Building a Small LiPo Pack

dilkes

100 W
Joined
Apr 11, 2012
Messages
196
Location
Toronto, Ontario, Canada
I have an e-bike and a small electric scooter, and have been using “48V” LiFePO4 (16s) packs for both, bulk charging. I decided I wanted to have a small “emergency” pack for my scooter, and thought I’d try LiPo for this. I ordered 4 of the Turnigy 5000mAh 4S1P 14.8v 20C hardcase packs and 2 Battery Medics. My intention was to put these in series to build the small lightweight pack, bulk charge with one of my LiFePO4 Chargers (goes to 59.8V), and balance periodically with the Medics. So far, all I've done is hook these up in series, bulk charged them once to a total of 59.8V (about 3.74/cell), discharged once with a load off the bike and recharged. My wattmeter broke and I am waiting for a new one so couldn't measure the watts/Ah used and I probably won’t actually try them much more till the spring as winter seems to have arrived a bit early up here in Toronto.

Anyways, my questions:
  • I probably screwed up by planning this as a 16s LiPo as I didn't think much about the higher full charge voltage delivered by LiPo over LiFePO4. I wanted to use my existing charger(s) (59.8V) and I’m not sure my bike’s controller/motor can handle much more voltage than that.
  • If I carried on with this config and charge setup, charging to the 3.74/cell and discharging to (say 3.0V/cell?)
    • Would I get much of the 5Ah capacity?
    • Any idea how much?
    • Is 3.0V/cell too low?
  • I am thinking maybe I should get a 2s LiPo and use that with 3 of the 4s packs to make a 14s1p
Any other thoughts?
 
Been there, done that.
First set your charger to 58.4V no load (CV) voltage. It is still more than enough for you 16S LiFe pack, and just enough for a 14S LiPo pack.
Hook 3 of your lipos in series. Buy a 2S lipo hardcase pack to make it 14S in total. Keep the remaining lipo pack for spare cells.
To set the voltage, you have to look for a blue screwdriver operated pot inside the case, usually in the corner of the board, near DC wire exit.
 
dilkes said:
...

Anyways, my questions:
  • I probably screwed up by planning this as a 16s LiPo as I didn't think much about the higher full charge voltage delivered by LiPo over LiFePO4. I wanted to use my existing charger(s) (59.8V) and I’m not sure my bike’s controller/motor can handle much more voltage than that.

  • Likely it has 63V capacitors which limits you to 14S of LiCo battery

    dilkes said:
    [*]If I carried on with this config and charge setup, charging to the 3.74/cell and discharging to (say 3.0V/cell?)
    • Would I get much of the 5Ah capacity?
    • oooo, that's the point where i stop discharging my LiCo batteries :lol:
      dilkes said:
      [*]Any idea how much?
      not much, the batteries are would already be highly discharged and to the point where their balance starts to become compromised (really gets bad below 3.5V)
      dilkes said:
      [*]Is 3.0V/cell too low?
    dilkes said:
    [*]I am thinking maybe I should get a 2s LiPo and use that with 3 of the 4s packs to make a 14s1p
dilkes said:
Any other thoughts?
14S-do it... and yes, 3.0 is too low in my opinion (and the batteries' opinion too as you are basically killing the poor things)
You should read up a bit more about LiCo battery issues before just jumping in the frying pan.
Mistreating them WILL cause you great pain and possible suffering... or at least a fire hazard.
...and get a balance charger for those times the batteries become unbalanced
 
miuan said:
Been there, done that.
Hook 3 of your lipos in series. Buy a 2S lipo hardcase pack to make it 14S in total. Keep the remaining lipo pack for spare cells.
Has anyone ever taken one of these apart?
T50004S-20HC.jpg
I was considering going in and removing 2 cells and changing it to a 2s config. It looks like the two pieces of the case are molded together pretty well though and would require some serious cutting.

I was trying to avoid just getting another 2s pack as the shipping up here to Canada would cost more than the pack.

If anyone has done it, exactly what would I see inside and would it be feasible to disconnect and remove 2 of the 4 cells?
 
You can cut the black plastic with plyers where the battery wires exit. The plastic comes apart pretty easy after that. Be very careful. do not short the battery. Then you will need a dremel or something like that to cut the cells out themselves individually. Then solder a new discharge wire, either red or black onto the new 2 series pack. There are several videos and instructions around here, ypedal has good ones.
http://www.ypedal.com/Lipo/repair.htm

http://www.ypedal.com/Lipo/repair.htm

search for lipo cell replacement or surgery here and you tube. Keep in mind your new pack will look a little different than Ypedals, because they stopped using the green plastic board.

However i reccomend you save that 4 series as a spare, YOU WILL have to repair a pack in the future or need an extra brick at some point, and it is easier
to order the 2 series pack - sorry it cost so damn much to ship.
 
Thank you very much for the pointers to the videos and the other info. When you say one can use pliers to cut the hardcase near where the wires exit, I assume you mean the case gets broken and not usable after that?

I believe I will take your advice and get a 2s pack(s) rather than mess with disassembling one of my 4s packs. I'll just have to order enough stuff from HK that makes the shipping worthwhile!
 
or you can hook a 6S onto two of the 4S to get to 14S but 16S is better if your controller is able to handle it. you can upgrade the controller more easily than cut the lipo pack apart imo.
 
dilkes said:
miuan said:
Been there, done that.
Hook 3 of your lipos in series. Buy a 2S lipo hardcase pack to make it 14S in total. Keep the remaining lipo pack for spare cells.
Has anyone ever taken one of these apart?

I was considering going in and removing 2 cells and changing it to a 2s config. It looks like the two pieces of the case are molded together pretty well though and would require some serious cutting.

I was trying to avoid just getting another 2s pack as the shipping up here to Canada would cost more than the pack.

If anyone has done it, exactly what would I see inside and would it be feasible to disconnect and remove 2 of the 4 cells?


http://endless-sphere.com/forums/viewtopic.php?f=1&t=62313
 
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