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Discussion Starter #1
Anybody have pictures of battery relocation to your Frunk while also maintaining the spare tire mounting? I would really like to keep the spare if I can. I need to relocate the battery to make room for my intercooler stuff.

Any pics are appreciated.
 

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Sorry i don't have specifically what you are requesting, but i do have a question...What size battery are you planning to run? I ask because relocating to the rear cubby is also an option that will let you keep the spare tire (unless you need the storage space).
 

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Have you considered putting a LFP (or LTO, PM me I'll send you some links) in the cabin instead? They're so light and small that it doesn't really make sense to run cables to the front.
 

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Discussion Starter #4
Hmm, I would consider using a Lion battery if it had a built in charge controller. However, I would never mount a lithium cell inside the cabin. If they fail it can be quite spectacular. I was looking at some ultracapacitor setups to supplement the cranking amps on a very small cell. Maybe mount on the firewall in the engine bay?
 

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Does that make you feel safe? LTOs barely get warm when they are destroyed. LFPs will get hot but won't ignite. I just ordered an H6 size LTO pack (reviews online say the vendor I bought from use defective cells with lower capacity than advertised, I guess that's why I thought it was a good deal...we'll see how it goes).

As for ultracapacitor solution, check this out:
Lazerhacker on Youtube was able to crank his Honda J35 engine with an equal capacity bank charged to 12V. Pair it with a cheap solar deep cycle or motorcycle AGM battery and you should be good to go. The cap bank should go closer to the starter motor of course.
 

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Lithium ion batteries mounted in the cabin do not pass tech in any type of motorsport because its very dangerous. If you want to mount in the cabin used a seal AGM battery. If you want to save weight, look into the Antigravity lithium ion batteries mounted in the stock location, they have one with a restart option and weigh about 3lbs
 

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Lithium ion batteries mounted in the cabin do not pass tech in any type of motorsport because its very dangerous. If you want to mount in the cabin used a seal AGM battery. If you want to save weight, look into the Antigravity lithium ion batteries mounted in the stock location, they have one with a restart option and weigh about 3lbs
Yeah I looked into those, they are like $600 iirc.
 

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Discussion Starter #12
What is the necessary "cold cranking amps" required to start a 1zz/2zz or even k series?
The CCA rating doesn't really matter if you add a supercapacitor bank next to the engine fuse box. What you really need then is a decent amount of watt hours but not cranking amps.
 

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The CCA rating is important for a starting battery since it gives a relative indication of the battery's internal cold resistance -> higher CCA = lower internal resistance.

Super Capacitors are kind of a double edged sword. They can have a very low ESR (equivalent series resistance) which allows for a very large, instantaneous, energy transfer but that energy transfer works during both the charge and discharge cycles. This transfer can stress the bus voltage needed by the electronics as well as the other components and wiring connected to it.

Watt-Hours are directly convert to Joules for a battery and the Capacitor rating value in Farads also relates directly to Energy stored/delivered in both Joules and Charge in Coulombs.

Just some things to think about...
 

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Lithium ion batteries mounted in the cabin do not pass tech in any type of motorsport because its very dangerous. If you want to mount in the cabin used a seal AGM battery. If you want to save weight, look into the Antigravity lithium ion batteries mounted in the stock location, they have one with a restart option and weigh about 3lbs
That's because most high energy-density chemistries will catch fire. Lithium titanate doesn't even emit smoke when failing; it's like lead acid. I even embedded a video in the post right above showing what happens when you throw a charged 40Ah Yinlong cell into a gasoline fire, drill it open, saw it in half, etc.

Antigravity prices are more reasonable when you get the higher Ah rated batteries, but the small ones are not very economical. 40Ah worth of high C rate cells costs around 300 dollars, the case and high current BMS should cost a bit under 200, and they sell that package for 820 with customer service. However the 24Ah one is 660 bucks... you can buy the 20Ah batteryspace battery with cell balancing for 200 and just replace it when it (probably never) goes bad.

