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Old 24-06-2013, 17:03   #16
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Re: 5 Farad caps

I thought RIPPLE is a red wine. It cost $3.64 a gallon. Return the empty bottle for a $3.00 credit refund!

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Old 24-06-2013, 17:33   #17
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Re: 5 Farad caps

Your battery bank is the biggest capacitor you could ever have. Ripple only ever comes from AC sources like shore power chargers where the AC/DC conversion is not 100%.
I cannot imagine why you'd want a capacitor.
However, take a look at Nisshibo, Japanese company that makes the huge dual film capacitors used in the Toyota LeMans prototype cars...now that's capacitor technology.
Charged up during braking the charge is enough to provide an extra 300BHP supplied through an electric motor in the gearbox, to supplement the 500 on BHP coming from the engine, on the next acceleration.
That's an interesting use of a capacitor !!
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Old 24-06-2013, 19:05   #18
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Re: 5 Farad caps

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Originally Posted by skipmac View Post
My understanding is that capacitors do have a finite lifetime, at least some types. For example electrolytic capacitors I believe are rated for about 50,000 hours (a bit over 5 years) and age as the electrolyte dries out.
There isn't a lot of MTBF data available on super-caps yet. The internals are vastly different than aluminum electrolytics or most other capacitor types so comparisons aren't appropriate. The promise is that they will have favorable lifetimes compared to LA batteries. There is even speculation that this technology can eliminate the need for batteries altogether.

Some manufacturers have decided to rate them in terms of charge/discharge cycles like batteries. They are claiming a few hundred thousand cycles whereas LA batteries are a few thousand cycles. Some vendors are rating them in terms of lifetime at elevated temperature and then they hope that the Arrhenius formula can be used to extrapolate to lower temperatures. Actual lifetime will become more apparent as time goes along but in "normal" applications their MTBF should be closer to 500,000 hours. However, for 12V banks it often takes series parallel combinations of capacitors so that will reduce the lifetime for a bank proportionally.

But it is not a given that a capacitor will totally fail within a definite number of years or cycles as is the case for most LA batteries (usually single digit years). The capacitor vendors define "failure" to be either 20% or 30% reduced capacity. Battery manufacturers would cringe if that were the definition of battery failure.
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Old 24-06-2013, 19:33   #19
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Re: 5 Farad caps

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Emmalina-
" For suppression and to take out surge ripple.... They work great in cars for this purpose... "

Uh, no, massive electrolytics are not used that way in cars, not by the folks who make the cars.
Actually there is furious research going on in this area and some manufacturers are designing them in. These devices can be used to start a warm engine without using a battery at all. They can do it for thousands of times thus making a plain car nearly as efficient as a hybrid in city driving using what is referred to as start/stop operation. At a stop light the engine shuts off then the capacitor starts the car without causing sags to the DC bus that would upset the large electronics suites in modern autos. Such a scheme would destroy a traditional battery in a few months but capacitors can do this job for many years.

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There's no ripple coming out of your alternator unless it is defective.
All alternators are 3 phase AC generators with full-wave bridge rectifiers thus they all have ripple at their output.

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Horses for courses and huge electrolytic caps are just the wrong ones for boat electrical panels.
Super-caps are not really "electrolytic" in the traditional sense and neither are they huge. Technology is changing very fast in the field of energy storage. Boaters should follow these developments and use the best tool for the job however one defines "best". Lead acid batteries are on balance a non-optimal technology for boats but we don't have anything better. The day is fast approaching when we should be able to get rid of lead storage batteries.
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Old 25-06-2013, 00:56   #20
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Re: 5 Farad caps

OK OK I used the wrong expression when i said ripple !!! I meant transient spikes ! I have just put one on my autopilot feed and apart from having a digi voltmeter on top it sure does stop my ammeter needle flying around. Just playing really as a friend has just pulled out his boom box from his car I have it on loan.....But the potential is enormous
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Old 25-06-2013, 01:40   #21
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Re: 5 Farad caps

I put a few of the 10F caps as replacements to rechargable batteries on a hand crank flashlight.

These capacitors have much higher ESR than electrolytic caps which are much higher than say ceramic.

For buffering an autopilot.. sure would probably work, but might not be good for the motor and/or control circuitry. It shouldn't actually cause problems I don't think.. but the autopilot probably turns the motor on and off 100% instead of slow start which has high inrush of current. The inductance and resistance in the wiring limits the initial current to the motor and controlling mosfets, where with a capacitor bbuffer, the initial current to the motor could be much higher and possibly cause problems. I am not actually sure on this issue.. maybe it's good maybe not.. but the real fix is you need an autopilot which can ramp up the current to the motor gradually instead.
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Old 25-06-2013, 12:31   #22
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Re: 5 Farad caps

dan, there's all sorts of esoteric and experimenal stuff going on, but it isn't mainstream production. Shutting and restarting idling cars? Yeah, nice green concept but expect that will go away once the acocuntants remmeber that starting a car engine causes the most wear on everything, the most failures, startes, bearings, all sorts of reasons why the big million-mile diesel rigs have always simply left their engines running, because "fuel is the cheapest part of your engine" compared to the shocks caused by every startup.

I'd still call a 5-farad cap the wrong way to protect gizmos on boats. Too big, too expensive, and I'd sure hope it was discharged before anyone tried to work on the system. Zener diode, zorb, so many smaller cheaper simpler ways to do it, and they can be rigged to crowbar a fuse and protect the gizmo from a regulator failure as well. Something the caps will never do.
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Old 25-06-2013, 15:25   #23
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Re: 5 Farad caps

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dan, there's all sorts of esoteric and experimenal stuff going on, but it isn't mainstream production.
Fully agree with this statement.

