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[ojays]

Hoping for a little advice please.
I have only ever used NIHM's in my builds, however my latest build came out a lot heavier
than I anticipated with a NIHM on board.

The motors (x2) are basic 6-12v 360 brushed can motors, the ESC is a motroniks Viper Marine 15 plug & play.

First question. Are the motors ok to be used with lipo's?
Second Question.  Is the ESC ok to be used with the can motors and Lipo's
Lastly. What capacity Lipo is suitable if the above answers are positive.

Thanks in advance.
Gregg

[Taranis]

LiPo batteries are 3.7 volts nominal per cell
So a 2s Lipo is 7.4 volts
3s 11.1 volts  etc
Your ESC is only interested in voltage and not the type of battery so yes it is fine.
Capacity is explained as mah and this will dictate the weight also. More mah equals more weight! but much less than Nimh
You will need a suitable charger


Best get a feel of other peoples batteries or visit a model shop before buying




EDIT very nice model BTW 


EDIT If you use for example a 3300 mah Nimh  then the corresponding size LiPo is your starting point and 2s is enough

[ojays]

Many thanks for your prompt reply.
Already have a Turnigy multi charger from my flying thingy days.
Will have drive down to my local model shop and have a word.
Thanks again.

[Taranis]

 


If you have a kitchen scales I would weigh the battery you have and take the scales with you to compare




Look at these offerings
https://hobbyking.com/en_us/catalogsearch/result/?cat=&q=Turnigy+2S+LiPo


Cheap as chips  SAYS 204 grams
https://hobbyking.com/en_us/turnigy-3300mah-2s-30c-lipo-pack-xt-60.html

[ojays]

Good idea, thank you.

[Taranis]

You will also need a voltage alarm so as not to over discharge the Lipo ( potentially fatal but there are recovery tips )
It's unlikely that your brushed ESC will have this function?
However an alarm that plugs into the balance plug is very cheap Circa £3




Typical example
https://www.amazon.co.uk/dp/B009LW48LK/ref=asc_df_B009LW48LK57822019/?tag=googshopuk-21&creative=22122&creativeASIN=B009LW48LK&linkCode=df0&hvadid=309816003291&hvpos=1o3&hvnetw=g&hvrand=2060042943773116456&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9046322&hvtargid=pla-561848290946




Notice edits to my previous post 

[Terry]

Your ESC is not Lipo safe, so stated on M-troniks website.

[Taranis]

Your ESC is not Lipo safe, so stated on M-troniks website.

I agree but for what reason? 2s fully charged will not exceed 12 volts so I can only assume it is due to no low voltage alarm?

[red181]

I seem to remember the mtroniks esc needs to be a "tio" which can be changed from lipo to nimh. Hobby king sell very cheap lipo friendly esc's just remember, most art for planes, so no reverse function, you will need to look for that. They do have a range of boat specific escs that are water cooled


Given your model will not require speed, or rapid discharge, I would probably stay with the nimhs

[Taranis]

https://www.mtroniks.net/prod/Boat-Speed-Controls/tio-Marine-15.htm


This device has auto LiPo cut off which will protect the battery.
Using the alarm I posted earlier should overcome this with the other ESC

[Taranis]

I seem to remember the mtroniks esc needs to be a "tio" which can be changed from lipo to nimh. Hobby king sell very cheap lipo friendly esc's just remember, most art for planes, so no reverse function, you will need to look for that. They do have a range of boat specific escs that are water cooled


Given your model will not require speed, or rapid discharge, I would probably stay with the nimhs

The OP issue is weight rather than performance

[coch y bonddu]

Also have a look at  Component shop website for Lipo's Speed controller and motors and obviously chargers and a personal service as well


Dave

[Andyn]

I agree but for what reason? 2s fully charged will not exceed 12 volts so I can only assume it is due to no low voltage alarm?

A fully charged 3s lipo is 12.6 volts.

[Taranis]

A fully charged 3s lipo is 12.6 volts.

A fully charged 12 volt lead acid is 14.4


The LiPo safe issue is the low voltage per cell cut off. One ESC has this the other does not.


Discharging a Lipo cell below 3 volts per cell will cause damage to the battery not the ESC

[Andyn]

A fully charged 12 volt lead acid is 14.4

   yes, but a fully charged 3s lipo is still over 12 volts




Another thing to factor in when considering your lipo purchase not mentioned previously is C rating - the multiplier of how much current a battery can give in relation to it's own capacity. An example being that a 1000mah lipo at 10C will give you a max discharge of 10 amps. Also, generally speaking a higher C rated battery will be larger that an equivalent capacity, lower c battery.

