LiFePO4 + Supercapacitor to replace starter battery

[knowpistons]

Due to my coach (starter) batteries going bad, I am thinking about replacing them with more lithium and then building and integrating a super capacitor for starting duties.

Benefits
66% more storage capacity
Elimination of a solar controller
Elimination of the unreliable Li-Bim
Faster starts
Buffer for spikes in inverter power draw

Questions
I am having trouble finding any downsides to this. Is there anything wrong with doing this proposed system?

The proposed super capacitor will have the equivalent to 1.8ah capacity. Will this be enough for starting in cold conditions?

Would a lithium titanate bank in place of the super capacitor be a better choice?

Current System
House Bank
6 100ah lifepo batteries
600w of solar

Coach Bank
2 100ah FLA batteries
200w of solar

Li-BIM 225 to connect the two banks

Proposed New System
House/Coach Bank
10 100ah lifepo batteries
16v 500f supercapacitor
60a DC-DC charger (alternator charging)

[nikitis]

I've never done such a thing, but If you can spec it to provide the Cold Cranking Amperage required which you want to be in the 900'ish range for CCA for most Bus Engines, and not overvolt it too much, 16V could potentially be a tad high for the ECM components. Most alternators are giving off 14V on start. The reason this is important is to not fry any computer components. (Which are sensitive) I wouldn't go higher than 14.7V so if you can voltage regulate from the super capacitor accurately, and have a sustained CCA during the cranking process.

Also the Alternator may require some fancy re-wiring for post crank scenarios as it needs to keep the ECM powered at all times which with engine running should do it, but consider how it's designed to also charge 2 batteries as well post crank, if no longer connected to said batteries to charge, I'm not sure how the extra draw will be handled by the alternator. Potentially the DC-DC charger is connected to it to take the power being generated will be enough for the alternator.

So we're considering the initial start up factors here, and we're considering how the electronics are handled and kept powered Post Cranking.

If you can match up your new set up in voltage and amperage in the seconds it requires them, I don't see why it should not work, but in practice I think others have tried to do this and it didn't work out so well for them, but that is the goal.

[knowpistons]

16v is only the max limit of the capacitor, the actual charge would be dependent on the charge of the battery bank, between 12 and 14 volts. Figuring 1000 amps of draw it should be able to crank for 6.5 seconds, without being recharged by the batteries. Figuring the battery bank recharging the capacitor at 500amps, it should be able to crank for and additional 7-10 seconds at 1000amp draw.

As for alternator charging, power flow would be as follows;

Charging
alternator > DC charger > supercapacitor > battery bank

Discharging(bus electronics)
battery bank > supercapacitor > electronics

[Booyah45828]

Drawback is cost. You'll have a lot more into a capacitor bank then a lead acid bank, not including your charging system, and additional lithium you're considering. Single ultra capacitor runs 50 or so bucks each. You need 6 to make them 12v. I can get 2 group 31's for that cost, and not need anything additional.

No doubt it's possible. Some guys have even built ones to work. However, I've never seen one post back regarding longevity of the system. You can't tell me that a capacitor charging/discharging like that will last forever.

[knowpistons]

I can get the 6 2.7v 3000F caps for around $25, the control board (bms in a lifepo) for another $25. The total, with the lithium batts, would be under 1,000, new FLA would be $300. So for 3 times the money, I would have 4 times the storage, everything would be much more durable, and simple.

Since capacitors use a static charge rather than an electric chemical reaction, they can last hundreds of thousands of cycles. Another benefit of not using chemicals is that temperature hardly affects them.

[Booyah45828]

I priced maxwell caps, which are a name brand. 6 for 25 I'd be leery of. But you do you.

Also, while no chemical reaction takes place, the flow of current creates heat, which isn't inconsequential.

[rossvtaylor]

I don't remember the brand, but a year or two before the plandemic I was at a trucking conference. One of the vendors had capacitor starting "batteries" for about $1000. I can't comment on your specific plan or specs, but wanted to at least say "it might be a thing" that's being done.

