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Discussion Starter #1 (Edited)
Rechargeable Batteries!

I've been exploring the concept of replacing our heavy stock battery with lightweight race-grade options. While some small and light lead-acid (Pb) batteries exist, absorbent glass mat (AGM) and lithium-ion (Li-ion) options offer better performance per unit mass.

I'll elaborate on my exploration, including theory, estimations, mounting ideas, and suggested products. I'll keep this OP current with that info. I'm also talking with various manufacturers and attempting to secure us some deals on products they can guarantee will fit our application.

STARTER MOTOR INFO:
Rated Voltage: 12V, 0.9kW
Number of Pinion Teeth: 10
Unloaded Current @ 11V: Max 60A
Unloaded Speed @ 11V: Min 5500 RPM

ALTERNATOR INFO:
Rated Voltage: 13.5V, 110A
Speed in use: 1,000-18,000 RPM
Voltage Regulator: Built-In IC Regulator
Regulator Output: 14.55 ± 0.3V

STOCK BATTERY INFO:
Model: CMF45L-DIN
BCI Group (size): 45
Dimensions, in millimeters: 240 L, 140 W, 227 H
Chemistry: Lead-Acid
Capacity [20 HR / 5 HR]: 45 AH / 36 AH
Cold Crank Amps: 410A (SAE) / 330A (EN)
Reserve Capacity: 80 minutes

Lightweight Pb Batteries
Most of these are intended for motorcycles, ATVs, or small watercraft. While they should work for our tiny engine, they'll also probably be burned out pretty quickly in the process. They're light (6-20 lbs) and cheap ($50-100)



AGM Batteries
These are a different approach to traditional lead-acid designs, but are fundamentally the same class of cell. They're a bit more expensive ($100-200) but plenty lightweight (6-20 lbs) are considerably safer. They come in all sizes and shapes.

MANUFACTURERS:
Deka: all products assembled in Pennsylvania
Braille Batteries: products constructed at time of order, can be customized.

NOTEWORTHY AGM MODELS:
Deka Sports Power ETX-20L: inexpensive, and will probably work, but might not last very long. not intended for automobiles. ~$100 ($82 on amazon at time of writing)
Braille B2015: confirmed long-term use in Subaru STi, rated for 4-cylinder engines, 3x our crank amps, but half our capacity. 15 lbs. ~$200 (B2015C is the same battery but with a carbon-fiber housing.)

Li-ion Batteries including Lithium Polymer (Lipo) and Lithium-Iron-Phosphate (LiFePO4)
BENEFITS:
  1. Reduced weight by 75+% (tons of benefits from this, of course)
  2. improved resistance to shock and vibration
  3. increased longevity through a magnitudinal improvement to charge cycle durability
  4. decreased Total Cost of Ownership (TOC)
  5. improved charging speed, resulting in reduced draw on alternator
  6. zero maintenance, so long as vehicle is regularly operated (2-weeks in between cranks max, due to on-vehicle electronics draining battery combined with limited capacity)
  7. very high crank amps, due to extremely low internal resistance
  8. almost zero self-discharge
  9. smaller physical footprint, makes for easy mounting in different locations
  10. decreased voltage sag from available capacity, resulting in more consistent performance from electrical systems.
DRAWBACKS:
  1. greater initial cost (2-5x)
  2. reduced total capacity (50%, or even 25%)
  3. special charger required (however, alternators work as intended)
  4. cannot be jump-started by a Pb battery
  5. deep-discharge can render the battery irreversibly inoperable (goodbye investment)
  6. different thermal properties, so ability to start vehicle during extremely cold weather may be different than with Pb battery.
  7. smaller physical dimensions means batteries will not fit stock mounting location without a riser and custom retention system.
SILLINESS:
I've read some accounts of racers using super cheap Lion batteries intended for airsoft guns and motorcycles to operate their cars. Apparently it works, and it's plenty cheap ($100-150), but since no protection or load-balancing circuitry is present within these types of batteries, they're extremely likely to be damaged by automotive use. They are made of huge arrays of the kind of lithium cells generally found in laptop batteries. They can supply tons of amps in very short bursts, but are incredibly light weight (0.5-1.0 lbs). I can't imagine they would be a viable solution. It screams "fire hazard" to me.

MANUFACTURERS:
Braille Battery: products constructed at time of order, can be customized.
Lithium Pros: very complete lineup of products across various pricepoints.
Lithionics: Extremely high-end manufacturer with impressive battery management computers onboard their products.

NOTEWORTHY MODELS:
Braille GU1R: fully compatible with our vehicles, mounting aside. ~$575
Lithium Pros C680: lighter and cheaper, but with very little protection circuitry inside. ~$525
Lithium Pros L680: beefy protection circuit version of the C680. ~$950


SOURCES:
BCI Battery Group Size Chart
Rechargeable battery - Wikipedia, the free encyclopedia
 

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Plus the stock battery is so bloody small there's no real point.

