Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: AlanP on April 10, 2014, 08:31:09 PM

Title: Lipo with ESC
Post by: AlanP on April 10, 2014, 08:31:09 PM
Thought I would ask the experts before I blow something up  :}

I have a small trawler that has 2 x 6v 4.5ah lead acid batteries in to give 12v,  but they are too heavy, it looks as though the holds are overloaded with fish.
I have a three cell lipo  11.1v battery and was wondering if this would be compatible with the Mtronics viper marine speed controller that is in the boat. I also have one of those blue Marine 50a forward 20a backward speed controllers that could be used (if compatible) 

Your thoughts would be appreciated

Regards Alan
Title: Re: Lipo with ESC
Post by: sparkey on April 10, 2014, 08:45:03 PM
 :-)) Yes that will be OK,ESC's see  DC voltage no matter what type of battery they come from,providing the battery can take the current the motor draws i.e. capacity of battery m.A.h.so you need a capacity of 4500mah to get same run time,Ray :-)) :-)) 
Title: Re: Lipo with ESC
Post by: More Coffee on April 10, 2014, 09:03:42 PM
I would caution you there.
Not because its a lipo.
but what is the fully charged voltage of the lipo.

A fully charges 12v battery can range up to 14.2volts
typically its 13.8v
standby is about 12.6v

Just make sure your fully charged pack dosent exceed 13.8v
Mtroniks can handle this fine. Ive never had a problem with a fully charged Lead Acid battery.
Title: Re: Lipo with ESC
Post by: sparkey on April 10, 2014, 09:20:42 PM
 :-)) Yes but it is a 3x cell lipo 3x3.7=11.1v so voltage should not be a problem,run time might be if the capacity of battery is to low if you only use 80% so a 3000mah battery running a 10amp motor is likely to only give about 16mins run time,Ray. :-)) :-)) :-))
Title: Re: Lipo with ESC
Post by: nick_75au on April 10, 2014, 10:10:00 PM
I would put a li-po alarm on the battery as the ESC has no form of low voltage cutout, cheap device that will assist in saving your battery
http://www.componentshop.co.uk/led-battery-status-indicator-alarm-for-1s-to-3s-3-7-11-1v.html (http://www.componentshop.co.uk/led-battery-status-indicator-alarm-for-1s-to-3s-3-7-11-1v.html)
http://www.hobbyking.com/hobbyking/store/__40909__On_Board_Lipoly_Low_Voltage_Alarm_2s_3s_UK_Warehouse_.html (http://www.hobbyking.com/hobbyking/store/__40909__On_Board_Lipoly_Low_Voltage_Alarm_2s_3s_UK_Warehouse_.html)


A fully charged 3 cell Lipo is 12.6 volts


If the amp draw is higher than about 4.5 amps the Lipo will have a longer run-time with capacity of 3500 mAH compared to the 4500 mAH of the SLA
Title: Re: Lipo with ESC
Post by: More Coffee on April 10, 2014, 10:36:51 PM
:-)) Yes but it is a 3x cell lipo 3x3.7=11.1v so voltage should not be a problem,run time might be if the capacity of battery is to low if you only use 80% so a 3000mah battery running a 10amp motor is likely to only give about 16mins run time,Ray. :-)) :-)) :-))

not fully charged, fresh of the charger its closer to 13v
Title: Re: Lipo with ESC
Post by: AlanP on April 10, 2014, 11:26:59 PM
Lots of information there lads, many thanks,  :-))  Ill take the answer as a yes then  :}

Must admit I had not thought about no low voltage cut off, thanks nick.

Ill charge the lipo tomorrow and then check the voltage, then try it in the boat, if the speed controller goes up in a puff of smoke, Ill split the cost of a knew one between you three  O0

Thanks again
Alan
Title: Re: Lipo with ESC
Post by: More Coffee on April 11, 2014, 12:10:40 AM
The only difference I can see is the available current.

