vehicular

iTrader: (3)

I can't say anything knowledgeable about those Ebay batteries.

I'm 99% sure that the EVO3 Ballistics are internally the same as the EVO2s. They just redesigned the cases, use different terminals, and have a bunch of new case configuration options.

asmasm

iTrader: (1)

Possibly. Based on the look of the cases I was thinking they might have gone down to using the smaller a123 18650 cells. If you email ballistic and ask what is inside (or any other battery manufacturer) they will tell you it is a custom battery chemistry. So far, every example of an opened battery I have seen says otherwise (including ballistic).

I have also noticed battery manufacturers using terms like 12 cell or 16 cell when it doesn't accurately reflect the number of cells in the box.

stefanst

iTrader: (1)

I recently bought an "Alien Motion" LiFePO4 battery. Just hooked it up with alligator clips and it started and ran the Miata just fine. Don't have any long-term data yet, since it's not installed. Planning on putting in where the passenger airbag currently resides.

Alien Motion Lithium Battery - LiFePo4 Lightweight Power Sports Battery

asmasm

iTrader: (1)

I put a 12 cell alien motion in my car and so far it is working well.

Joe Perez

iTrader: (8)

I'm curious to know what you've found here.

Assuming a nominal voltage of 3.3v, we can assume that any auto battery is going to be a 4S configuration of LiFePO4 cells. So I would think that 3P (12 cell) and 4P (16 cell) configurations would be commonplace. Are you seeing manufacturers use higher degrees of parallelism with lower-rated cells?

asmasm

iTrader: (1)

I get that is what they are referencing but it seems like some manufactures also use it as a convention to try and make a product hierarchy. For example, that alien motion AM16 is not a 4s4p configuration of the same cells in their AM12 - the specs don't work out to a total that would make sense if it was a 4s4p of those cells. Looking at the battery box, it looks like prismatic pouches and the 16 designation is just an attempt to differentiate it above the 12 cell.

stefanst

iTrader: (1)

Correct. Mine has 4 prismatic cells in the box.

asmasm

iTrader: (1)

It seems like the battery vendors really don't want people to know what is in the battery box. This braille battery that has been posted in the past, it is advertised at 7 amp hours, they went so far as to shrinkwrap the cells with their branding.

https://i.imgur.com/9BecH5f.jpg

Unless they managed to invent a new battery chemisty and create created a cell with the same external dimensions, and the same case coloring, as an a123 26650-a, but at 3.5 amp hour instead of 2.3, they are lying about the capacity.

Most of the other battery manufacturers are smart enough to call it PB/EQ amp hours if they want to make up numbers.

Joe Perez

iTrader: (8)

I'm sure you're right about the cells used in the smaller batteries being of a different construction. The molding of the case would suggest that they're cylindrical.

I hadn't noticed the AM22, but that one does seem to break the math. All of the others are an even multiple of 4, but 22 isn't; the next step after the AM16 should be AM20. And yet they very clearly claim it contains 22 cells.

That's rather curious...



4 cells, or 4 groups of 4 cells?

asmasm

iTrader: (1)

The two off the shelf pouches a123 advertises are 14 and 20 amp hour and 3.3v. They are definitely using something different since they are lower capacity but I think its just 4 pouches in series.

Joe Perez

iTrader: (8)

stefanst

iTrader: (1)

4 of the 'pouches' if memory serves right. And any number different from a multiple of 4 would have raised a flag with me, so I'm pretty sure it's 4.
No markings on the pouches either, so I couldn't confirm capacity without running a controlled discharge/charge cycle.

asmasm

iTrader: (1)

How were they packed? that has been my concern with the pouches.. They have less dimensional stability than cylindrical cells.

aidandj

iTrader: (5)

Damn you guys and your $250 batteries.

Any experience with my $25 option?

Leafy

iTrader: (1)

My prismatic type hobby battery is the biggest I've seen at 8Ah rating. The lower rated ones seem smaller. Stated the car better than the stock battery starts a stock miata when I moved the racecar into the garage in 40°F weather after it sat for 2 months.

asmasm

iTrader: (1)

Not anything both light and streetable in that price range. I got my alien motion 12 cell for $150 on sale over the holidays. I think that is a pretty good price to capacity balance.

The hobby king battery leafy posted is really good for $/amp hour:
ZIPPY Flightmax 8400mAh 4S2P 30C LiFePo4 Pack

aidandj

iTrader: (5)

Deka replacement.

asmasm

iTrader: (1)

That is scary cheap. My big crank etx9, which should be cheaper since it is smaller, was $60.

aidandj

iTrader: (5)

Deka's aren't $60 anymore. Most places want like $90. Found some at lowes for $75ish.

shuiend

iTrader: (24)

Sixshooter and I both use lawn mower batteries from Advance. They cost like $20-$25 and I have never not had it be able to start my car unless it had been sitting for a few weeks. I could get a new one every year and still get 10 years out of them before I hit the price point of those fancy smancy batteries.