TangoKilo
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 11:57 am

+1 :mrgreen:

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TonyWilliams
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:02 pm

mwalsh wrote:my car will typically be in this mode anywhere from 2-6 hours.
We can agree, I hope, that this is not "normal" ops, and even the current AGM battery needs a little love during that load.

I don't know, but I presume, that the traction battery is using the DC-DC charger in ACC mode? And if the car is outside, that you're getting the mega-awesome solar charge, correct ?

I'll have to go hook up the Fluke 117 / i410 combo and measure that power consumption in ACC.

And for everybody who is not jump starting other cars, leaving the car on ACC for hours, or other "not exactly what the car was designed for" type activities (I guess throwing in some super-huge stereo system, Baja flame-thrower type spot lights, etc, would all apply).....

... a tiny A123 technology battery the size of a cigarette pack would replace the 1850's technology lead / acid. Is there a monetary payback? Sure, in 10-15 years.... maybe. I'm not sure you could even measure the mileage increase with a lighter battery, or put a value on the price of not being left stranded when the lead/acid fails to boot up the car in a few years (my 2010 Toyota Sienna lead/acid battery failed at less than a year... in my lifetime, I can't count how many lead / acids that I've replaced in cars, planes, and other equipment).

Are there other cool things you COULD do with NOT having a heavy, sometimes failure prone, relatively short lived (compared to the life of the car or a lithium) battery? Sure. How about if you put a simple, cheap, water/dust resistant plastic box in the same place as the existing dinosaur battery that can store all the charger accessories? I plan to do that. All the maintenance things under the hood.

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mwalsh
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:06 pm

TonyWilliams wrote:
We can agree, I hope, that this is not "normal" ops, and even the current AGM battery needs a little love during that load.

I don't know, but I presume, that the traction battery is using the DC-DC charger in ACC mode? And if the car is outside, that you're getting the mega-awesome solar charge, correct ?.
Agreed. Correct. Correct.
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TonyWilliams
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:11 pm

TangoKilo wrote:I've been following this thread with some interest. As I see it, the current battery installation (25 pounds?) is well under 1% of the total vehicle weight. The performance gain in a lighter battery would be negligible at best... You've probably got that much weight with junk in the trunk anyways... If on the other hand you just wanna get the lead out...well...whatever... 8-)

How about if I took out the battery for a light one and swapped the wheels for lighter ones?

24 pound-ish battery savings
116 wheel savings (about 40-11 for a 29 pounds per wheel savings)

140 total, or almost 4% of 3600 pounds.

Would that make a difference? If not, what weight would?

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davewill
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:21 pm

TonyWilliams wrote:How about if I took out the battery for a light one and swapped the wheels for lighter ones?

24 pound-ish battery savings
116 wheel savings (about 40-11 for a 29 pounds per wheel savings)

140 total, or almost 4% of 3600 pounds.

Would that make a difference? If not, what weight would?
The battery means nothing, but the wheels are a special case. They represent a lot of kinetic energy as they are spun up and slowed down. Even a modest decrease in weight there should pay dividends.
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TomT
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:34 pm

Not as much as you might think because, depending on how you drive, it is not lost energy per se... Regardless, I personally again see no ROI in changing them...
davewill wrote:the wheels are a special case. They represent a lot of kinetic energy as they are spun up and slowed down. Even a modest decrease in weight there should pay dividends.
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TonyWilliams
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:37 pm

davewill wrote:The battery means nothing, but the wheels are a special case.

Individually, any single small weight reduction is probably not measurable. But together (and not just wheels), lots of small changes do become measurable.

Some bolts used in aircraft are center drilled to lighten them. It would be impossible to measure the savings of a bolt, but when the same processes of lightest weight are applied throughout, it does add up to something measurable.

If I could find another 140 pounds of savings on the car, would that be "worth it"?

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davewill
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:39 pm

mogur wrote:Not as much as you might think because, depending on how you drive, it is not lost energy per se... Regardless, I personally again see no ROI in changing them...
Unfortunate turn of phrase on my part. No, I don't think there's an ROI case to be made there, either, but comparing pound for pound, I would expect 40lbs saved there to actually make a measurable difference unlike 40lbs in general.
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davewill
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:40 pm

TonyWilliams wrote:If I could find another 140 pounds of savings on the car, would that be "worth it"?
Not if it cost me much in the way of time and money.
Last edited by davewill on Mon Jul 25, 2011 12:45 pm, edited 1 time in total.
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Skywagon
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Re: 12 Volt Lead Acid Battery Replacement

Mon Jul 25, 2011 12:43 pm

TonyWilliams wrote:
TangoKilo wrote:I've been following this thread with some interest. As I see it, the current battery installation (25 pounds?) is well under 1% of the total vehicle weight. The performance gain in a lighter battery would be negligible at best... You've probably got that much weight with junk in the trunk anyways... If on the other hand you just wanna get the lead out...well...whatever... 8-)

How about if I took out the battery for a light one and swapped the wheels for lighter ones?

24 pound-ish battery savings
116 wheel savings (about 40-11 for a 29 pounds per wheel savings)

140 total, or almost 4% of 3600 pounds.

Would that make a difference? If not, what weight would?
I am not sure where you are going to save 29 lbs per wheel as the stock ones are 21 lbs each. The lightest aftermarket wheels in a similar size are in the 11 lb range; most are around 13-14 lbs. Plus you cannot factor wheel weight as static/dampened weight as it is un-dampened and rotational mass (inertial) as well. Your 140 lb loss estimate is not correct.

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