My app does average amps (battery and motor). The issue with average is it takes in the time your not moving (unless you calculate it for only when your moving, but even then). You really want to look at the highest continuous that you do, and work around that number.
@Sander never seen anyone using it here. You need an efficient belt drive for a low discharge cell like that in at least a 10s4p.
All I can say is… Lipos fixed all of my issues!
I will have 12s4p and the motor will not take more then 30 amps for the Carvon 2.5 But Im waiting for the Carvon 3 so I plan on buying, and I think the amps will be lower for it.
Max Amp on Samsung = 15A Safe side Amp = 10A
4 in parallell = 10A * 4p = 40A
I can safley drive with 40 amps. And in the settings of the vesc I can limit the amps taken from the batteries. So I can set the max 20Amp on one VESC because I will have dual.
Use this site to compare the cells http://lygte-info.dk/review/batteries2012/Common18650comparator.php
The best to reduce voltage sag is the VTC6, way better than the 25R, but expensive, i dont know how it behave on other aspects such as cycle life
its lower sag than the HG2 and a little bit better than the 30Q
Li-ion are probably safer but has anyone tested if they are lasting longer than Lipo with the high discharges we do? The discharge ability of Lipo is awesome.
boosted stopped using the a123 lifepo4 (lithium iron) and went to Li-ion and then had issues. Speaking of lifepo4 the headway cells are awesome with good discharge and way more cycles possible than Li-Ion and their screw terminals are nice. Bit heavier and more expensive but the safest high discharge stuff
Why would you need 100A with 12s? Thats around 5000W o.O
They went to Li-ion just on the extended range pack that is not on the market yet, all the problems they are having is with battery packs that use A123 cells, the same as the previous gen board
One day i want to try a Lipo, with lower capacity but faster charge time
The biggest issue when it comes to life cycle is the temperature of the cells. When they test the cells then they always do the continuous discharge test. But that isn’t they way we use the cells on our boards. We don’t draw max amps all the time. Most of the time we don’t even come close to that. Next thing about life cycle is the voltage that we charge the cells and how low we discharge them.
But let’s say we do the worst case scenario and use them the hard way and get only 300 charge cycles. After that they only have a capacity of 60%. So in average during those 300 cycles we have 80% capacity. Let’s go with a 10S4P with 10Ah. That is 360Wh. So for a average rider 36km. But we only have 80% in average so it is only 288Wh. Let’s make it a bit worse and say we only can reach 25km instead of 28,8km with that. That would be 7500 km (25km * 300 cycles) on one battery pack. But that is under worst conditions with a max continuous discharge (nobody does that). In reality the pack should be good for 10000 km or more. But the most will never drive that many km with their board.
I see. So their lifepo4 are smoking. Surprising as they’re touted as the safest. Not catching fire at least I think.
Good points. I think these EV guys (ebike users and other regular commuters) ‘‘drain’’ their packs capacity over time… With lipo’'s it seems to be happen faster than for li ion. Dunno about high stress and such but still…
One more point to add for these 300cycles. I saw that they also use 4A charging per cell, which is the max recommended, so that is basically the worst case scenario - high discharge and high charge rate.
Average consumtion could be a good one but you should probably take out the time/data when board is not rolling, like evoheyax mentioned.
But that is the time the cells cool down. I am talking about the average consumption which brings the temperature up. just to have a realistic case. ´ The point i want to make is that i can’t even overheat my laptop cells which i treat like a bitch. And they are not made for that. So we should enjoy our ride and don’t feel bad when we have fun because we might do something bad to the cells and could loose a charge cycle.
You don’t need to pull it, but if you can pull 100a continuous, you’ll be able to pull 40 amps with far less sag than a battery with a max of 60 amps continuous.
Some sag will always exist. But you should try to mitigate it as much as possible. And easiest way to mitigate sag is to increase your max continuous amps far higher than you will ever pull.
If you pull close to your cells max continuous rating, you will sag very heavily.
If someone is on ES facebook group, this looks interesting -
Not entirely related with sag… but more with temp of cells.
