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[goBulawayo]

Hi all, having tried a number of options, it seems that the type of battery is my issue here. I ran my Perkasa on lipos before but recently bought a NIMH battery for the boat. Every time I try it in the water, it cuts out around half throttle. NIMH is 14.4v. When I put back a LIPO (7.2v but boat ran on 11.1 and 14.* LIPO before) no problem. Had the issue on two boats, both with different speed controllers. (photos of speed controllers to follow) running two motors in the perkasa but only one in the Acadamy F1 boat. motors run fine all the way up when out of the water, only cutting when in the water - Most of the time when the motors cut, rudder still works fine

Any thoughts what the issue might be please.

Thanks Wayne

https://photos.app.goo.gl/HREEKbmcYCGLrnLY9

https://photos.app.goo.gl/25B8aVzqWFd51HsGA

[Colin Bishop]

Your NiMH cells may be too low capacity and unable to deliver the power the motor needs beyond a certain amperage. LiPo cells have very high discharge rates.

Changing to higher capacity cells will add a lot of weight though.

Colin

[goBulawayo]

Hi Colin, by capacity is that referring to the MaH? The NIMH is 2600 - thanks

[Colin Bishop]

Yes a 2600 pack is 2.6amps.

There are others who can give you better advice as there could be a number of possibilities causing the problem. Presumably the boat is fitted with a brushless motor and matching ESC. It could be the case that the motor current consumption is causing a voltage drop to the NiMH battery and the ESC voltage monitoring safety function intended to protect LiPos is cutting in.

 It would be helpful if you could give details of the motor, prop size and the speed controller you are using.

Also, how big is the boat, is it a kit?

[ChrisF]

Agree with Colin's comments here. What was the MAh of the LiPos you were using? 2600 is quite low for a fast boat, especially with two motors, I usually aim for at least 4000.

Have you programmed the ESC so that there is no cut-off voltage?


Chris

[goBulawayo]

HI Chris, not done any programming to either ESC, two different ESCs in two different models as per the photos in post one - No idea on what motors are fitted, will photograph them tomorrow and the props - Lipos as 7.4v one is 1500MaH the other is 350MaH

[goBulawayo]

Also, how big is the boat, is it a kit?

Hi Colin, Perkasa (2 motors) and Academy F1 boat (1 motor) as per original post - I will get pics of them posted as I have no idea what motors are fitted

[Tug Fanatic]

The 2600mh batteries that I commonly see are AA size. AA batteries are designed for low current draw anything over say 3 amps is likely to generate your problem.

Are these what you have?

[Andyn]

Just my 2p - why would you want to run a nimh when you already know a lipo works with your setup, gives better power, likely better duration and a longer lifespan?

[goBulawayo]

Just my 2p - why would you want to run a nimh when you already know a lipo works with your setup, gives better power, likely better duration and a longer lifespan?

Safer battery

[goBulawayo]

The 2600mh batteries that I commonly see are AA size. AA batteries are designed for low current draw anything over say 3 amps is likely to generate your problem.

Are these what you have?

Hi, a pack made up of AA size batteries yes, thanks

[Andyn]

Safer battery

A very common misconception 

[captain_reg]

Yeah I wouldn't expect the AA sized NiMH packs to give you the current you would need. Have a look at the 'Sub C' NiMH packs, I use these in all my boats, fast, slow, twin motor & brushless without issue. The datasheets say 30amp discharge current but I wouldn't push more than 25... ask me how I know

[goBulawayo]

Thanks Captain_Reg

[Tug Fanatic]

I suspected that they might be AA.

I agree with captain_reg that subC batteries would give the necessary ampage but beware their weight. There is a slight variation between manufacturers and capacities but think 65gms per cell. Your 14.4v pack consists of 12 cells which would weigh around 780gms or 27ozs. Weight is the enemy of a planing hull whch is a good reason to stick with Li-Po where the weight would be little more than half NiMh.

[goBulawayo]

thanks all