13s+ discussion

#387

Have you ridden HV on a VESC based board though? It is faster. 12s is awesome, but there is really no comparison to HV.

Most of us enjoy using VESC based ESCs. Assuming I want to stay with VESC, my options look like I can run 80 amps on a 60D+ at 12s, or 80 amps on a 100D at 18s. Running much higher amps at 12s on something like a makerx 60D isn’t a good option for many people on 12s4p/smaller packs.

With that framework of options and pre-made decisions, HV gives you more wattage, so it’s faster (or gives more torque depending on gearing).

I suspect a lot of people are wanting HV with the same logic.

I doubt that SRB would not consider HV vesc based builds if there is a day when VESC outguns them in wattage (stares at next gen little foccers).

4 Likes
#388

and i have 3 letters in response to that

E. at
M. y
S. horts

that and dick swinging contest

2 Likes
#389

With hv it’s easier to get the most torque out of the motor as then can use a low kv and as the kv goes down it needs less amps for same torque. My motor at 50kv can only do maybe 60 amps before starts to saturate.

1 Like
#390

My 2 cents:

HV controllers just make it easier to use more power, not necessarily give you any more power than what could be achieved at lower voltages.

I’ve ridden a lot of 12s boards, not a great deal of HV boards, but enough to get a feel for them.

I built a 16s board to try and discover the differences for myself. Sure, it’s got heaps of power compared to my similarly geared 12s board, but it doesn’t hold a candle to Liam’s fucking supercharged 12s board.

Liam’s prototype board at 12s is easily the most powerful feeling 2wd board i’ve ridden, but it comes at the cost of running components quite hard.

4 Likes
#391

i fight for the theoretical
less A so there’s less load on the motors and batteries

lower temps, and a hair more efficiency

but don’t take my word, i have no such setup to prove it :joy:

2 Likes
#392

Your point is correct. Lower KV motors generate less heat for the controller, for same amount of torque as a higher KV motor would generate…cause fets gotta give the motor less Amps on the lower kv that’s where your efficiency comes from, but your overall power and speed is now less. And adding voltage to gain the speed back…well now you are back at square one with the efficiency and heat issue cause iron losses. This is the ultimate balancing act in sizing a system.

3 Likes
#393

first real board purchase was a 12s lonestar which i was cooking pulling max power, 100c on motors in Canada’s summer. On my 18s everything is much more efficient, pulling about 20% less amps. Im all about torque now so 12s doesn’t really cut it, i spend more time

my first boards were a 12s then 18s lonestar, i ride mostly the same but im more about torque now from the HV; but the 18s system is definitely running cooler and more efficient even when at those same top speeds(60-68km/h) while pulling like 20% less amps. on 12s I was cooking the system, and motors were struggling to not be burning hot ~100c

1 Like
#394

Is the motor KV the same?

2 Likes
#395

If it’s lacroix for both boards, it’s 190kv on 12s and 130kv on 18s.

1 Like
#396

I had a feeling, in this case the lower KV motor is responsible for the added torque and lower running temp

#397

after careful consideration I think you guys are all full of shit. I’ll go back to enjoying my 6s2p absolute unit of a board

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8 Likes
#398

I was gonna write a big long message but the answer is super long and complicated and i spent 7 years learning all this and I’m still learning, but i will say if you buy a Raith you won’t have to worry about it, it’s all done for you

1 Like
#399

Hi,

am new to DIY, I have a project to mount a parallel conected battery to my enclosure battery drilling a small wire hole in my deck. My enclosure battery is a 20S 8P, I want to connect in parallel a 20S 4P making a 20S 12P. My ESC can pull up to 200Ah at 84volt, am not sure what type of BMS I need, should I buy a BMS as powerfull has the one already in my enclosure or its relevant only to the power that my 20S 4P can push out ?

#400

If you are discharging through the bms, you’ll want to make sure that the bms you put on your 20s4p is suited to that.

1 Like
#401

yeah, what he said

i got ejected by my board because i was running 30 battery amps per side discharging thru a 50a BMS

#402

I think I will bypass BMS, soo the only thing that I woukd need to match is the charging current ? My 20S 8P charges at 84volt 14Ah. not sure how to calculate the load that my BMS would need to handle if I had 4 more P packs.

#403

Ah means amp hours, a capacity measurement.

Charge current is measured with A - amps.

I would make sure the bms is capable of taking the entire charge current, and also that the cells are capable of taking the entire charge current.

#404

Thanks for the clarification, how would you proceed to calculate the load of my second BMS knowing that the charge current is 84volt 14Ah roughly 1000 watts. Cells are INR samsung 50E 4900Mah to be prescis.

#405

Personally i’d use a watt meter on the line to the parallel battery to see if it takes half of the charger current or if it equalises to be a third of the current.

I’ve done the experiment before but i can’t remember what happened :rofl:

1 Like
#406

We cannot calculate that. It depends on something called the “internal resistance” of your two battery packs and we do not know those numbers.

The larger pack will probably take more current than the smaller one though. But in my opinion you should make sure the BMS for the smaller pack can handle at least 10A, just in case.

You also have to make sure that the cells (batteries) for the smaller pack can be charged at 10A. That is 2.5A per cell.

1 Like