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Half the guys in my class are running them and they just eat u on the first lap then u spend the next 2 - 3 laps re passing them as they are slower than you overall.
Also it seems to be alot more friendly on your tires as if u keep em in th blankets all weekend ur reducing the heat cycles u put ur tires through which was the main appeal pointed out to me. You chuck them on before first practice on friday and leave them on there all weekend and essentially ur only putting 1 heat cycle through rather than 6 in a weekend. Even if u turn them off each night ur still putting half the heat cycles through that you normally would. So hopefully youll get twice the use out of your tires before u gotta bin them.
Not to mention old tires seem to take 2 or so laps to come on and the laps before that are terrifying haha
I *think* there is a separate thread on this, but it was myself, Dallas and a couple others going back and forth on the batt topic. After trying many different configs I've settled on the smaller AGM because of the issues/dangers we've all had with Li. So it's kinda wiser to save the $, weight, and dangers elsewhere. Also worth considering - a LOT of the Li and AGM batteries are actually made by only a handful of manufactures and they get rebranded 2 or even 3 times and thus the price goes up 2x or 3x. My bamboozle was with Braille batt which is actually Penn, available at BatteriesPlus for like 1/3 the price, Braille does nothing but add stickers.
The rumor is that Duracell makes the Antigravity batt's and you can find the equivalent one but I haven't looked. Naturally AG is a marketing engine and if you call they'll explain how "their specs" and all that, which is likely BS.
Antigravity's differentiating feature is their battery management system. Normally, if you drain a Lithium Ion battery to 0V the cells will be irreversibly damaged. Antigravity has a low-voltage cutoff that disconnects the battery before the voltage gets too low. You press a little button on the battery to reconnect it long enough to start the car and recharge the battery. Supposedly they also have some cell balancing and some limited overcharge protection circuitry, too, which would be great to have.
I'm not sure Duracell makes a BMS like that. Antigravity certainly sources the individual Li-Ion cells from a different company. You could make your own Lithium Ion battery pack with some off-the-shelf cells and a spot welder, but I wouldn't recommend it. The BMS is where the value comes from.
Outside of the DIY car world, most Lithium Ion battery packs have a BMS. The challenge is that cars require several hundred amps of peak current during cranking, which is well beyond the current rating of most off-the-shelf battery management systems. I'd love to see photos of the inside of an Antigravity BMS to see if they used a solid-state cutoff or went with something like a bistable mechanical relay.
I still don't like Lithium Ion battery packs in the engine bay for other reasons. Lithium Ion cells are usually picky about charging voltages. Charging Li-Ion below freezing will usually damage it. Most cells are specified with a 45C (113F) maximum charging temperature, which I guarantee we're all exceeding in our engine bays.
I use a Deka ETX20L. It's slightly heavier than the ETX14L that everyone usually uses, but it fits perfectly on its side in the stock battery tray. I even use the stock battery hold-down with some shorter J-hooks.
Antigravity's differentiating feature is their battery management system. Normally, if you drain a Lithium Ion battery to 0V the cells will be irreversibly damaged. Antigravity has a low-voltage cutoff that disconnects the battery before the voltage gets too low. You press a little button on the battery to reconnect it long enough to start the car and recharge the battery. Supposedly they also have some cell balancing and some limited overcharge protection circuitry, too, which would be great to have.
I'm not sure Duracell makes a BMS like that. Antigravity certainly sources the individual Li-Ion cells from a different company. You could make your own Lithium Ion battery pack with some off-the-shelf cells and a spot welder, but I wouldn't recommend it. The BMS is where the value comes from.
Outside of the DIY car world, most Lithium Ion battery packs have a BMS. The challenge is that cars require several hundred amps of peak current during cranking, which is well beyond the current rating of most off-the-shelf battery management systems. I'd love to see photos of the inside of an Antigravity BMS to see if they used a solid-state cutoff or went with something like a bistable mechanical relay.
I still don't like Lithium Ion battery packs in the engine bay for other reasons. Lithium Ion cells are usually picky about charging voltages. Charging Li-Ion below freezing will usually damage it. Most cells are specified with a 45C (113F) maximum charging temperature, which I guarantee we're all exceeding in our engine bays.
I use a Deka ETX20L. It's slightly heavier than the ETX14L that everyone usually uses, but it fits perfectly on its side in the stock battery tray. I even use the stock battery hold-down with some shorter J-hooks.
it doesn't fit standing up? seems like it would. what kind of non-charging life does it have?
Half the guys in my class are running them and they just eat u on the first lap then u spend the next 2 - 3 laps re passing them as they are slower than you overall.