What is the necessary "cold cranking amps" required to start a 1zz/2zz or even k series?
The stalled rotor current should be something around 200A at most. That amperage drops as the battery voltage sags though, so you don't actually need "200 CCA". Lead acid batteries have much less power when at a low state of charge, so they need to be bigger if you want it to crank the engine when it's low.

While a capacitor will put more load on the charging system when it's emptied, people forget how powerful alternators are. We can calculate how much that load actually is. 1 full second of cranking requires on the order of 1kJ between the battery and capacitor. Let's say all of it comes from the capacitor.

At 83 farads, starting with a relatively dead lead acid battery at 11.5V, the capacitor discharges down to 10.3V to supply 1kJ. To charge the capacitor in ~3 seconds, it takes less than 30 amps average, and your electronics will be totally fine operating at 10.5-11V for a few seconds.

For a car with low parasitic drain and low starting current requirements, a small cap bank attached to a small lead acid battery is a very cost effective way to get a 10lb package that can sit without charging for 3-4 weeks. For cars with high parasitic drain, you can just skip the capacitor since the battery will be big enough to supply the necessary cranking amps.

If your car is daily driven or sits on a battery tender, the battery just becomes a backup, and you can get away with something really tiny whose weight, size, and cost are inconsequential. For example, here's a 10 dollar lead acid with nearly the same capacity as the Scorpion Stinger, and nearly the same weight as well (it doesn't have heavy conductors for high current): 12V - 7 Ah - AGM Battery - Bright Way Group BW1270F1 | 1000Bulbs.com

You can think of the capacitor-battery pairing like this: Adding the capacitor turns a lead acid into a quasi-lithium-ion battery by adding power at low state of charge, allowing a smaller battery. If you are willing to spend money on lithium ion, the rule of thumb I would follow is 10Ah per liter engine displacement, 7Ah per week of standby time (without car alarms, locators, etc. which increase drain), 20Ah per liter if using low-C-rate cells.
 

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The antigravity battery I posted is the same exact one in my race car. I’ve gone 11 days without starting and never had to use the restart feature yet. If you spend $800+ on a battery and have to add capacitors etc to the system you are out of your mind when options like that are available..... also has customer service and a warranty
 

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That's because most high energy-density chemistries will catch fire...

Lithium titanate doesn't even emit smoke when failing; it's like lead acid. I even embedded a video in the post right above showing what happens when you throw a charged 40Ah Yinlong cell into a gasoline fire, drill it open, saw it in half, etc
Thats right. That is because any useful battery has stored energy. When you short the battery, the stored energy gets out, and released stored energy causes fires. Just because you do not have a combustible reactant does not mean that you have a good ending.

So are you saying that this battery cannot be shorted, or are you saying that if this battery is shorted, it can't discharge into the short? Something is fishy about this demonstration. I bet that a lead acid battery will explode if you short it hard. The electrolyte will boil until the casing blows. I am open to technological breakthroughs, but some explanation is necessary for this to fly.
 

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So are you saying that this battery cannot be shorted, or are you saying that if this battery is shorted, it can't discharge into the short? Something is fishy about this demonstration. I bet that a lead acid battery will explode if you short it hard. The electrolyte will boil until the casing blows. I am open to technological breakthroughs, but some explanation is necessary for this to fly.
I think the point is that an internal short doesn't lead to a "chain reaction". You get localized heating which destroys the conductors and then it's fine. LTO is well known for its safety. You can crush the entire cell and it won't ignite.

Yes lead acid thrown into a fire could explode too, yet OEMs think it's safe to put AGM lead acid batteries inside the cabin (e.g. Aston Martin).

The antigravity battery I posted is the same exact one in my race car. I’ve gone 11 days without starting and never had to use the restart feature yet. If you spend $800+ on a battery and have to add capacitors etc to the system you are out of your mind when options like that are available..... also has customer service and a warranty
Where did I say to add a capacitor to that battery? You really aren't reading what I write at all. As long as you have ~200 peak amps available, any lithium chemistry can crank the engine. What I said was that you are crazy to buy a 600+ dollar 24Ah battery when you can treat a cheap 20Ah battery like a disposable lead acid, since they're comparable in price.

