Parallel to Series: "Ultra Capacitor" Turbo?
- Thread starter safe
- Start date
Safe i said it before, the capacitance is not the energy. the energy is 1/2CV^2. The total energy stored will not change. The loss in energy will depend on external factors, the biggest i imagine would be the ESR of the capacitor. ESR is the electrical resistance of the capacitor, and depending on the capacitors it can be very bad the maxwell capacitors i found would be ideal for this application, i didnt price them but im pretty sure they are obscenely expensive.
Fechter i think your talking about a charge pump of sorts when you say using fets and switching at high speed. Safe wants to just charge once and drop the whole load across the motor, i dont see any high speed switching going on.
Joe
Fechter i think your talking about a charge pump of sorts when you say using fets and switching at high speed. Safe wants to just charge once and drop the whole load across the motor, i dont see any high speed switching going on.
Joe
safe
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Maybe this might describe what I "think" might happen... (correct me if I've gone astray)
When charging the capacitors in parallel the ability of the capacitors is good and a large amount of energy will be retained. Parallel charging INCREASES the capacity of the capacitors... it increases it's "capacitance".
When the capacitors are switched with relays so that they are now in series this does NOT cause a problem since the total energy absorbed into the capacitors has already been achieved.
The final energy output is pretty much what we would want which would be the entire energy put into the capacitors being extracted at a rate equal to the combined voltage of all the capacitors in series (high voltage) and at a current that would be limited only by the motors natural laws.
So this idea "works"... and all you need is:
1. A bunch of capacitors.
2. A bunch of relays.
3. A push button and a little bit of wiring know-how.
Extra Credit goes to anyone willing to actually draw the diagram for this...
When charging the capacitors in parallel the ability of the capacitors is good and a large amount of energy will be retained. Parallel charging INCREASES the capacity of the capacitors... it increases it's "capacitance".
When the capacitors are switched with relays so that they are now in series this does NOT cause a problem since the total energy absorbed into the capacitors has already been achieved.
The final energy output is pretty much what we would want which would be the entire energy put into the capacitors being extracted at a rate equal to the combined voltage of all the capacitors in series (high voltage) and at a current that would be limited only by the motors natural laws.
So this idea "works"... and all you need is:1. A bunch of capacitors.
2. A bunch of relays.
3. A push button and a little bit of wiring know-how.
Extra Credit goes to anyone willing to actually draw the diagram for this...
Lessss
1 MW
Hmm. Another idea for hill climbing is not increasing to the voltage, but discharge the capacitors to suppliment the batteries so they aren't hit as hard on the climb.
Yes you have the idea. The capacitors in this situation would hold the same amount of energy in series or parallel. Think of capacitance as a resistance to a change in voltage when a current is applied. When the capacitors are mounted in series the rate of change of voltage is doubled(thus half the capacitance) but the total voltage is doubled so the energy is the same.
If i were you i would use a charge pump or boost converter to charge a capacitor bank already in series. This would be smaller and more humane on the relays than directly connecting a half charged capacitor directly to a battery. At the very least its less relays to change as directly connecting the capacitor to change as directly connecting the fully charged capacitors to a motor is no better.
Joe
If i were you i would use a charge pump or boost converter to charge a capacitor bank already in series. This would be smaller and more humane on the relays than directly connecting a half charged capacitor directly to a battery. At the very least its less relays to change as directly connecting the capacitor to change as directly connecting the fully charged capacitors to a motor is no better.
Joe
I seem to remember something about if you have a large voltage difference between a capacitor and a load, there's a big loss that happens when you switch. At the very least it will tend to weld relay contacts.
I'll try to check on that.
With a charge pump, you keep the voltage difference small, so they can operate at very high efficiencies.
Also keep in mind that a capacitor that can store the same amount of energy as a 12v 12Ahr battery would be about the size of a microwave oven (maybe bigger) and cost more than everything else put together.
A more reasonable sized cap, like the ones they use for car stereo amps, would give you a boost that would last for several seconds.
I'll try to check on that.
With a charge pump, you keep the voltage difference small, so they can operate at very high efficiencies.
Also keep in mind that a capacitor that can store the same amount of energy as a 12v 12Ahr battery would be about the size of a microwave oven (maybe bigger) and cost more than everything else put together.
A more reasonable sized cap, like the ones they use for car stereo amps, would give you a boost that would last for several seconds.
It seems to me it may help to break down the task into two smaller pieces. (At least 4 my simple mind it will). :?
1. A switch network that will rearrange the grouping of individual two terminal bi-polar devices from a serial chain to a set of shunts.
