# Hobby LiPo packs, bulk charging and discharging.



## Jayls5 (Apr 1, 2012)

I've got a Mars Electric 200A 72V motor, and I'm going to rig up a big pack of hobby LiPo batteries to run it.

I will be using 4S (series) 14.8V 5 AH packs. Each pack has 12 AWG main power wires and a separate balancer plug connected to each battery. I will charge and discharge with a protective thermal case. I have 20 packs already.

*Charging: *I have a 400W "smart" charger that charges one of these packs and balances it at the same time. It has a nice fancy algorithm that reduces current as it asymptotes near 4.2V (max). It has a max charge current of 20A and has a voltage setting for my battery pack type (4s).

Charging 20-40 of these packs will get annoying though, so I have been thinking about wiring up 5 packs in parallel to really maximize the potential of my charger. Setting the charger to 20A charge would be a safe <1 C charge rate per pack with 5 in parallel.

To keep the cells balanced, I was thinking about wiring each similar charge port wire between packs together in parallel as well. Can anyone think of a reason not to do this? Worst case, I can just see cells of higher capacity not reaching full charge easily... since the charger will cut the power to a set when a lower capacity battery hits 4.2V first. Correct me if I am wrong here.

*Discharging: *Balancing ports will all be disconnected prior to use. Each 12 AWG power wire will be wired in parallel up to a distribution block. Power will then be delivered via 00 AWG off the block.

I am thinking about doing sets of 10 packs in parallel to achieve 50 AH. This would allow a 100-200A discharge and each pack would theoretically only see a safe 2-4C rate. I don't want to get anywhere near the 25C rate, since I don't trust the rating one bit despite people successfully doing it.

Further sets of 10 will be wired in series to add voltage as high as I need, and this will depend on what motor controller (and gearing) I decide.

Any comments, suggestions, and concerns are welcome and encouraged! Thanks!


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## winzeracer (Apr 3, 2012)

Jay,

I am currently building a Lipo pack, you probably saw my "Lipo Pack Build" in the Batteries thread area. My setup is more extreme and like you pointed out more prone to failure. I am building a 30s6p pack with Turnigy 6s 35-70C nano-techs. I will be bulk charging at 2.67C using the 10kw EMW charger( non-balanced ) when I have it out and about, and will balance charge at home with PL8. This way I will never really go more than 10 charges without a balance charge. This was the best way that I came up with, without buying a spendy balancing BMS. With this I will have what you mentioned here

"Worst case, I can just see cells of higher capacity not reaching full charge easily... since the charger will cut the power to a set when a lower capacity battery hits 4.2V first."

I have had some good input from other senior members and professionals, and say that what I am doing sounds ok. I have been emailing with Steve at Jozztek he has quite a bit of Hobby Lipo experience and again he said it all sounds like it should work. So if my more extreme setup has a blessing you should do fine. There is also TONS of lipo threads about this over at Endless Sphere, most of the ebike and emoto guys have been running packs like this for years.


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## Jayls5 (Apr 1, 2012)

winzeracer said:


> Jay,
> 
> I am currently building a Lipo pack, you probably saw my "Lipo Pack Build" in the Batteries thread area. My setup is more extreme and like you pointed out more prone to failure. I am building a 30s6p pack with Turnigy 6s 35-70C nano-techs. I will be bulk charging at 2.67C using the 10kw EMW charger( non-balanced ) when I have it out and about, and will balance charge at home with PL8. This way I will never really go more than 10 charges without a balance charge. This was the best way that I came up with, without buying a spendy balancing BMS. With this I will have what you mentioned here
> 
> ...


Yeah, after further research, I discovered they sell pre-made 6x parallel balancing port splitters for cheap. Obviously people have already done this thing for a while. You are saying you will have 150 lipo packs in total (combination series/parallel)? That's nuts.


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## winzeracer (Apr 3, 2012)

No I am using 6s packs so, there will be 180 cells but it will only be made up of 30 6s "Bricks".


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## Jayls5 (Apr 1, 2012)

winzeracer said:


> No I am using 6s packs so, there will be 180 cells but it will only be made up of 30 6s "Bricks".


Oh. I really don't like this whole naming system. For example: 6S1P makes zero sense. That's six series cells, ZERO in parallel. Not 1.

I'm (eventually) doing 40-50 _battery packs_, each pack having a pack rating of 5 AH / 14.8v. The individual packs contain 4 cells in series each. Our total battery bank might actually be in the same ball park then.


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## madmike8 (Jun 16, 2011)

Since your going to run 4 - 4s packs in series, why don't you just wire it up as 2 8s packs and buy two good smart chargers to charge with? It would be real easy and they would balance. You can still have 10 packs in parallel to get your 50AH. You would need to a 8s balance plug, enough 4s plugs for your packs, a pcb strip board to to solder them to, and 2 copper buss bars to hook the power wires into.


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## Jayls5 (Apr 1, 2012)

madmike8 said:


> Since your going to run 4 - 4s packs in series, why don't you just wire it up as 2 8s packs and buy two good smart chargers to charge with? It would be real easy and they would balance. You can still have 10 packs in parallel to get your 50AH. You would need to a 8s balance plug, enough 4s plugs for your packs, a pcb strip board to to solder them to, and 2 copper buss bars to hook the power wires into.


Cost effectiveness my friend; I have to live within my means. The best bang for the buck I have found is a 25C discharge pack of the type I described.

I've even done price requests from most of the manufacturers listed on Ali-Baba for comparison.


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