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Author Topic: Need information of lip's and charging and run time  (Read 537 times)

phillnjack3

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Need information of lip's and charging and run time
« on: May 19, 2021, 10:31:38 pm »

Hello
This is now going to be a post showing how thick I am when it comes to Brushless motors, lipoo's charging them exactly what are they and what on earth is the difference in the c thing on them.
once again I am new to this , nothing on these seems anything like ive encountered before.

First what I need to know is
1/  what is the difference been a battery pack saying 30c 40c 75c etc and yet all the same number of cells and amp hour ?
 i.e  4s 5000mAH 30c   and  4s 5000mAH 75cc  ?

2 if I use a motor to say power a 36 inch huntsman or spearfish for example at a good turn of speed
any suggestions on what size and type of outrunner motor I would be needing ?
How many cells to power it, what sort of run time (longer the better )

what number on the batteries do I need to look for  / 30 c 40c 75 c etc

dont forget im very new to this stuff.

thanks in advance
phill
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kinmel

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Re: Need information of lip's and charging and run time
« Reply #1 on: May 20, 2021, 08:20:36 am »

This covers it quite well....  https://rogershobbycenter.com/lipoguide
A deeper guide......     https://learningrc.com/lipo-battery/
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phillnjack3

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Re: Need information of lip's and charging and run time
« Reply #2 on: May 20, 2021, 12:38:39 pm »

Thanks Kinmel


Wow, there is a lot more to these things than i thought.
from a quick read i am best to get the higher c number than the motor can ever get too (stalled ).
so roughly 40c "should " be ok in a boat ???  still not sure on this as not yet decided on what motor i realy need.


i am after something that would say propel a 36 inch huntsman at a good rate of speed , but also
last 20 minutes  (if possible). and preferably just a single motor.
im thinking something to give the performance of an ic motor about .40 size glow motor .
although if i realy like this i might then convert the big boats to electric as well. depending on prices .




another thing can i fast charge lipo's like the old nicads, or is this a NO NO.
im thinking if i am out and run the batts down, can i simply charge of a car battery or do i just have to have a spare
and use that.
if need extra batteries then this electric scene can get very expensive if i fancy running around for a few hours.


sorry to be a pain but ,like ive said very new to this.
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kinmel

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Re: Need information of lip's and charging and run time
« Reply #3 on: May 20, 2021, 01:05:00 pm »

A 5000 mAh, 30C battery can provide 150amps for a short period and that is way higher than needed, use a fuse to limit the maximum current to a reasonable rate even when stalled.
There are plenty of small motors that will power a Huntsman,  28/32 for example at around 1000KV.
The running time depends on the battery capacity and can be calculated once the boat is in the water - 5000 is a good starting point.
You must use a Balancer/Charger, they automatically adjust the charge rate and stop at the correct voltage.....  e.g.  https://hobbyking.com/en_us/turnigy-accucel-6-80w-10a-1-6s-balancer-charger-suitable-for-lihv.html  - many other makes available.
You should always have 2 batteries.  The upfront costs may seem high, but you only need one charger and batteries can be swapped between boats.


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phillnjack3

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Re: Need information of lip's and charging and run time
« Reply #4 on: May 20, 2021, 03:57:21 pm »

This is looking pretty good. not as much for the charger as i expected.


i fancy the outrunner motor for looks and ease of mounting them, plus using one i can use al lmy 2ba props from x40 to 2032 and even 4 bladeswith right motor . if i go in runner need different props as they dont have the torque from what ive readat the low end...


seems strange how the motorsareso small for the power they give out....


think i will be putting a good few bits n pieces up for sale that are no good to me and get myself a brushless set up.


i suppose it makes it cheaper than running glow due to the crazy fuel prices, plus can then go on any lake.
what they cant smell they cant moan about ha ha .


i need to try and get some vids of boat i see running and get info on their motors.