[Taranis]

 yes, but a fully charged 3s lipo is still over 12 volts
 



Another thing to factor in when considering your lipo purchase not mentioned previously is C rating - the multiplier of how much current a battery can give in relation to it's own capacity. An example being that a 1000mah lipo at 10C will give you a max discharge of 10 amps. Also, generally speaking a higher C rated battery will be larger that an equivalent capacity, lower c battery.

That is still less than 14.4 and I recommended 2s to replace the 7.4volt Nimh
C rating is not really relevant with such a small brushed motor

[Andyn]

Unsure how 14.4 came into this?


Like I say, higher C batteries are generally larger, so it may pay to look for a lower c battery to save weight whilst maintaining capacity, as long as max current draws are observed.

[Taranis]

Unsure how 14.4 came into this?


Like I say, higher C batteries are generally larger, so it may pay to look for a lower c battery to save weight whilst maintaining capacity, as long as max current draws are observed.

Sorry but I thought you were implying that a fully charged 3s battery voltage was too high
The ESC is suitable for 12 volt lead acid that will be 14.4 end of charge so a 3s will be less


However the original battery is nowhere near 12 volts so not an issue


This was my recommendation
https://hobbyking.com/en_us/turnigy-3300mah-2s-30c-lipo-pack-xt-60.html


Specs:
Minimum Capacity: 3300mAhConfiguration: 2S1P / 7.4v / 2CellConstant Discharge: 30CPeak Discharge (10sec): 40CPack Weight: 204gPack Size: 134 x 43 x 15mmCharge Plug: JST-XHDischarge plug: XT60

[chas]

It's worth noting that 2 MFA 360 motors will only be drawing circa 1.5 amps. So a small ah lipo, which will also be very light will give a lot of time on the water. The standard viper is fine, with a low voltage warning to protect the batteries.
 In such a small craft I would use 2 s lipo. No need to worry about higher voltages, it's not a high performance model.
Lovely build, I would be proud of that.
 

[cos918]

Hi
In my ferry I use both a 2s and a 3s lipo . I have standered mtronics esc and they are fine. It just the low voltage you need to watch out for. Like other have post get a cheap little low voltage alarm and plug that in to your lipo when you sail.
Best place for lipos with the best prices and selection by far is hobby king.There turnegy brand is very good Not when ordering from HK make SURE you select your goods only from the UK or EU warehouse . If you dont shipping is more and there could be import tax.
Finnal note. I know you said you have a charger. Just make sure its a good one and not a fake .

John

[malcolmfrary]

While agreeing with everything that has been said about LiPo batteries, in a case like this a set of NiMH AAA cells of around 2000-2500 mAH of the wanted voltage will do a very adequate job.  Should weigh a lot less that the sub-C cells shown.  Just sayin'.

[ojays]

WOW, never expected such a response.
Thanks for all the input, given me some food for thought.

I hadn't realised just how heavy it would end up, but as I hadn't followed the plans and
instructions I should have know it would end very low in the water. Too low for my liking.

I know it will be a fair weather sailer, but have others in the pipe line for normal
days.

Thanks for the positive comments on the build, it has been one of the most pleasant
projects I have done in a long time.
I have enjoyed it much more than just assembling/converting plastic kits, which is my norm.

[ojays]

While agreeing with everything that has been said about LiPo batteries, in a case like this a set of NiMH AAA cells of around 2000-2500 mAH of the wanted voltage will do a very adequate job.  Should weigh a lot less that the sub-C cells shown.  Just sayin'.

I have been using this charger for years, and has been loaned to a friend for his lipo's with no problem.

[Taranis]

110 grams/ less than 4 ounce but less capacity
https://hobbyking.com/en_us/turnigy-1800mah-2s-20c-lipo-pack.html

[JimG]

While agreeing with everything that has been said about LiPo batteries, in a case like this a set of NiMH AAA cells of around 2000-2500 mAH of the wanted voltage will do a very adequate job.  Should weigh a lot less that the sub-C cells shown.  Just sayin'.

High capacity AAA NiMh cells are a poor choice to provide power to motors. They have a high internal resistance so are incapable of providing higher currents without a high voltage drop. They are designed to power electronics with a low current draw.

Jim