Just got the batteries and considering my options of building a pack.
As you know, each battery is rated at 2500 mAh and I know that Boosted Board has, rather surprisingly, a 12s1p pack (please correct me if I am wrong…)
I will be using a single 200KV motor BTW, and a 4.12 VESC, which I will replace later with a VESC 6.
will a 12s1p be enough, how far will it get me?
If it is not enough, which will surprise me since Boosted Board is using it, then I will be considering a 10s2p (weight is an issue for this build).
How come boosted have only 2500 mAh?? I am still baffled by this…
Boosted has 12s1p of these. I see people citing they get about 4 miles? Range will depend a lot on your weight, how you ride, and conditions.
Some personal observations. I have 12s2p with dual 6355 208kv + vesc right now. I’m getting about 20wh/mile. This seems normal for larger people riding hard/fast. Somewhat surprisingly, I’ve gotten 20wh/mile with a variety of motor configurations. I also have trouble extracting the last, say, 25% out of the pack with how I like to ride.
At 20wh per mile and estimating last 20% unextractable, 12s1p (99wh = 2.5a x 3.3v x 12) has 80wh usable: 4 miles.
10s2p is 165wh, 132wh usable, so 6.6 miles.
These are rough estimates, probably on the pessimistic side. If you weight 130lb, ride slow and downhill on smooth pavement all the time, you’ll do better
I would suggest you build a 3p pack or better, 2p just doesnt offer enough amp delivery for decent acceleration or hills. Ive got a couple of 10s3p pack made with 25R’s and they are anemic as hell, but a 10s3p with 30Q’s is great, so alot depends on the cells constant and peak amp delivery. I had to use 3 10s2p 25R packs (for 10s6p) to get the same performance I get with a 10s3p 30Q pack.
6.6 miles does sound a little better than just 4…
What will be the advantage of having a 12s1p as opposed to having 10s2p with the superior range? Except for the obvious thing of less weight…
I am around 160lb and I think if people do fine with boosted board than it should be fine for me too… Do many complain about the short range?
I am worried that the 2p will add complexity to the pack and also, less voltage means less efficiency, right?
To my understanding having two cells in parallel will not increase the discharge rate of 50 A. It will only double its mAh rating…
Please correct me if I am wrong.
You bought a pile of A123 without knowing some basics? Yikes, jump in the water’s warm
You can kind of look at battery pack performance a few ways.
voltage. 12s vs 10s, higher voltage means you’ll go faster. 12s on A123 is similar to 10s on lithium ion. This is very common and probably a good sweet spot for vesc, and a good match for 200kv motor.
charge / discharge capability. For you 1p vs 2p, of course more is better and safer. For a single motor, 1p should be more than enough, discharge current wise and regen braking wise.
range / capacity. This is really a function of total number of cells. I find it’s easier to talk about in watt-hours (volts times amp-hours, e.g. 1 cell is 3.3v * 2.3ah = 7.59wh). Talking about this in amp-hours is confusing, because the meaning of 1 amp hour changes with voltage (6s 1ah is half of 12s 1ah).
Another thing about A123, because they have lower voltage than 18650, you need a different BMS (if you’re going BMS).
One of the characteristic of A123 cells that doesn’t get talked about enough, the number of charge cycles is at least 2x most 18650s. With how tolerant of abuse the cells are, this makes A123 packs really economical in the long term.
The TL;DR version, go 12s1p if you’re cramped for space and don’t need range. Go 12s2p if you have space for it. If you need more range, sell the A123s.
The LiFePO4 chemistry of A123 cells has very little sag. Less sag means better efficiency as you drain the battery under load, especially near the end of the charge. It seems from my experience with these cells so far that there is very little unusable capacity compared to the 20% or more on a 25R pack. Out of a 14S2P (A123 type A 2300mah=215wh) I got 8 milee riding pretty hard, I got 15.5 miles on a leisurely cruise.
Thanks for the info!
This is my second build, first one was with HobbyKing LiFePo4 batteries that swelled. So, yeah I am jumping in the deep water in terms of battery pack building. Add to that that I do not have a spot welder, so I ordered the batteries with soldering tabs to get a more harmless soldering.
Voltage:
My previous build was 6S1P 4200 mAh and it was 15km/h so I thought maybe 10 will be enough for me… no?
Discharge rate:
Why do you say it is safer please?
It is encouraging to hear that for a single motor it should be enough So now I am thinking maybe 12s1p is the way to go.
Capacity:
So I am getting 91.08wh which could be 151.8wh if I will compromise on speed and build 10S2P pack. Right?
BMS:
Of course I will be using a BMS, I am not that much of a noob Although, I will be using it only for charging. It is a BesTechPower LiFePo4 BMS. I ordered both the 12S and 10S, just to be sure
Also, why do you say this: “If you need more range, sell the A123s”?
The questions are getting fairly detailed and nuanced. I can give you hints but to be responsible, you should search/read on your own as well.
It looks like sweet spot for VESC is 10s (lithium ion voltage), around 190kv motor. If you go 10s lifepo, you’ll just be going slower and less torque. You might draw more amps from the pack, but if you build your pack properly, and monitor what’s going on, it should be fine.
more parallel groups means more discharge capacity. Your battery pack should be able to cover the max amp draw (and regen) from the esc, with some safety overhead (headroom).
A123 will give you maybe 40a continuous. 2p will double that to 80a. You can tell vesc to use less, but vesc can safely draw about 50a continuous.
Right. Or add 4 more cells and don’t compromise.
A123, even at 12s2p you get about 199wh. The characteristics are wonderful, but capacity is not. For comparison a samsung 30q 10s4p pack, which I believe is comparable discharge capability, is nominally 444wh. So double the range.
Looks awesome!
This is one pack?
Why do you have multiple BMSes?
How do you connect multiple BMSes to have a single charger?
I think I have see a thread about this build:
Why not have parallel first as someone suggested there? He said build “3 packs of 3 parallel and 4 series each” I guess he meant for you to connect these 3 packs in series, can you maybe explain what he meant?
Thanks for being so comprehensive!
Of course I will keep exploring, as I said, I have much to learn
I will make sure everything fits and the board and I believe that will make me decide.
you convinced me that both 12S1P and 10S2P are OK for me.
The purpose of the LiFePo4 is to have a safer and more durable battery, so I will keep them for now
I made 4 separate 14S1P packs with separate BMS’s. I did it this way for a few different reasons but mostly because I want to be able swap/split the packs to different builds at some point. Also, if a cell fails its much easier for me to replace it in a 1P pack like this. I also wanted to stick with the 4wd independent theme Ive been moving towards lately. 4 motors, 4 esc’s, 4 receivers, and now 4 batteries. If some thing fails, Im still running at 75%.
Im not sure how Ill set up the charging just yet. I can do 1 charging port or multiple.