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Shutting and restarting idling cars? Yeah, nice green concept but expect that will go away once the acocuntants remmeber that starting a car engine causes the most wear on everything, the most failures, startes, bearings, all sorts of reasons why the big million-mile diesel rigs have always simply left their engines running, because "fuel is the cheapest part of your engine" compared to the shocks caused by every startup.
In the US it's the EPA doing the accounting. All they care about is fuel efficiency and emissions (the latter is more important than the former). If start/stop increases the fleet mileage by 1 mile per gallon (and it will) it means hundreds of millions in revenue for the car companies. If it reduces emissions by 10% it means even more millions. And the reality is that starting a hot engine is not more damaging than leaving it idle. For a cold engine I agree that starting causes wear.

Nearly all trucking companies have long ago abandoned the practice of leaving diesel engines running at idle for long periods on the advice of their accountants. That's the main reason for the upsurge in sales of diesel fueled cabin heaters. In some (most?) states is is now illegal to leave a diesel truck or bus idling for more than 15 minutes and there are substantial fines for violations.

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I'd still call a 5-farad cap the wrong way to protect gizmos on boats. Too big, too expensive, and I'd sure hope it was discharged before anyone tried to work on the system.
Fully agree with the last part. The terminals have to be well insulated and current fault protection is mandatory. But these devices are not physically big and they can do a lot to handle localized peaks in current and allow much smaller wire sizes. This is because the wire size can be based on the average current draw and not on the peak demand. We will see these things used more and more.

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Zener diode, zorb, so many smaller cheaper simpler ways to do it, and they can be rigged to crowbar a fuse and protect the gizmo from a regulator failure as well. Something the caps will never do.
Agreed, but in my experience over-voltage transients are not a big issue on boats. I don't think I've ever seen one short of a lightning strike or disconnecting the battery from an alternator. In the case of lightning nothing guarantees protection. DC bus sags when starting big loads such as compressors, starters and the like are the main enemy of electronics on boats. The closer you can put the energy storage device to the load the better things will work.
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Old 25-06-2013, 21:28   #24
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Originally Posted by hellosailor View Post
dan, there's all sorts of esoteric and experimenal stuff going on, but it isn't mainstream production. Shutting and restarting idling cars? Yeah, nice green concept but expect that will go away once the acocuntants remmeber that starting a car engine causes the most wear on everything, the most failures, startes, bearings, all sorts of reasons why the big million-mile diesel rigs have always simply left their engines running, because "fuel is the cheapest part of your engine" compared to the shocks caused by every startup.

I'd still call a 5-farad cap the wrong way to protect gizmos on boats. Too big, too expensive, and I'd sure hope it was discharged before anyone tried to work on the system. Zener diode, zorb, so many smaller cheaper simpler ways to do it, and they can be rigged to crowbar a fuse and protect the gizmo from a regulator failure as well. Something the caps will never do.
Stop start is quite common here now, even range rover does it !

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Old 25-06-2013, 21:33   #25
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Putting a 5 farad cap on a boats system is a solution looking for a problem, they are exclusively used in car audio bass systems in order to provide power in peak demand , note this is an extremely short load transient.

If you do the maths 5farads doesn't provide that much sustained power, and often these " marketing caps" have high ESRs which further limits their usefulness.

In boats long term Voltage sag from high capacity loads is more of a Problem and these caps have little use in that regard.

Nor is it a protection device of any value.

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Old 25-06-2013, 21:38   #26
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Re: 5 Farad caps

Oh Dave, LandRover products, even under the new management, should never quite be mentioned in the same breath as engineering.

The old joke used to be that you could get a Landrover repaired anywhere on the planet in just a week. Even in middle of downtown London, just one week, to fix anything on it. And it WOULD still take the full week, no matter how small the repair required.

Of course few other manufacturers would give you a service manual that told you how to field-dress an antelope to use the skin as a spare head gasket in case you blew one while on the veldt...but that's not quite what most of us would call normal automotive engineering.
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Old 25-06-2013, 22:28   #27
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Oh Dave, LandRover products, even under the new management, should never quite be mentioned in the same breath as engineering.

The old joke used to be that you could get a Landrover repaired anywhere on the planet in just a week. Even in middle of downtown London, just one week, to fix anything on it. And it WOULD still take the full week, no matter how small the repair required.

Of course few other manufacturers would give you a service manual that told you how to field-dress an antelope to use the skin as a spare head gasket in case you blew one while on the veldt...but that's not quite what most of us would call normal automotive engineering.
That was then but in the last 15 years under German , American, and Indian Management , things have gotten far better , owned 5 , most made it to 150k miles or more. Terrible to loose Fords new 4,6L diesel in the recent Tatra buyout though , fantastic engine , was better then the supercharged heap of junk petrol engine , mine was chipped to outperform the petrol ones!

Of course now they need to be serviced by a IT technician.

Still however the best 4x4xfar !!! ( let's try guns or anchors instead )


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Old 26-06-2013, 11:16   #28
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Re: 5 Farad caps

"Still however the best 4x4xfar !!! ( let's try guns or anchors instead ) "
two out of three ain't bad: Aren't Toyota HiLuxes the choice of terrorists and rebels all over the third world? They've shunned Rover. Maybe that's because in some places

"We driving a tata" still sounds like something to make schoolboys twitter?

I give the man credit for keeping his name on company, but I'm not sure if that is or ain't great marketing.<G>
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