mah formula?

[melonballer]

I was wondering why for example in Q hydro class, most are using two 6s 5000 mah packs.
How many mah is sufficient for a 6 lap heat race plus maybe 2 practice laps, without pulling the battery down too far?
I just want to keep the weight down as much as possible without hurting the batteries.
This is just one of many "moving from gas electric questions".

[drwayne]

Q hydro has a 10,000mAh ceiling

5000mAh is 5i amps per hour...or 10A for 30 mins .. or 100A for 3min
The C rating of a battery identifies how hard you can draw current.
eg at 30C battery allows you to draw 30C x 5000mAh = 150A continuous
From 30C5000mAh pack equates to 150A for 2 mins

if you want/need more time/amps.. add another battery to increase amp availability, runtime., or both !.

W

[Fluid]

The OP brings up a good point about transitioning from fuel to FE. Fuel guys spend a lot of time worrying about weight, since total boat weight can have a major influence on performance (acceleration and stop speed). Their engines take time to climb onto the torque curve and lower weight helps with acceleration.

The situation is different with FE. We have maximum torque available immediately. A few ounces of extra weight is invisible for most uses. In many instances extra weight is helpfull:
- racing in rough water it helps the boat to stay level on on the water.
- racing with 'standard fuel'-designed hulls means the extra speed from FE power makes them flighty; more weight helps keep them on the water. I add a pound of lead to several of my P Monos to keep them on the water. Better to add weight in hull strength or in more pack capacity if practical.
- when running into the wind extra weight can mean the difference between bloing off and finishing at WOT.

Depending on the hull, an extra pound or two can be beneficial. FE racers who compete against gas boats see a real advantage with the higher weight in race water. Speed is not diminished and acceleration is not hurt much by the weight. Race reliability is usually helped.

With hulls specially designed for FE speeds, and when running on smooth water or by yourself (2-lap records) then low weight can be an advantage. Just realize that weight can be a friend too.