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[jaymac]

Hope to give  my PT596 a quick test in the lake tomorow.Anyone care to hazard a guesstimate of a safe min runtime.  Its 3x motors possibly550's and an 8.4 3800ma Nimh I have a  35A fuse twixt Batts and esc and each motor  fused at 16
Bath trial of a  couple of miutes  seemed fine
I;m wildly  thinking
3.8= 1hour
7.6= 30mins
15.2 =15 mins
30.4 =7.5mins now as  the last 2  figures are close to fuse limit can I assume    she is not pulling more than that? which would give around 5+ mins max
 Or  am I way out on theory
 
 

[Tug-Kenny RIP]

I think you'll find three motors running on a three and a half amp battery will last about 8 minutes at most.

I ran a 500 motor through an ammeter and it took 7 amps under load.

Just a thought.


Ken

[NFMike]

Simplifying it a bit, battery efficiency drops as the discharge current rises, so the theory you show is wrong. If you get 60mins at 3.8A, then you'd probably get maybe 20-25m at 7.6A. However, battery capacities are usually given at something like the C10 rate, so the 3800mAh will likely be at 0.38A and you maight only get (say) 50mins (or less) at 3.8A.
You need to see the spec for the battery to get the correct figures, or Google up a generic NiMH spec which should be close enough.

[jaymac]

 Well the theory may be wrong but I just had her running for just over  20mins on the lake

[malcolmfrary]

The battery holds what it holds, if the boat runs longer than the initial theory says, then either the boat was not running flat out all the time, or it takes less current than originally thought.  Probably about 8A, give or take, which should leave the battery comfortably warm to hold on a cold day.

[jaymac]

appreciate that Malcolm my initial post was really to maybe get some Idea of the safest minimum time  likely running at varying speeds. After the first near disaster  did not want to get caught dead in the water after a couple of mins anyroad well pleased with her first proper run
Thanks  to all for their input