LIPO's are known for there high current high discharge rates.

Outside of that you shouldn't have a problem.

Title: Re: Lipo with ESC
Post by: inertia on April 11, 2014, 08:52:14 AM
MTroniks rate the Viper for 5-10 cells. That would be 1.2v NiMH cells, which are actually nearer 1.5v when fully charged. That makes a fully charged 10 cell pack around 15v. Compare that with the 13v or so for the 3S LiPo or SLA batteries and you should be fine. Ref current, the battery will only deliver the current which is demanded by the load, so if the motor draws 3A then that's what the current will be. The pack will NOT try to feed a higher current into the circuit, even if it is capable of doing so. A geezer called Ohm established a matematical equation about the situation.
Those blue ESCs make good ballast..................  %)
DM
Title: Re: Lipo with ESC
Post by: More Coffee on April 11, 2014, 06:49:24 PM
Correct around the current.
I was looking at it from the point of view ,worst case a stalled motor or a short.

never mind it takes more current start a motor reverse its direction. than it does to run it,

But you knew that I'm sure, or you would have mentioned it.

Easily mitigated with a fuse.

A geezer called Ohm established a matematical equation about the situation

Take your shot I really don't care, its part of the reason this forum comes under attack ,and theres little movement.
Ive dealt with worse , ever notice a lot of talented builder's on other forum's don't bother here..you guys treat it like a basement.

And its spelled mathematical , an old geezer named Webster had book around the subject.

Title: Re: Lipo with ESC
Post by: sparkey on April 11, 2014, 07:14:30 PM
 :-)) Ohm was he not married to Millie Amp? :-))
Title: Re: Lipo with ESC
Post by: AlanP on April 17, 2014, 10:31:05 PM
I don't like to see a thread unfinished, so here I am with the end result  O0
The wiring has been altered (as it was a right mess) and the lipo installed, well two 11.1  3000mah to give a better run time, and it all works fine (in the shed) it just needs ballasting now as soon as the wife gets out of the bath   :}

I did get two of the alarms as suggested but I don't know if I will be able to hear it down in the hull

Alan 
Title: Re: Lipo with ESC
Post by: inertia on April 17, 2014, 11:01:08 PM
Take your shot I really don't care, its part of the reason this forum comes under attack ,and theres little movement.
And its spelled mathematical , an old geezer named Webster had book around the subject.
No need to take stuff personally, and there's nothing in the least clever about pointing out a typo. You're not immune from grammatical and punctuation errors, mate. I spotted ten in your post.
Lighten up - it's just a hobby.
DM
Title: Re: Lipo with ESC
Post by: AlanP on April 17, 2014, 11:25:06 PM
Wish I hadn't bothered posting now, it was just a simple question, no need for agro  :((
Title: Re: Lipo with ESC
Post by: nick_75au on April 17, 2014, 11:57:27 PM


I did get two of the alarms as suggested but I don't know if I will be able to hear it down in the hull

Alan


The cheapies i have are loud enough, I had long enough leads to put them up in the superstructure.


Just ignore the "agro"
Title: Re: Lipo with ESC
Post by: More Coffee on April 18, 2014, 03:22:11 AM
Just listen to Nick..

Leave the rest of us to our lager and ale.
Title: Re: Lipo with ESC
Post by: More Coffee on April 18, 2014, 05:44:45 AM
No need to take stuff personally, and there's nothing in the least clever about pointing out a typo. You're not immune from grammatical and punctuation errors, mate. I spotted ten in your post.
Lighten up - it's just a hobby.
DM

I didn't count them , I got ten fingers and only use three on a key board ...some details just have to be left out I guess.. :-))
Title: Re: Lipo with ESC
Post by: Tug-Kenny on April 18, 2014, 10:29:26 AM

                                          :police:


Title: Re: Lipo with ESC
Post by: vnkiwi on April 18, 2014, 10:37:42 AM
 O0