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JimG

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Re: Need information of lip's and charging and run time
« Reply #5 on: May 20, 2021, 08:28:20 pm »

another thing can i fast charge lipo's like the old nicads, or is this a NO NO.
im thinking if i am out and run the batts down, can i simply charge of a car battery or do i just have to have a spare
and use that.
if need extra batteries then this electric scene can get very expensive if i fancy running around for a few hours.


sorry to be a pain but ,like ive said very new to this.
LiPos are normally charged at what is called the 1C rate (C is capacity) e.g. a 2200 mAh pack is charged at 2200mA or 2.2 A for 1 hour. A 4000mAh pack at 4A for 1 hour etc. (The actual charge time will vary depending on far the pack has been discharged.) There have been packs sold that could be charged at a higher rate than this e.g 2C for 30 minutes or 3C for 20 minutes.This does put more stress on the cells and needs a good charger for safety and does tend to reduce the life of the cells.Best to have several packs and replace when needed, charge them up on the morning or the night before use. If they don't get run then you should use the charger to partially discharge them to the storage voltage, storing them fully charged is not good for the cells.If you use the balance charge setting of the charger the charge will take longer than the normal hour as it takes time to get all cells at exactly the same voltage. You don't need to balance charge every time, just occasionally. A decent battery checker will check the voltage of individual cells in a pack and warn you if they are out of balance so they can be balance charged the next time. It also tells you what percentage of charge is left in the pack after a run, best not to go less than 20% unless you are charging straight away ( allow the cells to cool down if they are warm after a run.)
Jim
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unbuiltnautilus

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Re: Need information of lip's and charging and run time
« Reply #6 on: May 20, 2021, 08:43:51 pm »

The best way to help square the circle regarding why brushless outrunners look too small for their own good.. On a typical, old school inrunner type motor like an old Mabuchi RS540 or Decaperm, how big is the rotating mass? The armature etc rotating inside the can of the motor. Now look at the rotating mass of an outrunner motor, most of the motor! Lots of torque is generated, which is great for us boaty types, as we can swing bigger props for lower current draw.
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phillnjack3

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Re: Need information of lip's and charging and run time
« Reply #7 on: May 20, 2021, 09:10:46 pm »

are now that makes sense about the outrunner , thanks unbuiltnautilus .


Jin G thanks for info, its all starting to sink in now.


so from what i am reading i can charge them back up in about an hour but give give them say 15 minutes or so to cool down atleast before putting them on the charger ? that would be fine. time i pour a cup of coffe ( it law i take a flask with me everywhere ) plus have a fag and fart about swapping other batt over.......

now as for safely charging and discharging etc,
can i buy a charger that will do everything automatically like charge/discharge etc or atleast do it by me pressing a button. and will this also balance the battery ? or is a balancer a totaly seperate thing i need to get ?

and would this this charger be able to work off 12 volt/ the car .
im thinking of when maybe going away for a week etc and not always being near electricity to use 240 volt...

is there any chargers to steer clear of and makes of battery's to steer clear of too.
i dont fancy blowing up lipo's  and i do know they can little buggers if they was to
catch fire etc.

is there a way that i could say run the boat and when it gets down to a certain point
of charge it simply stops using these batteries so i dont harm them, like a cut off point
of voltage etc ? 
i can easy rig up a get me home system that uses something totally seperate..


i know im asking loads of questions and might seem thick, but with electrics like this , i am thick ha ha
i dont want to be getting something then find for another fiver i could of got something safer.


i am taking all this info in and even copying a lot of it so i dont forget it.

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kinmel

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Re: Need information of lip's and charging and run time
« Reply #8 on: May 20, 2021, 09:57:39 pm »

Balancer/charger units such as the one above does everything you need to manage Lipos. It is almost automatic since it remembers the last battery type connected.  The input voltage is 11v to 18v, so a car battery is fine.
You can attach an alarm to the battery when you are using it and it will buzz loudly when the voltage is reaching it's safe minimum.......  https://hobbyking.com/en_us/cell-checker-with-low-voltage-alarm-2s-8s.html?queryID=&objectID=47061&indexName=hbk_live_magento_en_us_products

Keep asking the questions - Mayhem is at it's best when someone asks questions and members from around the world give an opinion. 
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phillnjack3

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Re: Need information of lip's and charging and run time
« Reply #9 on: May 20, 2021, 10:11:33 pm »

i hear what you saying about an alarm.
 but is there a way t oautomatically shut down the model if the batts get too low.
i might be  ina  place with the boat that is a bit on the noisey side..


another thing do lipo's drop down like the old nicads.. loads of power then wallop flat battery ?


and can i have 2 x 3 cell battery to make a up a 6 cell of do i have to have a 6 cell ?
i am thinking weight and balance etc in the boat.


