New hi-speed project

[BrianG]

The 1521 will fit, but I was able to get my hands on the 1515 at a very decent price so... If you have a 1521 of a similar kv (1700) you wouldn't mind trading/bartering, let me know.

The mechanical brakes lock up pretty good. The linkage I modded allows me to adjust the "progressiveness of engagement" (if that made any sense) so, it should be ok. Even so, I wouldn't want to use elec brakes on something this large/heavy running at 10s. The back-EMF voltage would be too high for the lipos IMO.

TBH, I wonder if this ESC "regenerative braking" effect is what causes lipos to heat up even on lower voltage systems. Just on the bench running on 4s, I saw some pretty substantial reverse voltage spikes and negative battery current (which means current was flowing into the battery). If braking hard enough and depending on gearing, I can imagine ample potential for this "charging" current to be well over the recommended 1C charge rate. I'm seriously considering some type of transorb/voltage clamping device to limit the amount of voltage getting to the battery on all my higher powered setups. Basically, I would choose a device with a voltage rating about 1v higher than the max battery voltage. When the voltage exceeds this rating, the device would simply shunt the excess voltage to ground. I'd rather replace a $2 part every so often than shorten the lifespan on $600 lipos!

[aqwut]

Originally Posted by BrianG

The 1521 will fit, but I was able to get my hands on the 1515 at a very decent price so... If you have a 1521 of a similar kv (1700) you wouldn't mind trading/bartering, let me know.

The mechanical brakes lock up pretty good. The linkage I modded allows me to adjust the "progressiveness of engagement" (if that made any sense) so, it should be ok. Even so, I wouldn't want to use elec brakes on something this large/heavy running at 10s. The back-EMF voltage would be too high for the lipos IMO.

TBH, I wonder if this ESC "regenerative braking" effect is what causes lipos to heat up even on lower voltage systems. Just on the bench running on 4s, I saw some pretty substantial reverse voltage spikes and negative battery current (which means current was flowing into the battery). If braking hard enough and depending on gearing, I can imagine ample potential for this "charging" current to be well over the recommended 1C charge rate. I'm seriously considering some type of transorb/voltage clamping device to limit the amount of voltage getting to the battery on all my higher powered setups. Basically, I would choose a device with a voltage rating about 1v higher than the max battery voltage. When the voltage exceeds this rating, the device would simply shunt the excess voltage to ground. I'd rather replace a $2 part every so often than shorten the lifespan on $600 lipos!

Maybe you're on to something.. ever since I did Nitro ---> brushless converisons with Mechanical braking... I have never had any heat issues at all....