14s6p brand new Panasonic PF pack test at 20-25A : Room temp 12°C Start state : charged/balanced pack at 58.4V, ~20°C Bms 30A continuous rated Note : the current is not constant, i have to use the CA current limiting feature in the future.
I think PF’s are rated for 10Amps, but he run them at +~3A or so (18/6 = 3). He also pinpointed that you cannot rely on data sheet data or such.
My conclusion - if cells are discharged at the max specicified discharge rating, they do get quite warm. usually probably hot…
So in order not reach this state, they probably should be ‘‘safely’’ discharged only at 50% of their max rating or so…
Though, like @Ackmaniac said, we dont push them such hard all the time and they have time to cool down also… the only instance would be hills where it would be possible to put the strain on batteries for longer periods of time (but the vaping forum somewhat shows that this does not mean the cells will get bad instantly)
Agree about not loosing fun. I believe we should not baby sit them all the time… just make sure they are not taken to the extremes… like running the cells at 90C degrees more than they need to.
@Ackmaniac is it possible to add external temp sensors to the vesc and also show this data in the app?
Would be cool to see the realtime battery temp along with all the other parameters!
(or perhaps, some of the vesc/motor sensors can be placed in between the batteries…)
So in order not reach this state, they probably should be ‘‘safely’’ discharged only at 50% of their max rating or so…
Can’t agree on that. Then we are back at being worried all the time. Get some proper cells. If you have a 10S4P of Samsung 25R you will be fine running them at 80 amps battery max. You could even go higher than that because we don’t draw that amps contentiously. When i buy a Ferrari then i don’t reduce the throttle by half to be safe. If we would draw constantly the max battery amps then i would agree. But we don’t do that.
Define fine?
Why do you think sag doesn’t matter? The cells will live, shorter than you’d like, but they will live. Really though, you’ll sag so hard though that you’ll loose 1/3rd of your range due to sagging vs with lipos. This is why I get more range from my lipos than my 18650s, even though my 18650s are 1/5th larger…
How hard do you push your boards? I haven’t seen any info about your builds, or your route/riding style. No offense, just trying to figure out were your mind set is coming from…
I’m telling you my numbers of sagging and the results I’m getting from it, and it seems like your saying I’m lying or something, cause your completely ignoring my results… It’s not going to kill the cells, but it will kill performance. You get 10s performance with a 12s basically, because it sags down to a 10s voltage like that when you pull 80 amps from my HE2 cells, and the graphs for the 25R are pretty much the same.
Sorry for the comparison / assumtion of 50%. That’s is just my ‘‘theory’’ of how not to make the cells reach very high temperature.
It is totally okay to push them to the limits… I did so once with my pack and got 60A peak (if I can trust my wattmeter)… that made me to think whenever the batteries were not able to offer more or there was something else at play then… The cells will probably live just fine if you do heat them up once or twice or even many times…
But Im seeing this more as a precaution - ‘‘oh better not accidentally scratch my car (batteries)’’ vs … ‘‘it does not matter whenever I scratch it or not… I dont really care’’…
So yeah, that’s just my opinion which I got from reading that the cell can get to like 90C degrees… and from other studies that I read that at higher temps the elements/chemicals just start to break down in the cell more…
If I were (or someone else is) running used laptop cells then I think it does not matter as much if you do heat them up or not… but it might matter more, if the cells you use have been bought for ~4usd, assembled in the pack and you expect them to deliver good results for quite some time and not fail prematurely…
If it did not matter… I think everyone could just buy 10A-15A (or even lower) discharge cells, make small packs and just drive them to the max limits without caring about the temperature… but - with high discharge there’s usually this counter-effect of getting less capacity, like @evoheyax mentioned…
You could have a dead cell or a bad cell. Have you done capacity testing and voltage testing?
I haven’t done testing for a dead cell or capacity testing, but did check the voltages of all cells before I built the pack, and the range at the beginning and sagging were still pretty poor.
There you have it if one of them have very much lower capacity it can cause some issues I think
I don’t know their capacities, but they all discharged and charged pretty close to each other. I don’t think any cells had any flaws, as I would of expected the cells to charge and discharge at different rates is one was bad…