if joing them up do i go positive to negative to make up the 6 cell like making up a normal 12 volt battery from 2x6

« Last Edit: May 20, 2021, 10:19:10 pm by phillnjack3 »
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kinmel

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Re: Need information of lip's and charging and run time
« Reply #10 on: May 20, 2021, 11:17:00 pm »

I don't know of a simple way for a shut down if battery is too low, certainly an OpenTx radio getting voltage data from the boat can do it.
You must not let the battery voltage drop below 3volts per cell, below that and the battery is damaged.
Only racing models require 5 or 6 cells, most of us settle for 3cell batteries. If you must join 2 together you can buy "series" or "parallel" Y Harnesses.    Series doubles the voltage, parallel doubles the capacity.  A 4S Lipo is cheaper than a pair of 2S batteries.
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phillnjack3

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Re: Need information of lip's and charging and run time
« Reply #11 on: May 21, 2021, 08:56:29 am »

oh ok so a 3 cell batery would still be a quick boat.


that sounds pretty good as i was sitting here last night thinking about converting all my stuff over to electric.
 i might be over thinking it all but been looking at motors that are probably a bit too much power.


its all looking pretty good



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kinmel

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phillnjack3

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Re: Need information of lip's and charging and run time
« Reply #14 on: May 21, 2021, 12:20:06 pm »

Kinmel. would that tiny little motor seriously get a 36 inch huntsman up on plane ?  its on 28 x 30 mm , thats tiny ..
i was thinking i need like a 40 x 50 size motor.. remember im new to this brushless stuff.


i am getting a proper lesson on this stuff here.
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JimG

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Re: Need information of lip's and charging and run time
« Reply #15 on: May 21, 2021, 01:17:49 pm »

i hear what you saying about an alarm.
 but is there a way t oautomatically shut down the model if the batts get too low.
i might be  ina  place with the boat that is a bit on the noisey side..


another thing do lipo's drop down like the old nicads.. loads of power then wallop flat battery ?


and can i have 2 x 3 cell battery to make a up a 6 cell of do i have to have a 6 cell ?
i am thinking weight and balance etc in the boat.


if joing them up do i go positive to negative to make up the 6 cell like making up a normal 12 volt battery from 2x6
Make sure that you are using a LiPo compatable speed controller. These have a low voltage cutoff built in which will stop power to the motor when the cells reach the minimum voltage. If using the BEC to power the receiver this will still work. If the low voltage cutoff works and the boat is in the middle of the pond just wait for at least a minute and the battery will recover enough to allow you to power it at low speed back to the pond side. High power use will drop the voltage below that of a rested cell. Before LiPo compatable were in common use there were separate low voltage cutoffs sold to be fitted between the esc and motor but these are rare nowadays.

LiPo s have a higher voltage when fully charged which drops quickly in use to the nominal voltage. This then slowly drops during use giving full power until at the end there is a rapid drop till flat. The slow drop in voltage is used by the battery checkers to measure the capacity left as a percentage. So not such a flat discharge as a NiCd but not far off.
No problems in connecting 2 3S packs to give a 6S, just connect then in series as you would with NiCd or Pb/acid.
Jim
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kinmel

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Re: Need information of lip's and charging and run time
« Reply #16 on: May 21, 2021, 01:29:06 pm »

Kinmel. would that tiny little motor seriously get a 36 inch huntsman up on plane ?  its on 28 x 30 mm , thats tiny ..
i was thinking i need like a 40 x 50 size motor.. remember im new to this brushless stuff.
i am getting a proper lesson on this stuff here.
My 36" RAF Fireboat uses a 2834 runner with a 3s battery and planes easily.   


You can go larger if you wish, a 3542 outrunner would show you how powerful brushless are and allow you to make your own judgement
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phillnjack3

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Re: Need information of lip's and charging and run time
« Reply #17 on: May 21, 2021, 02:59:30 pm »

do any of you have any video of your boats running these motors  ?
that would give me a real good idea of roughly what motor i need.
from what i am seeing i have definitely been over thinking on the size of a motor i need.
my first electric brushlesswould be this 39 inch planing hull thing, then i can use that as a rescue boat.


if all goes well then i might just sell up my ic stuff and go electric on all my boats.
i can swap batts around from boat to boat until i build up a bank of batteries....
« Last Edit: May 21, 2021, 03:36:23 pm by phillnjack3 »
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