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[Patrick Henry]

In my Aquacraft Alligator airboat I have a 380 motor (it came already installed), I've installed a Planet 2.4Ghz radio, and an Mtroniks Viper 15 Marine esc (with 1.2a BEC) and a 5g micro servo for the air rudders. The esc blurb sheet says it's capable of 6v-12v input...at present it has a rather tired 6 cell 800a/h NiMh pack installed which runs everything.

Now...I have a couple of 11.1v 25C 850mAh LiPo packs left over from my heli, plus a balance charger.

So the question is : Can I use them as a direct replacement for the NiMh pack?


Rich

[Roadrunner]

Should do since the esc can handle up to 12v and the lipos are 11.1

[andrewh]

Rich

The answer is still yes, but and 11.1 v lipo is NOT 11.1 Volts
It is 11.1 volts only when it is half-discharged - a bit like a stopped clock

This must be a 3-cell pack, so fully charged it is about 12.6V depending on the actual cells
This should be absolutely fine with a 6-12V ESC

go for it
andrew

[Mankster]

What voltage is the motor rated at? May need to sort out some cooling at the increased voltage.

[nick_75au]

A 2 cell Li-po is equivalent to a 6 cell Ni-XX so running a 3 cell Li-Po is going to give a big increase in speed. The motor will draw higher amps, you will want to be careful the motor does not pull more amps than the Li-po's C rating which will be around 12-13 amps if its a 15 C lipo

Edit
Ok they are 25 C so you should be fine but the ESC might be pushed, I would seriously consider doing a load test with the motor connected to the battery through a watt meter first before committing the ESC to the system

A 2 cell Li-po will be a performance boost over the tired 8oo mAH Ni-Mh, I would consider this first.

Chers
Nick

[wibplus]

You could use a voltage regulator to bring the voltage down a bit,or................I have a couple of 2 cell lipos going spare for the cost of a donation to RNLI. 

[malcolmfrary]

A voltage regulator to handle the current required by the motor would either sink the boat or break the bank.  The two cell option looks favourite.

[Subculture]

Be careful running lipos with an mtroniks esc- they're not configured for use with these batteries. If you run the cells in the pack below 3 volts per cell, you will knacker them. That's not to say you can't use them, but time your runs, or quit running as soon as the boat is showing a drop off in speed.

Brushed controllers designed for use with lipo are thin on the ground, just about all brushless controllers are designed for use with lipo, and will soften or shut off the power once the voltage drops below a preset voltage (this is usually programmable for different pack configurations).
As you have two lipo packs the simple idea would be to trim each pack down to two cells and make up a third pack with the remaing cells. Question is, does your charger support baalnced charging of two cell packs? Running a speed 400 motor on 11.1 volts at any sort of load will give it a rather short life span.

[HS93 (RIP)]

buy one of these not chep but will pay for its self over and over again .

http://www.teamnovak.com/products/lipo_cutoff_module/index.html

Peter

[Subculture]

Cheapskate version- http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7224

[HS93 (RIP)]

Cheapskate version- http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7224

the difference is one just beeps to tell you your batteries are puffed up and one has a slow cut out to stop you doing any damage , I know what I would buy , the buzzer can be hard to hear across a lake with the whirling of a motor..even harder in subs

Peter

[barriew]

I bought one of the more intelligent ones from HK for about £6, but I can't find the site again! However, Astec sell one for £13.99 - http://www.astecmodels.co.uk/catalog/product_info.php?cPath=53&products_id=979

Barrie