Also it seems to be alot more friendly on your tires as if u keep em in th blankets all weekend ur reducing the heat cycles u put ur tires through which was the main appeal pointed out to me. You chuck them on before first practice on friday and leave them on there all weekend and essentially ur only putting 1 heat cycle through rather than 6 in a weekend. Even if u turn them off each night ur still putting half the heat cycles through that you normally would. So hopefully youll get twice the use out of your tires before u gotta bin them.
Not to mention old tires seem to take 2 or so laps to come on and the laps before that are terrifying haha
Ya I'm attracted to it for all those reasons, I just haven't seen many folks here using them. Which tires/size you runnin? Also which kit did you get?
it doesn't fit standing up? seems like it would. what kind of non-charging life does it have?
The ETX20L is basically as tall as the stock battery is wide. AGM batteries can be operated on their side, so I just dropped it flat on its side into the stock tray. Stock battery hold-down fits right on top of it. Does require a short extension cable for the ground wire, though.
The ETX20L is basically as tall as the stock battery is wide. AGM batteries can be operated on their side, so I just dropped it flat on its side into the stock tray. Stock battery hold-down fits right on top of it. Does require a short extension cable for the ground wire, though.
is that why people use the 14? i purchased a d51 which is quite a bit taller, but i just bought longer tie downs to hold it down. very interested in trying the etx20l next though, 15lbs or so, right? pretty good savings. pic of it in the bay?
fwiw:
yellowtop d51 L x W x H : 9.31 x 5.06 x 8.94
deka ext20L L x W x H: 6.86 x 3.44 x 6.13
I'm not understanding why it had to be laid on its side? I'm kinda wishing I ran with this battery. like I said I'll probably give it a shot next time.
Ya I'm attracted to it for all those reasons, I just haven't seen many folks here using them. Which tires/size you runnin? Also which kit did you get?
I grabbed this kit off Ebay. Guy was really easy to deal with. shipped it str8 away. i enquired about the side covers wanting to pay extra for them and he threw them in for free.
Its not hugely common here. just over half of the top class guys use em. about 4 of us in my class are using them now. the perception is they are like $4000 to buy but people have only seen the really expensive ones and havn bothered to research incl. myself till my friend told me how cheap they were on ebay.
These have like a 36month warranty and everything on them. seem like really nice quality. Most expensive part was buying a generator to run them!
My tires are 280 640R18. they ask what voltage your country has and what tire size etc and make them to suit
fwiw:
yellowtop d51 L x W x H : 9.31 x 5.06 x 8.94
deka ext20L L x W x H: 6.86 x 3.44 x 6.13
I'm not understanding why it had to be laid on its side? I'm kinda wishing I ran with this battery. like I said I'll probably give it a shot next time.
I thought the Optima batteries were smaller than the OEM battery?
OEM battery (75D23L or Group 35) is has a footprint around 9" x 6.9". Flip the Deka ETX20L on its side and it has a footprint of 6.9" x 6.2".
Stock battery hold-down bracket goes across the 6.9" dimension, so it drops right on top of the ETX20L. You do need shorter J-hooks and a way to extend the negative battery lead, though.
I'll try to remember to grab a picture next time I'm in the garage.
I thought the Optima batteries were smaller than the OEM battery?
OEM battery (75D23L or Group 35) is has a footprint around 9" x 6.9". Flip the Deka ETX20L on its side and it has a footprint of 6.9" x 6.2".
Stock battery hold-down bracket goes across the 6.9" dimension, so it drops right on top of the ETX20L. You do need shorter J-hooks and a way to extend the negative battery lead, though.
I'll try to remember to grab a picture next time I'm in the garage.
it's a "miata" battery
and yes, please do - here's a link to how mine is just sitting in the tray, I don't see how/why it would need a different set up
it's a "miata" battery
and yes, please do - here's a link to how mine is just sitting in the tray, I don't see how/why it would need a different set up
I had a problem with my positive battery terminal rubbing on my IC piping, no matter what I did, so went with a smaller battery. Otherwise, I woulda just left it.
This is the most untrue sentence I've ever heard in my entire life
Here's my G13EP. It's a tad smaller than a PC680. No issues starting the car but obviously I don't drive it year round. I think this battery is marketed as a lawn mower battery? Lol
This is the most untrue sentence I've ever heard in my entire life
Here's my G13EP. It's a tad smaller than a PC680. No issues starting the car but obviously I don't drive it year round. I think this battery is marketed as a lawn mower battery? Lol
Weight that is behind the rear axle is take weight off the front. I'm not doing a bunch of weight reduction in my car because it's still primarily a street car. Full interior, no sound deafening removal, still has the sun roof, etc. I'd rather put a full size battery in the back then get a small battery and still have an extra 10lbs up front.
Jan 8, 2019, 09:36 AM