[cadillackid]

maybe its different? but in modern electronics ive gotten quite a few free monitors , PCs and TVs .. simply replaced the crappy chinese caps and up and running again... the caps didnt like heat at all over time..


maybe the caps used for a battery are different and not susceptible?

[knowpistons]

Maxwell caps, a family member has some connections in that field.

[Booyah45828]

Originally Posted by rossvtaylor

I don't remember the brand, but a year or two before the plandemic I was at a trucking conference. One of the vendors had capacitor starting "batteries" for about $1000. I can't comment on your specific plan or specs, but wanted to at least say "it might be a thing" that's being done.

I remember seeing those too. I don't remember the farad quantity, but they were rated at 1000 "cca's" for 3 seconds cranking in a group 31 case and cost about 1000 bucks. They were supposedly good "forever", but only carried like a 5 year warranty. I just remember it being absurd, as we were getting 31's for less then 100 bucks a piece at the time, and those would last anywhere 3-5 years. Spending 10 times the cost for something that isn't guaranteed to last longer?

Originally Posted by cadillackid

maybe its different? but in modern electronics ive gotten quite a few free monitors , PCs and TVs .. simply replaced the crappy chinese caps and up and running again... the caps didnt like heat at all over time..


maybe the caps used for a battery are different and not susceptible?

I agree. I've got a 4 year old 120vac-12vdc converter for some led lights that the capacitor in it failed(swelled up). I contemplated fixing it, but for 10 bucks for a new one, I can't justify it. I don't see how the caps in this would fair any different. The amount of amps involved would make it worse IMO.

[Booyah45828]

Originally Posted by knowpistons

Maxwell caps, a family member has some connections in that field.

So long as their genuine, then it would make sense to try. At the $50/cap that I found it's not worth it.

[DeMac]

Originally Posted by rossvtaylor

I don't remember the brand, but a year or two before the plandemic I was at a trucking conference. One of the vendors had capacitor starting "batteries" for about $1000. I can't comment on your specific plan or specs, but wanted to at least say "it might be a thing" that's being done.

-----------------------

Possibly Maxwell Technologies ultracapacitor-based Engine Start Module (ESM). Their ESM ULTRA 31/900 replaces one storage battery in the truck's tray.

The ESM weighs 16 lbs, delivers reliable starts and allows extensive use of a truck's electrical accessories while the engine is off. The ESM ULTRA 31/900 retails for about $950.

900 cold cranking amperes (CCA), or a three-seconds for diesel engines up to 9.9 liters at temperatures -40°F to 149°F


The downside?

1. Supercapacitors aren’t well-suited for long-term energy storage. The discharge rate of supercapacitors is significantly higher than lithium-ion batteries; they can lose as much as 10-20 percent of their charge per day due to self-discharge.

2. While batteries provide a near-constant voltage output until spent, the voltage output of capacitors declines linearly with their charge.

3. The graphene plates inside are ultra thin & can crack under vibration.

4. The press release above is from Mar 2014, Maxwell Technologies no longer exists.

5. Several bad reviews regarding faulures of the aforementioned product. See Rawze.com/forums/Maxwell for feedback from those who have used ESMs.



🚍 Interested skoolies might also check out Skeletontech.com/Skelstart-Ultracapacitor-Engine-Start-Module which are often used on European hybrid-diesel trucks. They distribute to North American, too.

🚍 We purchased a NOCO150 this past July. $299, its portable, delivers 3000 Amps, designed for gas & diesel engines up to 10 liters. (Love it, so far)

[nikitis]

Originally Posted by cadillackid

maybe its different? but in modern electronics ive gotten quite a few free monitors , PCs and TVs .. simply replaced the crappy chinese caps and up and running again... the caps didn't like heat at all over time..


maybe the caps used for a battery are different and not susceptible?

I can speak to that about electronics. They make quality capacitors that can last damn near forever, but at a price. You get what you pay for with them. Mass manufactured electronics often used lower and cheaper caps on them because they were making so many and the failure rate of the devices was low compared to how many they made. They would save tons on caps. I have a regular NES console still running on original Rubicon capacitors, and then there's the SNES which almost all of them in existence needs capacitor replacements. They went cheaper in the newer console.

