[Eric_Oz_S2]

Looking for a new battery (wife's car ate another and the Porsche one is in the wife's now).



Car is infrequently driven and spends its life on a battery charger. Used mainly for track.



I was thinking of a deka etx16L as a good price point. Odyssey batteries look ok, but more expensive. Braille seems overpriced for what you get, and although similar to deka gets poor reviews.



Looking for opinions.



Cheers



Eric

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[ds968]

For $155 , not sure you can get anything even close to the only 9 lbs Braille B 129 weighs . For a car that's used mainly for racing and is usually on a trickle charger, I would think that's an ideal battery . It has 831 amps cold cranking power but not sure how the amp-hour capacity factors in for a non-DD car.

Sure, $ 155 is not cheap but for what you get I definitely would not call it overpriced. Again, 9 lbs ! There was a thread a while back about 4 lbs batteries ( I can't remember the brand ) priced at over $ 2,000 - now that's overpriced, LOL

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[Cloud9...68]

The thing to be careful of with a small battery in these cars is that the fans run after the engine is turned off (to promote convective cooling), and they draw a ton of current - I've measured mine at over 12 amps! So, particularly on a hot day, a small battery only gives you a handful of starts before it conks out. Also, they won't start the car at anything below about 38 degrees F. I can't remember the brand I have, but I don't think there's much difference among them - they're all small capacity lead-acid batteries, after all, and there's only so much reserve power they can provide. But if it's mainly for a track car, and you're aware of the limitations, you should be fine. If I know I'm going to need to start mine more than a few times in the summer, I plug a solar charger into it.

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[flash]

yup - i know of a couple of guys who have already gone back to a conventional battery after having their braille die on them while waiting for their next lap at an autocross. the stopping and starting, and the fans running in between, made short work of that undersized battery.

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[Eric_Oz_S2]

The deka etx16l has around 20ah if I recall correctly. It weighs around 7.7 kg/ 17lb. So in context, around half the weight and capacity of the standard battery. Cold starts aren't much of a problem where I live.

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[flash]

while capacity is better at cold than hot, charging voltage is better at cold too, which is why the small batteries die at autocrosses. it's often so hot there that they don't charge as well. constantly having to start the car puts a heavy load on what capacity there is, as do the fans running after you shut it off. then you don't run it long enough, at a high enough voltage to fully charge it back up again. do that a few times and you have a dead battery.



remember too that every time you kill a battery, it loses some of its capacity to charge. do that to a battery that already has a smaller capacity, and it won't be long before you toss it.



best to have a piggyback to start it with

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[Cloud9...68]

Lithium ion batteries have significantly more energy density than conventional lead acid, and there are a few of them available for the aftermarket, but their prices haven't dropped much (kind of like carbon fiber). So that would be your best option for a lightweight battery, if you can afford it - last I checked, they were in the $1000 range.

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[flash]

i think i would run the smallest thing i could, and carry a piggyback on track days. in my race cars, i never used the battery that was in the car to start the car, unless i stalled it on the track. i always went to the piggyback



frankly though, battery weight isn't that big of a deal. it's static and positioned to counter driver weight.

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[Eric_Oz_S2]

Once you have removed everything you don't need, a light battery is actually a cheap mod to save 8kg. Much cheaper than a lexan hatch (-12kg) or carbon bonnet (-20kg). Already have race seats and no rear seat, so not much left to save while keeping the car civilised enough to use on the street.

[quote name='Cloud9...68' timestamp='1392820672' post='155265']

Lithium ion batteries have significantly more energy density than conventional lead acid, and there are a few of them available for the aftermarket, but their prices haven't dropped much (kind of like carbon fiber). So that would be your best option for a lightweight battery, if you can afford it - last I checked, they were in the $1000 range.

[/quote]

Yes, $ per kg saving is very high compared to an agm battery.

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[flash]

no chance of saving 20kg on a carbon bonnet. it only weighs 39lbs (less than 18kg) to begin with. it only feels heavier due to how long it is.

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[Cloud9...68]

Yeah, I saved less than 20 lbs (more like 15) with my fiberglass hood, and I don't think there's more than about 10 lbs (4.5 kgs) to be saved with a lexan hatch, either, unless you go really thin.

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[flash]

you can save more if you screw it down and lose the frame.

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[Cloud9...68]

Makes sense. But then I guess you lose the hatch opening capability.

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[Eric_Oz_S2]

Rear hatch saving is reported by many as 11 to 12 kg with 5mm polycarbonate. Poly is half the density and stock glass is 6mm thick.

S2 hood is also heavier than 968. Carbon hood is much lighter than fibreglass. Total hood weight is 5kg.



My point when I started this is a lightweight battery is a very cheap $/-kg improvement. I ordered the deka 7.7kg battery. We'll see how it goes.

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[flash]

carbon is not that much lighter than fiberglass. it's usually thinner, due to the rigidity of the fabric not requiring as many layers, which is why it can be lighter, but it still uses the same kind of resin. so, depending on how thick it is, it can actually weigh the same. it also makes a huge difference if you pin the hood, or use hinges, which require metal to be buried in the hood to attach the hardware. a hinged hood only saves a few pounds.



as for the battery, again, i would absolutely recommend a piggyback for track or autocross use. it's a real drag when your battery dies there.

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[986boxster1998]

Im happy with the Odyssey PC925T (925 cranking amps for 5 seconds/28 amp hours/50 minute reserve capacity with 25amp load/Weighs 24.5 lbs).

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[Cloud9...68]

Eric,



The Deka battery you bought should work well. I would invest in a solar charger, though. I connected mine to the battery by routing a wire through a hole I drilled in the ash tray. I got a 5W charger for something like $35 from Amazon, which was less than I had expected. Don't waste your money on anything smaller. I plug mine in anytime I park my car for any length of time.

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[Eric_Oz_S2]

Thanks. I already have a Ctek MXS5 (5A) which I use constantly, so I'll keep using this. It has a special program for the AGM batteries which like to charge at a slightly higher voltage (14.7V).



Cheers



[quote name='986boxster1998' timestamp='1393009088' post='155342']

Im happy with the Odyssey PC925T (925 cranking amps for 5 seconds/28 amp hours/50 minute reserve capacity with 25amp load/Weighs 24.5 lbs).

[/quote]

Wow, that's pretty heavy. Stock battery is only 15.5kg/34lb. New is 7.7kg/17lb (19Ah). I suppose if you DD it you would want this size though. Nice looking battery mount!

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[Cloud9...68]

I keep waiting for the price of Lithium ion batteries to come down. Hopefully by the time I have to replace mine, they'll be reasonably affordable.

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[Eric_Oz_S2]

[quote name='Cloud9...68' timestamp='1393082068' post='155380']I keep waiting for the price of Lithium ion batteries to come down. Hopefully by the time I have to replace mine, they'll be reasonably affordable.[/quote]



Prices are not too bad now, $330 for 1.5kg/ 20ah equivalent.



http://www.ebay.com/itm/Lithium-Ion-12V-...4ad05e532b



That's only double an AGM battery of equivalent capacity and 20% of the weight.

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