If you have a LEAD ACID battery, then capacitors are really useful, because they provide extra peak power when the lead acid battery is low.
 

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In addition to that:
Lead acid batteries of all types (that includes AGM) produce hydrogen and oxygen gas when getting charged.
Both gasses combined are notorious to blow up by the slightest spark.
So lead acid isn't 100% safe either and a shortcut with lead acid might start a fire just as well as lithium cells do.
And our engines aren't safe either, litteraly a bunch of fuel line not so far from an ignition source and the gas tank.
Nothing is 100% safe, it can't be.
Things can only be reasonably safe.

Lithium cells work reasonably safe in power tools, electric vehicles and all kinds of RC-vehicles and planes as well as in all kinds of mobile electronics except for one phone where Samsung fucked up big time.
So I see no reason why it would be unreasonable to use them as a starter battery as well.

In addition to that:
Cordless anglegrinder draw up to about 80A from their batteries, often no more than 4Ah Li-Ion packs.
So I'd assume a ~10Ah should allready be more than enough to start our not exactly large engines and may allready be hard on the starter.
However I would suggest a metal enclosure of the Lithium battery pack in the original battery position just in case something goes wrong, so the battery is protected from shrapnell and a potential fire is contained.
 

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...The stalled rotor current should be something around 200A at most. That amperage drops as the battery voltage sags though, so you don't actually need "200 CCA". Lead acid batteries have much less power when at a low state of charge, so they need to be bigger if you want it to crank the engine when it's low.

While a capacitor will put more load on the charging system when it's emptied, people forget how powerful alternators are. We can calculate how much that load actually is. 1 full second of cranking requires on the order of 1kJ between the battery and capacitor. Let's say all of it comes from the capacitor.

At 83 farads, starting with a relatively dead lead acid battery at 11.5V, the capacitor discharges down to 10.3V to supply 1kJ. To charge the capacitor in ~3 seconds, it takes less than 30 amps average, and your electronics will be totally fine operating at 10.5-11V for a few seconds.

For a car with low parasitic drain and low starting current requirements, a small cap bank attached to a small lead acid battery is a very cost effective way to get a 10lb package that can sit without charging for 3-4 weeks. For cars with high parasitic drain, you can just skip the capacitor since the battery will be big enough to supply the necessary cranking amps.

If your car is daily driven or sits on a battery tender, the battery just becomes a backup, and you can get away with something really tiny whose weight, size, and cost are inconsequential. For example, here's a 10 dollar lead acid with nearly the same capacity as the Scorpion Stinger, and nearly the same weight as well (it doesn't have heavy conductors for high current): 12V - 7 Ah - AGM Battery - Bright Way Group BW1270F1 | 1000Bulbs.com

You can think of the capacitor-battery pairing like this: Adding the capacitor turns a lead acid into a quasi-lithium-ion battery by adding power at low state of charge, allowing a smaller battery. If you are willing to spend money on lithium ion, the rule of thumb I would follow is 10Ah per liter engine displacement, 7Ah per week of standby time (without car alarms, locators, etc. which increase drain), 20Ah per liter if using low-C-rate cells.
Like I said earlier, the Capacitor can help or be a hinderance.

IF the car starts immediately with the addition of a capacitor bank, the bank can be charged from the alternator but there will be a large impulse current during the charge cycle. This large impulse current is due to the very short time constant and can damage the series connected electrical components over time.

IF the car doesn't start immediately and it requires additional cranking, this energy transfer from the battery back into the Capacitor bank needed to recharge it creates additional losses and reduces the battery energy needed to start which defeats its purpose.

Another issue with cheap, stacked, capacitor banks are their temperature and environmental ratings which can become an issue depending on where they are installed. Oh, and large electrolytic capacitors also have leakage current which will be an additional parasitic draw from the sitting battery.

Just a few more things to think about.
 

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I haven't had any issues running either a home made A123 lithium or Factory produced LifeP04 batteries in the six or seven years I have been using them in daily driving from 14 degrees to 99 degrees. I do use two batteries for the 14 degree mornings :) Otherwise it is a very slow start.
 
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