Car is a 97 M3. Primarily track driven but still streetable.
In the quest for lightness, I've decided to lose the factory battery. Weight 43 lbs. I have no rules to which I need to adhere. So, no limits other than cost. I'd like to be in for under $250. I can fabricate my own bracket if I need to.
I've seen two possible replacements:
1) AGM from Braille - 6lbs, or a little more for something that has a few more cranking amps.
2) LIon from several manufacturers - 1.5 lbs (!)
I'll have to fabricate or buy a bracket because these options are tiny and tinier, way smaller than the stock wet-cell battery. Indeed, the LIon battery is the size of a "pack of smokes". Amazing.
What do you use, and how well has it worked for you?
Last edited by emoore924; 01-17-2019 at 07:47 PM.
i bought the deka ETX16L. $86 on amazon.
it was recommended here on BF i believe.
its been in the car since mid-sep, track only/zero in car accessories, car so maybe 12 starts. immediate crank over every time.
i cut a plate from some 1/4" AL diamond plate material i had, bolted to the stock battery mount locations in the car. mounted to the plate are 4 L angle extrusion pieces, 1 front side and 1 rear side of the battery and 2 more on the sides which the j-hook battery bolts holds her down. i have it centered where stock battery was both OEM cables are still used.
cheers
We used to run a small tractor battery from Walmart … $30 or so, only like a pound more than deka, and it works fine to start the car many times. Only issue is when we run our heated windshield and electric PS, and electric waterpump for a long race … it can be an issue with voltage. Now we run a basic honda or miata size battery. The 10 lbs or so is worth peace of mind.
I’ve been running a DIY 16 cell LiFePo battery for about 7 years now. 3lbs, and as long as I’m not stupid enough to leave the lights on or not shut the door tight, I’m fine. I’ve run Autocross with a co-driver on a day where we’ve each gotten 13-14 runs, shuttling it down between each 1-2 minute run. Never had a problem in that regard.
And I mounted it in the engine bay, because I saved a further 7lbs by eliminating the long power feed cable that runs from the trunk to the engine bay.
Last edited by jakermac; 01-21-2019 at 09:15 PM.
Odyssey Pc680
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With regards to mounting, Stable Energies has a nice bracket made specific to Braille batteries but could be used for others of similar size.
http://www.stableenergies.com/Stable...info/BB-MOUNT/
Some popular Lithium Ion options from another forum:
https://shoraipower.com/lfx21a6-bs12-p102
https://shop.antigravitybatteries.co...-case/ag-1601/
https://shop.advanceautoparts.com/we...raft%20lithium
For those with full race cars, how did you determine the minimum amount of cold cranking amps you needed?
Last edited by BlackHawkRacing; 01-20-2019 at 11:39 AM.
Battery tender from Summit. 240cca, weighs 1.6lb. Started my 13:1 LS3 with no real issues, unless I forgot to shut the power off. I had it mounted underhood which like was said by jakermac above, saves an additional 7lb by getting rid of the cable to the rear.
Would the deka ETX16L be ok to use if you're running a 20amp pump for water/methanol injection?
-Phil
Braille G20. Amazing cranking power for such a tiny battery, even in very cold weather.
I installed Odyssey PC680 last year and it's been working well for me. However, car does not see any street use.
I like that. Nice bracket too.
I thought I'd give a Braille B129 a try. 9lb AGM. Now all I have to do is fabricate a hold down bracket and I'll be good to go
Anyone interested in a slightly used 43lb BMW factory battery :P
Thanks for the input everyone !!! Off to the track I go
Last edited by emoore924; 02-21-2019 at 08:05 PM.
PC680 here, never had a problem with starting and the car occasionally gets driven on the street. Have not had to use a tender over winter either, but I kill everything in the car when its parked.
Here's the bracket. Welded it up from a little angle steel, some flat steel and some threaded rod. Weight is less than 1lb. Uses the factory mount points. One end fits under the forward battery hold-down tabs and the other bolts to the factory mount point at the rear. So, no un-doable damage or alterations to the car. Fits like a glove.
IMG_20190310_100056475.jpgIMG_20190310_110255342.jpg
Last edited by emoore924; 03-16-2019 at 03:25 PM.
I used to run Shorai's largest motorcycle battery on my e36 M3 HPDE car and on my Subaru rallyX car. Leaving any circuit powered up overnight would overdischarge the battery, do that about 3 times and you get a $250 paperweight. Going with Odyssey now, but I like the PC950 instead of the 680. 20 lbs instead of 15, but you get 400 CCA instead of 170.
We went with the 680. Still kinda heavy, but nice and compact. Haven't really used it yet, but seems to be one of the go to's.
56440238_411960142701421_363213594537492480_n.jpg
We ran the Braille 9 at Pocono this weekend and despite a shortened weekend due to nasty weather, and flying the car off the banking almost every lap (that's fun) the Braille 9 performed flawlessly. No problems with several times on and off the trailer and 20-some starts during the day. I couldn't tell the difference when cranking between the BMW factory battery and the Braille. Well, except for the 34lb weight savings.
Recommended.
Quick comparison of some of the batteries discussed. Prices, sizes, are rounded off so not exact.
Screenshot-20190517132706-1442x408.png
Anyone know the (equivalent) Ah rating for the LFP-8 ?
It's 12 Ah over 10 hours.
See page 23 here: http://www.carquestprofessionals.com...%202015_16.pdf
That's an awfully good price for a Lithium battery.
Neil
Thanks for finding that!
Yes, seems TGTBT.
I have had 2 quality, expensive, Lithium motorcycle-size batteries enter thermal run away. It is NOT pretty. Both of those batteries were advertised to have thermal run away protection (and all the other protections that the high-end manufacturers advertise).
And, IMO, 12Ah is a bit low to hook up to the 80amp alternator on our cars.
I'm just not quite ready to put one of these in my car. Especially one that doesn't state it has those protection circuits included.
I've had no issues with the charging of my 9.2ah home made 3lb LiFePo using the 80amp Bosch alternator in my 93 325is. Discharging on the other hand has done in a couple of my packs. But that's on me entirely. I found the key to be picking the right model of cell. The A123 cells that I've been using are capable of accepting up to a 10C charge rate. That equates to 23 amps. And since my battery is configured as a 4S4P, that means the pack can take up to a 92amp charge rate.
And the LiFePo batteries that I've been using get really really pissed off when you overcharge them, and they hiss at you and get hot, but they DON'T catch on fire.
Last edited by jakermac; 06-01-2019 at 02:15 PM.
What cells are you using? I thought A123 was long gone
Last edited by dirtdiggler; 06-03-2019 at 10:38 PM.
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