2Likes17.5 tips and speed secrets
08-18-2016, 10:19 PM
#226
It's quite simple. Voltage drop = Amps drawn by motor * internal resistance of the battery.
Let's suppose we are talking about packs built with the same technology and materials.
Amps can be safely considered the same, resistance is inversely proportional to cell size. mAh value is linearly proportional to cell size.
It means voltage drop caused by load is higher with smaller cells/packs, and after the same amount of mAhs drawn they will also be further down the working voltage curve.
These two factors both work in the favor of bigger packs, in this case the saddles.
Let's suppose we are talking about packs built with the same technology and materials.
Amps can be safely considered the same, resistance is inversely proportional to cell size. mAh value is linearly proportional to cell size.
It means voltage drop caused by load is higher with smaller cells/packs, and after the same amount of mAhs drawn they will also be further down the working voltage curve.
These two factors both work in the favor of bigger packs, in this case the saddles.
now there's a key. does the "punch" that a shorty offers with it's lower IR cancel out the higher available voltage as the pack is drained? i would imagine on a track with a large straight, the higher voltage over time might be more desirable. on a smaller track, maybe the punch of the shorty is better.
socket brings up a good point with battery chemistry. the shorty's that we use are generally designed for stock racing and offer the lowest IR's available. there's no need for this with saddle packs as they are generally used for mod racing. from his experience, shory's also react better to high charge/discharge procedures.
not so "simple" as you state. i'll stick with my shortys.
socket brings up a good point with battery chemistry. the shorty's that we use are generally designed for stock racing and offer the lowest IR's available. there's no need for this with saddle packs as they are generally used for mod racing. from his experience, shory's also react better to high charge/discharge procedures.
not so "simple" as you state. i'll stick with my shortys.
08-18-2016, 10:42 PM
#227
This is how the internals of a Lithium Polymer battery looks
With that being said, the battery manufacturer determines the tolerances. The plates and how they transfer the power through the tabs is all part of this process. So how they manufacture the batteries determines the internal (inside the battery) resistance. Now the mah or milliamp hour of the battery is determined through the size of those plates. So an 8000mah battery can have the same internal resistance of a 200mah battery and vice versa. The size of that plate creating the larger milliamp hour does not increase voltage. They merely act as a larger fuel tank in the simplistic nature. Danny of SMC discusses this a lot on his facebook. He honestly is one of the most beneficial people to the industry. For stock a lower resistance pack will allow for more power to be transferred into the esc to be converted to the power needed for the motor.
Higher resistance = smoother (makes electronics work harder)
Lower resistance = punchier (makes electronics work easier, creating more power)
Higher mah = more run time
lower mah = less run time but possibly lighter (LRP sells these as lcg packs)
What I run in my cars:
Stock buggy 4250
Stock stadium truck 5400
Stock SCT 5400
I have ran the 4250 in all my vehicles until the 5400 have come out. I can make run time with the 4250 in stock sct (probably the most load pulling class raced at big races) but I can feel the discharge curve hitting its limit at eight minutes after two minutes of warm-up laps.
With that being said, the battery manufacturer determines the tolerances. The plates and how they transfer the power through the tabs is all part of this process. So how they manufacture the batteries determines the internal (inside the battery) resistance. Now the mah or milliamp hour of the battery is determined through the size of those plates. So an 8000mah battery can have the same internal resistance of a 200mah battery and vice versa. The size of that plate creating the larger milliamp hour does not increase voltage. They merely act as a larger fuel tank in the simplistic nature. Danny of SMC discusses this a lot on his facebook. He honestly is one of the most beneficial people to the industry. For stock a lower resistance pack will allow for more power to be transferred into the esc to be converted to the power needed for the motor.
Higher resistance = smoother (makes electronics work harder)
Lower resistance = punchier (makes electronics work easier, creating more power)
Higher mah = more run time
lower mah = less run time but possibly lighter (LRP sells these as lcg packs)
What I run in my cars:
Stock buggy 4250
Stock stadium truck 5400
Stock SCT 5400
I have ran the 4250 in all my vehicles until the 5400 have come out. I can make run time with the 4250 in stock sct (probably the most load pulling class raced at big races) but I can feel the discharge curve hitting its limit at eight minutes after two minutes of warm-up laps.
08-19-2016, 02:26 AM
#228
I thought revtech's had the best numbers.....bit pricey though
08-19-2016, 06:46 AM
#229
08-19-2016, 06:47 AM
#230
08-19-2016, 06:50 AM
#231
. Although I don't blame you...When the tracks don't check the easiest thing next to weight (which I know you cheat on too
) then why not?
08-19-2016, 12:24 PM
#233
Please, explain to me when have I EVER failed a tech inspection?
It's easy..Never. I can however point out the many times when other's have.
08-20-2016, 08:29 PM
#235
Sorry, I don't cheat. I follow the rules as given by ANY track I attend. My car is 1499 on the dot when it's set down on the track, and 4.35V is purely just for practice to see if a battery can handle it.
Please, explain to me when have I EVER failed a tech inspection?
It's easy..Never. I can however point out the many times when other's have.
Please, explain to me when have I EVER failed a tech inspection?
It's easy..Never. I can however point out the many times when other's have.
Yeah practice...
That's the ticket....IF it IS just practice run a 3 cell...
Last edited by thecman26; 08-20-2016 at 08:56 PM.
08-20-2016, 08:55 PM
#237
I'd like to know as well!
This one is close and pretty awesome!
http://www.smc-racing.net/index.php?...product_id=338
This one is close and pretty awesome!
http://www.smc-racing.net/index.php?...product_id=338
08-20-2016, 09:14 PM
#238
I'd like to know as well!
This one is close and pretty awesome!
http://www.smc-racing.net/index.php?...product_id=338
This one is close and pretty awesome!
http://www.smc-racing.net/index.php?...product_id=338
08-20-2016, 10:37 PM
#239
yeh practice haha
you guys crack me up lol
I've done so much charging/discharging cycles at 40/70.....all for practice haha
