Ultracapacitors, why no discussion?

[skipperpete]

I read with some interest, the battery and engine starting threads here but have only seen one mention of capacitor banks for engine starting. It’s not like they’re a new thing on the market, Cat uses them in its largest excavator, road transport uses them in their truck battery packs and in China I’ve travelled on capacitor powered busses that recharge instantly at every stop. I have a jumpstart cap pack that will fire up a 27 litre cold diesel almost instantly, it weighs 5kg ...( and a lithium jumpstart pack that fits in my pocket that will start a landcruiser V8 diesel with totally flat batteries) so why aren’t we using them in cruising yachts?

[Jammer]

Most of the available products are sized for larger engines and are a costly solution for, say, a 50 hp Yanmar.


Cruising boat Dc power system design is highly focused on the tradition of a separate house and start battery. People fall into two camps. One camp believes that the two separate batteries are absolutely necessary for safety and reliability. The other, smaller, camp believes that with a well designed electrical system and a modern BMS programmed with a suitable reserve, a separate start battery is not necessary.


Ultracaps serve the needs of a largely nonexistent school of thought that takes the middle ground.

[Adelie]

UltraCaps have very low specific energy (Whr/kg) and energy density (Whr/l). Like 1/3 or less that of lead acid batteries.

Self-discharge rates are similar to LA batteries.

What the have going for them is very high specific power, a small Ultracap can deliver a really big burst of energy in a short period. Zero-ish maintenance. And they have really good cyclelife.

In a starting application, cycle life doesn’t strike me as very important for a recreational vessel.

As long as there are no parasitic loads to drain the bank between starts it should do just fine starting the boat. Any parasitic load and it’s going to founder.

The you need to pay for it.

[Dockhead]

Originally Posted by skipperpete

I read with some interest, the battery and engine starting threads here but have only seen one mention of capacitor banks for engine starting. It’s not like they’re a new thing on the market, Cat uses them in its largest excavator, road transport uses them in their truck battery packs and in China I’ve travelled on capacitor powered busses that recharge instantly at every stop. I have a jumpstart cap pack that will fire up a 27 litre cold diesel almost instantly, it weighs 5kg ...( and a lithium jumpstart pack that fits in my pocket that will start a landcruiser V8 diesel with totally flat batteries) so why aren’t we using them in cruising yachts?

Maybe because a truck battery used exclusively for engine starting costs €150 and lasts 10 years?

Is this a solution in search of a problem?

[skipperpete]

Agreed, parasitic loads are one of the concerns, apparently slow steady release of stored energy is a major failing of capacitors..... but they fully recharge at phenomenal rates, some in 4 mins, some on electric ferries fully charge during the disembark- boarding cycle and that’s only 30 mins charging.
I really don’t know much about em but they seem to be gaining considerable acceptance in industry, particularly from Caterpillar.

[StuM]

Originally Posted by skipperpete

Agreed, parasitic loads are one of the concerns, apparently slow steady release of stored energy is a major failing of capacitors..... but they fully recharge at phenomenal rates, some in 4 mins, some on electric ferries fully charge during the disembark- boarding cycle and that’s only 30 mins charging.

But on a cruising boat, where are you going to get the very high wattage charging source to take advantage of that phenomenal rate?

[Jammer]

https://www.eaton.com/content/dam/ea...guidelines.pdf


https://www.eaton.com/content/dam/ea...data-sheet.pdf


2 ohm 100 watt charging resistor is $10:



https://www.digikey.com/en/products/...-2R-F/16163044


The 60 farad 18v banks are $150 each at Digikey. I would think that four of them in parallel would be enough to start a typical 3 cylinder diesel engine. The number required would be driven by ESR not capacity. They could be expected to last 20 years.



The resistor would limit charge current to 7 amps with a fully charged house battery and completely discharged supercap bank. Various more sophisticated charge control techniques could be used. For example a Victron TR-12/12-9a is supposed to have a current limited output and is under $100. Or it would be possible to add a series diode, e.g.:


https://www.digikey.com/en/products/...DqGrUtTJlaJCSA


For $600 you could have a very compact, lightweight, high-reliability alternative to a separate engine start battery. The whole thing would weigh less than 10 pounds and fit in a 3"x10"x10" cube.

[Jammer]

Originally Posted by Adelie

As long as there are no parasitic loads to drain the bank between starts it should do just fine starting the boat. Any parasitic load and it’s going to founder.

The idea is that you trickle charge it from some other source, shore power, house battery, solar, if you're going to let it sit for a few days.