The sized caps we're talking required for a Bus would need to be large in size and could potentially be built very well to last 1000's of cycles, but not so sure for $25. We're essentially just scaling up the tech for a larger application, so you'd need appropriate gauge wiring etc all along the chain.

[cadillackid]

Originally Posted by nikitis

I can speak to that about electronics. They make quality capacitors that can last damn near forever, but at a price. You get what you pay for with them. Mass manufactured electronics often used lower and cheaper caps on them because they were making so many and the failure rate of the devices was low compared to how many they made. They would save tons on caps. I have a regular NES console still running on original Rubicon capacitors, and then there's the SNES which almost all of them in existence needs capacitor replacements. They went cheaper in the newer console.

The sized caps we're talking required for a Bus would need to be large in size and could potentially be built very well to last 1000's of cycles, but not so sure for $25. We're essentially just scaling up the tech for a larger application, so you'd need appropriate gauge wiring etc all along the chain.

true that - consumer electronics are most often tossed aside before their caps die.. my old 1980 Atari 2600 i got for christmas that year still works (and yeah I still get it out and play it)..



its interesting you mention rubycon caps.. they have been my choice for years to replace bad caps.. ive rarely ever seen them OEM in anything.. I guess like you say the extra cost was too much and thus cheap china stuff wins out..



TVs are often tossed out because of bad caps.. we asre kind of hitting a threshold in the TV world now... when HD came out everyone rushed to buy a 1080p.. a short few years later everyrone riushed to go buy 4K.. but yet most cable companies dont even broadcast over 1080P.. and streaming at 4K needs a really great internet connection or it backs down to 1080P anyway.. people are figuring out that rushing to buy an 8K TV is not in the cards for a long time.. so will be interesting to see if ther public gets ticked off when the TVs all start dying at 5 years..



interestingly enough Samsung sells commercial Hotel TVs that among other features include higher quality capacitors.. knowing that the major hotel brands typically keep TV's 10-15 years at a minimum.. of course those sets are sold in high bulk.. ive never actually opened one up to see what the differences in the boards are.. one of these days.. time.. yeah time.. I once remember what time was

[nikitis]

8K is already out, and the latest Xbox's support them. But as you said adoption is low because people are happy with 4k. Before 1080p the quality was terrible. Just go back and watch any DVD on a 4k monitor to see just how bad.

The same effect happened when 720p TV's came out and the traditional 320x240 resolution televisions we had since the 50's, and now watch a VHS on a 720p or 4k, just how bad it looks.

12k is required for telepresence. Telepresence is for those who don't know when the pixel densitity is so high that you can't tell you are looking at a flat screen but will feel at the right angles that you are looking through a window. I've seen a 12k screen at a fair, and when looking straight at it, it just looks like you have a Window frame, and the image is see through. We're almost there, but I fear with the slow adoption of 8k we won't make it there for another 20 years. 4k is is good enough for most people and it will remain that way for awhile. If people could see the 12k screen though, they would change their minds. 8k meh, you can't really see a difference from 4k, and not enough to justify a price for it, but you can at 12k. I think screens will likely jump from 8k to 16k, but corps may just make a new aspect ratio to save on the extra 4k pixels to only meet up to 12k when that push is eventually done.

The NES did use rubicons for caps. And caps usually aren't the failing reason for those consoles. The CPU/PPU chips themselves are dying from age.

[Jono14]

Just posting to ask the question to the group. My understanding is the main limit of using LFP batteries for starting is max amps due to the BMS max of 100A in many 100aH batteries. So 1 or 2 LFP batteries would not do the job.

However, if you are planning 10 LFP batteries, it seems like that bank would be capable of the 900 CCA mentioned. Is there a version of this system that just uses the single large LFP bank for all electrical needs?

Maybe the alternator wiring would be confused as Nikitis described and I may be underestimating the risk of draining the main LFP pack with house needs and getting stranded - but I am curious if this seems viable to others?

[knowpistons]

nikitis- Its not really 4k vs 12k, its pixel density. A 32" 4k TV will have higher pixel density than a 100" 12k TV.

