Should i make a new battery?

Batteries, Chargers, and Battery Management Systems.
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HomeScape   10 mW

10 mW
Posts: 24
Joined: Jun 23 2017 4:12pm

Should i make a new battery?

Post by HomeScape » Jul 22 2018 2:53pm

Hey everyone,

I've owned a 1000w 48v bike for over 2 years now. I made 2 packs of cells myself for this, 13S6P * 2 in paralel.

I recently bought myself a sabvoton controller, 72150 (72v, 150A) so i needed a new battery pack to supply the voltage. I didn't really think everything through and bought the same cells for the pack as the other ones had a legit capacity etc. (Panasonic NCR18650B 3350mAh).

I now have a 20S10P pack of these cells.. I was watching a video of someone with a 5000w enduro bike and someone in the comments pointed out that he was over discharging his cells. At this point it hit me that i never thought about this being able to happen as it wasnt an issue with my 1000w motor.

After pulling up the datasheet i realised that the cells im using are only rated at 2C which is ~6.4A. This means that my pack can supply a maximum of 64A. So i'm basicly pulling ~2.5x the max current when im pulling full power with my controller, this doesn't sound too good to me.

Now i'm wondering what other people think about this, should i make a new battery? They're quite expensive as you guys know.
Any suggestion which cell i should be using for this build? What are you thoughts about buying a pre-made package from aliexpress, too dodgy?


Thanks,

Tim

HomeScape   10 mW

10 mW
Posts: 24
Joined: Jun 23 2017 4:12pm

Re: Should i make a new battery?

Post by HomeScape » Jul 22 2018 3:13pm

Options so far:
Samsung INR18650-30Q 3000mAh - 15A
15A discharge rate, which would be fine at the year of useage, but after 250 cycles the capacity (and max current?) drops to 60%
These cells are 3,40 euro when buying 200

Other option, more expensive but maybe better?
Sony Konion US18650VTC6 3120mAh - 30A
30A discharge, so degrading over time doesn't matter as much (at all)
These are 4,70 euros in bulk of 50 a time

30Q -> 680 euros, i feel like the lifetime of these drops (too) quick, but at the same time 250 cycles of this capacaty could last for +/- 2/3 years and even then it's not dead yet.

Sony konion -> 940 euros, i feel like these would fit the application very well and might serve me a longer lifetime of the battery. But this also comes at a 260 euro price difference. At which point i might be better off buying the Q30's and driving the battery until its dead and then buying a new one.

Opinions?

Tim

dustNbone   10 kW

10 kW
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Location: Vancouver, BC

Re: Should i make a new battery?

Post by dustNbone » Jul 22 2018 3:32pm

Another option is to get a second battery and connect it in parallel with the existing one (after they're both charged to the same voltage). That way they share the load.

HomeScape   10 mW

10 mW
Posts: 24
Joined: Jun 23 2017 4:12pm

Re: Should i make a new battery?

Post by HomeScape » Jul 22 2018 4:28pm

dustNbone wrote:
Jul 22 2018 3:32pm
Another option is to get a second battery and connect it in parallel with the existing one (after they're both charged to the same voltage). That way they share the load.
I think all cells would be put under equal load, so i'd need another (150-64=86A) 84A in battery of the same kind if im correct. I think if the type of cell is different then the discharge is different aswell and the packs would be unbalanced quikly. That would mean i need (84/6.4) another 13 rows of 20 cells in paralel which would put me at a huge capacity but also at the same cost of a new battery rated at 150A.

I think that the size of another 260 cells would be too much to carry in an enduro bike, sadly..

Tim

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thunderheart   100 W

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Joined: Oct 08 2017 10:01am
Location: Russia

Re: Should i make a new battery?

Post by thunderheart » Jul 22 2018 5:16pm

HomeScape wrote:
Jul 22 2018 3:13pm
Options so far:
Samsung INR18650-30Q 3000mAh - 15A
These cells are 3,40 euro when buying 200
They are US$3.25/cell at Queen Battery (shipping not included)
HomeScape wrote:
Jul 22 2018 3:13pm
Sony Konion US18650VTC6 3120mAh - 30A
30A discharge, so degrading over time doesn't matter as much (at all)
These are 4,70 euros in bulk of 50 a time
They are rated at 15A and at 30A if there is a 80°C cut-off. So i think they are hot guys))
They cost US$5.30 at Queen Battery (shipping not included)
HomeScape wrote:
Jul 22 2018 3:13pm
Opinions?
Good ideas about cells to choose. I'd like to ask why not 21700s? Is there any limitation in size/weight?
Miboxer C2-4000 smart charger/discharger review: www.youtube.com/watch?v=jrbJceNXv1g
XTAR DRAGON 4-slot charger/discharger review: www.youtube.com/watch?v=S6yVMsIuauE
Top 21700 cells LG M50 vs Samsung 48G: www.youtube.com/watch?v=KGJDogOG4zw

:arrow: All my reviews in one place: http://ThunderheartReviews.blogspot.com

Voltron   1 MW

1 MW
Posts: 1842
Joined: May 02 2013 4:53pm
Location: Santa Barbara CA

Re: Should i make a new battery?

Post by Voltron » Jul 22 2018 6:22pm

Re the 2 different types in parallel, it's not ideal, but they won't unbalance. They will always be at the same voltage while they're connected together.

HomeScape   10 mW

10 mW
Posts: 24
Joined: Jun 23 2017 4:12pm

Re: Should i make a new battery?

Post by HomeScape » Jul 23 2018 3:05pm

thunderheart wrote:
Jul 22 2018 5:16pm
HomeScape wrote:
Jul 22 2018 3:13pm
Options so far:
Samsung INR18650-30Q 3000mAh - 15A
These cells are 3,40 euro when buying 200
They are US$3.25/cell at Queen Battery (shipping not included)
HomeScape wrote:
Jul 22 2018 3:13pm
Sony Konion US18650VTC6 3120mAh - 30A
30A discharge, so degrading over time doesn't matter as much (at all)
These are 4,70 euros in bulk of 50 a time
They are rated at 15A and at 30A if there is a 80°C cut-off. So i think they are hot guys))
They cost US$5.30 at Queen Battery (shipping not included)
HomeScape wrote:
Jul 22 2018 3:13pm
Opinions?
Good ideas about cells to choose. I'd like to ask why not 21700s? Is there any limitation in size/weight?
I have never worked with 21700's but i'll look into it. Thanks for the links to the cheaper sites, saves me some cash if i were to make another one.

Tim

HomeScape   10 mW

10 mW
Posts: 24
Joined: Jun 23 2017 4:12pm

Re: Should i make a new battery?

Post by HomeScape » Jul 23 2018 3:48pm

21700's are way more expensive and are far off from worth it with the info i've gotten so far.

For example these are 7,25 euros: IMR21700 5000mAh - 10A

Side note; i think i'd have to pay import tax if i'd order from the website you listed, so i doubt that its cheaper for me.

HomeScape   10 mW

10 mW
Posts: 24
Joined: Jun 23 2017 4:12pm

Re: Should i make a new battery?

Post by HomeScape » Jul 23 2018 3:49pm

21700's are way more expensive and are far off from worth it with the info i've gotten so far.

For example these are 7,25 euros: IMR21700 5000mAh - 10A

Side note; i think i'd have to pay import tax if i'd order from the website you listed, so i doubt that its cheaper for me.

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