Model Boat Mayhem
Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: RAAArtyGunner on April 17, 2015, 07:54:23 am
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As per the TV show why is it so?
Can anyone explain what does this mean?
Have read on other threads that using an ESC that cannot handle the load, amps, will result in destruction of the ESC and also may damage the wiring.
This applies irrespective of battery capacity.
As long as the batteries are the same voltage, an increase in Amp hours, capacity, gives a longer run time.
That being the case why/how might a higher capacity battery, over 3600mAh as in the photo notice cause damage to the ESC.
Whilst this is on my Grandsons car the principle no doubt would also apply to boats.
I am missing something?
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High-capacity batteries are usually capable of supplying larger currents than lower-capacity ones of the same voltage. Typically a 3700mAH 6-cell Sub-C NiMH pack can deliver up to 35A whereas the same manufacturer's 4600mAH pack will deliver up to 50A. (Source: Component Shop).
This ESC is rated to handle only the maximum current which could be delivered by a 3600mAH NiMH pack - any more would damage it (usually fatally).
OK? 8)
DM
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Or in less words: Prospective short circuit current. :-)
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"Fewer" words, surely?
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With economic word use,:
Volts x amps = power = heat
Same volts x more amps = more power = more heat = magic smoke escapes.
Same applies with more volts x same amps
I think!
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Two Three possibilities -
i) In its intended use, the ESC might only last so long handling the max current continuously, a higher capacity battery might cause heat to build up for longer and take the temperature too high.
ii) Whoever wrote the label didn't know the difference between "capacity" and "voltage"
iii) With the battery technology available at the time of writing the label, higher capacity same size cells might have gone past the sweet spot, and not be able to deliver the required current, or sustain voltage at the required current.
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"Fewer" words, surely?
You are probably correct :embarrassed:
I'm sure it was discussed not long ago in this thread on another forum
http://hummy.tv/forum/threads/assume-v-presume.1453/
But it's currently 96pp long so I'm not going looking :-)
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Plague
Easy enough rule, m'duck:
If it's a smaller number of things which you can count e.g. words, people, widgets, then it's "fewer".
If it's a lesser amount or degree of something which doesn't come in discrete units e.g. noise, custard, pain, intelligence, then it's "less".
Confusion can arise with things which are generally referred to by their units of measurement. For example, it's correct to say less voltage but it's fewer volts. Isn't English complicated? It's no wonder that fewer of our children bother to learn how to write or speak it correctly.
BTW Stephen Fry regularly pulls up the panel on QI for this grammatical error, but then he is a pedantic old sausage. ;D
DM
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Thank you for the comments.
So the gist of it is that unless the ESC has a very high rating with capacity to spare, increasing battery capacity might fry the ESC.
Motor stays hot longer, has more current through it, and point is reached when it all falls apart and You wonder why because the ESC was slightly oversized but not enough.
So there is a cut of point, particularly when you can get 7.2V, 5000mAh packs.
So in this situation would fuses still be an effective preventative.
The Car is made in China what isn't, and I suspect the notice is Chinese English.
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At least the manufacturers are not only aware of the possibility but have actually printed a warning. This is virtually unheard of in products from ROC. If you're dead set on using 4600 or 5000mAH packs then why not just change the speed controller for a higher-rated one? Fuses are fitted primarily to save equipment from catching fire, not as current limiters.
Dave M
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Thank you all, :-)) :-)) O0 O0
The warning is also printed a couple of times on the carton, the one in the photo is in the battery compartment
It comes complete with1800 mAh battery pack and 2.4 Radio, so is ready to run but I will get him a 3600mAh pack so it 'drives' a little longer and he will have a spare battery on charge.
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Pardon me but I think you are going in the wrong direction. The battery is the source of energy (volts x amps = watts type of energy). It only puts out as much energy as the loads demand. Certainly the voltage needs to match what the ESC is designed for. But it is the motor (or other electrical loads) that determine how much energy is drawn through the wiring and ESC. If you exceed the rated amperage of the ESC (or the motor) things will heat up and perhaps fail. In other words, if you have a 15 amp ESC and you run a 30 amp motor on it, at high speeds the ESC will be greatly overloaded.
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Thank you, will stick with the nominated battery as supplied. O0 O0
Need to go back and re read Dave's Electrics treatise so it sinks in deeper.
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Pardon me but I think you are going in the wrong direction. The battery is the source of energy (volts x amps = watts type of energy). It only puts out as much energy as the loads demand. Certainly the voltage needs to match what the ESC is designed for.
True for most of the time and I personally think that point ii in reply #5 is likely the truth.
However, many ESCs have overload protection built in which means they may be called on to act as a fuse/circuit breaker. If the overload is a short circuit (on the output side of course) then the prospective short circuit current that the battery can supply could overwhelm the device (just as it can on a 'full-size' power system if the protection is not rated correctly).
So, although I'm doubtful that a model ESC manufacturer is really concerned about such finesse, technically that label could be correct in saying "capacity".
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The battery is only(!) the source of energy, but the rest of the system, worked to its max, might need a rest once in a while. Stopping and removing the lid to replace the battery might allow for a required bit of cooling off. Or not.
In the past, there was a generation of speed controls in the early days of ESCs that were designed, using the components then available, to be right on the limit thermally (Hitec gold brick?). Running too long at the limit was bad for them. The label could have been designed using received wisdom from back then.