Quote:
Originally Posted by Finnster
A123s can be tricky to use as they just come in one cell type. With lipos you can just pick a voltage and then decide what size lipos to get from there. A123s is the other way around. Example, my new little toy that came today:
Its an MGM 9032. I wanted to keep my A123s, but needed a reasonable cell config to do it. I'm switching my 5S2Ps to a 10S1P setup, and am looking at getting a 1515/2Y (1100kv) to go with it. I could have kept it at 5s2p and gotten a 1y with a 16018, but I wanted to go HV and super eff and cool. Any more than 10 cells it starts getting heavy and hard to fit. This controller will also allow me to run upto 2 xtra cells for some insane action @ 40V, but keeping amps below 60A hopefully. Its "only" a 1700W system, but should be more powerful than a 2000W+ XL system due to the eff increases.
A 6S lipo equiv is hard to do, as that is 14 cells A123, so really the next node seems to be 10S so you don't have to have a paralleled cell. |
Fnnster, when you say 14 cells is the practical limit, I assume your talking power to weight vs the high end li-pos? I've got 30 A123s (3 DeWalt packs) that I've broken out and originally had setup up as 6 - 5S1P packs and was thinking of going to 4 - 7S1P packs for the higher voltage and increased power to go with the higher end motor. That said, I'm on the fence with controller, the 16024 seems to give me head room, but at the cost of cell weight if I stay with the A123s.
Is the logic that the higher the voltage the general rule is the lower the aperage, weight to weight and power to power, hence your choice of the 9032 on 10S? What's your thought on 7S2P (dual 7S1P packs) on the 1515 1.5y, 1500 kv at 25.5v = 38225 rpm with 13 pound "hanging off of it"? Would I be better suited to dump the A123s and roll back to li-pos.. Thinking out load I used to run li-pos, Maxamps and it got real expensive, real fast, all I do is bash and it seemed every other week, even protected, I had a puffed cell and another dead li-po...
The A123s being "bullet proof" caught my attention real quick and they have decent power for what they are. Man, all in all brushless isn't that complicated when it comes right down to it, but when it comes down to spending 275\375 for an ESC and another 280\300 for a nice motor, wow, one really hates to make a mistake, lol...
It also appears, using the speed calc, that 16\47 gearing with 2nd gear of my 3 spd trans and "maxx" tires, 4.25 inch or so, only nets me 30 ish +\- mph, I'm not looking for 100 mph, but 700 out of pocket for 30 mph seems steep...
Savage diffs - 13\47
Savage 3 spd trans figured in second gear
7S2P A123 - factored at 3.6v
Nue 1515 1.5y
"maxx" tires 4.25 inch - I may be off on this, should have measured before I calculated and posted, apologizes if I am.
16\47 pinion\spur
Thanks!
purp