A fact to consider is that caps aren't damaged by low SOC and can sit completely discharged over winter for boats laid up seasonally.

[chris95040]

Originally Posted by StuM

But on a cruising boat, where are you going to get the very high wattage charging source to take advantage of that phenomenal rate?

Isn't excess charging capacity a common drawback in lead-acid installations, where you end up having this big alternator that rarely gets a chance to provide it's peak output?

Wonder if there are some energy storage technologies that are "better together", combined in one smart system where one's quick charging but crappy self-discharge is mated to another's slow charging but great self-discharge, for example.

Maybe, a capacitor at 20% (?) the capacity of your lead-acid bank that is there to do the lead-acid's absorption-phase?

[Jammer]

Recovery from a complete discharge of battery systems is a common concern. When this happens the usual failure path is an unrecognized failure of the charging system, lack of monitoring leading to loads being connected too long, or a shorted cell or other internal failure of the battery bank.


A fact to consider is that a cap requires little energy to recharge. The 240 farad bank I described in a previous post only has an energy capacity of 6.5 watt-hours and could be charged from zero to the point where it will start an engine by connecting it to either:
* a series bank of 10 AA NiMH batteries, through a resistor, for 30 minutes

* a 20 watt, 12v solar panel for 20 minutes on a sunny day, or under an hour on a cloudy day
* 20 minutes of cranking on a hand-crank generator (https://www.amazon.com/HUABAN-Genera...076Q22STW?th=1)
* a single fully charged 18650 cell with a suitable power conversion circuit, in about 5 minutes

[Jammer]

Originally Posted by chris95040

Isn't excess charging capacity a common drawback in lead-acid installations, where you end up having this big alternator that rarely gets a chance to provide it's peak output?

Wonder if there are some energy storage technologies that are "better together", combined in one smart system where one's quick charging but crappy self-discharge is mated to another's slow charging but great self-discharge, for example.

Maybe, a capacitor at 20% (?) the capacity of your lead-acid bank that is there to do the lead-acid's absorption-phase?

You could do it but the weight and volume of the supercap bank would approach that of the lead-acid bank it would be charging, and some reasonably sophisticated (and commercially unavailable) power conversion electronics would be required.



LIFePO4 would be cheaper and more compact.

[HeywoodJ]

And how about glow plugs? In warm temperatures my engine doesn't really need them, but in colder ambient conditions not using glow plugs leads to some very extended cranking. The glow plugs pull 40A @ 12V for about 30 seconds, that's only about 4Wh of energy, but would need to be added into the mix for our boat.

[Jammer]

That would auger for a larger supercap bank, as would extended cranking.


My experience with diesel powered snow removal equipment has been that nothing works quite as well as a water jacket heater left on overnight.


Next best is a carefully installed ether dispenser -- one of the ones that properly meter the amount dispensed and have interlocks to prevent use in warm weather or while the engine isn't being cranked.


Intake manifold heaters and glow plugs work less well, but are highly installation dependent, and of course will turn your intake manifold into a grenade if mixed with ether.

[Madehn]

They actually make a starter that you wind up with a socket wrench that will then start the diesel. this would cover both possibilities the starter going out or the batteries being drained. I know they have a model that will start my Perkins 6.354 which is a pretty good sized diesel. I was seriously considering taking one of these cruising but the cost was pretty steep-- ended up buying a spare starter and an extra start solenoid instead but i have often wondered how well it would have done- you wind it up with a couple of extensions and a ratchet wrench- attaches just like an electric starter.

[skipperpete]

If you ever spent any time with an inertial (windup) starter you’d never want to have one on a yacht. The endless winding and that moment of breathless anticipation when you pull the engage lever... no start... more seemingly endless winding.... bleed again, try again and again...I think the Germans used em during the war to start aircraft engines; lifeboats had em and ,for me..... we used them to start diesel engine powered LNG pumps in flameproof environments.
Actually, the “house” loads on an Australian highway trucks are becoming quite substantial with inverters for the TV, microwave, coffee maker etc and generally the single battery pack is 4x 6v or 4x12v depending on the truck voltage. Batteries here start at about $250 each and rarely, if ever, last more than 5 years.
I’m wondering if capacitor start cells can do damage either to the starter motor or the ring gear because the surge of power and almost instant start is more akin to hooking a 24v supply to a 12v starter... (yes, sometimes we do this in extreme situations).
I’m one of the group that believes in a dedicated start battery,even more so now that we have electronically controlled common rail engines that need reliable constant DC power just to run.