Thanks for the reply, the controller will likely be a 36v 17A and the motor a 36V350W geared front hub motor. From what I understand from your post, the BMS I have should be ok since the controller will never attempt to draw more than 17A anyway? And am I putting too much money in the cells with 10A discharge then and could instead get away with cheaper cells with 5-6A discharge?amberwolf wrote: ↑Jan 01, 2018 9:00 pmYour BMS needs to be rated to supply the maximum current your controller/motor system can draw from the battery at the maximum load it will see. If it is not rated high enough, it will shutdown it's output (or blow it's fuse or FETs, depending on design) if you exceed the max current long enough (how long depends on it's design).
Your cells then have to be rated to supply at least as much as the BMS is able to supply and the controller/motor system will draw. If they are not rated high enough, voltage sag (and internal heating) will be excessive, potentially damaging the cells. The closer you run the cells to their maximum ratings, the harder it is on them, and the shorter life they will have, with worse performance.
Instead of a separate post I ended up posting this as a comment Please ignore this
Basically, yes. It's a question that's been answered a lot (and even asked already by you in your first post), so it doesn't need it's own thread.
I don't mean to 'cheap out', rather I'm looking for an optimal combination of controller, motor, BMS and battery. I had narrowed down the battery to the Panasonic NCR18650PF 2900mAh 10A but if the Controller/Motor won't be close to utilizing its potential then I didn't see a point in having an expensive set of batteries.amberwolf wrote: ↑Jan 01, 2018 9:15 pmSince that question is basically teh same as what you already asked in teh first post, the moderators probably merged the two threads, to keep all the info in one place for you and for people helping you to see all the answers eveyrone gives you, so as not to waste time and resources.
As far as using lesser cells, remember that you get what you pay for, so the cheaper cells will then be pushed harder, and will last less time, and perform worse.
The battery pack is the heart of the system, where all the power comes from--if it can't handle the load, or ages prematurely, the whole system performs worse.
It's a balancing act--generally cells with lower C-rate (lower Amps output max) will have higher capacity (Amp Hour), and vice-versa, all other things being the same. So if you need more capacity for more range, you can get lower-rate cells and stay with teh same total number of cells, but the pack won't perform as well the closer it is pushed to it's limits.
A good battery is worth spending more money on--it's easy to go cheap on the motor and controller and still get adequate performance, but cheaping out on the battery doesn't have the same results.
So...you *could* use lesser cells--the pack just won't be as good or last as long.
No doubt there is a lot of information and a lot I've learned already considering I knew pretty much nothing about batteries and such. Especially when it comes to avoid fake crap batteries, the right cells for my usage, etc. However it can get confusing and overwhelming for a newbie when presented with such a vast amount of information and to avoid that confusion it sometimes is easier to post a direct question and be sure about the answer rather than reading a lot and still being unsure since the exact question might not have been askedamberwolf wrote: ↑Jan 01, 2018 9:26 pmBasically, yes. It's a question that's been answered a lot (and even asked already by you in your first post), so it doesn't need it's own thread.
If you look around the forums, there are dozens of threads about 18650 cells and packs, which will have all the info for stuff like that, including how to choose cells for your usage, avoiding fake cells and crap cells, building the pack (there are many ways), etc.
Mostly a search for
in the title of threads and displaying by topic will find many of them. Searching the first post rather than the title might be necessary to find some. Other terms like
will find others.
There's probably also some links in the Sticky Index thread at the top of this forum.
Yes, it is a LOT of reading--but it will definitely help you build a better battery pack.
Thanks999zip999 wrote: ↑Jan 01, 2018 10:58 pmSo 10s 4p or 40 max with 10 amp cells ( use 10amp cells at 6amp max. So a 30 amp or lower bms would work. If you could run at 10 miles an hour 410 miles why would I ask you to run at 15 miles an hour for 10 miles. The battery will melt and you would melt. But as said before is the controller that demands the amp draw from the battery the battery is as dumb as can be. So look at your controller first. A bms doesn't mean the battery has a brain. Do Not puff it or come to California.
Thanks for making this clearer for me Dan. Would it be prudent to always assume that the rated Amp capacity of the battery pack should be around twice the Amps of the controller (for builds in general)?
Do you mean 'cheap build' for the battery pack I currently will have or the one I will have if I were to downgrade them to cells putting out 5-6 Amps?
Thanks! Do you know where I can get them for 2.6Euro each? A lot of cheaper sources I checked didn't ship to Europe/Sweden.Joachim wrote: ↑Jan 02, 2018 12:57 pmJust take the 10s 4p panasonic pf please and use the 35A bms....save for the cells/compleet pack and twice the rating of the controller amps.You can get a panasonic pf cell for 2.60Euro so 40 cells like 104Euro.I think this is cheap for these good cells.
Lower 5 6A cells have more stress and higher internal resistance so the cell wil be warm/hot and you loos energy in heating....voltage wil drop under max load and the compleet pack wil have more stress so@ the end cheap will be expensieve
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Self welding yes. You mean these https://eu.nkon.nl/accessories/welding- ... 18650.html?
I don't have a spot welder myself but a friend of mine has built his own so I plan to use that. I will also peddle all of the time. I live in a hilly area so it would be nice to have some electric help