Lipo pack question for an FE novice

[Tim_Duggan]

Humor me if you will.

I'm playing a little with P spec O/B tunnels to learn these FE things without releasing expensive smoke. SO far so good and am at the point where I'm tweaking props a little more to suit the handling of the boat. (42x55, back-cut and slightly tip cupped). I'm finding that after our race distance my pack's cell voltages are in the range of 3.80 - 3.90v per cell, & generally pretty well matched cell vs cell.

Now for my question! What is the safe lower voltage limit on the packs I should consider is the point where I'm close to asking too much, or am I close to it now? Cells and Motor are not getting hot, just warm - enough to comfortably hold on to. Packs are 5000mAh 4S nano-techs BTW.

I know I could use an external logger to the T120 ESC but that would add steps to my processes and I'm lazy, plus the handling of this boat is very sensitive to minute changes to CG and weight! I already check my cell voltages after each run as a matter of course. If I'm close to a safe limit now, I'll go looking in other areas rather than continued efforts to refine the prop more.

Thanks in advance,

Tim

 

[Chilli]

Personally I try to finish a heat with 3.8 or more and don't like to go below 3.7 volts per cell. The more you run your cell down, the hotter they will get which will reduce their life span. The logger us a useful tool but more so if you are pushing the limits of your equipment which it doesn't seem like you are doing. What C rating is your Nano's?.

When your packs start getting tired, invest in a good quality pack such as a Hyperon or Dinogy. You'll notice the difference though fresh Nano-Techs perform pretty well.

 

[Tim_Duggan]

Thanks Mike,

They are advertised as 45-90 C rating 5000mAh packs, but am conscious that you get what you pay for with such things. Just didn't see the point in burning up good stuff whilst still learning and setting up a new boat.

Seems I don't have a huge amount of margin left before getting too low - voltage wise - on the Nano's.The packs I have probably have about 20 cycles on them so far. I do need to buy a few more packs as getting by with only 2 is not so fun, so will invest in better ones soon.

This hull is super sensitive to prop lift in the turns, and tip cupping to kill the lift has worked very well so far to make it a better behaved boat so I'm glad to hear I'm still on the safe side with my current packs (pardon the pun!).

Tim

 

[Kris Flynn]

Hello Tim, answer from Australia here.

Just checked my pack from the last heat and the cells are all around 3.84v according to checker thingo

I went hard for the "warm down" lap also, pretty sure you slowed right down? Meaning I might have uses more mAh...

 

[Kris Flynn]

Yeah I would say you do considering how much we could pull away from your boat....just think, if your boat was faster it would have been in front of my boat in Yarra so when it hooked you wouldnt have hit me! Bloody hell....

 

[Tim_Duggan]

Hello Tim, answer from Australia here.

PMSL!

 

[Kris Flynn]

Not particularly Greg

 

[Greg Moss]

Answer/ comment from Canberra, some would say not a real part of Australia!

I don't check the pack voltage after races, but I typically have to recharge 3100 to 3200 mAh.

One of these days when I get some local water to run on again, I'm going to work out what prop I can pull and use the rest of the pack to the cutoff, nearly

 

[Kris Flynn]

Only 3200 = heaps of room for improvement

 

[Greg Moss]

Agreed...

Now that I've got pretty good handling, need more speed!

 

[SeanKewley]

A resting voltage of 3.7v per cell after a two minute heat race is my limit. At 3.7 per cell the pack is depleted.