battery question

[iop65]

My buddy runs the blue 80c dynamite hardcase's in a v2 geico. He beats the crap out of it for atleast 5-7 minute run's and nothing comes back over 130* F but he's running a 1570kv TP4050. Maybe your strut is set a little to deep? I have video of it running if you want to see. I'd definitely ditch the hardcase with the small 4mm leads. I got rid of my hardcase's after one did this lol although I was over propped a little they still hold in heat

[ATTACH=CONFIG]153547[/ATTACH]

A 1570kv....probably running more then 4s so amps drop

[iop65]

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?!

No those caps have a different purpose!

[CraigP]

Tell us what they are for?

[Drkrieger]

No those caps have a different purpose!

I was under the impression they were there for that exact reason.

[Prodrvr]

Caps stop voltage ripple from the battery to the esc. Voltage ripple kills esc's .

[Mxkid261]

what cell count is he running?

4s, and he also run's it on 6s sometimes

[NativePaul]

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.

[Mxkid261]

A 1570kv....probably running more then 4s so amps drop

Pretty much just a 4s boat. He throws 6s in it sometimes but mostly just two 2s in series.

[CraigP]

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 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.

We are all talking the same thing... Fast, High amp draws force wires (inductance) to drop voltage. A "drop" in voltage is the same as ripple voltage when it's induced quickly. The capacitance in the circuit offsets the inductance voltage drop, thus stabilizing the voltage at the point of the applied capacitance. For those interested, voltage drop across wires just due to inductance (not taking resistance drop into account, which is going to cause a higher magnitude ripple voltage) is expressed as: Dv = Di*L/Dt. Delta time is in the order of 2-4uS for the leading edge of the current surge. L is calculated as 0.1nH*Xin of wire, to a close approximation. Di is the current change that for me, is viewed in the ET data logger. The resistance drop is I*0.00025ohms/inch of 10 gauge wire, high strand count.

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....

[rol243]

wow craigP. you lost me when the letters Dv = Di*L/Dt started. now what do you know about electronics ., say no more.

[Drkrieger]

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.

[properchopper]

I prefer Ripple Blackberry to Ripple Current

And this too :

https://www.youtube.com/watch?v=4xgx4k83zzc

[CraigP]

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.

Your right in thinking. But I can't express enough how much current these things use and how small of parasitic inductance (wire loss) can cause such damage to these electrical systems. General rules: use as big of wire and connectors as you can when running over 150A. Keep wire runs SHORT, high priority! Get cap banks as absolutely close to the the ESC that you can. Make not good solder joints, but great ones. Most of these boat to boat problems brought up on the sight are probably due to a short coming or two in the things listed above. It's hard to nail a definitive reason without detailed pics and info on components used. These ESC's can take some over current, but will not tolerate any overvoltage excursions, AT ALL!

[Fluid]

Enjoy:

https://forums.offshoreelectrics.com...ghlight=Answer


.

[NativePaul]

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?!

Honestly what you wrote with the formulas is beyond me, I only know the basics. One of the basics I know is that one Farad of capacitance holds roughly one amp second of energy.
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 it