B. Implement a capacitor bank to serve as a turbo boost pack.
Switch Network
If you really prefer a hardwire solution, then it doesn't matter if you're talking about caps, batteries, leds or whatever. Figure out a mechanical switch arrangement using batteries first. The electrical characteristics of supercaps actually function more like batteries rather than conventional capacitors anyway.
Essentially this identical requirement was posed a while ago on PA by someone who wanted a simple way of switching 3 SLA from their 36V series connection when in use discharging, to 12V in parallel for the purpose of charging. Reason being (obviously) he only had a single 12V charger & was tired of constantly pulling wires on & off as well as save wear & tear on the wiring. I believe the concensus of the brain trust was that it's simpler & cheaper to buy a couple more chargers. But if you figure it out, I'm sure there are numerous tightwads that will be grateful.
Supercap Turbo Pack
Supercaps have been demonstrated on several prototype electric cars, so the idea seems to have merit. However for motive applications I have basically written it off as pie-in-the-sky for my purposes. Primarily due to the price & that I can't get ahold of the very large sizes in small quantity. By way of example, the largest size I can readily lay my mitts on is from DigiKey. Which ones did you have in mind?
50F aerogel, 2.5V, 25 mohm ESR. Dia. 18.5mm, length 42mm (4/5A size)
Unit cost $23.80, $1660.00 hundred lot.
http://www.digikey.com/scripts/DkSe...earch?vendor=283&mpart=B1840-2R5506-R&site=US
Additionally they fry rather quickly with slight overvoltage & do not have a flat discharge curve, but those problems can be dealt with the proper circuitry. So I would have to be strongly convinced, why bother with caps, what's the benefit? I would agree that the A123 gives you way more bang for the buck & has cut them out of contention. At least until their price comes down, which I would expect at some point because there's really not much to them.
1. A switch network that will rearrange the grouping of individual two terminal bi-polar devices from a serial chain to a set of shunts.
B. Implement a capacitor bank to serve as a turbo boost pack.
Switch NetworkIf you really prefer a hardwire solution, then it doesn't matter if you're talking about caps, batteries, leds or whatever. Figure out a mechanical switch arrangement using batteries first. The electrical characteristics of supercaps actually function more like batteries rather than conventional capacitors anyway.
Essentially this identical requirement was posed a while ago on PA by someone who wanted a simple way of switching 3 SLA from their 36V series connection when in use discharging, to 12V in parallel for the purpose of charging. Reason being (obviously) he only had a single 12V charger & was tired of constantly pulling wires on & off as well as save wear & tear on the wiring. I believe the concensus of the brain trust was that it's simpler & cheaper to buy a couple more chargers. But if you figure it out, I'm sure there are numerous tightwads that will be grateful.
Supercap Turbo PackSupercaps have been demonstrated on several prototype electric cars, so the idea seems to have merit. However for motive applications I have basically written it off as pie-in-the-sky for my purposes. Primarily due to the price & that I can't get ahold of the very large sizes in small quantity. By way of example, the largest size I can readily lay my mitts on is from DigiKey. Which ones did you have in mind?
50F aerogel, 2.5V, 25 mohm ESR. Dia. 18.5mm, length 42mm (4/5A size)
Unit cost $23.80, $1660.00 hundred lot.
http://www.digikey.com/scripts/DkSe...earch?vendor=283&mpart=B1840-2R5506-R&site=US
Additionally they fry rather quickly with slight overvoltage & do not have a flat discharge curve, but those problems can be dealt with the proper circuitry. So I would have to be strongly convinced, why bother with caps, what's the benefit? I would agree that the A123 gives you way more bang for the buck & has cut them out of contention. At least until their price comes down, which I would expect at some point because there's really not much to them.
Matt Gruber
1 MW
my mbike has this capability already.
it has mounts for 6 sla. i would just run 2 parallel 36v packs, then switch to series 72v in turbo.
http://community.webtv.net/MATTGRU/turbo
it has mounts for 6 sla. i would just run 2 parallel 36v packs, then switch to series 72v in turbo.
http://community.webtv.net/MATTGRU/turbo
safe
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Leeps said:
Very good then!So all you really need is to have a few big ultra capacitors in series and allow whatever "surplus" energy that the motor doesn't demand while in use to flow into them. When they get charged up completely you then can press the button and "somehow" you wire it so that it bypasses the "regular" wiring and goes directly to the motor.
The extra voltage means HIGHER RPMS. This is more important than amps because we really don't want to blow up the motor, but we do want to get it to "over rev" for a brief time. This way you can have a 20 mph machine most of the time and then on occasion that machine can go 40 mph or above. (in a sudden surge)
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