How many MAH packs for "p" mono

[T.S.Davis]

High flow in piping makes more pressure loss due to friction. Same thing with amperage. The higher the amps the more loss of voltage.

It is a difficult thing to get the brain around.

[CraigP]

You got that right! I know plenty of people with BSEE’s that don’t have a clue how a battery really works...

[CHowarth]

Thank you both. It's all new to me and most likely way beyond where I need to be right now, but I like understanding what's happening. I'll quietly try to follow along!

[CraigP]

We don’t want to squelch your questions! One of the base goals of this site is to support new interest. It’s a difficult thing, and we wouldn’t know if you don’t chime in. I welcome your comments 100%!

[NativePaul]

I will beg to differ on the C rate being maximum current at which point battery has the ability to maintain 3.7V. / Cell under load.

It is the maximum current that the battery can maintain for a full discharge cycle without heating up past 62c where the battery is likely to puff. It can be argued whether a full discharge is to 0%, to the rated capacity, or to 20%, and whether the puffing point is 60, 62, or 65degrees C, but that is essentially it.

While the C rate in the current crop of good cells at the moment may well coincide with a 3.7V/cell output somewhere during its discharge curve, that is a temporary thing. When LiPos first came out they were 4C and you could only expect an average of about 2.8V/cell during the discharge at that 4C and it would only be over 3.7v/cell for a second or so. As the cells have improved that voltage had risen and each generation of high C cells is capable of holding a voltage under load closer to the resting voltage than the previous generation. Extrapolating consistent past improvements into the future the next generation of cells should average a higher voltage per cell.at maximum constant C rate/cell than current ones. Although there has already been huge improvements, and the biggest increases are generally when a technology is new, 3.7v/cell is about the resting voltage of a flat LiPo, so there is still plenty of room for improvement.

[T.S.Davis]

I like it Paul. That makes more sense to me than the 3.7v nominal. Discharge on a curve and the curves shape looks different at a higher C rating.

Thinking back, I remember someone telling me he felt that the cells would eventually lose zero voltage over the entire discharge. This would correspond to you explanation.

[NativePaul]

That is not what I am saying Terry. While I can't rule out the possibility that some future battery technology wont lose voltage over the discharge, I can say that LiPos always will, and as all previous battery technologies have done, and I find it hard to imagine that future ones won't.

The best I could hope for with technology based on our current understanding of science is a superconducting cell with zero IR, in which the voltage under any load would match the resting voltage. With lithium based chemistry it would still start off at 4.2v/cell and come off at 3.7v/cell, it would just maintain those voltages at any ampage you wanted to pull. There would still be a discharge curve, it would just look the same at 1mA as it would at 1000A.

[fred685]

Ok. That's a bunch of info. Next question is "P" limited? Will 5000 mah do in that class? Thanks to everybody for helping out the new guy.

[T.S.Davis]

No I follow Paul.

Might seem a strange analogy but a similar course has transpired with fire pumps. Available pressure drops on a curve based on gpm. As manufacturing improved so did the curves. Now you can get a pump that has very nearly a flat curve. Still a curve though. Eventually when you exceed the design points the curve gets steeper.

[T.S.Davis]

Fred, limited depends on the class. 5k can get it done. Again, propped accordingly. Not great in offshore. It still could work for offshore but you have to prop accordingly. I like to use a pair of 2s6500's wired in series just because they fit in the boats well. Puts the weight low in the boat. Give me a little cushion too.

With the right setup you can get away with even less in limited hydro. Less will work in sport too but it has to be light on it's feet if you know what I'm saying. We've used a pair of 4s2200's in sport. Usually you need more weight though.

[JohnZ]

Those Giant Power packs look interesting. I just may spring for a couple to run in my 21" Oval Master. I had planned on using a 2S system but have decided to go 3S and 2950KV Leo 3650 motor. Using more volts is more efficient.
I also fly electric planes and discovered several years ago that using more cells and propping down is more efficient...also using a larger motor works wel but that;s for model planes not necessarily for boats.
I used one of those Fine design gearboxes in a 26" FD deep vee mono several years ago. Thought it worked quite well.
Up where I live in Northern Michigan, there are no RC boat clubs that I know of so I just burn around the lake.

[hispeed10k]

Hi all!!!

I am new to fast electrics, but not new to racing. Really loving my new Promarine Skater X2 This is a very interesting thread for me as i was wondering how the motors/esc's work as far as power ratings go(don't know if i'm saying this correctly) So for eg i know that with my gas boats once i have a high revving motor, a smaller higher pitched prop will get me in and out of the corners quickly, and gives me enough speed down the straights. This battery discussion is interesting as i am wondering the same thing as far as power/battery life/ for a six lap race!!

[Mad Hatter]

I was going to ask a seemingly stupid question as to which is better 1 4s or 2 2s. I must have had too many beers. Please forgive me, it's my birthday. More packs = more amps. It's that simple.

[rearwheelin]

I was going to ask a seemingly stupid question as to which is better 1 4s or 2 2s. I must have had too many beers. Please forgive me, it's my birthday. More packs = more amps. It's that simple.

I’m glad not to be the only one who drinks then gets on forums

I believe it’s the same difference 2x2s=4s 1p and the C rating stays the same as a single 4s pack of same spec cells.

[don ferrette]

I’m glad not to be the only one who drinks then gets on forums

I believe it’s the same difference 2x2s=4s 1p and the C rating stays the same as a single 4s pack of same spec cells.

One thing to consider is battery placement. In some cases two 2S packs work better than one single 4S pack.........