12V center-taps on each)
I am also considering adding a center tap to each pack, for 3s @ 12V applications. 12V could possibly be used for charging as well.


What are you guys thoughts? Got any input or advise for a setup like this?

Picture for reference:

 

[wesnewell]

I'd just bulk charge the 24s pack with 100.8V or less, if you want to be safer, charger.

 

[RageNR]

I'd just bulk charge the 24s pack with 100.8V or less, if you want to be safer, charger.

I'd like to stick with the separate packs. 24V /pack is for all my powertools and what not. Center taps on each pack will give me 12V for just about any 12V application.
And my hope is that the 12V taps will allow me to rely on 1 piece of equip. for on-the-go charging. That 1200W HP SPS I'm looking at is about 8in x 4in x 1in. Super tiny for the amount of power it can put out. And since those server supplies are designed for 12V, I should only need that one piece of gear to top my packs up.
All I should need is the correct wiring config for parallel charging on 12V, then forward voltage wiring to make the 24s. (that's my theory, at least)

You got a better suggestion? I may be misunderstanding your reference of bulk charging.

 

[t_tberg]

wes is suggesting that you charge in series. "bulk" charging battery "bricks" is preferred by most because you can maintain your modularity but you don't have to disassemble/unplug a pack every time you want to charge. I used to charge in parallel with that exact turnigy reaktor hobby charger, all of the plugging and unplugging gets old fast (and wears out connectors). If you already have the RC charger, I'd keep it around the house for balance charging and get a bulk charger to make things easier. Fast charging isn't quite as fast when it takes 5 mins to get the batteries off the bike then disassemble them and hook them up in parallel.

 

[RageNR]

"bulk" charging battery "bricks" is preferred by most because you can maintain your modularity but you don't have to disassemble/unplug a pack every time you want to charge. Fast charging isn't quite as fast when it takes 5 mins to get the batteries off the bike then disassemble them and hook them up in parallel.

As I stated previously, this particular HP SPS I am looking at is rated at 1200W (12V) in a 8 x 4 x 1in package. I would require additional power supplies or another piece of equipment to bulk charge @ 100.8V right?
Asking for suggestions on a bulk charger (brand/make/model) that would better suit my criteria.

Note that all the packs combined will be ~16lbs. Keeping the charging equip. lite weight is ideal.
Main mode of transporting the battery in use will be in a backpack. I am also going to make a quick-detach frame for the batteries to hang from the bike as a secondary method of transport. (ex: at grocery store, need space in backpack, put batts on bike)
I do not have any of the stuff yet. Part of the plan is to have charging equip. that can charge my other batteries, not only the ebike pack. Most of those range 12V-24V. Severely limited on funds, so trying to make a multiple use setup out of this.

 

[t_tberg]

As I stated previously, this particular HP SPS I am looking at is rated at 1200W (12V) in a 8 x 4 x 1in package. I would require additional power supplies or another piece of equipment to bulk charge @ 100.8V right?

I might be misinformed but I believe you still need a CC CV charger in addition to the power supply, even to charge the 12v packs. I don't know if the power supply is "smart" enough to taper the current. I'm no electrical engineer but I would imagine it would be safer to use a device designed to charge batteries.