proboat 1/8 scale. need someones opinion!

[sailr]

They run 20C because:

1. They are old batteries.
2. They are cheap
3. They won't spend the money to get the good batteries!

no wayy really? so why do some people have expensive components yet run 20c lipos? well in that case im getting 40c. man, im totally clueless about this stuff. i have to study about lipos.

[Alexgar]

or they dont demand 100amp spikes out of there setup

[dreamland s4]

or they dont demand 100amp spikes out of there setup

ok guys tell me if i got this right....my motor requires 78a, so if i choose a 5s 5000mah 18.5v 40c lipo, i multiply 40×5000= 200000. then divide 200000/ 1000 = 200amp ??? well over 78amp which is what my motor requires. please let me know where im wrong!

[sailr]

You are correct, but remember, your setup can 'spike' way over that 78 amps from time to time. Best to have the batteries to carry it. If you only had a 20C setup, you would only be good for 100A. Going over that a few times can fry a battery pretty quickly. The 40C rated batteries will last much longer and deliver a bigger 'punch' out the gate.

[Make-a-Wake]

You're right................that batt will deliver 200 amps of power if it is a 40c constant rating...............if burst rate is 50c, then 250amps can be delivered for the short burst period. Just make sure your batts provide at least 50% more power than the motor will ask for to be safe. This way the batts will run much cooler and last longer.

Sailr, i've been using the term voltage dip for a while, kind of a "caveman" term i guess, in essence its correct as i am referring to a dip/sag of the voltage under load. However, i have always kind of stabbed at the exact figure, knowing it existed, but never sure how much.

My curiosity had me looking and i found that simply put, you are absolutely correct for an "under load" voltage rating.

here's what i found: "Since most discharge curves are neither linear nor flat, a typical value is generally taken which is close to the voltage during actual use."

Being in the hobby for several years, i have known many like myself who really werent aware that it was that simplistic, and still dont realize it............... thanks

[dreamland s4]

You are correct, but remember, your setup can 'spike' way over that 78 amps from time to time. Best to have the batteries to carry it. If you only had a 20C setup, you would only be good for 100A. Going over that a few times can fry a battery pretty quickly. The 40C rated batteries will last much longer and deliver a bigger 'punch' out the gate.

kool!!!!

so ill be fine with those batteries???? 5s 5000mah 18.5v 40c???? how many do i need???? man you guys are the ship!

[AlanN]

30-40C 5000+mah cells should be fine for heat racing. I run 10S 1P 5000's but am considering 5500-6500's. If you want to sport around go with more mah's but if you are setting this up to heat race 1P 5000's should be sufficient. I use Hyperion cells and there are others that work fine too but I stay away from the cheap chinese direct hobby houses for cells.

ps my motor runs around 825Kv. The Kv is on the high end of what I would use for a 10S setup.

[Brushless55]

Good info here guys!

[dreamland s4]

30-40C 5000+mah cells should be fine for heat racing. I run 10S 1P 5000's but am considering 5500-6500's. If you want to sport around go with more mah's but if you are setting this up to heat race 1P 5000's should be sufficient. I use Hyperion cells and there are others that work fine too but I stay away from the cheap chinese direct hobby houses for cells.

ps my motor runs around 825Kv. The Kv is on the high end of what I would use for a 10S setup.

china will burry us thats true!

i have a buddy that went through (a ball park guess) 7 esc's! in less than 3 months.

"seaking esc's" be careful, for some reason, the caps get really hot!

i purchased a 80amp HV 5-12s seaking esc and ran it on 6s and after 3 laps i checked the temps and everything was fine and cool except the capacitors THEY WERE ABLE TO FRY EGGS! i dont understand why.

SO HOW MANY BATTERIES SHOULD I GET? 1P 5000 MEANS 2 5000'S IN PARALLEL????? CORRECT ME PLEASE LOL

[Doby]

2P means two packs in parallel

There really is no such thing as 1P.

[Doby]

Read this before you do some damage to your equipment or yourself.

http://forums.offshoreelectrics.com/...ad.php?t=12020

[sailr]

No, 1P is a single. Two packs in parallel are 2P. 2P means 2 parallel.

FWIW. The Seaking esc's are very good. If your buddy is blowing that many of them he is overamping them, pure and simple. Remember, in airplanes, there is no 'ripple effect'. That is when the amperage goes from a steady rate to an extremely high rate very quickly. That is what happens in boats when the prop leaves the water and then 'bites' again. THAT is what you have to allow for with boat ESC's. LOTS of capacity. Many times it blows the capacitors because they can't take that big a surge in a nanosecond! The most normal reasons for overamping is too big a prop.

[sailr]

80 amp is WAY WAY WAY too small! No way! You're lucky you didn't blow them right away.

For a big boat on 10S you want at least a 180A esc that will handle 10 cells. You start talking big bucks when you get up to the preferred esc for that setup, a Castle 240HV.

china will burry us thats true!

i have a buddy that went through (a ball park guess) 7 esc's! in less than 3 months.

"seaking esc's" be careful, for some reason, the caps get really hot!

i purchased a 80amp HV 5-12s seaking esc and ran it on 6s and after 3 laps i checked the temps and everything was fine and cool except the capacitors THEY WERE ABLE TO FRY EGGS! i dont understand why.

SO HOW MANY BATTERIES SHOULD I GET? 1P 5000 MEANS 2 5000'S IN PARALLEL????? CORRECT ME PLEASE LOL

[sailr]

No problem. I learn something new every day! Electrics are a long learning curve. Take all the help you can get!

You're right................that batt will deliver 200 amps of power if it is a 40c constant rating...............if burst rate is 50c, then 250amps can be delivered for the short burst period. Just make sure your batts provide at least 50% more power than the motor will ask for to be safe. This way the batts will run much cooler and last longer.

Sailr, i've been using the term voltage dip for a while, kind of a "caveman" term i guess, in essence its correct as i am referring to a dip/sag of the voltage under load. However, i have always kind of stabbed at the exact figure, knowing it existed, but never sure how much.

My curiosity had me looking and i found that simply put, you are absolutely correct for an "under load" voltage rating.

here's what i found: "Since most discharge curves are neither linear nor flat, a typical value is generally taken which is close to the voltage during actual use."

Being in the hobby for several years, i have known many like myself who really werent aware that it was that simplistic, and still dont realize it............... thanks

[Brushless55]

No, 1P is a single. Two packs in parallel are 2P. 2P means 2 parallel.

FWIW. The Seaking esc's are very good. If your buddy is blowing that many of them he is overamping them, pure and simple. Remember, in airplanes, there is no 'ripple effect'. That is when the amperage goes from a steady rate to an extremely high rate very quickly. That is what happens in boats when the prop leaves the water and then 'bites' again. THAT is what you have to allow for with boat ESC's. LOTS of capacity. Many times it blows the capacitors because they can't take that big a surge in a nanosecond! The most normal reasons for overamping is too big a prop.

I never thought of that