ESC and Lipo Problem

[qbas]

Hello everyone

I a question regarding my esc and what batteries to get i am running a dynamite 80 amp esc on my boat with batteries in series know can i use this setup with this ESC 2 2S 4000mah 20C batteries my question sice 20 X 4000 will give an 80 amp draw right ?
So if i am using a two battery setup in series is it safe to say that i will have 160 amp max draw so the esc should be fine?

[sanyijr]

No....

Please read all the intro to lipos and such. I bet no one wants to re-do all the info again... But in short, You are correct in BATTERY amp draw. Each pack can discharge at a recommended 20C or 80 amp output. You ESC is rated at 80 amps continuous... So really, 60-70 amps continuous.... Your Boat, hardware setups, motor, prop, and combo of all establishes you power system Amp draw. So you are working with half a dozen variables.

But bottom line- if esc is rated at 80 amps... keep it under 80 amps. If packs are rated for 80 amps. Shot for under 80 amps. Your ESC cannot handle more amps because you are running packs in series. It will have 2X the voltage, but the esc will blow if you try to push 160 amps throught it.

But again, the setup is what controls the power draw from Packs/Esc, so only knowing that can you really say if you are in a safe range.

But a word of caution: Judging from your question, I strongly recommend reading alot of the forum info here as I am quessing you may be a little new to the concepts. It took me LOTS of reading and a few failures to get my head around all this... GL

Sean

[qbas]

Hi there Sean

Ok i think that i need to ask the question in another way this my fault i forgot to mension that the ESC is a dual and that supports two batteries in series my mistake terribly sorry this is my setup.

A3630-1800Kv, 6-pole, Water-Cooled

Dynamite ESC 80A in dual battery configurations (80A up to 6S Li-Po compatible)

2 2S 5000mah 30c batteries

This is my current setup wich is the one that the boat manual says to be used.

Know for the question above i know that i can't supply a esc that is not prepared for dual batteries with a higher Amp draw that is supposed to so that said my question is really if you can use the other battery pack that is also sold as a kit for this boat wich is 2 2S 4000mah 20c bat there are these two setups on sale on the website the one i am using wich is the one above and the one with the battery pack that i wrote in this phrase.

Another thing is that i was under the impression and this a have read on this and other forums that depending on the engine your ESC should have a higher C rating than your motor so that you don't push the ESC to hard and you have a safety margin ?

Another thing is that it's a good thing to have batteries that a have a higher Amp draw than you esc this will allow you not be pushing the batteries close to their design limit so if you have a esc that can handle let's say a 80 amp constant rate with a 160 amp burst if you get a battery that as a 100 amp constant rate and a 200 amp burst your ok to be on the safe side.

Best regards Sean

Manuel Sousa

[sanyijr]

Manuel,

You have a good motor there, though I think you are missing the big picture here... The batteries supply the power and that is it. As long as you are not demanding more than they are capable of giving, they will stay healthy and relatively cool...

Your setup is what will drive the power demand from the esc/battery combo... You have a very efficient motor that is used for 20-29" (more or less) hulls... So you are running a 4s setup. That is fine.... BUT your power draw will be based on your prop size and boat size. IF you put a prop that is not efficient based on your boat size and type, you can really increase the power damand on the motor and esc and batts...

Now if I understand your question (I think there is a bit of a langueage translation barrier, but i will do my best) You are asking if you can use the 4,000 mah batteries instead of 5,000 mah based on a constant discharge rate of 20C on the 4000 mah packs? If all else is the same you are close to your limit, but i would reflect on how things are with the 5,000 mah packs after a run. Is the ESC very warm? Are the 5,000 ma packs warm? If either one is on the warm side, using lesser packs will NOT improve the situation. But again, if your power system in general in not pressed to it's limit, you might be just fine. But if you are pushing a larger boat and/or prop and your esc is close to 80 amps constant, I would stick to packs that are either 4,000 mah 30C or 40C or 5,000 mah 20C+

Under sized/low "C" packs starve an esc and can cause failure...


But your understanding of batteries is a bit missinformed as well. A 2s pack is nothing more than (2) 1 cell batteries put together in series and shrink wrapped to make a pack. When you put (2) 2s packes in series, you are creating a single 4s pack. So (4) 1 cell lipo cells in series. The capacity of the packs is NOT related to the number of cells. Your mah and AMP (or C rating) does not change from a 2s to a 4s if the cells are 20C and 4,000 mah cells. The only thing that cahnges with the number of cells is the Voltage. 2s = 7.4V 4s = 2(7.4V)=14.8V

Here is a little Lipo info.
http://www.offshoreelectrics.com/lipo.php

What is the boat, prop etc? That is always helpful... So much for the short reply.... Oh well

[qbas]

Sean

Thank you very much for your quick response you have been a great help and i love this hobby i am really into rc boating and to be honest e really don't want to break speed records what i really want is to have good solid platforms that i will enjoy for a long time without being worried that the ESC will fry or that the engine is being pushed to hard so this is why i ask these questions.

Ok know for the rest of the reply here are some pictures of the boat it's a Proboat Impulse 31 (just love the way it looks in the water).

IMG_5940.jpgIMG_5958.jpgIMG_5999.jpgIMG_6113.jpg

Know your questions i am using all stock parts from proboat so the prop is the stock so i would think that the prop will not be a problem it's a 1.6 in x 2.5 in stainless steel prop.

After reading what you have written i don't think i will be using the 2s 20c batteries.

My ESC is setup in the following way :

High Cutoff for the Lipos.
Brake is on.
Low timing (so that i can get longer run times).
Throttle Curve Logarithm: 45% power at half throttle and 80% power at full throttle (Being new to rc boating don't really wanna take any chances)

Best of regards Sean

Manuel

[qbas]

Ops forgot i wanna build my own setup so the better i understand these conceps the better thanks for your help.