Jono14- In theory, 10 batteries would be enough, however all batteries and wiring to the junction box would need to be IDENTICAL or it will over pull from the battery/wiring with the least resistance causing the BMS to cut power.

I have my current 6 batteries wired in parallel, identically, to a fuse box, each on its own 50 amp fuse. I would of course wire the four additional the same way. This currently allows me to pull 300amps which is plenty for my inverter, 4 more batteries will extend that number to 500amps. The supercapacitor is going to allow the bus to be started without causing any problems for the BMSs and smooth out voltage dips caused by the inverter for starting high power draw appliances. Alternator wiring also seems easy, there just needs to be a DC-DC charger between the alternator and batts.

[cadillackid]

pixel density is it for me.. I have a 4K laser projector in my home office blasting out a 132" brioght daylight readable image.. at 132" pixel density is low.. when I look at 13" retina screen on my laptop its really hard to tell theres pixels at all..


so alas an 8K or 12K projector would be an awesome thing.. prob cost more than the house itself in today's world to build it..

[Albatross]

Originally Posted by knowpistons

Due to my coach (starter) batteries going bad, I am thinking about replacing them with more lithium and then building and integrating a super capacitor for starting duties.

Benefits
66% more storage capacity
Elimination of a solar controller
Elimination of the unreliable Li-Bim
Faster starts
Buffer for spikes in inverter power draw

Questions
I am having trouble finding any downsides to this. Is there anything wrong with doing this proposed system?

The proposed super capacitor will have the equivalent to 1.8ah capacity. Will this be enough for starting in cold conditions?

Would a lithium titanate bank in place of the super capacitor be a better choice?

Current System
House Bank
6 100ah lifepo batteries
600w of solar

Coach Bank
2 100ah FLA batteries
200w of solar

Li-BIM 225 to connect the two banks

Proposed New System
House/Coach Bank
10 100ah lifepo batteries
16v 500f supercapacitor
60a DC-DC charger (alternator charging)

So I've only seen one vehicle successfully replace a battery with a super-cap bank, it was not in-person, and it was something like a Ford Festiva--basically the exact opposite of a bus. While it allegedly worked fine as a daily-driver, and could retain enough of a kick to push it over after sitting for a weekend, I think part of the problem with it was how much it drained energy when not powered. For an RV purpose, this strikes me as particularly problematic, unless you're going to also build-in some kind of crossover that allows you to push a button and use other batteries/banks as a jump-box.

Another potential problem I see with this is longevity. When I was working in the big studio I worked in, boss-man had an SSL 4000G+ mixing console (it's a monster), and part of his 'maintenance' on it was to go through it and replace all of the electrolytic capacitors in all of the 128 channels, as well as the 8 bus channels, and the 4 master channels. While I'm not familiar with the chemistries or constructions of 'super capacitors', and I know that electrolytic caps are particularly sensitive to degradation when used regularly, or stored for extended periods of time, and that they're particularly sensitive when not maintained in a climate-controlled environment; this is a concern that may or may-not apply to these "super-capacitors".

Glass, mica, film, and ceramic capacitors all last longer than most electrolytics other than tantalum caps, but these are all tiny and usually less than a microfarad in capacity. I've heard of supercaps using stuff like aerogels or even graphene or carbon-nanotube tech--which is exciting, but I've never seen, used, or heard of them outside of a lab-setting. I've been wanting to find or build a few to attach to a power-supply for a laser or rail-gun; but it's so low on my priorities list that it may never happen.

Starting motors is an excellent real-world application for this kind of tech, but I would also wonder how you're going to warm-up a diesel engine to properly kick-over the starter without a big battery.

[knowpistons]

Quick update on this, 10 100ah lifepo4 batteries with the super capacitor works to start the bus no problem, way better than the lead acids. I have the starter wired directly to the super cap and then the super cap wired to the bus. Each battery is wired in parallel with a 50amp fuse, I have even tested it with 30 amp fuses, none have blown while starting. I now have a single electrical system that serves as both chassis and coach battery, hugely simplifying things.