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Old 02-13-2019, 06:30 PM   #41
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I talked to Maxwell back when I first brought it up here, and before Tesla bought them to discuss the use of Maxwell supercap starting modules on boats and was told they "were not approved for marine use" and they didn't see any value in such a small market.

There are numerous benefits to using supercaps for starting batteries since they are lightweight, last nearly forever, handle cool and hot temps with ease and can be charged from low voltage sources. They say you can charge a 24 volt starting supercap from 9 volts, but it takes AMPS to do it. The supercap simply accumulates the amperage from another source, it does not create any energy. I wouldn't want to see a battery that charged up a 24vdc supercap from 9 volts, because you're killing one set to get the supercap charged.

Another limitation of supercaps is that they are limited in power duration. Since the energy is stored as electrostatic energy inside the cap, it wants to dump all the power at once. The best starting module I've seen will only generate cranking amps for about 24 seconds tops. Displacement boats don't mind the weight of lead-acid batteries and only planing hull boats are really penalized for weight.

I like the fact that a 24v dc supercap starting module has charging ports and discharge ports, and some allow you to use 12vdc or 24vdc to charge a 24vdc module, means you don't need big ACR systems, since they only charge when needed, and at the voltages most boats have. All 12-volt battery charging systems would remain the same.

You would still need 12vdc house banks since you can't trickle power out of a supercap efficiently. Running the radio on a supercap could discharge it in a couple of hours. It can provide lots of amps for a short period and quickly recharge if you have the charging side power. I'd love to see a marine test bed with supercaps if you could find a vendor willing to back the install. I don't think Maxwell has much of a future for boating, so we'll have to find some other company...
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Old 02-13-2019, 08:25 PM   #42
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Interesting.
I have a start battery on the genset that is failing (needs a few minutes on battery charger to get grunt to pull solenoid in) and means either a trip ashore, organizing a car and paying around $100 or ......buy this online for $60 with free delivery to a near by post office

Not sure yet how I'd connect the large terminal eyes to it.





https://www.ebay.com.au/itm/New-6X-2...edirect=mobile
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Old 02-13-2019, 08:41 PM   #43
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Looks like the same one as above

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Old 02-13-2019, 11:27 PM   #44
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I think the results are poorer then even among car buffs who have tried these. These things do fail - electrolytic capacitors, which is what these are, are about the least reliable electronic component there is since we quit using vacuum tubes. Shown above are six wired in series for a maximum rated voltage of 16.2. In good electronics design the margin would be higher. If just one of these fails, your 'battery' is an open circuit and then what's your alternator going to do? These may be used to augment a battery, but really not replace one. Electrolytic capacitors have an "unlimited" cycle life, but they do have a rated life in hours, and that's otherwise of the failure rate. I doubt those numbers are available from the sellers of these battery replacements, but it is on the datasheets available from the major capacitor manufacturers and their vendors. And, there is more to be said about the discharge voltage curve, it is nothing like a battery. The shine of ultracaps is in how they capture energy.
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Old 02-14-2019, 09:22 AM   #45
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Will a simple bank of capacitors make more than one cranking attempt?
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Old 02-14-2019, 01:21 PM   #46
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Quote:
Originally Posted by sleaper View Post
I have big diesels that require some serious power to crank them, much like the rest of you.

Batteries are around $450USD each conservatively and last around 4 years. They get a real hammering. (that means $900 for a 24v bank).

If I was to add 2 of these (one for each engine) https://www.skeletontech.com/ultraca...983/category=0

I'm 24v starting so I'd be investing $3200 plus shipping in USD. On the surface it doesnt seem worth it.

Where it does seem worth it however, is in dead battery situations. The technology allows me to rapidly (less than 10 minutes) charge these things up using any source (including my dead batteries as long as they have more than 9v) - to a point where I can get my main engines started - and I could even use a small booster battery to do this.

In automotive settings this could be a massive plus where kids and adults alike are draining their car batteries below the voltage required to get the cc to start - but where they still have enough power to full power up a capacitor bank.

I think the benefits are clearly their, but like anything - its whether it solves enough of a problem / reduces cost enough to make it worth doing.

At the end of the day - for most of us - it comes down to the "cost benefit" -

Has anyone fitted these to their boats?

Wow! That's a lot of power and greenbacks every few years. There's something to be said for air starters on some diesel engines.
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Old 02-14-2019, 01:41 PM   #47
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A single Maxwell 24vdc ESM starting module is about $900 and weighs 18 lbs. and outputs either 900 or 1100 CCW and can recharge in 12-15 minutes.

https://www.maxwell.com/products/esm/24v-esm
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