Now if I was pulling that massive battery out of my Durango ..
 

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Discussion Starter #8
I have had a Deka (~16 lb.) battery sitting here waiting to be installed for a couple of months now. Pierce was going to build a battery mount for smaller batts but we all know how busy he is.
That's a pretty big improvement, but the one I've examined the most, the Braille GU1R, is only 6.6 lbs and able to push 3x the crank amps as our stock battery. It only has 1/4 the actual AH, but recharges and discharges much more efficiently, so the extra capacity isn't really as important. With only a 20% charge, it should have enough power to turn the starter. The only question is, how much current do the off-mode electronics (bluelink, clocks, etc.) draw? If only a tiny bit, then the capacity shouldn't matter much.

The GU1R is BCI U1R, which is the following dimensions, in millimeters: 195 L, 130 W, 182 H.

I need to use CAD to mock up a U1R-to-45 adapter. U1R has opposite polarity and terminal position, so rotating the battery 180º on the X-axis (horizontal) would position the terminals approximately correctly. The battery would then need to be raised by 45mm to be at the right height, with a spacer 45mm L and 10mm W. That should be easy enough to construct. The trickiest part would be developing a hook on the riser to use the stock retention clamp.
 

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Odyssey and Braille are some of the best for the price point they are in.
As far as a mounting solution
Drill out some jokes in the current box with some washers to distribute the weight and a battery tie down and done.
This ensure you can bounce between the stick and lw battery freely
 

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This would be something that I might consider if I was building a dedicated race car or track car but I just can't see the benefits outweighing the cons for a daily driver that sometimes sees the track.
 

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Discussion Starter #13
Saving 20+ lbs. for a few bucks more than a stock batt is definitely worth it.

I've done research on Odyssey & Braille in the past and they don't last long. The Harley guys use the Dekas which are made in PA, last a long time & are underrated powerwise. Not to mention a whole lot cheaper. Lots of positive reviews.
My understanding about the criticisms of Braille's products boil down to, people like to cheap-out and buy the most inexpensive option that "will work" whether or not it is way outside the design parameters for that product. Running a motorcycle battery on a car will subject that battery to way more wear & tear than the engineers had intended. But, it'll work at least for a while, and undersized batteries are always going to be the lighter than oversized batteries. I prefer running something beefier than stock, but with a newer tech that reduces weight, rather than just being under-spec.
 

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Kaishi: Would be great if you could add the weight of the stock battery and physical dimensions in inches as well.
Oh you pesky Colonials with your Imperial measurements.
 

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The propensity of lithium ion batteries to fail spectacularly and burn surrounding shit completely down has me with no interest in being around lithium batteries bigger than a laptop battery.

One of my neighbors had some kind of little chinese toy consume itself and part of his house when it threw 7's. I can't remember now what the name of the by product of the fire was, but it is highly toxic and if i remember correctly attacks the liver and other internal organs causing irreversible damage. He lived in a hotel for about 3 months while the insurance company gutted his entire house of anything that had been in contact with the smoke.

There have been a number of fires associated with the Fisker Karma going to flame, with the cause being lithium ion batteries.
 

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Discussion Starter #16 (Edited)
See, I'm doing the opposite. I'm looking into the how and why of lithium ion cell failures and what to do to make those failures impossible. I'm actually thinking about DIYing my own battery pack as a proof of concept, but implementing all the necessary safety features to prevent stranding myself.

Cells explode when they overheat. They overheat when they overcharge. They overcharge when they're given more voltage than they can take. The solution is to wire the cells up in a configuration where they can take more voltage than the alternator can ever supply, so they will never be fully charged by the alternator and therefore cannot overcharge, nor overheat from overcharging. This has been demonstrated on some other automotive forums.

Kaishi: Would be great if you could add the weight of the stock battery and physical dimensions in inches as well.
the dimensions of BCI Group 45 batteries in standard measure is available in one of my source links. I find standard measure to be imprecise compared to millimeters. All the nuts and bolts in our vehicle are metric, so I figure using metric here makes sense.
 

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Discussion Starter #18
Kaishi says "NEEDS MOAR ACCURACY!"

So:
9.45189"x5.51257"x8.980025"

Stick that in your metric pipe and smoke it buddy. :)
I love this. I would prefer decimal inches to metric, but that's incredibly petty. I just don't like all the fractional math.
 

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I suppose based on the 'metric fastener' logic that weights are to be specified in kilograms & boost pressures are to be in kilopascals going forward?
Henceforth we shall use Stone for weight and Atmospheres for boost!
 
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