Lightweight battery snobs...
 

Cliffs: this guy has built a couple of replacement car batteries out of surplus Maxwell brand ultracapacitors.




Normally I wouldn't post stuff like this, as the source doesn't appear to be wholly credible (eg: his claim that he's getting these capacitors for $6 seems dubious), but it's an interesting concept for those folks who find LiIon batteries to be far too heavy and/or don't want to risk the possibility of killing one due to over-discharge.


That, and the manufacturer of the capacitors in question actually does product a couple of "battery" modules intended for automotive engine starting:

Maxwell Technologies Engine Starting Module

http://www.maxwell.com/images/docume...00552_EN_1.pdf

People in the comments say those caps are $60 a pop. It's hard to take the guy seriously when his reason for doing the conversion is saving 20lb for fuel economy (plus is awful glued together plywood). Also, caps in his engine bay without any kind of battery box? Seems like a great way to start a massive car fire.

Erm, I'm pretty sure my LiPo battery weighs less than the plywood he used to hold that pack together.

This was my thought.
My aluminum battery box weighs more than the battery..

-Ryan

The brass terminals that most people put on the motorcycle type batteries to work in cars weigh (~1200g) more than my battery (~1000g).

Leafy, what battery do you use.

https://www.hobbyking.com/hobbyking/...dProduct=58820

Between this battery, my volvo electric power steering pump, and the geo tracker alternator (55amp at idle) it will pull this battery down to unsafe voltages in 20 minutes if I hold the power steering pump against the stop as hard as I can (80 amp in this case) while idling. In other words, its fine because I'm sure the pump would have problems in less time than that. Havent run it long enough to need to balance it. Another guy that I race with was running one in his daily driver civic as a test, he left his headlights on while at work one day and killed the battery, like it swole up and wouldnt hold a charge anymore kill, but thats a problem with all lipo batteries.

Are you just using that 4S pack with no charge circuit? What prevents the battery from being over charged?

I only ask because I can get 4S lithium batteries through work....just concerned about safety over the course of several hours of running.

No circuit, if you're really concerned you can build one, but the alternator's own circuitry works well enough. Motorcycles work the same way or even less sophisticated and they've been using 4s lipo and lifepo4 packs for years.

Couldn't you use a simple charging chip to keep the battery from over-charging. Or draining too much?

Hmmm...Interesting, I guess I've just seen too many batteries puff and get sketchy with our RC cars that makes me a little more apprehensive especially since there is nothing to ensure the cells stay balanced. I think some of my apprehensiveness also comes from my lack of knowledge of how the stock alternators circuit works.

I do have a spare 4S that I use for jumping cars in case of emergencies, but maybe I'll give this a try, but just build a battery enclosure (just to be safe!).

Tell me more about this. I've been looking for a cheap jump box for a while.

I just have small gator clips that I put on the 10ga wire that goes to my 4S battery and its cranked over plenty of full sized cars with ease. I will periodically check the charge of the battery and just re-peak it on my charger.

I can take pictures of this tomorrow if you'd like.

Pictures, links, instructions, etc would all be awesome.

Have any links? Because that sounds real stupid. How are you going to keep the cells balanced when charging with an alternator?

It stays balanced pretty well naturally. If you're really concerned you can buy a blinkly balancer for $40 and it'll automatically bleed amperage from any of the cells that over volt as it charges normally. Its not a big deal pretty much all of the LiFePO4 motorcycle batteries do not have internal balance circuits (ballistic, braille, anti-grav, etc), and they're fine I would take it off the car yearly and throw it on the balancer. This is way less traumatic to the battery than being run in an r/c car, it'll pretty much never see any sort of low charge levels. Oh, and dont use a normal LiPO, the voltage is too high it'll over volt the car and then it wont even come close to being fully charged. And LiPOs are the explody hydrogen batteries, LiFePO4 much less so.

Here's what it looks like in the back of the car for more size reference. Maybe I'll come up with something that doesnt involve a zip tie when I have more time in like 3 years. The battery weighs about as much as the tiedown hardware and tray from the stock battery.

Attachment 233440

Is there any reason someone couldn't ditch all the wire to the trunk and just shove that little thing under the hood? If we are talking weight that should add up, plus better cranking volts with less drop?

I don't really agree with running it with no protection circuit though, I don't really know much more than 18650's and discharge rates though.

That wiring looks like the shit in my trunk. I burned the grey rubber positive boot cover. After that I kinda quit messing around with zip ties and all that to hold it down, actually bought factory hold downs.

Sure go ahead and move it. This was quick and dirty because my oem battery died. I eventually plan to rewire the car and I'll move the battery then.

Perhaps if you guys feel like reading?

12V BoostPack

Leafy What battery is that your using?

The one I linked in post 7.

Fuck everyone who didnt +prop leafy's photo.

Here is the jump battery and plug adapter with gator clips, works great for jumping cars but would be even better with proper gator clips.

https://www.miataturbo.net/attachmen...ine=1427742124

I had this same battery. It started the car quicker than the stock battery. I also used the Astro Blinky balancer. My battery didn't survive so well. I have 1 dead cell, but that's how it goes some times. For the price, I can just get another one and not worry about it.

Thats kind of a problem with HK batteries in general. I nuked 2 of their normal LiPOs on the death scooter project till I got one that powered it further than 10 ft.

Agree. Until this happened, I was really happy with the performance of the battery. It's stupid cheap for the amount of CCAs it can deliver.

So... buy two, hook one up, put the other in the glove box as a spare?

They have like a 30 or 60 day warranty on batteries. I wouldnt expect one thats shitty to last longer than that.

Well i mean... sometimes i don't have a 60 day window before i need to be on the road. :P

Push Start ;-)

Naa, build in a crank starter.

https://www.miataturbo.net/attachmen...ine=1427805827

I have had a Deka ETX20L in my car since September 2012, including about 9 months sitting on the workbench after which it still started the car excellently.

It's tall enough to work ok with the stock tie down (with minor mods), and my local battery recycler gets ~$90 out the door for them.

I also ran a Ballistic 16 cell for a while that was awesome, but they won't warranty one if you use it in something other than a motorcycle, and they cost an absolute fortune.

If you think those cost a fortune, go on pegasus and look up the price of the ballistic battery that they do warranty for use in cars.

They actually came down a bunch. Ballistic wasn't happy with how the product turned out and has dropped the price dramatically, and is going to cancel them when Pegasus sells the last of them.

Anyone have info about Apex batteries? Deka "replacements"

Deka ETX14 Motorcycle Battery

Claims to be made from "Environmentally-Friendly Recycled Green Plastic."

Is orange.

https://www.miataturbo.net/attachmen...ine=1451931284

If you want a 16 cell there is a guy on ebay selling batteries in the same configuration as the ballistic evo 2 16. People are RC forums say the cells are legit and that the quality is good:

A123 16 Cell 4S4P 13 2V9 2AH motorbike Battery Starter with Black Case | eBay

Ballistic has the evo 3 line now, it would be good to find out what is inside the cases.

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.

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.

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

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

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?

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.

Correct. Mine has 4 prismatic cells in the box.

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.

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?

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.

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.

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

Damn you guys and your $250 batteries.

Any experience with my $25 option?

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.

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

Deka replacement.

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

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

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.