battery question
Collapse
X
-
Agreed. 100A average is about it for that connector. I have peak draws (prop cav recovery) about 135A, data logger shows I'm not sagging too badly on volts during that time. But the peaks only last 0.5-0.8 seconds. I expect the caps are supplying much of that peak, fast draw. That's why we put them on, right?!Comment
-
I got the impression from other theads that you knew a lot about electrics. That is just the marketing guff car ESC sellers spin.
The caps are there to flatten out the ripple in the input voltage caused by inductance one the input side, in order to reduce temperature on the ESCs internal components.Last edited by NativePaul; 08-30-2017, 03:41 PM.Paul Upton-Taylor, Greased Weasel Racing.Comment
-
I got the impression from other theads that you knew a lot about electrics. That is just the marketing guff car ESC sellers spin.
The caps are there to flatten out the ripple in the input voltage caused by inductance one the input side, in order to reduce temperature on the ESCs internal components.
The capacitance offsets this by supplying current according to the formula: Di =C*Dv/Dt, where C is the total capacitance at the ESC and any added caps, as long as the wire runs from said caps is less than 0.5". Dv is the magnitude of voltage change, as calculated above. Dt is the same time frame of the leading edge, 2-4uS. So, for a volt change of 0.25V in 3uS (mid-point), a capacitor bank of 10,000uF will give up 833A. Now, we don't see that in real life, because of a undesirable property in all capacitors called ESR (Equivalent Series Resistance). This is what is meant by the term used here a lot, "Low ESR" capacitors. But even the lowest ESR caps available isn't actually good enough for FE boats, that have huge current magnitudes. At best, you're going to get only 40% of calculated value (sucks, yes?), leaving us with a real life amperage of 333A.
It's actually even more complicated than this, since this is only a first order of equations evaluation. But it's pretty close. These are calculus formulas that express outcomes over units of time. These equations show why poor quality connectors, caps, wire and solder joints kill your power to the motor and create lots of heat.
That's what I know about electronics....Comment
-
I do have quite a bit of electrical experience. Just applying it to a very specific situation. Also just getting into Brushless and LIPO batteries.
That is why I ask about my issues. Verify what I am thinking before I alter something incorrectly, wasting time and materials.
The Cap bank takes the spike in current draw from sudden changes in load. Yes we are all talking about the same thing. Ripple is a term used I think for a much more subtle change in voltage and current. output oscillation from a car alternator is a good example.
These are far larger changes in current resistance, and voltage throughput.Comment
-
I prefer Ripple Blackberry to Ripple Current
And this too :
2008 NAMBA P-Mono & P-Offshore Nat'l 2-Lap Record Holder; '15 P-Cat, P-Ltd Cat 2-Lap
2009/2010 NAMBA P-Sport Hydro Nat'l 2-Lap Record Holder, '13 SCSTA P-Ltd Cat High Points
'11 NAMBA [P-Ltd] : Mono, Offshore, OPC, Sport Hydro; '06 LSO, '12,'13,'14 P Ltd Cat /MonoComment
-
I do have quite a bit of electrical experience. Just applying it to a very specific situation. Also just getting into Brushless and LIPO batteries.
That is why I ask about my issues. Verify what I am thinking before I alter something incorrectly, wasting time and materials.
The Cap bank takes the spike in current draw from sudden changes in load. Yes we are all talking about the same thing. Ripple is a term used I think for a much more subtle change in voltage and current. output oscillation from a car alternator is a good example.
These are far larger changes in current resistance, and voltage throughput.Comment
-
ERROR 403 - This is not the page you are looking for
Comment
-
Agreed. 100A average is about it for that connector. I have peak draws (prop cav recovery) about 135A, data logger shows I'm not sagging too badly on volts during that time. But the peaks only last 0.5-0.8 seconds. I expect the caps are supplying much of that peak, fast draw. That's why we put them on, right?!
If your peaks were 135A, and you had 1F of capacitance for example, assuming the lower peak time of 0.5 seconds you said for easy maths and best case scenario , the capacitor would supply under 2% of that energy, not what I would call much of itPaul Upton-Taylor, Greased Weasel Racing.Comment
Comment