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Will a consumer friendly lithium option EVER be available?

  • Definitely

    Votes: 12 21.4%
  • Probably

    Votes: 10 17.9%
  • Maybe

    Votes: 20 35.7%
  • Never

    Votes: 14 25.0%

  • Total voters
    56
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I'll have to read that thread very thoroughly, and color me surprised. I actually found out about this property of supercaps (where you have to divide the original farads by the number of caps in a series) experimentally, when a pack of "400F" caps wouldn't start my car, even though 400F was way more than enough on paper.
That is covered in EE 1 or Ph 1 (or 2 or 3, depending on the school). Admittedly that property doesn't come up much in signal or digital logic electronics because a single cap will almost always do the trick, and those are the circuits usually encountered in introductory courses. Schools tend to reserve power electronics labs for students who have more experience and so are less likely to kill themselves with a big capacitor or inductor. Ie, like this one:

EE 462L: Power Electronics Laboratory | Texas ECE

It seems that supercapacitors are never going to have high voltage variants (they work because the dielectric is very thin, and a high voltage would punch through). My gut feeling is that in the end automotive applications of supercapacitors for driving the main electric motor are going to use mostly parallel capacitors paired with high current DC-DC converters, along the lines of what is described here:

https://www.researchgate.net/publication/282154953_High_Power_Buck-Boost_DCDC_Converters_for_Automotive_Powertrain_Applications

Devices like that are not the proper domain of hobbyists. When that sort of high current high power device goes wrong extreme heat, exploding transistors, device fire, and even a full blown car fire are all on the menu.
 

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I'll have to read that thread very thoroughly, and color me surprised. I actually found out about this property of supercaps (where you have to divide the original farads by the number of caps in a series) experimentally, when a pack of "400F" caps wouldn't start my car, even though 400F was way more than enough on paper.
Think of it this way - a capacitor is essentially two parallel plates separated by a dielectric (usually the parallel plates are rolled up, like in an electrolytic capacitor, for space optimization). The space between those plates is mainly what determines how much capacitance the capacitor has. If the plates are close together, the capacitance goes up, and if they're further apart, it goes down. This is how capacitive touchscreens work (your finger is one plate and the screen is the other, and it measures the capacitance).

If you have two capacitors in series, then you've essentially just doubled the distance between the plates in the capacitor, so the capacitance is halved. If one capacitor has distance X between the plates, you now have distance X * 2 in total.

Parallel, of course, creates more surface area with the same distance of the plates, so the capacitance doubles.
 

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Think of it this way - a capacitor is essentially two parallel plates separated by a dielectric (usually the parallel plates are rolled up, like in an electrolytic capacitor, for space optimization). The space between those plates is mainly what determines how much capacitance the capacitor has. If the plates are close together, the capacitance goes up, and if they're further apart, it goes down. This is how capacitive touchscreens work (your finger is one plate and the screen is the other, and it measures the capacitance).

If you have two capacitors in series, then you've essentially just doubled the distance between the plates in the capacitor, so the capacitance is halved. If one capacitor has distance X between the plates, you now have distance X * 2 in total.

Parallel, of course, creates more surface area with the same distance of the plates, so the capacitance doubles.
Oh I understand how it works now, I'm just astounded Peter was able to get 30 seconds of 100 amp assist out of 50 2200F caps in series. That's something like 40x what the math says he should have been able to get.
 

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Ecky said:
50x 2200F caps in series makes a 44 farad pack, which is 2/3 the capacity of the pack I was using to run my 12v starter.
Oh I understand how it works now, I'm just astounded Peter was able to get 30 seconds of 100 amp assist out of 50 2200F caps in series. That's something like 40x what the math says he should have been able to get.
I think the source of your confusion might be from thinking in units of Farads or Ah , when you think of the ability to do work .. ie IMA Assist , or move your starter .. but the ability to do work is Energy .. not Farads or Ah.

The formula for the Energy stored in a Capacitor:
E = 1/2 * C * V^2 (V Peak)

Energy here does not have the same relationship to voltage as it does in terms of Ah .. like the energy stored in chemical batteries:
E = Ah * V (V Nominal)

In the capacitor energy equation peak (not nominal) Voltage exponentially increases the stored energy .. in the battery style Ah version the nominal V (not peak) only linearly increases the stored energy.

So .. 1/2 * 44 * 180^2 = 712,800 Joules (aka ~198Wh)

~198wh (top to bottom) .. of which he probably didn't use 100% of that.

If it was a nominal 180v for ~0.8Ah would have been ~144Wh .. If his nominal V was 140V for ~0.8Ah that would have only been ~112Wh .. His nominal voltage will be between the peak and the bottom voltage .. so from an energy PoV .. ie the capacity to do work .. it does line up.

A ~44F capacitor at only ~12V ..
1/2 * 44 * 12^2 = 3168 Joules (aka ~0.88wh).
~0.88Wh @ ~12v (nominal) = ~0.073Ah

The 180V is 15x more voltage than the 12v .. but .. in a capacitor that exponential voltage difference means that it stores about ~225x more energy .. not just 15x more energy.
 

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I have been working on a solution that I have only been dropping hints about so far. Not sure on when it will be available to others, but I plan to demo it in my car at Insightfest this year.
 

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OK Time to revisit this thread.

ZE1, BOJUM and any others wanting a drop in Lithium solution.

How much are you willing to pay for a comparable capacity P&P Lithium setup?
 

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^ Yeah, but....

It would cost a builder nearly that much just for new cells which could carry a warranty. They are getting cheaper, but it will take a while to get primary component prices down to level that it is worthwhile in a commercial sense. Buyers are going to want warranties, IMO.
 

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I'd probably pay $3k for a drop-in LTO solution.

I don't know how many of these modules are available or for how long, but they're extremely cheap and you only need three of them to make a pack for an Insight. You get 60% more usable capacity as well (assuming a 10-90% SoC range). The cycle life is huge compared to NiMH, about an order of magnitude more. A pack with these should easily last a decade or more.

Edit: Not 60% more, over 400% more! Thanks, retepsnikrep: Who here REALLY believes a viable CONSUMER friendly...

 

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I voted "probably"


I look at this issue like someone does in the car tuning world, when they are faced with a car or truck that has no aftermarket support, yet you want to have fun with a turbo, or supercharger, or nitrous. In that scenario, we car/truck guys use what is called a "piggyback" tuning system.


In the electric hybrid world, seems the answer is just as simple, yet difficult to implement CORRECTLY.

In my eyes, the first basic step (and of course the hardest) is to simply trick the factory honda system that all is going well.
The next step would be to design a battery pack that has its own brains. balancing, system voltage control, and "smart" assist and regen ability.

If you simply want a replacement pack with similar voltage, then you are left with tricking the honda IMA that the battery pack is doing well, then piggyback power so the stock IMA still has full control of assist and regen, based on driving load and throttle position. This still leaves you with needing to maintain the health of the new battery pack.

LTO cells are the easiest to purchase that have the widest range of operations, both in charging/discharging features, and temperature conditions. There are some pretty neat chemistries out there, but a daily driven car needs to be treated just like the car manufacturer does - wide thermal/climate/elevation range ability. NO ONE wants to pioneer a near-drop in battery solution if only a small percentage of users can even properly operate it. Wasted money.

The downside of LTO is its low cell voltage, so you are still stuck with handling a large number of individual cells. FAR more work than factory with its simple bus bar panels and 40 connections. (well, not including temp sensors)
 

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I'd probably pay $3k for a drop-in LTO solution.

I don't know how many of these modules are available or for how long, but they're extremely cheap and you only need three of them to make a pack for an Insight. You get 60% more usable capacity as well (assuming a 10-90% SoC range). The cycle life is huge compared to NiMH, about an order of magnitude more. A pack with these should easily last a decade or more.
You actually only need two packs for a minimal install, but it does need more electronic fooling. ;)

If you have three LTO packs 60 x 2.4V cell nominal 144V and 20ah (10-90% = 16ah) that's ~2304 wh useable.

The standard pack is about ~576wh useable 144V nominal x 4ah useable (20-80%)

So that's four times as much capacity (400%) not 60% more. ;)

They are a real bargain. Hopefully people will adopt them more widely.
 

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They are a real bargain. Hopefully people will adopt them more widely.
+1. That's the honest to god truth, IMO also.

There's a bit of fabrication needed, but it isn't of a "rocket science" nature and is in reach for anyone reasonably handy with handtools. If metal baseplates intimidate you, then do it in wood, with several good coats of urethane varnish to seal. Aethos thread shows the way to do it in wood :)

LATER: Though Atheos made his wood plate work fine, I thinK the wood plate shown here works a little better because it keeps the BCM/MCM accessible from the top of the plate. Rather than the underneath angle bracket shown, put two brackets on top and clamp the BCM/MCM between them so that they can be removed. Probably need a little rubber of some type between the brackets and the electronics pair to avoid rattles.
 

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You actually only need two packs for a minimal install, but it does need more electronic fooling. ;)

If you have three LTO packs 60 x 2.4V cell nominal 144V and 20ah (10-90% = 16ah) that's ~2304 wh useable.

The standard pack is about ~576wh useable 144V nominal x 4ah useable (20-80%)

So that's four times as much capacity (400%) not 60% more. ;)

They are a real bargain. Hopefully people will adopt them more widely.
You're right about the capacity, I totally messed up my math! In fact, it's almost 5x:
Stock pack: 144V nominal * 6.5Ah * 0.6 (20-80%) = 562Wh.
LTO pack: 165.6V nominal (2.3V * 12 cells * 6 packs) * 20.5Ah * 0.8 (10-90%) = 2716Wh.
2716 / 562 = 4.8!

You could use two packs, though I'd definitely want three for the higher voltage so you get lower currents for the same amount of power. This equates to less heat generated in the pack and longer cycle life. Plus 50% more capacity. :)
 

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The Insight lithium batteries at least are $69 x 4

 

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The Insight lithium batteries at least are $69 x 4

Unfortunately the Insight 50A regen might kill those. :(
 

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The Insight lithium batteries at least are $69 x 4

Being more traditional li ion this wouldn't be great for cold climates unless you go to a lot of work for heating cooling the battery.
 
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